Whole engine vibrates while reving

[barry_scotland]

Hi guys i just picked up a 1991 kx 250,
I swaped it for a 2003 tm with a blown gearbox ( tm are very expensive to repair) and the guy gave me ?300 as well as the kx,

the kx has had new piston and rings fitted and has weeks of compression,

Now i have some issues,

The whole engine is vibrating / shaking/ just not healthy at all,  when i rev it or even on tick over,
What could cause this?

Also i gad a shot of it in its poorly state ( prob not the best idea, but rules out the gearbox it drives ok )

It wasnt hitting powerbands, and was quite smokey,
White smoke, But i klnow i have water in the oil, and i have the seal here to fix that,

Everytihng else looks brand new on the bike, including the recently diped chrome frame,

Any input would be greatly apreciated,
I am ordering a bearing back for the engine, and also a seal and gasket kit , ( ebay is amazing )

Think this will sort the problem, or could it be the flywheel thats causing the vibrations.

[jonny500]

first of all check the engine mount bolts as its quite common for them to come lose. after that i am afraid things get more serious. remove the ignition cover and give the flywheel a tug and see if there is any movment up and down or in and out. if there is any movment the main crank bearings are gone. so i think you are looking at a complete rebuild of the crank. i supose it could be the clutch but they tend to be noisy rather than serious vibrations. if its not something obviously lose then i would say its the crank either the mains, big end or out of balance as these or the only things i know that would cause the vibration you describe. i hope it is somthing simple but im sorry to say it dosent sould like it
best regards
john

[Coop]

I agree with Jonny500. Check the motor mount bolts (and mounts), then do the flywheel test he described. Unfortunately major vibes in a two stroke usually leads to bad bearings; either in the case, or in the big end of the rod.

[Hillclimb#42]

Great advice guys. Copy that for me. Probably a bad crank, in the beginning that causes the bearing wear, and motor mount bolts to loosen. Motor mounts do get loose sometimes,  especially after a recent rebuild. I'll keep my fingers crossed for you, that its just your mounts.

[barry_scotland]

thanks guys checked the engine today and the two plates, at the front bottom of the engine ( under the exhaust) were cracked,

So i made up a bracket from some old 2 mm stainles i had lying around and voila sorted,

Next the powervalve issue,
I took of the pv case on the side of the head, and noticed the round wheel was missing,
Quick rake through my spares drawer produced one and once fitted with the new circlips in place, i have the pv's opening and closing no problem,

Although my suspension feels soft in the rear so might get the shock revalved or just replace with a newer shock.

[ktmdude]

Glad to hear it was a simple fix. No major surgery. Now go have fun on her.

[snoopjonnyjon]

The thing that stood out to me most in this post is the "recently dipped chrome frame". I would love to see a picture of this.

[maddoggy]

The thing that stood out to me most in this post is the "recently dipped chrome frame". I would love to see a picture of this.

ditto on that, lets see a pic.

[Hillclimb#42]

I believe he means polished Aluminum. Looks good. I have polished parts also. Lots of work, but well worth the time spent.

http://www.kxriders.com/forums/index.php/topic,7622.0.html