Bandit Alley
MODEL SPECIFIC => SUZUKI BANDIT 250 & 400 => Topic started by: stormi on May 03, 2006, 02:50:40 PM
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Grr,.. one thing after another with Dita this spring. Got the new Gear shift Link rod in, now she's doing other things.
I got a set of straighter bars ( meaning,.. that I hadn't bent by dropping her. :sad: ) and put them on. The bars have a lower rise than the original ones, and are the same length.
According to the wiring diagrams in the service manual, we've routed the cables right, but she races if you turn the bars to the right lock.
Taking everything apart, and routing cables the wrong way ( I know, I know. :roll: ) in order to troubleshoot, we notice a few things:
1. Until the cable gets to the fork area, there's no problem with binding.
2. Tank on or off, the engine still races if you route it the way the book says, or any other way.
3. Bar position (rolled forward, rolled back) makes little to no difference
4. You can actually watch the throttle get pulled at the carb end, when you move the bars to the right.
5. Certain routings allow her to race the engine no matter the position of the bars.
6. There's ZERO free play. There's no room for adjustment on the carb side or the grip side.
It's as if the cable shrunk overnight. But they're supposed to stretch, no?
The cable is lubed, and moving freely.
We're at a loss to explain this, and getting more and more frustrated by the moment. ( I actually hit her tank and called her a b*tch. My little lady! :shock: :crybaby: Ok,.. it was the end of day 2 at this, and I was tired of watching her put together right, and racing to 8k rpm as soon as we started her, with a not even broken in engine.) Now, neither of us has touched her in 2 days, and both of us have started looking for reasons not to.
I know, deep down that it's something simple, and stupid. Suggestions? Is there adjustment on the carb anywhere that might be doing this? Besides the idle screw, and the nut/bolt combo for the cable itself? The service manual is vague about this area.
I can post pictures this evening if needed.
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Sounds like you need to observe where the cable is getting caught in right lock situations and route it to prevent that from happening.
Had a similar situation with my little 50 I bought for the grandkids. First time I started it and took it for a spin around the yard, the motor started screaming the first time the bars were turned left. Seems the factory had misrouted the throttle cable. Had to pop the tank off and correct the issue.
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Got the nut on the right side? I f'd that up before...
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Sounds like you need to observe where the cable is getting caught in right lock situations and route it to prevent that from happening.
That's the frustrating part. We have been looking. It seems to be when the cable goes through the triples, but no matter what angle we try to use, it seems to only change the problem slightly. It seems like it binds up where the cable makes the right at the front of the triples, to go to the grip.
The amount of cable that lives outside the cable sheathing, once the cable is hooked to the carb end, seems too short to hook up to the grip. So you have to give it a little tug to get it onto the grip, and this is with the adjustment all the way in, for maximum free play.
If you put the bars straight, and "blip" the throttle, it will settle down to the stop on the carb. If you turn the bars, it may even stay there. If you blip the throttle when the bars are turned, it will race, and you have to turn the bars back to center to get it to drop.
About the only way I seem to be able to route it so it doesn't do this is to route it straight out the right side of the bike from the carbs, and then up to the throttle grip. Of course that doesn't work for obvious reasons. :duh:
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Got the nut on the right side? I f'd that up before...
:lol: Which side is correct? Bottom, right?
I was sure it went on the top (10 speed bike style), the other half thought the bottom. The bottom maximizes free play, the top allows more adjustment, but also holds the throttle open a little as this cable is right now.
Where it is currently, is at the bottom, nice and snug in the openning that seems made for it.
edit: in fact: This -is- Dita, and it shows it on the bottom, but it doesn't look like it's nestled into the spot that I mentioned.:
(http://i7.photobucket.com/albums/y278/stormigerl/IMG_3446.jpg)
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The cable shouldn't have that little kink going on... it should be a striaght pull!
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The cable shouldn't have that little kink going on... it should be a striaght pull!
