cam chain jumped--convert to manual adjuster?

[AlanDog]

Greetings, I bought a Bandit 400 a week ago and last night it started making a 'chain' sound when letting off the gas. I have been riding it every day since I bought it and until last night it was fine. So some research in this forum made me suspect the chain adjuster was loose or stuck and read about how the chain could jump while starting it. Sure enough, I went out this morning to start it and I could clearly hear just after turning it over the engine 'bump' to a stop... then it wouldn't start and the exhaust sound is bizarre when I'm turning it over, like every third revolution it is farting.

Relieved to find out (the PO did give me the FSM) the engine does not have to come out.

So this bike has only 12k miles, supposedly. I assume the cam tensioner should be replaced, but what is the consensus on manual versus OEM? I see the ones on ebay for $50, is that what I want?

I almost sold my old bike (2006 ninja 250) but took it off CL this morning. I was hoping the bandit was going to be reliable... I guess not yet. The joke was that the seller was telling me how he's only owned it a year and the previous owner was a mechanic. The joke being that the clutch cable was too tight, the chain was loose, the rear brake was out of adjustment, and the modified handlebars put the MC at tilt making the brake lever sit above the handlebars. I was obviously in love when I inspected it, since none of these things were noticed then!   

I've only been riding a couple years but I have already fixed up (and sold) a 1981 Honda cx500 that was sitting for 10 years. I was really hoping for a bike I could ride and not a project to work on, but here I am.... I do love the engine, and the suspension seems to work well.

Thanks in advance.

[bullet5]

There have been good and bad reports about manual adjusters, but if they are so great, why have companies gone back to fitting auto adjusters?

You're almost certianly right, when you've let off the gass the chain goes slack for a moment, so it's probably jumped one or two teeth on the drive sprocket (lower one).

As long as there is no damage to the pistons, valves or cam chain, then it's an easy fix usualy. I don't know if you've done this before so I'll give a quick list of what to do:

• Remove tank, coils, choke cable (from the carb side), clutch cable (from lever side), take out the top radiator cooler bolt and allow it to lean forward onto your forks.
• Take off the rocker cover (only 8 bolts on top) and remover oil feed pipe to the top of the rocker cover.
• Remove left side engine casing.
• Line up timing marks behind the left hand engine casing by turning the engine over by hand (Don't force it forwards, instead if you have to, turn the wheel in reverse to try and free the piston and help prevent chain damage) You may find it is easier if you remove the spark plugs too release the pressure.
• Find out how many pins are meant to be between your cam sprockets. (Make SURE that you have got the pin number for your exact engine. There are a few differnet numbers (21,24,20).
• Remove the chain tensioner
• Add new or rebuild current tensioner
• Remove top half of cam holders (5 bolts per side I think, 10 to a cam).
• Rotate cams to the correct position as illustrated in your manual for THAT engine, starting with the exhaust cam and keeping the chian tight between it and the lower sprocket.
• Check number of pins between that one and the inlet for your bike.
• Adjust inlet cam to correct number of pins.
• Check that at this point, the right side of your cams have the notches facing inwards towards each other
• Double/Tripple check all adustments and stages.
• Once happy, put chain tensioner back in along with the cam holders (to the correct torque), rocker cover, and side casing.
• Now try to turn the engine over.
• If all is turning over smoothly, job done and rebuild rest of bike.

That's rather long, but I think it covers just about everything.

[bullet5]

The 400 tensioners are renound for breaking, but they can easily be split and fixed if you know what you're doing.

There is a guide on here about how to adjust a manual tensioner.

[AlanDog]

Bullet5, thanks so much! Exactly what I needed! Maybe this should be posted in the FAQ?

My thought was that if you're really going to adjust the valves every 4-5k miles, adjusting the chain tension at the time is not a big deal.

But right, if there is no factory spec on manual chain tension... does anyone out there have a rule of thumb on measuring this--what is the proper chain tension/slack?

[bullet5]

If you haven't already seen it here you go:
http://forums.banditalley.net/index.php?topic=9408.0

[AlanDog]

If you haven't already seen it here you go:
http://forums.banditalley.net/index.php?topic=9408.0

Great! Thanks for the link!

[AlanDog]

So I have the covers off and using the factory service manual, it appears that the crankshaft and camshaft timing is correct! I can post pics but basically the marks all line up... so maybe it was just having problems starting and I was freaked out because I had just read the night before how the cam chain can jump??? Maybe... well I can adjust the valves (which are out) and replace the tensioner... I feel more confident in a manual tensioner, I will order that today.

• Find out how many pins are meant to be between your cam sprockets. (Make SURE that you have got the pin number for your exact engine. There are a few differnet numbers (21,24,20).

Okay, so how would I find the correct pin spacing for my engine? The factory manual says 20, I have the engine apart and my spacing is currently 20. When the cam chain jumps, it always jumps the crankshaft sprocket, or can it jump between the camshaft sprockets?

Thanks,

-Alan

[AlanDog]

So, is it easier to remove the cam tensioner with the carbs on, or is it actually less work to just take the carbs and air cleaner off? It's awfully tight down there, but is pulling the carbs even more time consuming?

