Alignment Issues?

[OldManBrooks]

I recently got a rear flat on my 79 GS550. I took the old wheel assembly off and took to a local shop to get it fitted for a new tire (Shinko 712 - 120/90-18). I put it all back together but the bike feels quite loose around corners. This is at very low speed <25mph. My concern is that the alignment is off since it seems worse when leaning left than when leaning right. When leaning left it feel like the back end wants to track to the outside of the turn rather than stay on line.
When I first installed it I couned threads on the tensioner bolts to get the axle even (or so I thought). After the above experience, I tightened the left bolt a bit more to counter what I felt. It seems better, but it still feels a little off in the same direction.

I've only had the bike a short time and don't know it's history. I have been searching for a proper way to align the back tire and tension the chain, but can't find anything in the manual or online. I have found mention of the string method but all the links people have posted to its detailed description are dead. I also ca't find any specific method for measuring chain tension. I can read the manual and see that it's supposed to be between 20-30mm but I don't know how that's measured. Can anyone please help? I have been working on it for a couple days and trying to figure it out with what I can find, but I feel like I'm missing something.

 

[Crankthat]

Try this, handle your tools and bolt threads a bit nicer though.
https://www.youtube.com/watch?v=n4vZTrc3IAQ

The alignment marks on these are not always correct.
The welds sometimes distort the swingarm making the alignment marks useless.

I bought a tool for my rear alignment.
Makes things much easier.
It consists of a part you clamp on the rear sprocket with a rod that sticks out towards the front sprocket over the chain.
You then eyeball the rod and chain to make sure they are even with the front sprocket.
But......

I like to remove my front sprocket cover to insure the chain is riding evenly on the front and rear without to much pressure on any side when done.
You will want to make sure your axle bolt is torqued correctly.

After alignment is achieved adjust your chain play.
When adjusting, turn each adjusting bolt the same amount, turn one a quarter turn then the opposite one a quarter turn on and on until desired play is achieved.
Therefore keeping adjustment even.
Recheck alignment before tightening down.
Keep one wrench holding the adjustment in place and another tightening the lock nut.

Recheck alignment after tightening axle bolt also.


The play in the chain needs to be measured upwards from the chain, 10 inches towards front from the rear sprocket should be fine.
Having somebody around your weight sitting on the bike when taking this measurement would be best.
You are putting the play in the chain to compensate for your rear shock/shocks movement.


Do me a favor and make sure that tire is beaded correctly around the rim before starting the above.

 

[Guest]

According to the specs I found, the '79 GS550 uses a 3.75 18 tire. So a 3.50 or a 4.00 would do, but that translates to 100/90 18 in new sizing. So a 120/90 is way too wide and would handle strangely.

Basically, I think the shop sold you the wrong tire. If you check out the rim it probably says 1.85 X 18 which isn't compatible with a tire much over 4" wide. What happens is that the tire gets pinched in at the bottom and pointy at the top and tends to fall into turns, especially when new.

Aligning the chain with the front sprocket is nice, but the reality is that it has to align with the front wheel as a priority. Two long and straight pieces of wood will establish whether the marks on the swing arm are accurate or not; I've generally found them to be close enough. Counting threads on the tensioner is irrelevant; there are hatch marks on the swing arm and a notch on the tensioners at the axle hole that are how it's done.

These bikes commonly get loose swing arm bearings, especially the drive side one [ mine's needing them at the moment] and that can make for odd behaviour. Check the rear wheel for side to side play when on the centerstand and if there's anything more than maybe 2mm you're due. The bearings are cheap, but you have to get the old ones out and the new ones in which is probably best left to a shop with a press.

 

[OldManBrooks]

Basically, I think the shop sold you the wrong tire. If you check out the rim it probably says 1.85 X 18 which isn't compatible with a tire much over 4" wide. What happens is that the tire gets pinched in at the bottom and pointy at the top and tends to fall into turns, especially when new.