Which kink? At the bottom,.. or at the top where it heads toward the grip?
:lol: Poor girl.
The one at the bottom sort of indicates some slack - that's not there anymore.
The nut being off kilter at the top is due to the tank resting on it.
I object to this design, btw.
That's an old pic, from the choke cable how to I posted a while back,.. but nothing's changed (except the slack).
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:lol: Which side is correct? Bottom, right?
I honestly can't remember but your logic for the bottom sounds good. You screwed the top nut at the carb all the way in? That top nut is adjustable as well.
If that doesn't work then try using a cable stretcher. <jk> :lol:
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:lol: Which side is correct? Bottom, right?
I honestly can't remember but your logic for the bottom sounds good. You screwed the top nut at the carb all the way in? That top nut is adjustable as well.
If that doesn't work then try using a cable stretcher. <jk> :lol:
Yup,.. it's screwed all the way into the bottom.
nope,.. last time I used a "cable stretcher", the cable got ripped in half. :shock:
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My bike does the same thing, turn it to the right and twist the throttle and it doesn't go back to idle. It seems to do the opposite when turning to the left too - the engine dies (but I only notice it when arriving home and turning around in the driveway which faces downhill, so that might have something to do with it?).
I'll keep an eye on this thread to see if you figure it out...
I'm not sure if it did it when I first got the bike. I oiled the cable shortly after getting it and I've been wondering if the oil might've made the cable stick more and prevent the throttle spring from closeing the carbs?
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In your picture, I can only see the wire rope of one cable, and it looks off kilter.
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Take a look at Jays gigantic carb pics. See how much threaded rod sticks below? Your picture doesn't show that. Check to make sure you have that adjusted properly.
http://forums.banditalley.net/viewtopic.php?t=5412
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Jay's pics are of his race carbs, that's why they have more thread sticking out the bottom. HOWEVER, it doesn't look to me like the nut is tight enough in the picture. The threaded bit is a loose fit in that support on the carb, so if there is any free play, then turning your bars will pull the cable housing, causing the threaded bit to skew and open the throttle. Make sure the threaded bit is tight and not moving at all.
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In your picture, I can only see the wire rope of one cable, and it looks off kilter.
The funny part of this is that the pic is of the carbs when they were working. That's one of the pictures of the "How to build your own throttle cable" thread from a while back.
These days, everything is tight, the bolt is screwed right to the bottom, and the nut is tight against it, no room for movement. The cable is now tight, no more kink.
I'll try to step out there today and take a current picture.
(BTW, the B4 only has one throttle cable. It's not a push/pull system, like the B6/12 or the 919)
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Jay's pics are of his race carbs, that's why they have more thread sticking out the bottom. HOWEVER, it doesn't look to me like the nut is tight enough in the picture. The threaded bit is a loose fit in that support on the carb, so if there is any free play, then turning your bars will pull the cable housing, causing the threaded bit to skew and open the throttle. Make sure the threaded bit is tight and not moving at all.
OK,.. I'm going to head outside then and grab a new pic. I think I confused everyone. Sorry about that.
That pic, strangely enough, was on the bike when it was working (circa 12 months ago). The current situation is that there is no free play with the "adjustment" as tight as it can go, i.e. the nut screwed up tight against the erm,... cable guide thingy, as well as tight at the grip end.
There's no kink left in the cable, since there's no slack in it at all. It's as though the cable itself shrunk maybe 5mm overnight.
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Alright. The wiring diagrams be damned. :roll:
I routed the throttle cable straight up from the carbs to the front of the bike. Fed it through the clamps to the throttle grip, and tightened everything up. This means that there's only one bend in the cable, rather than the several introduced by the "recommended" routing.
One little snag when I tightened everything too tight against the bar end (free cruise control). Fixed that, and wheeled her outside for a bath. (Just waiting for some shade now.)
