Author Topic: Intake cam in exhaust pt 2  (Read 8178 times)

Offline tomacGTi

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Intake cam in exhaust pt 2
« on: June 28, 2007, 09:53:28 PM »
So now that most of you have heard of what happens when you mis-time some cams and disaster strikes. A new-to-me engine and a month later, I have a Bandit again.

I was originally looking for a new head but once again, ebay saved the day with an 11k motor and a shot set of carbs. The shipping was more expensive than the engine itself and arrived yesterday so with some help from the little lady, I got to work (no we didn't do the swap in the kitchen but she did help me hoist it into the frame).

This time around I was unbelievably anally retentive in the cam installation. I should have just left the stock cams in the motor just to make sure the damn thing worked but I decided to just turn it over by hand as many times necessary to make sure everything cleared sufficiently. Plus I needed to beat the thing that originally beat me. Some anal-retentive hints on cam installs:

-Disregard the markings at the end of the cams and match up the cam wheels/pin count. E/1 flush with the head and 20 pins to the "2" on the intake.  Doing this will make the marks on the ends of the cams not match but those only matter when you're setting lash. That's it. Also, don't be alarmed by the excessive amount of slack in the chain inbetween the cams. The adjuster will take it up (manual or otherwise). The other good part: you now only need one feeler guage to set lash: .005".

-The cam sprockets are the same for both intake and exhaust, just positioned differently. Same part number and all, make sure you have some loctite on hand when you spin the bolts off.

I originally had set everything up using the end marks on the cam and that was my demise. The exhaust cam had enough clearance but the intake cam following behind didn't and met Mr Pistons.

-Make sure you turn the motor over by hand until you are sure that Mr Piston is not about to smack Mr Valve. I must have dry-spun the motor 50 times honestly, I was that nervous. When I had placed the cams in using the end marks, it was obvious that there was some resistance which made me rethink and go back to the manual again.

-Things are going to sound a bit different. The cam will make the motor sound different, a bit deeper and more sharp. It didn't sound like the same bike. I had also modified the collector in the headers with the thought that it was opening things up by removing the silencer. There is now a straight shot from the header tubes into the 2-1 splitter into the midpipe. Call it the poor man's header.

-Midrange is where the swap shines. That dead spot at 6-7k before you hit the mains? Gone. Mid-throttle roll-on just has acceleration now till you get to 3/4-full throttle. It's nice and fat and you can roll onto it as early as 4-5k if you wanted to.

For reference sake:

-3.5 turns out
-105 MJ (Mikuni) Dynojet needles
-middle needle position with one shim
-modified airbox using a different snorkel

I think I may be fat on the mains, but we'll see. I'll get some miles on it and check the plugs (new) for some color.

Now, the downsides or, "not everything is a bed of roses".

-Jury is still out on valve to piston contact in the upper ranges. Maybe its me but when I brought it up above 10k, it had the same sound as when it broke on me a month ago. Maybe I'm paranoid, but time will tell. Jay did you rev out beyond that when you did this with no ill effects?

The tone that the motor makes is even different. Very vtec like once above 10k. You can hear it from the headers right on out the back of the bike.

-Idle is really low for some reason. The cam overlap at low revs is probably so much that there is a huge wave blowing back through the carbs reeking havok on the CV slide. I had it set at 1200 and anything more than that would cause the rev to hang up around 2k and then come very slowly back down. Backing the screws out another 1/2 turn helped but not by much. It did die out on me a couple of times but whatcha gunna do?

-It's LOUD. The bike isn't nearly as quiet as it used to be. It really is like a different bike the way the power delivery has changed. This is regardless of the collector mod or not, the cams have changed the breathing of the motor.

-If you F it all up, a motor weighs in the range of 150 lbs or so. Start lifiting weights, saying your prayers and taking your vitamins Hulkamaniac because it's cumbersome as hell to work with.

-Re-jetting. Yes it sucks and I'm not looking forward to it either. That and having to relearn the damn bike. Yet another thing.

So there you have it. Just in case you want to take this on yourself, there's something to refer back to. I can't stress it enough to be anal about the cam timing, it cost me nearly $300 once it was said and done. Don't make the same boneheaded mistakes I did. I'll report back with some ride impressions as I get some miles on the new setup.

-Randy

Offline interfuse

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Intake cam in exhaust pt 2
« Reply #1 on: June 28, 2007, 11:30:33 PM »
At least you were able to source another motor and get back on the road.  :congrats:
Mike

'91 GSF400
It's more fun to ride a slow bike fast than a fast bike slow.