[bullet5]

Hello again, what year is your 400? I'll check my records, but I need the year to be certain.
Is yours a VC engine?

Yes the chain can jump the cam sprockets, but only if the tensioner is shot, the chain is worn and the bike has experienced very harsh throttle action. (Throttle upto red line rapidly, then throw off the throttle). This can cause the automatic adjusters to go slack allowing the chain to jump the exhaust cam.

Usually this is only in extreme circumstances. So don't worry about it

As for removal of the cam chain tensioner, I have done it with the airbox removed, but it would be a lot easier if the carbs were out of the way aswell. (Just undone and thrown ontop of the engine would siffice). Otherwise with them in place it is a very tight job and you may need an assistant.

It's a good job you aren't putting the auto one back in, as that definitely requires two people if you leave the carbs on, as the tension in the spring has to be held by a screwdriver, the device needs to be inserted and held straight, then the screws need to be put in.
Bloomin' nightmare.

All the best, and good luck with it!

[AlanDog]

1991 Bandit, I assume it is not a VC, since it is a Calif legal model.

My chain is in good condition, it looks new, and is not stretched per the FSM specs.

Cool, I will remove the airbox and carbs, it doesn't look too crazy.

Thanks for your help!

[bullet5]

If it was a VC it would have the letter VC on the side of the engine just under the rocker cover, the rocker cover would be red (usually) and the both inlet and outlet cam shafts will have 3 lobes per valve (This is for the early model VC's)

Good luck with it all!

[AlanDog]

Well, the manual adjuster went in without a problem. I adjusted it just looking at the deflection of the cam chain with the cover off, and it seems to run without any noises, so I'm just leaving it at that. I was hoping for a trouble-free maiden trip on Sunday, but the bike broke down 3 times. The second and third times, it seems the low fuel was part of it, as when I filled up, the problems went away. So either petcock, fuel filter or just carb problems. So on monday I bought a new inline filter and thought if I just left the petcock on the secret 'prime' setting, I'd be good.

No chance. I watched my inline filter and the carbs continued to gulp down fuel... until it was dripping out from underneath the air intake clamps. So I can understand one of the carbs or even two having stuck floats, but all four carbs? That's what it looks like--what else could be causing this?

So I guess it's carb time. I'm a bit disappointed, because I bought this bike after selling a 1981 Honda cx500 that I spent over a year restoring--full carb rebuild, new petcock, tank coated, electrical system fixed, etc, etc. That bike had not run in 10 years and was intended to be a project bike, I bought it for $400. This bike I test rode and was assured was running perfect, I paid $2k... so I'm pissed.

The first time it broke down--that's a mystery. It was still cool out, I had ridden 15 miles, and the gas tank was full. I removed the tank, played with the ignition wires, and after a while it fired up. No idea if my poking around had anything to do with it running. Then it ran for a full 2 hours without a problem, not a hiccup, then it started to die again when the tank was more empty...

But I did take it through the twisties for the first time, and I think largely due to the radial tires and upgraded suspension, it was definitely sweet.

[tomacGTi]

Inspect the float needles themselves.

They're viton tipped and should have a distinct point to them, if they don't, they'll leak.

At the very least, this is a common part amongst Mikuni carbs and can even be found at the local dealer. If you're new to the bike, do yourself a favor and go over the whole bank: do all the o-rings, bowl gaskets etc and give yourself a clean slate. At least you'll have a good starting point.

Welcome to B4 land: land of the most finicky carbs next to a V4 Honda. Really though, once you get over the hump it's not so bad.

[AlanDog]

So does the needle jet come out? How? any tips for getting it out? It screws out from the throttle body side? Counterclockwise? Can I just stick an awl or something in there and twist?

These carbs were in bad shape, with rust-colored fuel dripping out of them, rust debris everywhere. I am Kreeming the gas tank.

So I can see why the float height might go out of adjustment easily with that thin metal tab and also why the O-rings are so critical. Surprisingly, the float needle tips look okay, but replacing the needle anyways. Everything seems so fragile...

Oh, I've been reading and doing searches on this forum and all the carb jetting mods I read.... I'm just wondering if people are doing them to get the bike running right, or for added performance? Are clean stock carbs are sufficient, or do these bikes take more  tweaking to have them run right? I don't really care about a few more horsepower (after riding a ninja 250 for 2 years, this thing feels like a monster)... Thanks!

[AlanDog]

Completely unbelievable how much rust was in the gas tank. The outside of the tank is shiny and the paint is perfect.
The inside of the tank had rust everywhere I could see. Five days of vinegar with screws and the stuff I poured out
was like red paint. I used the Caswell epoxy kit (I actually bought a bottle of Kreem, but then read of all the bad
experiences online)... The Caswell kit is $45, but well worth it, second time I've used it. They say you can coat two
tanks with it, but the bandit tank has so much surface area, I used it all and poured out maybe 1/4 before it
hardened.

Carb rebuild was straightforward. Relative to the cx500 carb that I've done, these are simple. Hopefully will get it
all together today. I've signed up for a two-day track weekend at Reno/Fernley--my first time--on Sept 15th and
hoping will have the bandit ready for it.