If you turn her bars all the way to the left, she bumps her idle up to about 2k rpm (from 1500) , but holds there. All the way to the right, no change from idle. I can live with that.
Now to spend some time breaking this engine in and get some hours on her. :banana: :motorsmile:
Should be nice when the other half gets home and doesn't have to fight with her. Maybe he'll put his CR250 back together, and we'll have some room in the shed again. :shock: two bikes in pieces really take up a lot more room than when they're together.
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Seems to me, if you have to reinvent the routing, something is still wrong somewhere. Lock-to-lock, there should be no change in your idle.
BTW - sorry about those canuck comments in Off Topic. :beers: :bigok:
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Seems to me, if you have to reinvent the routing, something is still wrong somewhere. Lock-to-lock, there should be no change in your idle.
BTW - sorry about those canuck comments in Off Topic. :beers: :bigok:
Yeah,.. I think so too,.. but apparently the bars I just put on her are wider, I didn't think they were. I do know that the rise is lower, so maybe the bar change forced a change in routing.
Which canuck comment are we referring to? :wink:
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I found out what was causing my bike to stop when I got home and turned around on the drive (downhill and turning the bars to the left).
The choke cable was a bit tight and was pulling the choke when the bars were turned.
I think the tendency for the throttle to stick when moving the bars to the right might have reduced as well, but I don't know if that's due to loosening the choke cable or not.
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Interesting.. I know this is an old thread but i've been battling this issue with my bandit 400 for 12 years.
I bought a new OEM cable, didn't solve it.
Tried every possible routing, didn't solve. I even had the cable directly from the carb to my throttle, straight through the air, and it would still do it.
It does not shoot up in RPM when I'm not touching the throttle. Instead, it only happens when I'm already on the throttle, e.g. 10km/h constant throttle. If I now move my handlebar to the right, it shoots me from 10km/ to 30kmh.
I think the issue is because the 400 only has 1 cable and no return. I can literally reproduce the issue with a bare cable (not connected to anything), then holding one end of the cable, and bending it slightly. The other end of the cable will move almost 1mm - and therefore twist the throttle plate.
I even had a custom cable made but it makes no difference. I have no idea how to fix this... I would like to use my 40 for moto gymkhana but this issue literally prevents me from it :banghead:
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Do you know if you have the original bars or if they've been replaced with a different bend? That seemed to be the bulk of my issue. The smallest change in the distance that cable needs to travel seems to play havoc.
I feel like the shielding is a little too long for the cable. The slack it has should be greater and able to be taken up with adjustment. Instead, the cable has no leeway and jerks the idle up.
I always thought Gymkhana would rely mostly on clutch control - but I suppose that sudden rpm changes could be disruptive.
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Do you know if you have the original bars or if they've been replaced with a different bend? That seemed to be the bulk of my issue. The smallest change in the distance that cable needs to travel seems to play havoc.
I feel like the shielding is a little too long for the cable. The slack it has should be greater and able to be taken up with adjustment. Instead, the cable has no leeway and jerks the idle up.
I always thought Gymkhana would rely mostly on clutch control - but I suppose that sudden rpm changes could be disruptive.
I have the original bars. Bike is completely stock except the muffler.
Last week i've had a custom cable made, it's 15cm longer and with a tinner outer cable, but it made no difference. The cable hardly moves at all, doesn't touch anything but the slightest movement makes rpm shoot up.
What do you mean exactly no leeway? You think the outer cable should be longer relative to the inner cable?
No Motogymkhana is all throttle and rear brake. No clutch. It's very disruptive because I literally shoot out the corner in 1st gear very low speeds.
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What do you mean exactly no leeway? You think the outer cable should be longer relative to the inner cable?
No Motogymkhana is all throttle and rear brake. No clutch. It's very disruptive because I literally shoot out the corner in 1st gear very low speeds.