Offline gsxr400 racer

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Intake cam in exhaust pt 2
« Reply #2 on: June 29, 2007, 12:15:34 AM »
mine revved to 14+ fine , but worth it to look down the bore with a flash light just bump the starter w/ all plugs out till the piston you want to look at is close to the bottom and you should be able to see if it has marks. just take it easy till you feel confident it what you done. always good to do a compression check to.
1988 gsxr 400 sp (sprint bike)
*  SELLER OF THE 442CC BIG BORE PISTON KIT FOR THE BANDIT 400,GSXR400, GK73 and 76.* And carb kits(orings)too. Email me from here.
has been a wera expert #610 lol

Offline tomacGTi

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Intake cam in exhaust pt 2
« Reply #3 on: June 30, 2007, 01:33:29 PM »
Alright, so now a ride report. This is all with the butt-dyno, one of these days I'll get to a real dyno to suss it out.

-Bike has much more midrange than it did prior, there isn't as much of a midrange flatspot anymore at 6-7k. 8k is a whole different animal as the bike has a bit more urgency than it used to. It basically flies into the upper ranges and max power feels as though to be around 10-12k leaving some room for over-rev on shifts.

-Has a bit more vibration than it used to through the bars/bike. I'll resynch the carbs when I change out the oil at 150miles just to see. It synch'd out pretty damn even with my manometer when first put together.

-idle is a little tricky so I just sucked it up and set it so it comes down to 1400 when it's warmed up smoothly. Any more idle screw and it hangs around 2k way to much. Once again, I think this is because of the extra overlap that may have been introduced. I don't have degree wheels or slotted sprockets so I can't dial it out.

-This will change the sound of your bike. It is going to sound more shrill and has a growl at 8k+ that surprised the hell out of me. The airbox absolutely screams now at those revs with induction noise.

-I would advise to adjust your cam chain tensioner (if you have a manual one) when the bike is hot and oil has circulated. I adjusted it cold and it endt up being a bit too tight.

In all, it's a damn neat mod that should tide the HP bug in me over for a little while longer. Out of corners in the same gear as before, it leaps out and has a bit more punch. I know why Jay said that he had to re-gear and rejet after this mod. Of course he's no longer running it so maybe it isn't the cat's meow but for those of us without access to GSXR cams, it's not a bad compromise.

Here's the mod list for the jetting database.

-1991 bike
-At sea level, tested at around 75-80*f
-Modified airbox with no holes but a larger homemade snorkle, stock airfilter
-CBR thermostat (if you don't change this, you're chasing your tail jetting)
-3.5 turns out on the screws
-Dynojet needles, stock spring, 3rd clip with 1 washer
-stock float height
-stock pilots
-105MJ (Mikuni)
-factory headers with removed silencer from collector/Cobra F1S exhaust
-Pingel Fuel valve

Might be a bit rich on the main but pulls well, still have to check plugs to be sure but it should be close. Great midrange punch and low end is ok. It's probably close to the same just outshined by the stronger mid-high end from the cam.

Offline gsxr400 racer

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Intake cam in exhaust pt 2
« Reply #4 on: June 30, 2007, 03:01:09 PM »
no im running the same brother just had to take it out to clear up some issues i thought where the cause but i don't write things down like i should.
1988 gsxr 400 sp (sprint bike)
*  SELLER OF THE 442CC BIG BORE PISTON KIT FOR THE BANDIT 400,GSXR400, GK73 and 76.* And carb kits(orings)too. Email me from here.
has been a wera expert #610 lol

Offline Herr Tod

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Intake cam in exhaust pt 2
« Reply #5 on: July 01, 2007, 06:20:41 PM »
How did you put them in, from which mark to which mark did you count the pins of the chain? Sounds really interesting, since I'm mostly between 10000 RPM and the rev limiter anyway :bomb:

Offline gsxr400 racer

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Intake cam in exhaust pt 2
« Reply #6 on: July 01, 2007, 06:33:58 PM »
just like stock just swap the for the intake cam you be looking at the same mark as if it where stock just have to set valve lash to the intake spec
1988 gsxr 400 sp (sprint bike)
*  SELLER OF THE 442CC BIG BORE PISTON KIT FOR THE BANDIT 400,GSXR400, GK73 and 76.* And carb kits(orings)too. Email me from here.
has been a wera expert #610 lol

Offline tomacGTi

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Intake cam in exhaust pt 2
« Reply #7 on: July 01, 2007, 11:23:15 PM »
Tod, make sure you install them using the sprockets as your guide and not the marking at the end of the camshafts.

That was my very, very large mistake that cost me my old top end. Everything spec's out to the sprockets. and you only need one feeler now to adjust for lash.

