Puzzling problem maybe you can suggest

[chiz]

Hello all My 84 FJ is resting peacefully under cover, my other working bike though is confounding me.  My 80 XS850 triple shaftie was converted to chain, I bought a cheap DID light duty chain from Fortnine, the swing arm and wheel is XS650 non cush rear sprocket, it was my wish to find a KZ 650 set up but my machinist blasted the job out in a week with the available swing arm and wheel.
    Whenever I ride the bike the chain becomes slack I adjust it nearly every day, Idid have a heavier chain but I would have had to carve away a bit of the gearbox casing they are not thick. The original output shaft has been retained and the original outboard bearing supports the shaft with a 13 tooth sprocket attached. A 14 tooth is common but would only work with a wider swingarm eg KZ with the wider arm the sprocket could be moved further outboard.The crank drives the clutch via a chain on the right there is a disc spring cush drive attached to the clutch
   Perhaps the bike cant handle a chain or whatever...maybe engineered incorrectly but cant figure out why the chain is always slack, chain too light?  Thanks for reading

[Pat Conlon]

Is your axle on the same index marks? If so, it sure sounds like your chain is stretching
What back sprocket size? (Tooth count)
13 tooth on the front sounds awfully small. That alone will play hell with your chain life,
i.e. small sprocket = less teeth to transfer engine power to chain = more stress on chain = more stretch.
What size chain are you running? Please don't say a 520...

My buddy Paul had a Yamaha 850 triple. That was a silky smooth engine with good torque.

[Motofun]

Pat, What's wrong with a 520?  I've run a DID 520 setup on my 750 track bike for years.  As always, buy a quality chain.

[chiz]

Is your axle on the same index marks? If so, it sure sounds like your chain is stretching
What back sprocket size? (Tooth count)
13 tooth on the front sounds awfully small. That alone will play hell with your chain life,
i.e. small sprocket = less teeth to transfer engine power to chain = more stress on chain = more stretch.
What size chain are you running? Please don't say a 520...

My buddy Paul had a Yamaha 850 triple. That was a silky smooth engine with good torque.

Hey at the present width of rear swing arm and rear wheel sprocket fitting a 14  is not possible as the 14 would have to be moved further outboard and would no longer line up with the rear sprocket, it is not possible to move rear sprocket out on this swingarm/wheel fitting. My investigation told me a 14 was as big as one could go before fouling the cases.
  Chain is 530, the most interesting bit though is that the chain alignment marks on the swingarm never change massively after adjustment, in fact the adjustment is so critical that a mear turn of one flat of the adjustment bolts will cause the cain to go banjo string tight WHEN I SIT ON THE BIKE just a hair less it seems right but after a ride of short distance I am back to the same looseness.
  Think I will ride up to the bike shop not a dealer they seem to take a certain delight in pointing out my stupidity and I come away with new direction.

   Anyone here watch on YTUBE every Wednesday a new topic between Cycle World editor and Kevin Cameron? interesting stuff. Oh and if brake cleaner kills hornets does hornet spray clean brakes?

[FJmonkey]

Just a thought here. What if you are adjusting the chain a little too tight. It seems good, not too loose. But if it is slightly tight, the action of suspension will stretch it that little bit. Then when you see it next, it seems loose. Review the slack. Or better yet, use a strap to compress the rear until the front sprocket, rear sprocket and swing arm pivot point are in alinement. In this position, the chain cannot get any tighter. I hope you figure it out before breaking a chain. Good luck, keep us posted.

[Pat Conlon]

Pat, What's wrong with a 520?  I've run a DID 520 setup on my 750 track bike for years.  As always, buy a quality chain.

Hello Jack, yep, I agree, quality 520 or 525 chain on a track bike is fine, very common, however on a 500+lb street bike laden with rider and passenger, a "cheap, light duty DID chain" in a 520 size is to too light.....especially with a 13 tooth c/s sprocket.
Chiz said he's using a 530 chain so all is good there, so it's just a matter of upgrading the quality.
 Perhaps he is over tightening?