Exactly the opposite. I felt like the outer cable sheathing was too long. So if you have 1cm of inner cable on the carb end and 1cm on the bar end, I feel like it would do better with maybe (as a completely arbitrary number here because I can't even reference the bike because I don't own it anymore) another 1/2 cm in total length. That would let you assemble it AND take up some slack using the adjustment. As it sits with the stock cable - by the time you assemble it, there's zero slack to take up with the fine adjustment at the bar - meaning that adjustment ability is useless and - ultimately - needed if the cable were a better length and it could be assembled properly so that installing the tank couldn't raise the RPM or turning the bars or looking at the
bike while Mercury's in retrograde or whatever.
I remember that throttle cable being the most fiddly cable to ever reinstall for the same reason. It was a bear to do even if you did it 100% right.
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What do you mean exactly no leeway? You think the outer cable should be longer relative to the inner cable?
No Motogymkhana is all throttle and rear brake. No clutch. It's very disruptive because I literally shoot out the corner in 1st gear very low speeds.
Exactly the opposite. I felt like the outer cable sheathing was too long. So if you have 1cm of inner cable on the carb end and 1cm on the bar end, I feel like it would do better with maybe (as a completely arbitrary number here because I can't even reference the bike because I don't own it anymore) another 1/2 cm in total length. That would let you assemble it AND take up some slack using the adjustment. As it sits with the stock cable - by the time you assemble it, there's zero slack to take up with the fine adjustment at the bar - meaning that adjustment ability is useless and - ultimately - needed if the cable were a better length and it could be assembled properly so that installing the tank couldn't raise the RPM or turning the bars or looking at the
bike while Mercury's in retrograde or whatever.
I remember that throttle cable being the most fiddly cable to ever reinstall for the same reason. It was a bear to do even if you did it 100% right.
Yes that's true, I always had the adjustment all the way max out (max slack) or close to it.
That said, I'm not sure if giving it more slack would solve my problem, because when you're on the throttle there is no slack.
Also, I have 2 other throttle cables lying around from other bikes. If I hold/pinch the cable steady on the throttle side, simulating i'm holding steady throttle, and then bend the cable in mid-air, I can see the throttle-end moving 0.5-1mm.
Just this fact, tells me it's not at all about cable routing or slack. All 3 cables I have do it disconnected from the bike.
I'm starting to think 1 throttle-cabled-bikes are just not really suitable for slow technical turns let alone motogymkhana. :shrug:
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Yes that's true, I always had the adjustment all the way max out (max slack) or close to it.
That said, I'm not sure if giving it more slack would solve my problem, because when you're on the throttle there is no slack.
Also, I have 2 other throttle cables lying around from other bikes. If I hold/pinch the cable steady on the throttle side, simulating i'm holding steady throttle, and then bend the cable in mid-air, I can see the throttle-end moving 0.5-1mm.
Just this fact, tells me it's not at all about cable routing or slack. All 3 cables I have do it disconnected from the bike.
I'm starting to think 1 throttle-cabled-bikes are just not really suitable for slow technical turns let alone motogymkhana. :shrug:
If you have room to adjust it for more slack - it should lessen your issue. I never had any adjustment to gain slack on my b4. Ever. The cable isn't long enough.
You wouldn't necessarily be giving it more slack - you'd be giving it proper slack to be able to absorb the movement of the cable from the tank being put on it (yeah - watch it when you put the tank on if the cable isn't attached at the throttle end. You'll see it shorten), or your "bending the cable", or even the natural couple of mm of freeplay that a throttle cable should have. The cable on my b4 had no slack or freeplay. None.
All cables will shorten if you bend their sheathing. That's expected. Free play allows that to happen without it causing the motor to rev at the same time. Free play also lets you hit a bump and have your right hand move without causing you to whiskey throttle it.
I'm obviously not being clear. Think of walking a dog. If you walk with the leash with adequate "slack", the dog can turn its head and look at things without jerking your arm around but you still have control if he tries to take off. If you walk with a choke hold, as soon as he turns his head he's going to jerk your arm, right? This is the same as bending your cable in mid air and watching the throttle end move when there's no slack at all or what happens when you turn the bars and the idle rises.
