RECENT POSTS

YZ250 Vibration

lwsmithjr

Subscriber
Joined
Sep 18, 2002
Messages
194
Likes
0
#1
First, if this has been covered in the past, I apologize. I did a search and only came up with handlebar info.

I have a '99 YZ250 that I have owned now for about 4 months. This past week, my 15 year old (who races a YZ125 and YZ250F) rode it for the first time. After 1 lap he brought it back and said "How do you ride this thing? The vibration is awful."

It's been awhile since I've riden a 250 two stroke so I don't know if mine is "normal" or not. I do know that my hands start tingling after about two laps, and after 4 they feel like they are asleep, but I thought it was just because I'm old.

What is excessive? Is what I'm experiencing normal? Is there things I can check or do I not worry about it and fill my bars up with silicone? (they are 1 1/8' Pro Tapers BTW.)

Thanks for the input.
 

jmics19067

Lifetime Sponsor
Joined
Jan 22, 2002
Messages
2,097
Likes
0
#2
things too check since it was a used bike. all bolts especially motor mount bolts should be tight. take off the ignition cover and see if you can wiggle the flywheel up and down, if you can you need main bearings. Piston clearance being excessive and all of your exhaust hangers,springs and rubber grommets.

I would say that if your hands get numb from vibration not from arm pump something is amiss with the bike not you.
 

Studboy

Thinks he can ride
Joined
Dec 2, 2001
Messages
1,818
Likes
0
#3
Most modern 250's are fairly smooth. I would check the engine mounts and then check the main crankshaft bearings......it shouldn't make your hands go numb.
 

lwsmithjr

Subscriber
Joined
Sep 18, 2002
Messages
194
Likes
0
#4
Checked the engine mounts -- good and snug. The pipe however was very loose. What I don't know at this point is if that was the cause of the vibration, or the result of it. Flywheel is tight. Main bearings and/or piston slop could be the problem.

Thanks!
 

marcusgunby

Lifetime Sponsor
Joined
Jan 9, 2000
Messages
6,450
Likes
2
#5
Make sure the pipe o rings or what ever seal it uses are in good condition-also the pipe springs-these slacken over time.
 

bclapham

Lifetime Sponsor
Joined
Nov 5, 2001
Messages
4,340
Likes
0
#6
250s make lots of noise and viibes, getting on a 125 after riding my 250 i cant even tell if its running or not. just check everything and put a new piston in at some point since they dont last forever.
 

darringer

Lifetime Sponsor
Joined
Dec 2, 2001
Messages
1,029
Likes
0
#7
If you want to feel vibration, come ride my 99 CR250. Now that's a vibrator! I've done all of the tricks and I can still feel it through the bars more than other bikes I have ridden. I have gotten used to it, and had to alter my riding style a bit. I try not to use a "death grip" on the bars and relax more.
 

lwsmithjr

Subscriber
Joined
Sep 18, 2002
Messages
194
Likes
0
#8
I got to ride at Monster Mountain this past weekend. The loose pipe was not the cause of the vibration -- it's still there. The guy I bought it from had supposedly put in a new topend just a few months prior but I'm guessing it was probably longer ago.

I had fun anyway -- just can't stand more than 4 laps at a time. I'm gonna pull it apart.
 

Rcannon

Subscriber
Joined
Nov 17, 2001
Messages
1,886
Likes
0
#9
I noiticed much less vibration on my YZ 250 after installing aluminum bars. I used pro tapers in the Henry bend (thanks Studboy!!!!!!

I still cannot help but think that a piston bad enough to cause all this vibration would have broken up by now.

I know how you guys all love apple and orange comparisons so here goes.

I just replaced my YZ 250 piston that had been in my bike for 2 1/2 years. I know I have at least 60 hours on the piston...maybe more. The vibration level is identical to the old piston. The power might be slightly better, but if I changed the piston to lower vibration I would have been mad!

Best of luck and let us know if you find anything out.
 

darringer

Lifetime Sponsor
Joined
Dec 2, 2001
Messages
1,029
Likes
0
#10
I agree with the Rcannon. Aluminum bars will help with vibration. Also, I filled the bars with silicone caulking and it cut the vibration even further. I've had a bike with so much piston slap I was amazed the skirt didn't break, and it did not vibrate any more than when I rebuilt the engine.
 
Joined
Mar 9, 2003
Messages
44
Likes
0
#11
yeh my 99 cr 250 has some serious headshake too but i got used to it after millions of hours of riding i have twin walls with super soft grips and it helps but its nice to get used to that bike cuz i have never got arm pump on any other bike i ride some races here in the worst wooped out track that are sand and when i first got the bike i could only do 1 lap and now i can do at least 5 or 6 at my fastest pace just keep riding and go thourgh the pump it makes your arms stronger and remember BREATHE!!
 

lwsmithjr

Subscriber
Joined
Sep 18, 2002
Messages
194
Likes
0
#12
I've got Pro Taper's on the bike now with some really soft Tag grips. I have not tried the silicone fill yet, but I will do that before I tear the motor down.

Incidently, the bike came w/ an 11 oz. Steahly flywheel weight (not installed now or when I bought the bike). Is there any possible way that the additional weight, when it was on the bike, could have gotten something out of balance? I realize it shouldn't, but could it?

BTW, kdxmadman, when you're over 40 you have to breathe. Holding your breath for more than 30 seconds is life threatning!
 
Joined
Feb 16, 2003
Messages
171
Likes
0
#13
I've heard that flywheel weights put more strain on the crank bearings. (I personally have a 12oz aloop flywheel weight thats been welded on since 1998 and have yet to have a problem...knock on wood, though i do find it vibrates a bit... Might be time to take a look at that too. thats what winter is for! :) )

Eric
 

darringer

Lifetime Sponsor
Joined
Dec 2, 2001
Messages
1,029
Likes
0
#14
I have a 12oz. flywheel weight on my CR and have not noticed any additional vibration from it. I have made back-to-back runs with and without the weight and there is no change, other than mellowing the powerband. Oh, by the way, when you're over 40 almost everything done on a dirt bike can be life threatening!
 

Studboy

Thinks he can ride
Joined
Dec 2, 2001
Messages
1,818
Likes
0
#15
Weird.... I've never really thought that my 250's vibrated much. My 02 YZ250 feels silky smooth to me, my KX vibed a little bit but NOTHING CLOSE to making my hands go numb. My dad's Mod. LT500 vibes a lot, but that is expected...
I would still check your crank out.