When riding my 1984 silver bullit I get a vibration, like a bad tire( thump,thump) I put on 2 new tires~~~no change. When I pedal the bike while on its stand I notice the chain gets taut momentary then goes to its normal tension. could it be a bad chain or something out of alignment?~~~need help PLEASE.~~`thx
It sounds like your chain isn't tight enough, do you have a lot of play in it? If so, you may need to adjust your rear wheel accordingly.
Did you put a 27 tooth sprocket in it, and forget to grind out part of the engine housing to accomodate it?
Make sure your wheel bearings are o.k..
This was taken from the tech. bulletin for a Batavus, but I feel it holds true for any moped.
Quote:
In the past few months, we have experienced a few rear wheels with bearing problems. We feel at this time, that the bearings, cup, spindle and cones are not the problem. When servicing or preparing a new moped, make sure that the tension of the "drive" chain is not too tight.
The drive chain should have at least 3/4" to 1" slack or play in it. Be sure to rotate rear wheel a full revolution while adjusting drive chain to assure the proper adjustment of 3/4" to 1" in all positions. If the chain is too tight, this will cause unnecessary wear to the bearings.
End Quote:
I'm sure tightening the chain will temporarily fix the vibration problem, but this may be an early warning sign that your rear bearing is going bad. It's easy enough to replace a bearing, but a lot harder to find a replacement wheel with a good hub that hasn't been destroyed by a neglected bad bearing. I hope this helps.
Brian
Lamborn's Miniature Engines
One way to check if your rear wheel bearing is bad is to check for play before removing the wheel from the moped. Remove the drive chain and with the moped on the kick stand grab hold of the rear wheel and pull back and forth. If you can feel play in the wheel then you know where your vibration is coming from.
Brian
Lamborn's Miniature Engines
Right,Brian! Good info.! But one thing: In that bulletin they failed to address a big mistake people tend to make;Not adjusting the chain while loaded with at least 165 lbs.load.You well know that when the swing arm is compressed it tightens the chain on most `peds and if they only hgave 3/4" play unloaded ,it's gonna be way too tight when they moujnt the bike AND when the bike hits bumps in the road.Just my 2 cents,`cause I haven't got the 20 bucks yet!BYE!
I would also check to see that the tire is well mounted in the rip. Sometimes they can unseat themselves a little bit. Lift up each end of the ped and spin (or pedal for the rear wheel) and see if the tire or rim is moving up or down. Perhaps that could be the cause.
Check your rear wheel alignment also - if it's out of alignment, or the tires have unseated at the bead, that might explain it.
Also, check the rims for slight warping, cause I have noticed that any bending of the rims is super-noticeable when you put new tires on.
-Ree
The reason the Batavus Tech. Bulletin failed to include this information is because the engine swings with the rear swing arm therefore the slack will always be the same on this type of moped. You are correct in your statement though for the other type of mopeds with the motor mounted to the frame. Good counter point.
Brian
Lamborn's Miniature Engines
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