Topic: 1977 CB750K Cafe Racer Project - $$ Can't Take It With You

[algophobe]

It would appear that the PO by mounting the sprocket backwards, created the slop issue and the need for a shim.

Actually, I think the PO found that the sprocket was loose without the shim washer which seems to be normal   Then the PO added the washer to tighten things up.  By reversing the sprocket and adding the shim washer the centerline of the sprocket remains unchanged.  It kind of all makes sense but it puzzles me why Honda would have designed the sprocket to float on the countershaft to begin with?  Bit of a head scratcher!

Not sure why they made it float but it makes for a very forgiving system that is very secure and easy to switch sprockets on. Rather than a big nut on the end with a safety tab.

a build/post worth salivating over in more ways than one. newbies like me can only hope the next build can come close to this. I had the same questions regarding the slight play in final drive. it wasn't clear what the responses have said, but... so is the "slop" intended to be there or should I worry in my own build? (stock sprockets/chain size btw)

[Godffery]

 Looking good man!

[BRAD CHIEDUCH]

+1 motor looks great! 

I love vapor blasting, did it on my last Kawasaki engine project.
But I didnt buff it, the finish came back beautiful.

Was buffing it with scotchbrite necessary?

Thanks Stev-O.  Is the Scotchbrite necessary?  Not really, but it does give the motor a nice satin finish which is visually different than what vapor blasting alone does.  The nice thing about this approach is that if I get a scratch or some pitting from rocks etc. I can simply buff it up again with a Scotchbrite pad and it's good as new. 

[BRAD CHIEDUCH]

It would appear that the PO by mounting the sprocket backwards, created the slop issue and the need for a shim.

Actually, I think the PO found that the sprocket was loose without the shim washer which seems to be normal   Then the PO added the washer to tighten things up.  By reversing the sprocket and adding the shim washer the centerline of the sprocket remains unchanged.  It kind of all makes sense but it puzzles me why Honda would have designed the sprocket to float on the countershaft to begin with?  Bit of a head scratcher!

Not sure why they made it float but it makes for a very forgiving system that is very secure and easy to switch sprockets on. Rather than a big nut on the end with a safety tab.

a build/post worth salivating over in more ways than one. newbies like me can only hope the next build can come close to this. I had the same questions regarding the slight play in final drive. it wasn't clear what the responses have said, but... so is the "slop" intended to be there or should I worry in my own build? (stock sprockets/chain size btw)

I did look at the drive sprocket on another motor at a wrecker in my area and discovered the same sprocket axial float on the splined shaft so I am rather confident that Honda designed it this way.  If you asked me why I could not answer with certainty.  Perhaps to compensate for some chain misalignment which might occur with swingarm flex but I am only speculating.  The final drive sprocket on earlier bikes had a retaining ring/clip that fit in a groove on the spline shaft and bolted to the sprocket to hold it in place versus a center bolt and washer on the countershaft as was provided on later bikes and I don't think had the same amount of free play.

A lot of guys have done the 630 to 530 chain conversion without issues so as it stands my sprocket no longer floats on the countershaft - maybe Hondaman will chime in and offer his comments on the subject.

[BRAD CHIEDUCH]

After some further thought, perhaps an explanation as to why the final drive sprocket was designed to float axially on the spline shaft was that if the sprocket is held tight in place (no float) with a center bolt then possibly some of the torque created while braking could be transmitted to the bolt causing it to loosen over time.  If the sprocket floats then there is really no load on the bolt unless of course if the sprockets aren't aligned properly.

After this revelation, I'm considering a drilled bolt and safety wire to keep it from loosening - just in case and it would be easy to do.  Call me paranoid.

[slikwilli420]

You are way over thinking this. Honda designed it to float, let it float. If you are really worried, then safety wire the two small bolts together, as required by many racing organizations. That will keep it from coming off and allow it to float properly. I would also suggest that if you are going to a 530 chain, might as well just go to 520.

[BRAD CHIEDUCH]

You are way over thinking this. Honda designed it to float, let it float. If you are really worried, then safety wire the two small bolts together, as required by many racing organizations. That will keep it from coming off and allow it to float properly. I would also suggest that if you are going to a 530 chain, might as well just go to 520.

