Topic: CB750 rear wheel truing vs replacement / CB550 rear wheel swap

[Reganator]

Hello gentlemen.

I've had a pretty great summer on my 71 CB750 I fixed up.  I love the bike and I can't take it out without someone stoping me to ask me what it is and to tell me how much they like it.

However, there is trouble in paradise.  I took it out on the interstate the other evening and noticed my rear wheel wasn't quite cooperating with me.  It felt a bit like it was slipping and having a little issue deciding which direction to grab in.  I took it home and popped it up on the center stand, and after rigging up a fixed reference on the frame I noticed the wheel is not true laterally.  It had an area with maybe at most a mm of play out to the side.  I've trued bicycle wheel before so I went to work on it.  It has improved pretty significantly, but it still has an area where it is maybe .5 mm out.  I'm planning on getting it up to speed to test it again, but I'm not wild about what is going on.  Initially, the issue was only noticeable once the bike was up to about 45 mph, tolerable until about 50.  In order to correct it as much as I've had to one of the spokes seems uncomfortably tight based on the tap tone method, so my concern is that my rim may be bent and the spokes are doing their best to compensate.

So... My question is what is the tolerance on these things?  What is acceptable?  Also, I have a shot at a CB550 rear wheel that appears to be in good shape.  Would the hub be the same as the 750 or am I going to need to look into other solutions?

Thanks for your time and expertise gentlemen.

[lucky]

IF you rim is that close to being true you do not need to get rid of it.

Get someone to help you that is more experienced at truing wheels.

[Greggo]

550 should have the same hub, just make sure you use the matching brake plate and spacers, BUT the rim is slightly narrower.

[Reganator]

I think I'll go test ride it and take it from there then.  Might have to talk to my friend at the salvage yard about rear wheels.

I know the bearings are good, and the bushings seem good as well.  Anyone have any other ideas on what could cause the floaty back end feeling before I start spending money?

[Greggo]

I think I'll go test ride it and take it from there then.  Might have to talk to my friend at the salvage yard about rear wheels.

I know the bearings are good, and the bushings seem good as well.  Anyone have any other ideas on what could cause the floaty back end feeling before I start spending money?

Swing arm bushings warrant a proper check if the back end feels floaty...

[Reganator]

In that case, please describe propper... I've checked for free play, there is none.  Maybe floaty was the wrong term to use... like I said it almost feels like I have poor traction back there, back end feels like its kicking to one side or the other ever so slightly at high speed.  Tire is good and the road is dry, so it isn't actually slipping.  Figured it was just the wheel.  Just wondering what else I can do to improve handling here / what else should be checked.  If there is a more thorough check for bushings, lay it on me.

[Black 750K8]

How do the dampers (cush drive) rubbers look? Could be slop there. Also check the big o-ring that locks the sprocket carrier to the wheel hub it needs to be good and tight.

[Reganator]

The dampers in the cush drive look good, just had the wheel off to replace the tire a week or so ago....

Big o-ring?  Do tell.... that... may be missing.

The rest of the spacers are in there.

[EDIT] My bad, the o-ring is fine.  I looked at the schematic and that is in there, thought you may have meant something else.

[lucky]

I think I'll go test ride it and take it from there then.  Might have to talk to my friend at the salvage yard about rear wheels.

I know the bearings are good, and the bushings seem good as well.  Anyone have any other ideas on what could cause the floaty back end feeling before I start spending money?

Low tire pressure.
Swing arm bushings.
Rear shock bushings.

[Reganator]

Ah.. Thanks Lucky.  I hadn't thought to pay close attention to the shock bushings.  I'll check that tomorrow.  Tire pressure seems good but i'll double check that.

[david 750f]

Axle nut torqued properly? Tire pressure?

[bryanj]

500 wheel WILL NOT FIT, rim is narrower, brake drum smaller and spacers different.

The limit for wheel rims is 3mm laterally and vertically don't forget that the rim has a "weld" point and that you will never get true.

What type of tyre did you fit as what you describe is typical of cheepo tyres

[Reganator]

500 wheel WILL NOT FIT, rim is narrower, brake drum smaller and spacers different.

The limit for wheel rims is 3mm laterally and vertically don't forget that the rim has a "weld" point and that you will never get true.

What type of tyre did you fit as what you describe is typical of cheepo tyres

Yeah, after I hear the 550 whel was narrower that was out regardless. 

I'm going to see if I can find that spec for these wheels.  I'm aware of the weld point, but 3 mm?  That seems like it would cause problems at speed....

I have roadmaster TT100s on it.  Supposedly quite good tires.  Supposedly.

I'll check the axle nut as well.  My friend actually torqued that while I was wiping my hands off after holding the wheel up for him.  He's competenet, but not beyond making the ocasional mistake.  Who is?

[Black 750K8]

The dampers in the cush drive look good, just had the wheel off to replace the tire a week or so ago....

Big o-ring?  Do tell.... that... may be missing.

The rest of the spacers are in there.

[EDIT] My bad, the o-ring is fine.  I looked at the schematic and that is in there, thought you may have meant something else.

