installing a swingarm w/ drive box in a Tonti frame

[mtiberio]

When you say you offset the rear wheel to the left, do you mean that when you built the spoked wheel that you purposely offset the rim from the hub? OR did you use a spacer?

My Dad managed my Uncle's precision sheet metal fabrication shop. Back during my racing days, I had him make me some thin shims which I inserted between the pressed in axle spacer that is pressed into the rear drive unit and the rear drive unit itself. That is between item "O" and item "I" in the diagram above. In the diagram above, it looks like item "O" is the pressed in spacer paired with a shim. Interesting, I didn't think guzzi made this shim part. Still don't, many Guzzi parts diagrams are effed up. At any rate, yes I used a shim on the spacer.

Charlie Cole used to dish his rear wheel, but he had an interesting theory about shifting the rim/tire right to reduce the effects of motor torque during left turn cornering by giving the bike a leftward weight bias. If you race a guzzi you realize that turning left can be much harder than turning right. If you offset the rear wheel to the left (to clear the swingarm) without moving the swingarm right, you make the bike want to fall right (line connecting tire contact patches is left of the CG of the bike).  I had this issue because I ran fat tires when running pro. Charlie only raced vintage which limits your tire choices. He ran a rather narrow rear tire, and was able to get the CG of his bike to the left of the line connecting the contact patches. This "preload" of a leftward weight bias helped his bike turn left against the motor torque.

[oldbike54]

assuming that equal amounts of the swing arm pins showing means that the output shaft and driveshaft are co-planar is a big assumption.

Agreed. After all the frame is just a big weldment with all the warping that involves. Still.. I try to do the best I can to center it.

 A friend who was a long time MC mechanic taught me to count the threads on each side before disassembly , of course that is assuming the factory got it right  Also that requires writing down the info , and then remembering where you put said info , now my head hurts 

 Dusty

[rodekyll]

I think that counting threads before disassembly and returning them afterward is dangerous.  Waaaaay too many assumptions about bearing wear, previous mechanic's asumptions and aging parts.  If the bearings are changed all bets are off.  You wouldn't do your steering head that way and these taper roller bearings are no different.

[oldbike54]

 David , the thread counting method is only a baseline .

 Dusty

[Idontwantapickle]

I think that counting threads before disassembly and returning them afterward is dangerous.  Waaaaay too many assumptions about bearing wear, previous mechanic's asumptions and aging parts.  If the bearings are changed all bets are off.  You wouldn't do your steering head that way and these taper roller bearings are no different.



 David , the thread counting method is only a baseline .

 Dusty

I suppose that if you REALLY wanted to get it spot on you could put the swingarm on with only the carrier bearing and a center finding jig at the bevel box flange then line it up El Perfecto with the transmission shaft. Mark and measure, take it out, put all the bits back on and done.
But as Mike noted, it's probably not necessary.
Hunter

[rodekyll]

Or you could just throw away the bike at every service interval and all this crap wouldn't count anymore, too. 

[Idontwantapickle]

Or you could just throw away the bike at every service interval and all this crap wouldn't count anymore, too.

 :1:
I think that is the best plan. I will be glad handle disposal for any forum member free of charge.

[Tom]

A member of the MG Recycling Corp. 

[charlie b]

I measure them with a caliper.  But, I always wondered how necessary that was as the engine is not located that precisely in the frame.  Just for grins I think I'll check the center of the bearing this time and check against the trans output shaft and see where it ends up.

[Tom]

Sayyyy........you must be bored.