bad engine vibration!! need help!

[180 nytro]

hi everyone, i could use a bit of help, i have just finished rebuilding a 270 nytro engine and something has gone wrong!??
so this isnt my first time rebuilding one of these engines so i was quiet confident that i had put all the parts back in the right places, but when i went to start it it wouldnt fire right away and it turned over kinda rough as if maybe the cams were out of timing slightly, but it did start and reved up to about 2300 rpm and firing pretty well normal, but there is a wicked vibration coming from the engine!! i dont have the clutch on ethier so it should be quiet and smooth.

And while it was running there was a bang and something had let loose and cracked the oil pan right to the side of the oil pump sprocket?

So my question is what could be causing the vibration?(i know there is alot of things).

Could have i mixed up connecting rods for each cylinder?

will the timing being out make a horrible vibration? if so why is it firing smooth?

sorry for all questions guys, just kinda in a real bind .

thanks
Tim

 

[Srxspec]

You could have the counter balance shaft not in time with the crankshaft. There is dots on both of these gears that should line up. If they are out even 1 tooth they will vibrate like crazy.

 

[180 nytro]

ok yep that is something i did not know??

i must have just lucked out on the last one i did cuz it runs smooth, hu.

well i have the engine out again and will be taking it apart, and that is gonna be where ill start, cuz it seems to run fine just vibarating bad, and of course figure out what let loose and cracked the pan?


also on the cam shafts, being that it has the head shim and the cams should be advanced a tiny bit, shuld the timing marks line up perfectly?

the sprocket marks straight across and the dots on the cams line up with the dots on the caps?

thanks for the reply, big help!

Tim

 

[4x4]

Hornet Handler you should delete that comment.
Some engines need the clutch to run smoothly.

 

[Mountaintech]

The Yamaha service manual is your best friend when it comes to working on your machine. They are cheap and readily available.

 

[180 nytro]

Sorry I haven't replied on my outcome on this, it was in fact that the counter balance was out a few teeth,

And for the hole in the pan, it was just a simple mistake of not tightening the oil pump spocket bolt, o well my expense and the sled is now up and running better than ever.

Thanks for the help guys

as for u hornet handler, it wasn't an attempt I have been doing this stuff since I was a kid, ya I defiantly am not an tech but even the best of techs can screw up pretty bad! Thanks anyways.

 

[180 nytro]

By the way this is a site to ask questions and find answers is it not?

 

[TurboTime]

By the way this is a site to ask questions and find answers is it not?

Couldn't agree with you more. Hornet's mrs or maybe mr might have turned him down this morning putting him in a bad mood.

 

[DooAssassin]

X2

 

[Sled Dog]

Sent hornet handler a PM! This kind of post was not necessary or helpful and rude as well. If he does not remove it I will. By the way Allen way to nail it on the first shot good work!

 

[rxrider]

By the way this is a site to ask questions and find answers is it not?

Yes it is.

If people can't behave please let one of the Moderators know!!!!

rxrider
TY Management Team