This is what I feared and really hoped was NOT the case. I think my wheel may be a bit wider than the 1.85 X 18. I'll post pictures of the markings.

These bikes commonly get loose swing arm bearings, especially the drive side one [ mine's needing them at the moment] and that can make for odd behaviour. Check the rear wheel for side to side play when on the centerstand and if there's anything more than maybe 2mm you're due.

The wheel feels solid once everything to torqued.

CrankThat,
I had already done most of what you listed. However, I think I can refine my technique from what you suggested. One problem I have is that the alignment notch in the left tensioner is no longer there. I'll post pictures to show what I mean.

 

[OldManBrooks]

Hopefully the picture is large enough. It looks like the size is 2.15 X 18. I'm not sure if that makes enough diference to run a 120 width tire.

EDIT: From the charts I can find online, a 120 is the largest tire that will work on a 2.15 rim.

 

[OldManBrooks]

As you can see, there is no notch in the tensioner. I put a couple marks with a marker so I could tell how far I moved it with the tensioner bolt. These obviously won't provide any usable reference when compared to the other side that does have the notch.

 

[bonanzadave]

As you can see, there is no notch in the tensioner.

You probably, or someone, put the tensioner on up-side backwards. The notch is there, its just on the inside....

 

[Crank]

Try removing both tensioners, clamp them together, measure the location of the existing notch, measure and mark the position of the intended notch and use a hacksaw blade to make a new one, using the existing one as a reference.

Or (as I was typing this came to me) check that the tensioner is not on upside down or the notch is on the inside facing the sproket.

 

[Crank]

Bonanzadave just beat me to it

 

[Guest]

View attachment 41864As you can see, there is no notch in the tensioner. I put a couple marks with a marker so I could tell how far I moved it with the tensioner bolt. These obviously won't provide any usable reference when compared to the other side that does have the notch.

Maybe the tensioner is on backwards/upside down and the notch is on the inside?

With the 2.15 rim you shouldn't get into trouble with a 120 tire, but the diameter is pretty huge. Should be really easy to get on the centerstand? A 100/90 or 110/80 would have been my choice. But then I'm not a 'wider is better' guy.

I'd check the axle for straightness - it's been hammered on by the look of it - and also make sure the front end is not bent. You can usually eyeball the planes of the front and rear tires and if they coincide you should be OK. Also check the head bearings for smooth operation [no notchiness] . They went to rollers after 1980, but on 79s the smaller bikes were mostly ball bearings and they crapped out early. Surprisingly, the balls hammered out mostly from engine vibration coming up the frame tubes so you couldn't maintain them. A pain to replace them, but you'll never have to again as the rollers are pretty tough. If they're smooth and tight, it won't matter which kind you've got.

Hang in there; there will be a [hopefully] easy fix, once you find it.

 

[OldManBrooks]

Thanks for all the help. I am a new rider and I don't have much experience to draw from in either the riding or wrenching departments. I've worked on cars and I've ridden bicycles a lot, but neither translates much to the realm of motorcycles. However, one thing I have found is I hate to work on something mechanical and just go by feel. I like to measure and know. So after all the adjusting and guessing yesterday, I tried the string method this morning. The alignment is right on. After all the fiddling I did last night I did end up getting it right. This provides some peace of mind. As for the tensioner, I will check to see if it's flipped around the next time I have the wheel off. This should be soon, as I have plans to replace brake rotors, pads and lines in a couple weeks.

Now that I know it's aligned, I suspect it might just be my lack of experience combined with paranoia after nearly laying the bike down when the old tire/tube went flat in the middle of a corner. I lost traction and the back end swung out. I suspect it's my lack of experience because all I know is this bike and the old tires that were previously on there. New tires, in a different size, should feel different, I assume.

I'd check the axle for straightness - it's been hammered on by the look of it - and also make sure the front end is not bent.

I would imagine I would have had issues previously if the axle/ swing arm/steering where in bad shape.

 

[alke46]

I just sent you a pm.