On the down rev on my 99 banshee it vibrates, im not sure why. I checked the flywheel hoping that maybe it was on crooked. No such luck. I checked the clutch side for anything else that might be causing a vibration. Im not sure why it is vibrating. And it is noticeable when sitting there idling but not when you are riding it unless you come into a corner and engine brake by down shifting. It vibrates then too. Im not sure what is causing the vibration im thinking that it may be the crank, or the counter balancer. The bearings could be going bad on the crank causing vibration. I also tried for movement in the crank trying to move it up and down and in and out. No play. It doesnt make any sense. I heard from someone that if you mod a banshee motor too much that the crank can start to separate.
For the engine i only have the following mods.
Pro circuit pipes
Mx ported and polished
Bored .010 over WSM pistons
33mm keihin carburetor
trinity stage 4 intake
Boysen reeds
Pro design cool head
i think thats about it. The whole lower case is stock. As far as i know.
Any help is greatly appreciated. I cannot figure this one out.
Thanks for any help, Andy

 

has it been doing it ever since you bored it out (assuming you blew it up before forcing you to bore it out)? I was talking to my local cycle mechanic that has worked at the yamaha/suzuki shop for quite some time, about the vibration i was having on my quadzilla. But anyways, he mentioned that bansee's are notorious for distorting crank shafts. (say when one piston seizes up and the other one dosen't you can see the problem)

 

No i didnt blow it up. I was just having it rebuilt because of poor compression. And before i rebuilt it im not sure if i recall or not. Now that i think about it maybe i didnt. But like you said i have heard before that the banshee cranks do like to distort. I think im gonna wait until this winter and rip it down. I really dont want to but i leave myself no choice. Either that or part it out. Maybe ill have to tear down the head and make sure everything is ok. If everything looks fine then i geuss ill have to tear into the lower end.
Im not sure if you noticed but i have a 1988 lt250r and before we rebuilt it. And i mean rebuilt totally the motor is like off the showroom floor. There was a bad vibration. And we looked into it to find out that the counter balancer was slightly bent. Causing lots and lots of vibration. But the more i think about what you said about the crank i actually think thats what it might be. Thanks for the input quadzjr.
Thanks Andy

 

Any other help? I badly need it. Someone has to know something.

 

Unless the vibration is real bad, then its normal......

 

Personally i do not think that the vibration is normal, i have had 2 other people look at it and they both are also stumped on what it is. The vibration is as bad as when you rev it up you can hear the vibration. And if you put your hand on the clutch or stator side the vibration is majorly felt. Thanks for the input enforcer. I dont know what if causing this. I had another guy tell me that i need a new clutch basket. But im not sure ill have to look into it. Thanks for any responses.
Andy

 

never torn into a banshee bottom end, but even though it might be simple you can check to see if all the timing marks line up. I was one tooth of when installing the gear on my crank shaft. even though the two dots were lining up for the counter balance shaft on my 500. I would pull the clutch cover to see if everything is tight. Capture all you fluids and if you don't see anything you can re-use them. Maybe your clutch basket is loose or not shmimed correctly. for that matter if anything is loose you might get a vibration. Also if the incorrrectly installed the main bearings you owuld have a high frequency vibration. (happened on my warrior took forever to blame the shops work). That would pretty much cover the exterior stuff. Other than that you would have to break into it.

 

I bet a steak dinner that the left hand side crank webbings have separated. They will do that on a lot of stock cranks. Some motors will run awhile like that and others will twist the end journal a bit and cause vibration. If it has happened and you catch it quick enough you can send your crank in to someone and have it repaired, trued, and then welded. My 00 model done it and it was owned by a woman and was not rode much until I got it in 03.

 

The bets on im gonna take apart the shee and if the crank is separating im gonna buy bubba a steak dinner from anywhere he wants. Or ill just order him a pizza. Thanks for all the info guys. Im gonna rip into the bottom end this up coming late fall. Ill post up and tell you how it goes. If you want to chat Im me on Aim at lrdlt265.
Thanks for the input again Andy

 

If the crank has not been trued and welded get it done. Banshees can twist cranks out a few degrees and then vibrate. The crank will not be loose to touch though.