Try this: https://www.youtube.com/watch?v=zy2dj9VvEdI - Ari talks about the cable lengthening with age - which is why you'd usually make a fine or gross adjustment of the throttle cable. If you look in the comments, "Rowdy Bikes" says they like 0.0mm free play. Notice the first response? "Yup - as long as it doesn't rev when the bars are turned,"
Ari also mentions at the end that you need to re-adjust if the idle goes up when you turn the bars. (Because that means that the cable is adjusted too tightly and needs to be backed off) What he can't know is that there's no way on the B4 to back off your adjustment that's too tight because there's no adjustment built into this cable because it's too short to begin with. The cable is too short in relation to the sheathing thus no freeplay, and no forgiveness when turning the bars.
In fact, we simulated this exact issue on that dirt bike in my signature. The carb was assembled with an incorrect jet needle (too tall) while my other half put a JD jet kit in (because I really needed that much extra power and throttle response on a bike I'd never ridden... :roll:) - the effect of the new jet kit with the wrong needle - was taking up too much slack in the throttle cable. We couldn't even assemble the throttle at the grip side because it had shortened the cable so much. The sheathing didn't change length - obviously - but with the taller needle, more of the cable's "slack" was used up at the carb end so it wasn't even long enough to assemble.
If your throttle snaps back when you let it go - it's doing it's job. The "push pull" cables aren't really that necessary on a small bike. The return spring action is enough. If the return spring action wasn't enough, that also would cause an issue where the bike wouldn't return to idle when you wick the throttle open and let it go - or it would stay open when you opened the throttle. The issue you describe - idle rises when you turn the bars - is usually directly related to "free play" / slack adjustment but you don't have any on the throttle cable on a b4.
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All cables will shorten if you bend their sheathing. That's expected. Free play allows that to happen without it causing the motor to rev at the same time. Free play also lets you hit a bump and have your right hand move without causing you to whiskey throttle it.
Well, then I'm out of luck. As I said, when I'm constant throttle at 10km/h, there is no free play, because I'm on the throttle.
I understand everything you said in the rest of your post but it it's always about slack. Slack is irrelevant in my problem. At idle my revs are not going up when I move the bars, because as you said the slack is taking care of any movement caused by the bending. However, again, it's when I'm holding steady throttle and then move the bars, where I have the problem, because there is no slack to absorb any movement caused by bending.
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Well, then I'm out of luck. As I said, when I'm constant throttle at 10km/h, there is no free play, because I'm on the throttle.
I understand everything you said in the rest of your post but it it's always about slack. Slack is irrelevant in my problem. At idle my revs are not going up when I move the bars, because as you said the slack is taking care of any movement caused by the bending. However, again, it's when I'm holding steady throttle and then move the bars, where I have the problem, because there is no slack to absorb any movement caused by bending.
Slack is one component of the cable being too short and the thing I found easier to explain but it's all part of the same issue. This cable's still got constant tension on it regardless of the state of motion - so if something's able to jerk it, you're going to get more throttle when that condition happens.
Assuming a properly lubricated cable and proper routing (did you download the service manual and double, triple and quadruple check it? I know you said you've tried every routing - but that one's easy to mis-read.), there isn't much to jerk that cable to pull the throttle open - other than the bars at full lock once the bike is assembled again. If the bars are making the rpms rise then there's an issue with either cable or something at one or the other end. Something is making that cable pull the throttle.
So, as I see it - there are 2 things you can look at:
1.Check your return spring - I sincerely doubt this is it because you say it's accelerating from 10 -> 30kmh, which is a significant increase in speed which indicates a lot of extra throttle being pulled. As in - not that it was being used but slowed by the brake and the brake was suddenly released because I think you'd notice if you suddenly stopped riding the rear brake. Also, there wouldn't be an audible change to the sound of the motor. I assume there is now or you wouldn't be talking about an rpm rise. But if you check it, you can say you did your due diligence. Triple check that the free play adjustment at this end is correct while you're there. Mine was always adjusted to be the loosest it could be and still caused all of these issues.
