huge vibration

[emilios]

Hi...its been a long since i wrote in this forum...the reason: no problem with my Plunger A10..
But a friend just bought one plunger A10 1953 and on the first ride he told me that the bike has huge vibration..
Also the compresion on the kickstart doesnt look like an A10..more like a B31..
I did the compression test with the one piston at 125psi and the other one at 100psi...both with close throttle position..
The different compresion can cause the vibration or i have to check something else before a crank balancing?
Thanks

Emilios

[bsa- bill]

Hi Emilos
I think compression test is done with the throttle wide open, so maybe that would give different result, don't think that is too bad though for a low compression ratio.
Others here will have more knowledge of vibration causes, maybe timingside bearing, worn primary chain ??

[a10gf]

Start with the basics, and from there eliminate possible causes. Are all the engine mount bolts tight?

[emilios]

Yes tonight im going to check the engine mount bolts and the ignition timing...
Ill let u know

[Beezageezauk]

Don't forget the head steady bolts!!

[wilko]

Broken crank, too tight primary chain,piston weight wrong!

[orabanda]

Check all engine bolts are tight. Double check the head steady bracket!

Also, check petrol tanks bolts are tight; especially the front bolt (below the handlebars).

Richard

[manosound]

Emilios,

The Cultural Centre project may yet come to life, so maybe we eventually get to meet.

Compression should not need the throttle open. Adequate air supply will get to the cylinders for the test. Otherwise, our engines couldn't idle.

100 psi does not indicate a broken piston, and firing with that compression imbalance would not lead to "huge" vibration. Running on one cylinder, in my opinion, also does not lead to "huge" vibration, but is easily checked by pulling one plug wire off while the engine is running and feeling the difference. Compression problem sounds like one of the following: gasket leak; valve leak; ring leak; test method error. To test for ring issues, shoot two or three squirts of oil into the cyclinder and test again. If the rings are at fault the compression should rise.

I am thinking you did not find engine or head-steady bolts to be the problem, or you would have told us.

If it's a broken crank, as far as I know, the engine isn't running.

Is there noise in the area of the crankcase? When I lost lubrication to one rod journal (in 2007), the bearing spun and the rod became very loose, but the engine kept running. Plenty of vibration. I think, you could get different degrees of the same problem that result in even more vibration. Here is the video I sent to SRM for help. They replied, "Don't start the engine again before a tear down." Lifting off the barrels exposed the loose rod right away. Anyway, eliminate the easier and more accessible possibilities before tearing down.
 
http://www.youtube.com/watch?v=T9grUuIEzM0

Richard L.

[emilios]

Thanks to all of u..
Richard if u are coming to Cyprus let me know..it would be pleasure to meet u..
Well the engine mounting bolts were tight...the ignition timing was far wrong (full advance on 3 degrees BTDC)
I set the ignition to 30 degrees BTDC and run the bike for 20 miles...a very bad noice from the crankcase..bigger when  engine got hotter..
I believe is a conrod..but for sure i will see when i will strip down the engine..
So a lot of work to do..