Topic: Sprockets Not Aligned...Please Help

[Harsh]

Alright, I know this isn't a SOHC4, but I am getting a bit desperate and hoping someone has a DOHC4 in their garage or has a buddy that has one or something.  I am helping a local guy get his DOHC4 1980 CB750K up and running and have come across an issue I can't figure out.

A little back story.  The guy bought it off of CL after being told it only needed a hundred bucks or so to get street worthy.  I have found so much wrong it is laughable.  Wiring...a rats nest, end caps not installed on swingarm, wrong rear axle, wrong rear axle brake side spacer, stepped spacer not installed in rear wheel, no cush drive rubbers, spacer missing from engine mount, and on and on.

I installed the chain yesterday, but when I went to adjust and align it I noticed the sprockets were not aligned.  With a straight edge across the rear sprocket there is a 1/8" gap at the front sprocket.  The rear axle and spacers were replaced with the correct parts.  I do not know if the stepped spacer is the correct one, but the hub flange does sit flush with the hub unlike the pic below shows.  I found the stepped spacer in a bag-o-bolts that came with the bike.

I am not sure if the hub flange is the correct one.  The wheel and hub were powder coated, but the flange was not.  So that has me asking why?  Why would you leave it the stock flat black when everything else is a nice shiny black powder coat?  I know Honda changed the height of the flanges on different models to run wider rear tires so I wonder if the flange is not the correct one.  I am fairly certain the front sprocket is the stock one. 

My measurement is 1 3/8" or 35mm.






Gap at the front sprocket.



Would it be possible for someone to measure their hub flange and let me know the measurement they get?  According to the fiche the same hub flange was used on 1979-1982 CB750K's.  Or if you have any other suggestions on what to check I would be greatly appreciative.

[Harsh]

From everything I can tell the front sprocket is the stock part.

I am telling you Cal, the WTF moments with this bike haven't stopped since it rolled into my garage.

[Harsh]

I don't wonder that at all.

What should have been a max of a week job to get the electrical and brakes in working order has now turned into a month of this thing occupying vital space in my garage.  The safety related issues that I have discovered are staggering.

[jgger]

Harsh, with all the parts related to the swing arm and rear axle my thought at this point would be, is it the correct swing arm? Or is it, or the frame tweeked?

[Jerry Rxman Griffin aka MuthaF'er]

Not sure if this will help a DOHC or not but when I installed a later 78 K engine with the 10mm offset DOUBLE row output bearing in my 75 frame I had to deal with the 10mm offset all the way back. This involved a later offset swing arm and a later offset rear sprocket carrier and a different front sprocket. 

[Harsh]

Based on pics of correct swingarms it looks to be the correct one.  I haven't taken detailed measurements, but the frame does not appear to be tweaked.

I have read a lot about the offset on the earlier bikes.  Cycle X actually has a nice little write up on it.  They say that the 77-78 carrier has a height of 36mm.  My measurement with the ruler could easily be off 1mm.  They also say that the 69-76 carrier has a height of 26mm.  Unfortunately, they never state what year range I am dealing with should be.  Hell for all I know the hub could be from a different bike and the carrier is correct.

[Jerry Rxman Griffin aka MuthaF'er]

Yep, that's the 10mm offset to match the front.

You may need to find a DOHC4 site for some measurements of the carrier. Maybe you can get lucky here.

[Harsh]

I have a post in the DOHC forum, but so far no one knows anything.

[Harsh]

So in my quest to figure out is I have the correct length spacers I started checking what other bikes used the same spacers.  Well a 78K uses the same spacers as the bike I am working on. I found a post here where madmtnmotors measured the spacers from a 78K.  What he measured is the same as to what I measured.

I have also been thinking about the bearings. I wonder if the floating bearing on the brake side isn't set in enough. It is flush with the hub, but before I replaced them it was inset just a bit. The center spacer between the hub bearings is just touching each bearing like it is supposed to be though. The drive side hub bearing is set all the way to the seat. The brake panel has a little lip on it. I haven't measured it, but I am willing to bet it is real close to 1/8". If I were to set the brake side bearing in so the lip on the brake panel fit into the recess that would take up the 1/8" I am off.