2. Take it to a bicycle mechanic - preferably one who builds bicycles. While they may not be able to make you a legal cable, they're experts at cable routing, reducing friction inside the cable and making sure bends aren't too aggressive and proper cable length vs housings. Better still if they also ride motorcycles but it's not necessary. They should be able to tell you what's going on (and also properly explain why a cable has to travel "further" through a bent housing than a straight one, thus producing the effect of "shortening" or pulling it which is why I said that all of the cables you mentioned were behaving as expected. I can't effectively explain it, it's just a truth I know and have seen in action - so have you based on your description.). The bicycle mechanic I know could troubleshoot and explain it in about 5 minutes flat. He could also probably make the cable but not every bicycle mechanic can do that. I'm 100% sure if I had known him when I had my b4 and took the original issue to him, he'd have questioned all sorts of things about that setup: The fact that it comes straight off the carburetors and has to bend under the tank aggressively and is forced down by the tank causes a lot of friction. The fact that it can't be assembled with any sort of free play and I bet even the factory routing with all of its bends.
That would be after checking the return spring that I don't think it is. My b4 never raced only when in motion or only when not in motion. Her 500rpm bump was if you turned the bars to full lock to the left regardless of her state of motion. What you're describing is not normal for the bike, nor is it particularly safe if it can triple your speed for "no reason".
I wouldn't say all single cable throttled bikes can't do Gymkhana because of one bike. That's a really broad statement to infer from a single bike with a mechanical issue.
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Assuming a properly lubricated cable and proper routing (did you download the service manual and double, triple and quadruple check it? I know you said you've tried every routing - but that one's easy to mis-read.), there isn't much to jerk that cable to pull the throttle open - other than the bars at full lock once the bike is assembled again. If the bars are making the rpms rise then there's an issue with either cable or something at one or the other end. Something is making that cable pull the throttle.
I bought a new OEM cable, and it didn't make a difference at all.
And yes I did double-check the routing. I even tried tightening it down with tie wraps, or the complete opposite. Left side, right side, through the middle hole in the frame. I tried everything. Bot old and new OEM cable. But like I said, even if I have the cable straight through the air with the tank off or even disconnected out of the bike I can make one end move by bending it. It is not related to routing or slack.
So, as I see it - there are 2 things you can look at:
1.Check your return spring - I sincerely doubt this is it because you say it's accelerating from 10 -> 30kmh, which is a significant increase in speed which indicates a lot of extra throttle being pulled. As in - not that it was being used but slowed by the brake and the brake was suddenly released because I think you'd notice if you suddenly stopped riding the rear brake. Also, there wouldn't be an audible change to the sound of the motor. I assume there is now or you wouldn't be talking about an rpm rise. But if you check it, you can say you did your due diligence. Triple check that the free play adjustment at this end is correct while you're there. Mine was always adjusted to be the loosest it could be and still caused all of these issues.
Return spring is fine, throttle plates close instantly when I let go of throttle.
2. Take it to a bicycle mechanic - preferably one who builds bicycles. While they may not be able to make you a legal cable, they're experts at cable routing, reducing friction inside the cable and making sure bends aren't too aggressive and proper cable length vs housings. Better still if they also ride motorcycles but it's not necessary. They should be able to tell you what's going on (and also properly explain why a cable has to travel "further" through a bent housing than a straight one, thus producing the effect of "shortening" or pulling it which is why I said that all of the cables you mentioned were behaving as expected. I can't effectively explain it, it's just a truth I know and have seen in action - so have you based on your description.). The bicycle mechanic I know could troubleshoot and explain it in about 5 minutes flat. He could also probably make the cable but not every bicycle mechanic can do that. I'm 100% sure if I had known him when I had my b4 and took the original issue to him, he'd have questioned all sorts of things about that setup: The fact that it comes straight off the carburetors and has to bend under the tank aggressively and is forced down by the tank causes a lot of friction. The fact that it can't be assembled with any sort of free play and I bet even the factory routing with all of its bends.
