So what's the best way to adjust this setup?

wildbill59

wildbill59

Member
#1
#1
Put a new engine on my Sears puddlejumper today. I had to tap and drill the crank, it was a breeze with my drill and tap jigs (thanks ScooterBoy!:thumbsup :) . Anyway, as you can see, the frame has a swingarm suspended with shocks. My problem is getting the chain adjustment right. When I sit on the bike, the shocks compress fully, and the chain becomes slack. With no weight on the bike, the shocks are extended, and the chain gets tight because of the change of angle. When it's too loose, the chain falls off the rear sprocket when I ride. Too tight, I can barely push it when I'm not on it. I got it feeling pretty good, but it seems like there's still too much tension on the chain when the shocks are fully extended, and don't want to wreck the shaft that the driven cluch spins on. Sure, I realize I need to find a happy medium, but it's tricky to find it while trying to slide the engine in its slots with the the springs and swingarm fighting back. I guess I'm answering my own question: "Keep trying til you get it right!", but I'm sure I'm not the only one who's struggled with this. Any ideas? Thanks in advance!
 
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george3

george3

Active Member
#2
#2
Your shocks are too long prob. 13"? the oem sprocket Prob. was larger also. Use 1" shorter shocks. might need a chain tenchner on the bottom as well if the prob. dosent go away. Any slop in the swing arm bushings? when chain and rear wheel is removed?
 
jeep2003

jeep2003

#4
#4
sounds like your jackshaft isnt properly in line with the pivot point. if you can shim the front of the engine up just a hair it will lower your jackshaft and give you better alignment I think
 
roccosbike

roccosbike

#5
#5
jeep2003 said:
sounds like your jackshaft isnt properly in line with the pivot point. if you can shim the front of the engine up just a hair it will lower your jackshaft and give you better alignment I think
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Yep jeep is right, The sprocket of your TAV must be in line with the pivot point of your swingarm or your chain will bind. Your TAV mouting plate may be able to be clocked downward in the back where it mounts to your motor which will help your problem.
 
wildbill59

wildbill59

Member
#6
#6
Interesting, great ideas to work with. George, you're right, those are new shocks, and they're about an inch longer. The old ones were shot and would bottom out when I rode the bike, might want to look for a different pair. Swngarm bushings - good and tight. And Beal, yep, a tensioner might be an option. First I'm gonna try changing the angle of the jackshaft like Rocco and Jeep sugested. You all definitely know your stuff, thanks guys! :thumbsup:
 
george3

george3

Active Member
#7
#7
wildbill59 said:
Interesting, great ideas to work with. George, you're right, those are new shocks, and they're about an inch longer. The old ones were shot and would bottom out when I rode the bike, might want to look for a different pair. Swngarm bushings - good and tight. And Beal, yep, a tensioner might be an option. First I'm gonna try changing the angle of the jackshaft like Rocco and Jeep sugested. You all definitely know your stuff, thanks guys! :thumbsup:
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If you clock the tav 1" it might help. is it also lined up with the drive sprocket with a streight edge? Your issue is usually swing arm pivot angle.
 
jeep2003

jeep2003

#8
#8
I think 1" will be too much . and you wont be able to tell much with a straight edge either. it will still get loose and tight even if its directly centered so youll still need to find that happy medium but it wont be as bad. the only way to keep the chain the same tention is to have the jackshaft integrated with the swingarm pivot. So you really just need to get as close to it as possible
 
wildbill59

wildbill59

Member
#9
#9
That TAV is a Comet 20, there's only 2 sets of mounting holes in the plate, so not much clocking goin' on there. Looks like either for a level engine plate, or an angled engine plate like mine, no other real adjustment. I noticed on the newer models, they have lots of different mounting holes, might be a good way to go if I can't get this squared away. Haven't been able to get to it yet, but I'm gonna try shimming the front of the engine with a couple of washers. You're right Jeep, it's still gonna get loose and tight, and I'm dealin' with it a little at a time. Played with it a little yesterday, did a little adjusting by sliding the engine in it's plate grooves, still a little tricky with all that tension from the shocks! But it's feeling better already. Gonna shim it, check it's straightness with a straight edge, oughta be fine. Also, looks like I'm needing some bearings for my jackshaft, that'll be on another post. George and Jeep, thanks again!:scooter:
 
jeep2003

jeep2003

#10
#10
no problem. you can also oblong the holes in the mounting plate to give you a little adjustment. can be a bit of a trick to get them all lined up right just takes some patience especially if using a regular drill bit. iv found using a round file in a drill works great for that kind of job
 
george3

george3

Active Member
#11
#11
jeep2003 said:
I think 1" will be too much . and you wont be able to tell much with a straight edge either. it will still get loose and tight even if its directly centered so youll still need to find that happy medium but it wont be as bad. the only way to keep the chain the same tention is to have the jackshaft integrated with the swingarm pivot. So you really just need to get as close to it as possible
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Yea in a perfect world. You could rotate the swing arm in a 360 degrees without any changes with the driven on the pivot point. this is what he wrote.
When I sit on the bike, the shocks compress fully, and the chain becomes slack. With no weight on the bike, the shocks are extended, and the chain gets tight because of the change of angle.
This tells me the back of the tav needs to go down a bit not sure how much. Like you said slot it and move it down a bit. a short slot about the size of a drill bit 5/16 or what ever the size the oem hole is. that little bit will rotate the end alot. After you slot the tav snug it down lower it on the end a bit then with some help un-bolt the bottom bolts on the shocks hold the wheel with the chain on it push it up 3" or 4" depending the shock travel and back down to shock bolt highth when it dosent get loose and tight by clocking the tav back and forth for the happy medium spot. This will work. the further the sprocket is from the pivot point the harder it will be to fix. I can do it easier than explain it, LOL What it boils down to you lowered the sprocket now you have to confiscate for it. If you had a fixed jack shaft you could only fix it with shorter shocks or chain tensioner, but with an adjustable tav it can be corrected. You got your work cut out Have fun. Get Her Done, LOL
 
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