That o-ring has to be in good shape. To test it you should be able to pick the wheel up by the sprocket and shake hard and the wheel should not fall off leaving you holding the sprocket and carrier. When putting it on after a tear down with the wheel on some plywood sprocket side up you should have to jump up on the sprocket with some wood on top of it with your feet to pop it down in place.

[crazypj]

K81 or K181?
K81 will feel a little 'squirrely' unless you have matching front, then it gets real scary around 110~120 mph unless your cornering when the larger contact patch works properly
K181 are much rounder profile and probably better for 99% of riders
You can't use stock Honda tyre pressures and need about 34~36psi rear (plus another 2~4 psi with a passenger) with 30~34 front
To check swing arm bearings, grab tyre at 3:00 o'clock position (on left side of bike, staedy frame with left hand and try to push/pull wheel side to side (make sure drive chain isn't too tight as that can prevent movement to right)
More than about 1/16" is going to be noticeable when riding, I prefer to have zero movement just the normal tyre flex which can easily be 1/8"

[01Thomas]

If you only had 1mm run-out and now only have 0.5 mm run-out - then run-out is not your problem. As someone else said 3mm is still acceptable.

I think the clue lies in the fact that you've just had the tyre replaced. It seems to me that this floaty feeling only came to you after replacing the tyre, correct? That would mean the wheel wasn't replaced properly.
Is the axle nut tightened? Tyre pressure? Are you really sure the bearings are good?

[Reganator]

Ok, based on all the feedback I'm getting I'm eliminating runout.

Just checked all the bushings again, no free play anywhere.

Tires are K81 Dunlop roadmaster series, front and back.

As for the O-ring, I'm not so sure it is there anymore.  Based on the feedback here, I'm going to proceeed with sourcing some new ones to see if that can help out my situation.  Still havent gotten a moment to test drive it, and it's warm here so I'm not so hot about getting the jacket and everything on, but one must do what one must do.

I'll check the tire presure when I run out, and I'll report back on the feel with wheel a little more trued, but I don't get the impression it will help all that much.

Forgot bearings, I'm 100% certain those are good... anyway, I'll report back.

[Reganator]

Ok, I think this may be resolved.  Still need to really get it up to speed, but I just got it over 50 and it had smooth road feel the whole way.  I think that work I did on the back wheel did help, it was somewhat out, but I also upped my tire pressure.  I had around 32 in the rear, so I upped to the high end, 38 (cause I'm a big heavy mf, so I consider myself to be a rider + passenger) and I found out that the pressure in my front, which seemed fine, was fairly low, so I took that up to about 35. 

I'm a little surprised at how much difference a few PSI makes, but I know how much it means in a car, so I guess I shouldn't be to surprised.

[bjbuchanan]

It is surprising the difference the pressure makes. I neglected mine in the winter up front and it felt like almost a slipping/squishing without even really leaning in to turns. Low rear tire will feel wiggly under your @ss, feels like it is disappearing from under you

[Reganator]

It is surprising the difference the pressure makes. I neglected mine in the winter up front and it felt like almost a slipping/squishing without even really leaning in to turns. Low rear tire will feel wiggly under your @ss, feels like it is disappearing from under you

Yeah, that is pretty much what was going on.  Odd that the front tire didn't feel off given it was even lower.

[Stev-o]

Certainly could have been air pressure. I had a flat two years ago and felt that "floaty" feeling, did not like it.  Slow leak and lose to home, so no problem.

Consider changing the swing arm bushings if it has not been done.  When at speed, you don't want a wobble back there.

[Reganator]

Actually my swing arm bushings are really good.  I guess I got lucky.  Po took care of this one.  It wasn't super pretty when I got it, but man, every time we pull something off and check wearable parts, they're always new, or right next to new.  The only thing that is kind of buggered are the coils, and they're still functional, they just take a dump on me if it rains.  Oh, that and PO must not have had the plug tool because the plug in #2 was of indeterminant age, but very obviously much much older than the other 3 when I got it.

[crazypj]

The coils are always like that, they pretty much stopped working in the rain even when new (guess they were designed for southern California?  )

[Reganator]

The coils are always like that, they pretty much stopped working in the rain even when new (guess they were designed for southern California?  )

Not exactly pleased to hear that.  Maybe it is time to upgrade to something with a replaceable wire and built in cap.

[Black 750K8]

The dampers in the cush drive look good, just had the wheel off to replace the tire a week or so ago....

Big o-ring?  Do tell.... that... may be missing.

The rest of the spacers are in there.

[EDIT] My bad, the o-ring is fine.  I looked at the schematic and that is in there, thought you may have meant something else.



That o-ring has to be in good shape. To test it you should be able to pick the wheel up by the sprocket and shake hard and the wheel should not fall off leaving you holding the sprocket and carrier. When putting it on after a tear down with the wheel on some plywood sprocket side up you should have to jump up on the sprocket with some wood on top of it with your feet to pop it down in place.

EDIT I forgot to give credit to HondaMan for this info.. It is in his book.
Thanks Mark