I did, in fact I did one better and went to a cable specialist, he only works on throttle/brake/clutch cables for 12 years. He changed my OEM cable into a custom one but it didn't resolve the issue, and told me it was the first time he couldn't solve a cable related problem.
I wouldn't say all single cable throttled bikes can't do Gymkhana because of one bike. That's a really broad statement to infer from a single bike with a mechanical issue.
Well, it's probably not true, but I think most 1/2 cylinders bikes are not so sensitive on the throttle, and most other bikes have a return cable. Even the Honda CB1 has 2 cables which is closed to bandit 400 I can think of.
As you can imagine, this problem is driving me nuts. The 400 is no longer my primary bike but still.
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I bought a new OEM cable, and it didn't make a difference at all.
And yes I did double-check the routing. I even tried tightening it down with tie wraps, or the complete opposite. Left side, right side, through the middle hole in the frame. I tried everything. Bot old and new OEM cable. But like I said, even if I have the cable straight through the air with the tank off or even disconnected out of the bike I can make one end move by bending it. It is not related to routing or slack.
Tie wraps would likely make the problem worse by increasing friction because of tiny bends.
The cable will move if you bend the housing because physics. I can't explain it well enough but if you can find a good bicycle forum where they are building / modding - someone will eventually explain it better than I can but the distance the cable has to travel through a bend is greater than through a straight. Therefore you're describing normal behaviour.
What you're describing points to exactly what I'm saying: There's a flaw in the way that cable is designed. You could buy 30 OEM cables with the same part # and they will all be as frustrating.
Return spring is fine, throttle plates close instantly when I let go of throttle.
That's what I suspected you'd find.
I did, in fact I did one better and went to a cable specialist, he only works on throttle/brake/clutch cables for 12 years. He changed my OEM cable into a custom one but it didn't resolve the issue, and told me it was the first time he couldn't solve a cable related problem.
I don't necessarily think a cable specialist is better. He wasn't necessarily the best person for this particular job. Sometimes they're way too set in their ways or they fixate on one way being the right way and can't see the problem for what it is. When he changed the cable - did he duplicate the length difference between the cable and the housing or change it? If he duplicated the length difference, he more than likely built your custom cable with the exact same flaw. Without knowing what he did, I'm just guessing.
A really good bicycle builder would probably have it licked very quickly. Bicycles are way less tolerant of cable issues because they can't use an engine to overcome anything.
Well, it's probably not true, but I think most 1/2 cylinders bikes are not so sensitive on the throttle, and most other bikes have a return cable. Even the Honda CB1 has 2 cables which is closed to bandit 400 I can think of.
As you can imagine, this problem is driving me nuts. The 400 is no longer my primary bike but still.
I'd look up some of the more traditional gymkhana bikes. I bet you'll find more than a couple with single throttle cable setups. There's nothing really wrong with a single cable setup when properly set up. At this point, I believe you can't set it up properly with the equipment you have. When I mentioned it to the other half, the response was "That damn cable! Yes, it always seemed too short!" Neither of us misses having to fight with it every time the carbs were off.
I should also mention that my original bars were swapped for another set of what I was positive were original bars (off of another 400) and the bend was different. Minutely different but different.
It was little issues with my b4 that lead me to finding another bike too. I got tired of having her torn down to tweak something or having to put up with issues I didn't have on my other bikes. She made me a better mechanic but like the little kid in the Honda commercial: "Please sir, I just want to ride!"
I also notice that Honda's cable routing seems a little more sane.