Maybe I ponder things at length sometimes but so far it's kept me alive and out of jail.  That aside, the '77 CB750 (and other later bikes) only have a single bolt and washer holding the sprocket on - the splined retaining plate along with 2 bolts was on earlier models.  I decided to go with a 530 chain and sprockets because they seem to be more available than the 520's.  Further, this is not a race bike so the 530 setup was an easy compromise and still a significant improvement over the 630 chain.

The original 630 sprocket was 10.7 mm thick and the 530 sprocket is 12.7 mm thick.  This difference in thickness does not allow the sprocket to float.  So this prompted the question, why did Honda design the sprocket to float and what are the implications of having it fixed versus floating to which I think I offered a reasonable explanation and solution earlier.

I'm sure there's other ways of solving the issue (eg. custom/thinner sprockets) but I've already been accused of giving this too much thought!   

[Ivan X]

Good job so far man. The engine is so clean and shiny  . btw what rear shocks are those?

[BRAD CHIEDUCH]

Good job so far man. The engine is so clean and shiny  . btw what rear shocks are those?

Thanks Ivan.  No rear shocks as of yet - I just have a piece of bar stock in place to hold the swingarm up.  Once I get the wheels on I will need to check the length of shocks that I need.  The plan is to install a set of Fox Podium shocks.

[BRAD CHIEDUCH]

After some further thought, perhaps an explanation as to why the final drive sprocket was designed to float axially on the spline shaft was that if the sprocket is held tight in place (no float) with a center bolt then possibly some of the torque created while braking could be transmitted to the bolt causing it to loosen over time.  If the sprocket floats then there is really no load on the bolt unless of course if the sprockets aren't aligned properly.

After this revelation, I'm considering a drilled bolt and safety wire to keep it from loosening - just in case and it would be easy to do.  Call me paranoid.

So here's my final solution - should hold things in place.

[BRAD CHIEDUCH]

I was eye-balling this beauty recently and it really made me consider mounting a fairing.  It's a bit of a deviation from what I had originally visioned for this build.  I always think that less is better but the look of the BMW sure is cool!  Not sure yet.

[BRAD CHIEDUCH]

So I'm about to install the rings on my new pistons and have a question.  With reference to the Wiseco illustration, the oil ring expander gap is located 90 degrees from the wrist pin center line.  I was always under the impression that it was a bad idea to have any ring gap 90 degrees from the wrist pin center line.  I'm inclined to believe the Wiseco instructions (it is their product) or is this a bad idea?   

[SOHC4 Cafe Racer Fan]

That's a good-looking RNineT Racer.  I wish they made it with adjustable forks and the better brakes.

[JoeCooley]

After some further thought, perhaps an explanation as to why the final drive sprocket was designed to float axially on the spline shaft was that if the sprocket is held tight in place (no float) with a center bolt then possibly some of the torque created while braking could be transmitted to the bolt causing it to loosen over time.  If the sprocket floats then there is really no load on the bolt unless of course if the sprockets aren't aligned properly.

After this revelation, I'm considering a drilled bolt and safety wire to keep it from loosening - just in case and it would be easy to do.  Call me paranoid.

So here's my final solution - should hold things in place.

My front sprocket is done the same way. The p.o. did it this way and I haven't changed it. Seems to work fine...

[BRAD CHIEDUCH]

Installed the gearshift drum and stopper, springs, etc.  It took a bit of fiddling around and thankfully I had some pictures when I first tore it apart which made reassembly easier.  I did encounter a problem when I first installed the countershaft bearing retainer.  The bearing outer race was a slip fit in the housing which didn't make any sense.  Long story short, I got my hands on a new retainer which measured approximately 0.0005" tighter than my original.  In addition, the NTN bearing I had used was approximately 0.0003" smaller on the outer race in comparison to NSK, SKF, and FAG bearings.  So I believe it was combined tolerances on the housing and bearing that made it fit loose in the bore.  I installed the new retainer with an SKF bearing which gave me a reasonable interference fit and the problem was solved.

[JoeCooley]

Nice! Keep up the good work. 🤘😎

[BRAD CHIEDUCH]

I took a little break from the engine assembly and decided to mount the oil tank in the frame.  The tank is from the boys at Cognito Moto – always happy to give them a plug because there products and service are fantastic!  I went with a rear mount tank because the frame cross-bracing I added up front would have made mounting difficult.  I wanted to mount the tank somewhat differently (cleaner) and get away from the standard rubber clamps that come provided with the tank which normally secure around the frame.  My solution was to weld some tabs to the tank and corresponding mounting bungs on the frame.  I installed rubber vibration isolators in the tabs which are automotive windshield motor mounts that you can get at any parts supply store.  My big V-twin has a similar mounting arrangement which holds the oil tank and battery together and has proven to be solid.  I had to slightly trim the upper frame cross-member to provide access for welding the upper mounting bungs.  Once I get the pan in under the seat and the inner rear fender installed, the mounts will be totally hidden.  I’m pretty happy with the way it turned out!
I also got the front end mounted and it’s slowly coming together.  Next up is mounting the rear wheel and I’ll finally have a rolling chassis.  Yayyy!

