Hardtail Shaking

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Gmorrone1214

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Some info: 79 xs650 hardtail , tc bros
springer front 4 under , stock rake
ex500 carbs
stock engine
straight pipes , unipods

So I just got the bike road worthy and took it for a ride. It gets this weird back and forth shaking that is very minimal at cruising at 2-3k rpms ,possibly carbs?...but; then I tried to go faster 3k+ rpms and 30+ mph and the bike started to shake not left to right though but back and forth really bad.

The shaking started to get really bad to the point I thought I might lose control, so i let off the throttle and it kept shaking till I slowed down maybe 15mph. It was no subtle shaking but some extreme shaking.

Rpms and mph are speculations due to no tach or speedo.

Rear rim is bent some (got shipped with bent, using for now since ebay seller did not refund) - Possible cause?

Posted via Mobile
 
Did you put new steering bearings in? Running a top motor mount? Was the rim/tire mounted and balanced professionally? Trued up before tire? Front rim is trued? Hard tail welded on straight? Just throwing out some things to think about....
 
figure8 said:
Did you put new steering bearings in? Running a top motor mount? Was the rim/tire mounted and balanced professionally? Trued up before tire? Front rim is trued? Hard tail welded on straight? Just throwing out some things to think about....
Click to expand...

Hmm no top motor mount I could put back in and see how it goes. I say a lot of posts about people saying its not a big deal.

Front rim brand new with new stearing bearings.

Lined up rear and front sprokets and all motor mounts line up.

Rear tire like I said is bent

Posted via Mobile
 
If your rear wheel has a gimp in it. Get that sorted out sharpish. I'd hazard a guess that's the cause of your issues. While you have the bike in the garage, go through it front to back checking alignment and also structural parts welds etc
 
I agree with the rear wheel diagnosis, especially as it is a damage product. Check for a loose axle as well.

Go over all bolts and check they are tight and all things are aligned.
 
Okay thanks everyone, I just ordered a new rim. I will get it installed and see if the problem still occurs.

In the mean time I look over what you all have mentioned.

Posted via Mobile
 
Why don't you just have the rear wheel fixed (trued ) a lot cheeper than new I'm sure there is a shop around that will do it prob only cost about 50 bucks
 
DIRTY DOG said:
Why don't you just have the rear wheel fixed (trued ) a lot cheeper than new I'm sure there is a shop around that will do it prob only cost about 50 bucks
Click to expand...

hmm mainly because I am an idiot lol :banghead:
Honestly didnt think about it. Just contacted the ebay seller, they didnt ship yet maybe they will refund 50$ is cheaper than 160 lol.

Posted via Mobile
 
Here is what I would do if I had to check bike. Block up rear wheel so it can spin and tie front end down so bike can't move. Fire bike up put it in 3rd or 4th gear and let it spin and see if it is rim or tire. I had a bike that had bad rear bearings and it lunged back and forth under power. The owner put new bearings in but had no idea how to do it and cracked some of the balls and with riding it got worst . If you are stuck and have a truck bring it up and I will look at it. I am right off the Garden State exit 82 .
You have to check things one at a time REAR WHEEL - TRANS - CLUTCH BASKET
Hoping its just rear wheel.
DADDYGCYCLES@YAHOO.COM if you want one on one
Rich
 
Hi Gmorrone,
no matter if there's something else wrong, that rear wheel has to be fixed.
But you say it's "bent"
That could mean anything.
If the rim itself is D-shaped or has sharp kinks in it, you are screwed.
The only option is to check if the hub is OK and lace on a replacement rim.
If the rim is oval instead of round, round but off center to the hub, round, centered but not square to the axle, wrongly offset, has a smooth curve in it or any combination of all those things; enough work with a spoke wrench can fix it.
 
DADDYGCYCLES said:
Here is what I would do if I had to check bike. Block up rear wheel so it can spin and tie front end down so bike can't move. Fire bike up put it in 3rd or 4th gear and let it spin and see if it is rim or tire. I had a bike that had bad rear bearings and it lunged back and forth under power. The owner put new bearings in but had no idea how to do it and cracked some of the balls and with riding it got worst . If you are stuck and have a truck bring it up and I will look at it. I am right off the Garden State exit 82 .
You have to check things one at a time REAR WHEEL - TRANS - CLUTCH BASKET
Hoping its just rear wheel.
DADDYGCYCLES@YAHOO.COM if you want one on one
Rich
Click to expand...


Thanks for the offer, I will try and sort it out and if all else fails I will take you up on that offer :D.

Here are some pictures of the rim, where it is bent the tire is actually being squeezed a little. Its hard to tell but in the one picture the tire gets narrow where the rim is bent.


56667939aa.JPG


4f1a2ab87b.JPG


Posted via Mobile
 
Gmorrone1214 said:
- - - where it is bent the tire is actually being squeezed a little. Its hard to tell but in the one picture the tire gets narrow where the rim is bent.
Click to expand...

Hi Gmorrone,
the rim being distorted from it's original cross-section is the one failure mode I forgot to put in my previous post's "you are screwed" list.
If you completely remove the rim you just may be able to re-shape the rim's cross-section back to normal so the tire will sit properly.
But I doubt it.
Once you have taken the effort to de-spoke the wheel I reckon you will be better off paying for a new rim than you will be trying to lace up the home-fixed old one to be square and true.
 
Mat not be the rim............Looking at the first pic the markings on the tyre disappear at 9 o'clock and 12 o'clock.

Tyre not set in the rim properly, the rim may be causing this but i have my doubts

This will cause the feeling of surging.

Love to see a pic of the other side, looks real dangerous.
 
That rim might be straight enough, but THE TIRE IS NOT ON THE BEAD OF THE RIM. See that molded line on the tire close to the rim. That molded line should be equal distance to the rim, all the way around the tire. With that crappy job of mounting the tire, I wouldn't be surprised if the tube is folded up every which way in there. If that was a tubeless tire you would have rode it right off the rim by now.

You need to dismount that tire, check the rim for true, inspect tire and tube, have someone mount the tire that knows what they are doing.

Scott
 
On second thought, replace the tire. There's enough wear on that tire to suspect that its structure is ruined just by being distorted like that.

Scott
 
umm the tire and tube are mounted correctly on the rim, everytime it is inflated the tire conforms like that on the rim at that given location, I had done it several other times.

Posted via Mobile
 
No..... the tyre is not mounted correctly...........If it was those lines would not be disappearing into the rim. If you don't believe us go and get it done by a professional bike tyre fitter and see what they say

Do not ride with the tyre like that anymore.

Pics of the other side
 

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