Now the chain drags on swingarm.....???

[Steve Minor]

I recently installed a pair of 14" shocks on my 77 400 GS6. The original shocks were 13 1/2" Marz. Now the chain seems to drag on the top of the swing arm, even after proper chain adjustment. Could it be because of the additional 1/2" in shock length? Could the longer shock change the angle of the rear sprocket so much that it makes the chain drag? I'm considering attaching a piece of teflon to the top of swing arm where the chain rubs....Any better suggestions?







Edited by - steve minor on 08/09/2003  08:14:42 AM

[tmc3c]

Steve,Would changing the front countershaft sprocket help?

Thomas Carmichael

[James]

Steve- not looking at it but..
Thomas is right on. Are you running the largest countershaft you can. I was always told to do this and go to a larger rear sprocket to compensate(gear down) if needed.
While this always has helped me reduce wear on chains-it may not solve your prblem entirley.

 How about a spring loaded tensioner like an AW Maico. Perhaps even with a roller instead of a block. Yes I would still put some kind of a rub block on the swingarm. They dont make those swingarms anymore you know.
 hope this gives some ideas, James

I have bike parts in the kitchen cabinets where most people have dishes..

[Doug Wilford]

Steve the frame was not designed for 14" shocks you have changed the fork geometry as well and now having no clearance at the swing arm pivot, use your plastic piece, I hope it has clearance when you are sitting on it.

 

[Steve Minor]

Am I correct in thinking there 2 upper shock positions on the 77 GS6 frame? One more laid down and one more upright? If so, I might be able to reduce part of the swingarm/chain drag I am experiencing by repositioning the shock.

 

[Rocket]

Steve
I think the GS6 had a chain block over the pivot point of the swingarm to keep the chain from rubbing on metal.
Rocket

 

[hrbay]

The 78 did. GC

GC

[tomale]

Steve,
Yes the reason for the chain rub is because of the longer shocks. I did the same thing to my bike, only I went to 14 1/2 inch shocks. The reason was to change the angle of the forks. What I found was that it changed enough to make it stick better in tight corners. As you found out it caused some problems. I have not yet fixed the problem but I have been giving it alot of thought. what I had determined to do was to put a teflon strip on top of the swing arm and I have ordered a teflon roller from AMS I am going to try to make up a tension arm to take up the slack on the chain. What I also found that getting the chain to the right tension was difficult. When I adjusted it to what I thought was correct. I discovered that the chain was too tight and it would put too much tension on the sprockets. so much so that I could feel it when I rode. It did not show up when it was on the stand but it showed up on the trail. In order to fix the problem I had to loosen the chain to a point that was way to loose and the chain would jump all around, I even found marks on the chain for where it hit the tire. It is my hope that by adding the teflon skid plate and the tensioner, it should fix the problem. At least this is my opinion.and it is what I am going to be working on.

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.

[cecmwilson]

Hi Steve,
I replaced my stock Marz's with 14" S&W gas shocks "back in the day" to save some money (couldn't afford Fox Shox). It really messed up the geometry; so much, in fact, that I endoed 2 times giving me a hospital-bound concussion and a broken collarbone. Once I figured it out, the bike handled like it should. Just a word from the "not so wise"! Mine was a 77 MC5 400 as well.
Charles

[Bill Campbell]

My chain has always run on the top of the swing arm on my 76 MC5. It has worn a small track over the years but the swing arm is still ok. Be that as it is I added a nylon chain guide & protector from a 79-81 model keep things together. I have since restored a 400 MC5 and another 76-78 250 where I have welded a tab to the swing arm as in later models to take the chain guide protector. I have always run my chains with about the correct looseness and this has meant the chain runs along the swing arm. Have used 13.5 shocks all the time. 14 inch shocks definitely push the swing arm further away from the CS/swingarm/rear axle centreline thus providing more chain run on the swingarm. Hope this sheds some light and a Merry Christmas from we enthusiasts in Australia. Cheers Bill

[skiracer]

If you are having problems finding the "correct" slack for your chain, here is what you should do; Unbolt the lower shock bolts.  Then raise the swingarm (with the wheel still on the bike) up until the rear axle and the countershaft sprocket form a straight line.  This is the position that the chain will be the tightest.  Adjust the chain so that it has just a little slack at this point.  Then re-connect the shocks, and measure the amount of slack in the chain for future reference. I have a 13mm wrench that I use to adjust the chain that has a mark on it that I use to measure the chain slack at a particular point on the swingarm.  It is a fast way to tell the status of the chain.  I have been doing this since I bought the bike in 1976......

1976 MC 5 Original Owner
1976 Penton 175 XC