Wobble at low speeds

[stossboss_gaming_and_news]

So I finally finished up my bike enough to take out for a test drive. I rode it a few blocks and back to see if it had any issues, of which one is quite concerning - the bike is wobbling at low speeds (starts around 25 mph) and I'm trying to diagnose the cause.

Here is everything I've done that I think could have affected it -

- replaced chain and sprockets
- replaced front tire
- rebuilt brake caliper with new piston + lines, old seal but it wasn't leaking previously (the seal I purchased seems a little small, I'm leaving it on the old piston for a few days hoping it will take shape)
- changed fork oil with heavier weight

Some other issues - I noticed my rear brake is rather loose and squeaky and my speedometer stopped working half-way through the ride, I think either of these could be related (maybe I didn't correctly reinstall the axles?)

My current guesses

- front wheel not properly installed/misaligned (especially because of speedometer failure),
- suspension difference between front and back, with the heavier fork oil maybe I need to tighten up the back? But I can't imagine it would make such a difference at 30 mph
- loose or badly adjusted chain. I had a little trouble figuring this out but I think it's done well, they are within .5mm of each other measured at the adjusters and not an excessive amount of slack
- fork pinch bolts overtorqued/steering bar misaligned - I don't know if this could cause the issue but I may have overtorqued the upper pinchbolts and the bar feels a little low

I think my rear brake possibly just needs adjustment to fix the squeal, but I'll double check the pads.

Anyway, any help is appreciated as I'm kind of at a loss as to where I should look first, but at least I'm passed my starting and idling woes and have learned a lot on that... starts right up and idles at 1100-1300, no more stalling when I let go of the throttle...

 

[KiwiAlfa156]

Could be a number of things. If it was me I'd start at the nose and end at the tail.

• Front wheel bearings OK?
• Front axle spacers correct?
• Pinch bolts/caps correctly gapped/nuts torqued correctly?
• Fork tubes straight?
• Fork yolks (triple trees) not bent?
• Forks aligned correctly?
• Steering stem bearings not worn/notchy/properly greased?
• Steering stem tension set correctly (use a torque wrench and follow the workshop instructions)
• Is the frame straight? Check wheel alignment using string lines.
• Swingarm bearings not worn/no play/properly greased?
• Swingarm pivot tension correct?
• Rear wheel bearings good?
• Rear axle spacers in correct order?
• Rear wheel alignment correct (check with drive chain or rear axle to swingarm pivot center to center measurements on each side).
• Are the tires worn? Squared off? Different brands? Out of round? Incorrectly seated?
• Inflation pressures?
• Are the rims buckled?

Good place to start?

 

[stossboss_gaming_and_news]

Could be a number of things. If it was me I'd start at the nose and end at the tail.

• Front wheel bearings OK?
• Front axle spacers correct?
• Pinch bolts/caps correctly gapped/nuts torqued correctly?
• Fork tubes straight?
• Fork yolks (triple trees) not bent?
• Forks aligned correctly?
• Steering stem bearings not worn/notchy/properly greased?
• Steering stem tension set correctly (use a torque wrench and follow the workshop instructions)
• Is the frame straight? Check wheel alignment using string lines.
• Swingarm bearings not worn/no play/properly greased?
• Swingarm pivot tension correct?
• Rear wheel bearings good?
• Rear axle spacers in correct order?
• Rear wheel alignment correct (check with drive chain or rear axle to swingarm pivot center to center measurements on each side).
• Are the tires worn? Squared off? Different brands? Out of round? Incorrectly seated?
• Inflation pressures?
• Are the rims buckled?

Good place to start?

so I took your advice and started from the nose, and found an issue almost right away, I must have forgotten to tighten up my left fork drain bolt because I it was finger-loose so I took them off and hardly any fork oil came out of that one... I think that that was possibly the main problem. I never noticed it leak because I made a mess when I first changed the fluid...

 

[salty_monk]

That could do it... also make sure you "settle" the forks by bouncing them after securing the top bolts before you do up the lowers.

 

[stossboss_gaming_and_news]

That could do it... also make sure you "settle" the forks by bouncing them after securing the top bolts before you do up the lowers.

it was a lot better after fixing the fork, but something is still off. Going to take a deeper dive into the alignment when I fix up my control lights, just felt dangerous testing it out without turn signals/brake lights. Brake lights the switch was just filled with grime... The turn signals - at first I thought I was just too dumb to read to wiring diagram, so I coloured it and realised the PO added a bunch of cables that just do not correspond, and a replacement brake switch with different colours. took me a while to realise whats going on...

 

[stossboss_gaming_and_news]

Alright an update and I'll take some pictures before putting back together. Fixed up the control lights and I was just going to do wheel alignment, but I had forgotten to grease my rear brake and I remember it was squeaking, so... I really should inspect the swingarm anyway since it's on that list and I'm taking the rear wheel off anyway and I'm glad I did.

Not very well greased, there was a considerable amount of rust on one side of the outside of my spacer/sleeve and had a substantial burn line across it, I think my swingarm was seized on that rusty side. This was my first "big" street bike and it always felt unstable at speed (I thought it was supposed to be the opposite!) and especially through corners like my rear wheel was almost "skipping". And boy, I'm no strongman and at a measly 145 lbs getting it unstuck and the axle out was quite the ordeal.

After a good cleaning the bearings are both operating smoothly and the rust is out of there, will probably change the sleeve next rear wheel removal. I imagine this will significantly help that wobbly "disconnected" rear that I encountered.

 

[Rob S.]

After a good cleaning the (swing arm) bearings are both operating smoothly and the rust is out of there...I imagine this will significantly help that wobbly "disconnected" rear that I encountered.

It might solve it 100%! :clap:

 

[rphillips]

Hopefully it will.

 

[stossboss_gaming_and_news]

Much, much better. I almost have a fully functioning bike! I do think there is some instability caused by my #3 not firing, I noticed its exhaust never really gets hot - so I guess my bike is more of a heavy gs550 at the moment. Checked for spark and its there, this carb was rebuilt so I think either the air-mixture screw is in too deep or possibly diaphragm was mispositioned as I kept taking the carbs so I had to keep unscrewing its top.

I do have on question, when tuning the carbs it showed about equal vacuum to #2 (this was before I took everything apart again), would that indicate that it was indeed working or could it be generated elsewhere and leak in if the cylinder is not firing?

 

[first timer]

vacuum just shows air is flowing through the carb. You need fuel mixing with that air to make the carb work.