Shift Kit Chain Tension Issue

GoldenMotor.com

Brent436

New Member
Feb 14, 2010
55
0
0
Massachusetts
Hey guys,

Ive got a shift kit from Thatsdax.com. Its been working great for about 2 or 3 months now, probably around 600-700 miles. Ive recently come across a chain tension issue concerning the chain that goes from the right side of the jackshaft to the crank.

The first problem was a motor mount problem. The 2 screws that go into the motor itself were coming loose. I fixed that problem with the help of some loctite.

The problem now, (I think... pretty sure) is that the plate that holds the right side of the jackshaft is sliding down as the motor vibrates. Ive corrected this by pulling it back upwards but once i start the motor and ride for a bit it pulls back down again. Tonight Im going to put some loctite on those bolts to see if that will help, but I doubt it because the bolts dont loosen up, the plate just slides down.

Does anyone have any ideas for a chain tensioner for that chain? If they sold them somewhere that would be great because with chain stretch I assume it will always be a tad bit loose. I'm running the bigger chain (not sure of the number...) for the right side of the jackshaft and it doesnt interfere with the pedaling chain.

If anyone would know how to keep that plate from sliding down that would more than likely fix my problem. Im just sick of the chain falling off when trying to start the motor or while riding when it gets really loose.

Any help would be greatly appreciated. This forum has helped me time and time again, so once again, thanks everyone!

-Brent
 

BarelyAWake

New Member
Jul 21, 2009
7,194
21
0
Maine
I'm afraid part of the problem is that the shiftkit you purchased is simply a copy of a now (very) outdated design - later editions included an upgraded rear backing plate with a vertical support & tensioning bolt (threaded rod actually lol). While this still entailed periodic adjustment to account for chain stretch - at least it solved the mount movement issue. Check http://www.sickbikeparts.com/Manuals/SBP2 Manual001 Rev A.pdf to see what I'm referring too - while it's the installation instructions for the newest design it still incorporates this vertical support.

Another thing you can try is what I did to help prevent kinking the tubing with the U bolts;



I just took a chunk of pipe with the same ID as my seat post tube's OD, cut it in half and ground a taper to fit it in the U bolt - then tack welded the steel "pads" to the U bolts (don't hafta do that, but it helps during assembly). Don't try this with any sort of soft padding as it'll make the movement far worse. Roughing up the inside of the "pad's" surface should give you enough grip w/o having to tighten it so much as to crush the seatpost...

...but I think you may wish to replicate the threaded rod vertical support that the SBP kit has had for quite a while now - a couple of chunks of angle steel, threaded rod, a few nuts & another U bolt clamp would be all ya need ;)


As for the chain stretch - if you pick up a quality, heavy duty BMX chain, it'll still stretch a bit as it breaks in and fits to the sprockets, but after a while it'll settle down and you'll not hafta mess w/it nearly as often (^)
 
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Brent436

New Member
Feb 14, 2010
55
0
0
Massachusetts
Thanks for your input!

I'm thinking of either buying another shift kit (from SBP this time) or just fabricating that threaded rod idea. I'm probably gonna go with another shift kit just to have some spare parts lying around. Until that comes in I will probably get a BMX chain and shorten it up real tight so it doesnt fall off while i wait for the new kit to come in.

Just cant wait to get this bike to its nice reliable ways again haha. I just added a dellorto carb, billet intake, and SBP expansion chamber to it so its running the best it ever has right now and its killing me that i cant ride it too much haha.

Again, thanks for the input!
-Brent
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
I have that whole threaded motor assembly kit support parts I didn't need.
You can have it, just pay the shipping.
As barley mentioned, it is just a U bracket, some angle pices and a long rod with threads on each end with nuts.

The new Sick Bikes jackshaft has a 1 piece U shaped back plate so there should be no issues with one side plate moving now.

Can't wait to try one.