Although, if I were to set the brake side bearing a little deeper I would then have to move the drive side bearing out to accommodate the center spacer. That would affect the stepped spacer. Right now the stepped spacer just barely makes contact with the bearing. So in the end I don't really see moving the bearings accomplishing anything.

Right in the middle there is what appears to be a pressed in spacer. I will measure when I get home today, but it appears to be about 1/8".

[Harsh]

Successfully backed out the drive side bearing which allowed me to set the brake side bearing a touch deeper (about 1/16").  The pressed spacer in the brake panel just ever so slightly makes contact with the bearing now.  Re-set the drive side bearing and re-assembled everything.  The sprockets now appear to be aligned.

[RAFster122s]

Crazy ride you are on... buying a bike on ebay is as much peril as one off of CL, difference is you usually get to look at and inspect the CL bike before handing the money over.
David

[Harsh]

The guy that bought this bike had no clue what he was doing, much less what to look for.  This list will be shorter than what I have found in reality because I am old and forget things.

Wiring:  Hack job.  Looks like an attempted minimal wiring job.  Zero fuses, house wiring used, a single power line split into three feeds.  All frame ground points covered in powder coat.
Never installed CCT bolt.  However, he said he heard the engine run.  That means the valve lash has to be done.  Missing an engine bolt that mates the case halves together.  Missing spacer for engine mounting.
End caps on swingarm not installed, zerk fitting not installed on swingarm, front brake caliper seized, gauge cluster cracked all to hell and covered in clear silicone to seal them, incorrect and mismatched chain adjusters and both had stripped threads so the bolts basically fell out, wrong rear axel, missing brake side spacer, stepped spacer not installed, bearings looked like they were beat on, missing bearing retainer, threads on the hub all sorts of goobered up, no wheel dampers, missing tach cable.  The passenger peg brackets were hacked off.  Unfortunately, they served as mounts for the exhaust, rear brake return spring, and rear brake adjustment/stop.

[Bodi]

"Successfully backed out the drive side bearing which allowed me to set the brake side bearing a touch deeper (about 1/16").  The pressed spacer in the brake panel just ever so slightly makes contact with the bearing now.  Re-set the drive side bearing and re-assembled everything.  The sprockets now appear to be aligned."
Well... that sounds fscking scary. The stack of parts on the axle must be 100% referenced to the retained hub bearing. No part should "ever so slightly" contact its neighbor, either it fits against it as tight as the axle nut pushes or it doesn't touch.
I admit I don't understand what you've done but the retainer must be tight on the fully seated bearing, and the axle nut must tighten on a solid stack of metal sleeves - bearing races, spacers, etc.

[Harsh]

With the brake side bearing too far out and not on its seat the pressed spacer in the brake panel (see last pic) was originally making contact with the bearing as you would expect.  However, with the bearing too far out that pushed the brake panel a bit too far out as well which caused the entire assembly to push to far to the drive side.  With the bearing on its seat the brake panel and bearing make just the right amount of contact allowing the brake panel to sit where it is supposed to.  Once that spec was achieved, I reset the drive side bearing to make contact with the distance collar and tightened down the bearing retainer.  With the axle nut torqued down a solid stack is achieved and everything lines up.

I originally set the bearings like I have done with the SOHC mantra.  Set the drive side bearing against its seat and secure it with the retainer.  Drop in the distance collar from the right side and set the brake side bearing.  For some reason which I do not fully understand this wheel did not like that.  Even the manual says the set the brake side bearing first, drop in the distance collar form the left, and then set the drive side bearing securing it with the bearing retainer.  Had I followed the manual originally this more than likely would never have even been an issue.  It worked, things are aligned, and the wheel spins smoothly.  I don't know what else to tell yah.