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Symptoms of a twisted crank?

Posted: Sun Apr 05, 2009 9:13 pm
by bazman
Can anyone shed any light on the symptoms of a twisted crank? Reason i ask is the handlebars have adopted a vibration at speeds above 45-50mph (more than normal!!) more noticeable when flat out on motorways/a roads, very on off constant gap between the vibrations, checked out the normal things ie forks too tight , hub bearings, etc all ok not dropped the forks yet to check bearings but when built after respray last year all ok and well greased, just wondering if the crank being out of true would resonate up to the handlebars?
Cheers Baz.

Re: Symptoms of a twisted crank?

Posted: Sun Apr 05, 2009 9:18 pm
by eibargum
Dont know if you,ll feel it in the handle bars but look at your flywheel as someone turns your engine over with the kickstart, if the flywheel moves ecentricly the cranks twisted, regards.

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 7:33 am
by bazman
Ok mate cheers , scoot runs ok would have thought with a crank twisted it would possibly cause the flywheel to affect the pick up on stator? Another thing to try though thanks for reply :)

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 8:37 am
by Bufficus
bazman wrote: just wondering if the crank being out of true would resonate up to the handlebars?
Cheers Baz.
In my experience yes.

It might be worth removing the flywheel to see if there are any deposits of T2 oil in the bottom of the mag housing.

If the crank has spun the mag side oil seals will fail and you'll end up with a small pool of oil below the stator.

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 9:53 am
by eibargum
Bufficus [simon] knows alot more than i do, but when i twisted mine the seal remained intact and there was no oil in the maghouseing but the flywheel moved ecentricly and as you said baz it started shaveing the pickup, not good flat out on the M180 on a RB230, didnt feel any vibrations through the handlebars though. regards.

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 5:09 pm
by Bufficus
eibargum wrote:Bufficus [simon] knows alot more than i do.
I don't know about that Gary. Everyday and every new problem is a learning curve with Lambrettas. ;)

I think it proves that the same problem can manifest itself in slightly different ways.

We can only speak from the experiences we have.

I reckon our different experiences can be explained by the difference in the quality of our seals and the production tolerances of our flywheels.

The crank I had twist on me recently was one of the most expensive ones you can buy and it was a mile out when I had it checked. I did have excellent service from the Doncaster based supplier though, who had it repinned FOC within a week.

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 5:30 pm
by bazman
Cheers chaps going into Andy Francis on wed to check over as i've not got the time and need it fixed for Tenby, don't fancy 320 odd mies the way it is the now i'll have no fillings left!!!

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 6:20 pm
by davidblythe
worn main bearing lead to excessive vibration as well

as do li style engine mounts or the extended engine mounts (not the standard SX/TV/GP ones) you can now buy

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 8:53 pm
by teamv
Maybe you've ran over a hedge hog :bouncyeng: ,or it could be the extra weight of those easter eggs thats the problem,hope thats a help :lol: :mrgreen:

Re: Symptoms of a twisted crank?

Posted: Mon Apr 06, 2009 9:15 pm
by bazman
Cheers Nelly :frog: :lol:
Think Mr Sanderson will be getting an order for outboard dampers and disc brake as well, as that ting tong one i've got's a bit harsh to say the least!! don't know if thats caused the problem :|
Enjoy Scarbourgh and hope ya scoot runs ok........ ;)