 After the small initial stretch on my DID ZVMx chains, they stay in perfect adjustment until the end of their life. I like to run my chains on the slightly loose side.  A loose chain is a happy chain.

[chiz]

Just a thought here. What if you are adjusting the chain a little too tight. It seems good, not too loose. But if it is slightly tight, the action of suspension will stretch it that little bit. Then when you see it next, it seems loose. Review the slack. Or better yet, use a strap to compress the rear until the front sprocket, rear sprocket and swing arm pivot point are in alinement. In this position, the chain cannot get any tighter. I hope you figure it out before breaking a chain. Good luck, keep us posted.

Ok the atoms in my axel nut decided not to corporate and the threads stripped so I dug out another nut set the chain on the side of tighter, yup you guessed right loose again after 2 clicks
  Yup your right Think Im looking to deep...no cush on rear sprocket small front sprocket and lighteish chain most likely contributing to this issue. Being a Cafe though with an inch of foam on a wooden base the bike is not lending itself well for long trips anyway, rather short spurts.

[Motofun]

Not sure why a larger sprocket causes a chain misalignment.  Changing to a different chain size could possible cause interference issues with casings, swing arm or even the edge of a tire if things were extremely tight to begin with.  Absolutely keep things on the loose side of chain tension.  Every manufacturer that I've seen always specs out chain tension advice that is too tight.  When tech'ing bikes at the track I've seen some chains that you could pluck like a guitar string!  On the flip side I've never seen a "loose" chain jump off a sprocket where things were in reasonably good shape to begin with.  (Kavin's chain at Tellico many years ago is a whole different story!) 

[chiz]

yes I know its difficult to impossible to visualise similar description on your 400f. If I move the primary sprocket further outboard to say fit a bigger one it would misalign with the rear one and the rear one cant be move outboard an appreciable required amount. This could be solved I think by engineering a KZ arm wheel and sprocket...maybee.  Dont know if the XS750 cases were any different that would allow more space for a bigger primary sprocket but I doubt it.
   Anyway I think I have come to a realization that a warm/hot chain is looser than a cool one as it seems that when the bike sits the next day the chain appears less loose. Think Ive hurt my head enough over this problem and will take a rest now.

[fj1289]

A picture of the countershaft and housing might help people understand the limited room for the countershaft sprocket - an why a larger one requires spacing out?  Luckily that is not the case on an FJ!

Is there a website for the shaft to chain conversion you used?  I'll bet a donut a high quality chain costs less than the conversion - and if you break that chain the conversion will probably get damaged too!

I really think a higher quality chain will overcome all the issues - even deal with the small front sprocket OK.

A few years ago I tried grabbing a chain from a farm supply to use temporarily on an XS-650 while waiting for the good chain I ordered to arrive.  That chain stretched so fast it was scary!  I was very lucky not to break the chain and cause a lot of damage to the engine cases - or myself!  Higher quality chains ARE worth the cost!  Even on something with less torque than the FJ.

Chris

[fj1289]

I'll also add - a top of the line 520 chain would be better than a bottom or mid level 530 chain...

Another option for a slightly narrower 530 chain might be one of the heavy duty drag race specific chains without o-rings?  Just have to stay on top of chain maintenance!

[chiz]

Looking into if XS850 crankcases were different in the area of the sprocket area as fitting a 14 tooth seems unlikely.

The legendary XR750    https://www.youtube.com/watch?v=oooES-UbJLg&pp=ygURdGhlIGhhcmxleSB4ciA3NTA%3D

[red]

Chiz,

At the risk of being obvious, are your chain sprockets worn?  Even new sprockets may not be exactly round.
As you rotate the rear wheel, with worn or out-of-round sprockets, the chain will be loose at some wheel positions, and tight in other places.
Set up the chain tension where the wheel position has the chain tightest, then rotate the wheel to see where the chain has the most slack.
If there is too much slack in the chain then, replace sprockets as needed.
P.S. Bolt holes in the sprockets may be too large, or drilled off-center; also, bolts may be smaller than the bolt holes (needing a bushing).