setting isolastics

I took my first ride with my MKIII adjustable isolastics installed on the 850 and they're obviously too tight. It like they work in reverse of normal... no vibration at low rpm increasing to a nasty buzz at 4000. I didn't take it above that, as I am breaking in a new motor.

I have the adjustments front and rear set for "one hole" before snug, as was recommended in the installation instructions. On the bench that measured .010" with a feeler gage. I'm puzzled as to why it would be different on the bike.

Which of the two isos has the biggest effect on vibration? Or should I start backing both front and rear off equally until it smooths out?

Thanks

Dave — you mentioned that you set the iso clearances on the bench. When you tighten the front and rear engine bolts, the slack in the threads of the adjusters means that the clearances you set before can be reduced to zero.

Take the bike off the centre stand, if you have not already done this. It's ideal if you can get the bike vertical sitting on both wheels, which you can do if you have a ramp with a front wheel clamp or use tie downs. Set the clearances, front and rear, larger than the recommended 10 thou and then tighten each engine bolt. Then measure the clearance. Repeat until you get the 10 thou with the engine bolts torqued up. I set mine slightly less, at 8 thou, to minimise lateral movement at the rear wheel. Some people use a lever to push the engine away from the adjuster side to get a more accurate measurement.

Do you have the standard head steady or a Dave Taylor head steady? If you have a Taylor head steady, it needs setting up properly and there are other threads on this. If not, then what you describe sounds like your iso clearances are definitely too tight.

Did the front isolastic tube need machining to get it to fit properly in the frame?

Its normal following a rebuild to let things settle in. I find doing a routine of slack off and re-torque works well for a lot of frame stuff. However on adjustable vernier Iso's I found the manual spec was not very applicable as it was rough as rocks in a cement mixer! The only way for my 850 was to slacken the front and rear main bolts, turn the adjuster collars in until they pinched up and then slacken them 1/4 back, retorque the bolts and go for a test ride. I did this several times until I found the comfort right, progressively reducing vibes until 2500 and dead smooth at 3000.

Mick

maylar said:

I took my first ride with my MKIII adjustable isolastics installed on the 850 and they're obviously too tight. It like they work in reverse of normal... no vibration at low rpm increasing to a nasty buzz at 4000. I didn't take it above that, as I am breaking in a new motor.

I have the adjustments front and rear set for "one hole" before snug, as was recommended in the installation instructions. On the bench that measured .010" with a feeler gage. I'm puzzled as to why it would be different on the bike.

Which of the two isos has the biggest effect on vibration? Or should I start backing both front and rear off equally until it smooths out?

Thanks

Click to expand...

Les Emery at Norvil recommends setting the verniers out one half turn. One full turn is supposed to equal 0.050 clearance so Emery's recommendation should translate to 0.025. This seemed like too much clearance to me so I set mine at 2 holes out to start which should have translated to 0.008. Way too much vibration. So then I tried 3 turns out and this was much better. I am still getting a little bit of vibration in the handlebars but none in the footpegs so I think I am pretty close. "One hole" should be less than 0.010 so I am not surprised you saw a lot of vibration with them that tight.