[Jnel]

I took a little break from the engine assembly and decided to mount the oil tank in the frame.  The tank is from the boys at Cognito Moto – always happy to give them a plug because there products and service are fantastic!  I went with a rear mount tank because the frame cross-bracing I added up front would have made mounting difficult.  I wanted to mount the tank somewhat differently (cleaner) and get away from the standard rubber clamps that come provided with the tank which normally secure around the frame.  My solution was to weld some tabs to the tank and corresponding mounting bungs on the frame.  I installed rubber vibration isolators in the tabs which are automotive windshield motor mounts that you can get at any parts supply store.  My big V-twin has a similar mounting arrangement which holds the oil tank and battery together and has proven to be solid.  I had to slightly trim the upper frame cross-member to provide access for welding the upper mounting bungs.  Once I get the pan in under the seat and the inner rear fender installed, the mounts will be totally hidden.  I’m pretty happy with the way it turned out!
I also got the front end mounted and it’s slowly coming together.  Next up is mounting the rear wheel and I’ll finally have a rolling chassis.  Yayyy!

Man... that looks great!  Very impressive.   Like the weld work, but the imagination and creativity and exacution is incredible.   Love the oil tank and the mounting system. 

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[BRAD CHIEDUCH]

Thanks for the kind words Jnel but truth be told I vaguely recall seeing another forum member using a similar upper mount setup on another project - so I can't take all the credit.  For the record, there is nothing wrong with the original mounts that the tank comes with, and a lot of members have used the Cognito Moto tanks and they look and function great!  However, I don't think there's anything wrong with taking a good thing and trying to improve on it.  I think that's why we enjoy putting our stamp on these old bikes to begin with. 

[BRAD CHIEDUCH]

Got the rear wheel on and it's now a roller.  Next, I need to check neck angle and determine length of rear shocks.  I'm starting to see the final shape of this bike in my mind - so far so good!

[PGF550F]

Those are some good robust looking frame gussets you have made and tacked in there! clearly some professional level skills, this bike is going to be awesome once you get it done.

[Jnel]

Thanks for the kind words Jnel but truth be told I vaguely recall seeing another forum member using a similar upper mount setup on another project - so I can't take all the credit.  For the record, there is nothing wrong with the original mounts that the tank comes with, and a lot of members have used the Cognito Moto tanks and they look and function great!  However, I don't think there's anything wrong with taking a good thing and trying to improve on it.  I think that's why we enjoy putting our stamp on these old bikes to begin with.

I'm very impressed with level of workmanship.  Professional, clean, and fictional.  Nice job.  Can't wait for the finished product.

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[BRAD CHIEDUCH]

Those are some good robust looking frame gussets you have made and tacked in there! clearly some professional level skills, this bike is going to be awesome once you get it done.

Thanks PG, I wouldn't consider myself a professional at anything but each day I just try get a little bit better.  By the time I'm 60 I'll be a bloody genius!!

[BRAD CHIEDUCH]

Thanks for the kind words Jnel but truth be told I vaguely recall seeing another forum member using a similar upper mount setup on another project - so I can't take all the credit.  For the record, there is nothing wrong with the original mounts that the tank comes with, and a lot of members have used the Cognito Moto tanks and they look and function great!  However, I don't think there's anything wrong with taking a good thing and trying to improve on it.  I think that's why we enjoy putting our stamp on these old bikes to begin with.

I'm very impressed with level of workmanship.  Professional, clean, and fictional.  Nice job.  Can't wait for the finished product.

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Thanks again Jnel - I can't wait to see it done myself!  Time and money always seems to get things done but I never have enough of either!

[BRAD CHIEDUCH]

I'm back on engine assembly this weekend.  I gapped all the piston rings, installed some Kibblewhite cylinder studs, and made up some piston ring compressors which I clamped in place with some hose clamps.  Next is cylinder and head installation - baby steps!