-Randy

Offline Herr Tod

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Intake cam in exhaust pt 2
« Reply #8 on: July 03, 2007, 08:03:51 PM »
Cool. If I have time I'll do it next friday, gotta do some other work too as I'm going on vacation. I never look at the markings on the side, lol I took the cams in and out about 6 times when I changed the engine a while ago because it only idled and blew back through the carbs when I touched the throttle... eventually the starter clutch, with the timing plate, was put on by the previous owner without the key :annoy:

Offline gsxr400 racer

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Intake cam in exhaust pt 2
« Reply #9 on: July 06, 2007, 06:05:55 PM »
tomac how it coming? do you like it ? herrtod has done it and doesn't care for it id like to hear some more opinions maybe you guys can chat about it , I seemed to like it and was going to go back to it. He says that it seems to have a power loss from 12500 on.
1988 gsxr 400 sp (sprint bike)
*  SELLER OF THE 442CC BIG BORE PISTON KIT FOR THE BANDIT 400,GSXR400, GK73 and 76.* And carb kits(orings)too. Email me from here.
has been a wera expert #610 lol

Offline tomacGTi

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Intake cam in exhaust pt 2
« Reply #10 on: July 06, 2007, 06:30:39 PM »
I haven't gotten out much mainly because of work and it being busy. I got out today for a little bit, here's another thought/impression.

LIke I said, the mid (6-9k) is definately better with the exhaust cam setup versus stock. That's where I spend the abundance of my time so I notice it more coming out of corners and setting up for the next. I don't think it's less power than stock, just different in the way it delivers it. I actually have found myself having to relearn alot of the corners just because of how different the power delivery has become. Since there's more mid, I can keep level throttle versus downshifting and balancing the throttle between engine braking and neutral/throttle.

It really feels like where I was rowing through the gears previously, I can hold a gear longer because I can let the revs come down further (since there's power there now) and still have room to spare up top. It isn't as frantic up top as it was prior but like I said, I think it's because it gets there with more urgency. Looking at some old dyno sheets from the board etc, it looks as though power tapers off at 11k even with the stock cams so for me 14k is more of a novelty since there isn't much after 11. Even when stock, the only time I would bang the limiter was on downshifts or just trying to pass a car and being inbetween gears, YRMV.

Most of the backroads around here are 3rd gear affairs rolling in and out of the throttle 35-70mph (50-110k or so) so that elastic powerband from 6k to 12k is really what works for me, the upper end is more insurance than anything.

Do I like it? Yes, because of the way I ride. It could also be my setup as well since all of my jetting is with 32mm carbs, etc.

-Randy

Offline gsxr400 racer

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Intake cam in exhaust pt 2
« Reply #11 on: July 06, 2007, 08:18:59 PM »
thanks , I beleive it's all in what you like. cheers
Jay
1988 gsxr 400 sp (sprint bike)
*  SELLER OF THE 442CC BIG BORE PISTON KIT FOR THE BANDIT 400,GSXR400, GK73 and 76.* And carb kits(orings)too. Email me from here.
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Offline Herr Tod

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Intake cam in exhaust pt 2
« Reply #12 on: July 06, 2007, 08:58:45 PM »
I don't like it at all. Idle is crap, flatspot at 6000 has gotten very bad but could be fixed by lowering the needles. No power after 13000, I used to hit the rev limiter in 2nd gear very easy but now it takes noticably longer. Strange thing is it starts to rattle at 10000 RPM and above. Everything is timed right though.

I'm putting in the exhaust cam again as soon as I have time. Hopefully the rattling will be gone, otherwise something went wrong... oh well I have a spare engine around already :roll:

Offline gsxr400 racer

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Intake cam in exhaust pt 2
« Reply #13 on: July 06, 2007, 09:42:19 PM »
cool thats what this board is about opinion good to hear them.
1988 gsxr 400 sp (sprint bike)
*  SELLER OF THE 442CC BIG BORE PISTON KIT FOR THE BANDIT 400,GSXR400, GK73 and 76.* And carb kits(orings)too. Email me from here.
has been a wera expert #610 lol

Offline tomacGTi

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Intake cam in exhaust pt 2
« Reply #14 on: July 07, 2007, 12:56:03 AM »
Quote from: "Herr Tod"
. Strange thing is it starts to rattle at 10000 RPM and above. Everything is timed right though.

:roll:


I'm not the only one then. Strange because I only notice it in the lower gears, 4-5-6 I don't, as much anyway. Is it the same for you, you can hear it from the right hand side in particular?

Tod, I guess I guessed the jetting right for the bike because it all was better for me. The idle is a little wonky but once the bike is warm, it's sitting right at 1200.