Uneven Chain Stretch

[Dusty]

Hi all, I have a problem. At 53 mph my bike has a vibration. It goes away at a higher speed, or less speed. I don't know what rpm it comes on at 'cause I don't run a tach. I run an 18-34 sprocket combo, and have noticed a tight spot/loose spot in my chain.
Could this change in chain tension at speed be my prob, or is this standard chain function ? Before I pony up $ 100 plus for a new chain I'd like some input, and see if anyone else had this problem.

 

[Gordon]

All chains have a 'tight' spot and a loose spot. Allways adjust at the tight spot.

 

[Dusty]

Well, I put a new chain on, and the vib is still there. I'm thinking now it could be timing or carb sinc. When the bike cools off, I will adjust EVERYTHING. I don't have a manometer so I think I will try to make one. I would like to have this figured out before Sturgis. The bike only does this under load, when I coast, there is no vibration so I have ruled out wheels, and tires.

 

[manofsteele]

Hmm, I have a vibration above 45mph, I've narrowed it down to the rear tire. I ordered a new one, I'll see if it fixes it this week hopefully.

 

[pamcopete]

Loose rear spokes can cause a vibration.

 

[Chuck]

Referring to the chain... OK I am not a MC expert, but on my single speed bicycle, a loose spot and tight spot on the chain is becuase of an out of round chainring. Its pretty common on a bicycle and sort of a hasle, but on a motorcycle could be more serious. Cause on bicycle, cheap chain rings. MC, probably the same.

 

[Chuck]

Referring to the chain... OK I am not a MC expert, but on my single speed bicycle, a loose spot and tight spot on the chain is becuase of an out of round chainring. Its pretty common on a bicycle and sort of a hasle, but on a motorcycle could be more serious. Cause on bicycle, cheap chain rings. MC, probably the same.

Or it could be a bent axle or bad bearings. Does the wheel wobble? I would check it out. Power Take OFF (PTO) bearing??? This is out of my experience but worth taking a look at.

 

[Chuck]

So you got me thinking about the uneven chain. I checked mine out and it is the same way. I think its a crappy rear sprocket. I have another sprocket, I think I will try it out.

I had heard before that sprockets are hard to make perfectly round, that the machineing equipent to make the sprockets can get old and they don't produce as precisely as they should. So its about commitment to quality from the sprocket manufacturer. Or you get what you pay for.

 

[swbill]

Why has nobody mentioned a wheel out of balance? I didn't catch if its mags or spokes but since its at higher speeds I would suspect that. Have the mag balanced or if its spokes get it trued.

 

[Dusty]

Hey swbill, that was my next move. I laced and trued those wheels. I have another set that came off a stock XS. they have weights on them so I think they are balanced. I put them on, and alot of the problem went away. You know what really made most of it go away was when I tightened all my loose motor mount bolts.
I took my wheels to a shop today to have them spin balanced. The front was out alot. The rear was beyond balance. 10 was the number he told me it was out, and he said 4 is considered real bad. I guess I'l start shopping for a ne rear tire.

 

[swbill]

Sounds like you found the problem, good deal.

 

[XSLeo]

www.innovativebalancing.com
How old are your tires? If they are over 4 or 5 years I would replace both tires.
On the sidewall is a DOT number. The last few digits will be in an oval.
If the oval has 3 digits then the tires were made before 2000. In 2000 they started usung 4 digits. The first two digits are the week they were made, the rest are the year.
If you have three digits like 276 then the tire was made in the 27th week of 1996. If the number is say, 3410 that means the 34th week of 2010.
Old tires can kill.
Leo