Proper chain tension?

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RADDUCK
Posts: 51
Joined: Sat Jul 07, 2007 12:00 am
model: 750 Paso
year: 1987
Location: San Francisco, CA
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Proper chain tension?

Post by RADDUCK »

Being that my bike that suffered a countershaft bearing catastrophy I wanted to check with you guys about proper chain tension. When I set it up I had the girlfriend sit on the passenger seat and bounce up and down... Yes it was exciting to watch. :eek: I supported the bike while feeling the chain tension. I tested it about a little forward of 1/2 way between the front and rear sprockets. It had some tension and I adjusted it so that it had 1/2" to 3/4" play when pressed up or down firmly with my fingers. It wasn't a sloppy 1/2" to 3/4." I noticed the inside side of the chain was occasionally rubbing on the verticle cylinder's exhaust header pipe. The fact that the guy I bought it from (2nd owner) said the front sprocket was missing two teeth when he replaced the chain, and sprockets would lead me to believe the 1st owner may have run the chain too tight. I checked alignment of both while I was there. It did not appear as though the chain was ridding correctly on the nylon slider/guide thing on the top of the swing arm.

So what is your chain adjustment proceedure?
Anyone else find missing teeth on a front sprcket?

Maybe a stupid question... but I'm having a hard time visulizing the geometry behind why the chain gets tighter as the suspension compresses. I mean the swingarm remains the same length and the radius from the center of the sprockets remains the same on both the front and rear.
RADDUCK

02 Honda RC51 SP2
87 Paso 750 - Dropped but ride-able
03 Triumph Bonneville - Basket case (resto in the works)
88 Porsche 911 Carrera
04 Subaru STI
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jcslocum
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model: 750 Paso
year: 1988
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Post by jcslocum »

1 inch is the proper slack for the chain with the max load, so if you ride 2 up you need 1" in that condition. You had the chain set too tight at 1/2" to 3/4".

The chain rotates around a circle from the center of the counter-shaft and the center of the rear wheel. The swing arm rotates around a different circle; swing arm pivot to center of wheel. These 2 different circles have different geometries and this causes the chain to go tight. Think of the SA as a lever that can go from the 6 o'clock position to the 12 o'clock position. If you tighten the chain at 6 o'clock it cannot reach the 3 o'clock position due to the distance between the 2 points at 6 is shorter than 3. This is the same effect on your bike.

Leave the chain loose. 1" is the minimum slack. Loose is much better than tight!
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