New Vibration

[Deleted User 62]

On my last couple of rides, I've noticed a new vibration that comes on at around 4200 rpm in any gear. I couldn't hear anything at speed, but could feel it in my hands and seat. I checked compression, carb balance, timing and valve adjustment. With it on the stand, I could rev it to 4200 rpm and noticed a slight mechanical rattle coming from the right cylinder/carb area. The heads were rebuilt recently, so I'm assuming no problems there. Any ideas on what could be causing this? I'm going to check the diaphragms next...

[Garnet]

Does it go away again up at 4500?

One bad diaphram would continue to get worse as revs rise.

4200 is a buzzy spot on most 900 and 1000cc engines.

[Deleted User 62]

This is a 1973 R75/5, hard to tell if it gets worse at higher revs, so I guess not.

[Garnet]

"The heads were rebuilt recently, so I'm assuming no problems there."
That may be a good place to start.

My /5 has more vibes than I would like, but most of that is due to me being too lazy to realy sort my carbs out.

How do you check your carbs for balance? For me balancing by ear and feel only works at idle and just off idle. So at times I have vibes once I'm off the idle circut. For me vacume sticks work better at getting a true balance. Rember GSPDs little thumbwheel he had on the throttle control? That's what I need.

[Deleted User 62]

I use the $4 carb balancer to check what my ears tell me. The fluid is rock solid steady all all rpms.

[Garnet]

I use the $4 carb balancer to check what my ears tell me. The fluid is rock solid steady all all rpms.

Can I borrow it?

[Deleted User 62]

I use the $4 carb balancer to check what my ears tell me. The fluid is rock solid steady all all rpms.

Can I borrow it?

You can make your own for $4 (or probably a bit more, adjusted for inflation) read about it here: http://www.airheads.org/content/view/183/98/ Note: you need to have carbs with vacuum ports. The early /5 didn't have them.

[Kurt in S.A.]

The plug-shorting method also works...might even be cheaper.

Kurt in S.A.

[Deleted User 287]

Good thing Duane isn't dead - he'd be spinning in his grave.
But we could hook up a dynamo and generate free electricity!


Here you go! You can buy some plug shorting-out tools here!

http://www.northwoodsairheads.com/Tools.html

[Garnet]

Here you go! You can buy some plug shorting-out tools here!

http://www.northwoodsairheads.com/Tools.html

I can feel the power pulsing through my veins already.