Topic: '78 CB750k conversion to cafe racer (yes, more issues)

[iron_worker]

I'd let it cure completely (24hr), scuff it up, and apply another coat if needed.

IW

[deafcaferacer]

Thanks IW, that's now the plan.

Well, with all the oil out of the engine, I decided to replace the oil filter as well and went with a Fram CH6009 which should be okay for a '73 cb750 engine? At least as far as I can tell, reading from the archives.

[deafcaferacer]

If you are still using the 78 rear sprocket carrier then your chain line is also 10mm out , the K8's had a 10mm wider sprocket carrier on the rear and 10mm wider out put shaft from the engine, if you have a 73 engine and a K8 rear end then you have a problem with alignment........

The engine is a '73 and the rear sprocket carrier and hub is also a '73, and is on a harley 16" rim. Cleared this up after taking a closer look and talking to the PO. Also while taking off the front sprocket, I noticed it has around a 10mm play, and I recall reading that earlier models had this play in the front sprocket.

[Stev-o]

Did you use the high heat JBW?

[deafcaferacer]

Did you use the high heat JBW?

 No I didn't, I used the original formula cold weld, but it's supposed to hold up to 550 degrees.. (per the product description)? As far as I can tell, high heat holds up under continuous exposure to 400 degrees, and intermittent to 550..  Did I royally screw things up?

[Elan]

I think you will be fine. that area probably isnt more than 275deg. Ive used regular jb on an exhaust hole thats still holding.

[deafcaferacer]

I think you will be fine. that area probably isnt more than 275deg. Ive used regular jb on an exhaust hole thats still holding.

Thanks Elan, good to know.

Well with the bike out of commission, I've taken the chance to order a bunch of stuff, including the missing side covers. I also ordered a new 530 chain on the premise that the chain I have is structurally compromised because it got slapped around hard enough to open up a crack. Better safe than sorry, I'd think.

[deafcaferacer]

Ordered '78 style sidecovers from Frankenstuff.. looking forward to getting them!

EDIT: as soon as I posted this and went outside, there was a package from FS for me with beautiful side covers. I tell ya, that guy is psychic.

[Jayhawk]

I have a set of his side covers that are in the queue for paint & installation.  Outstanding quality; the man does good work.

[deafcaferacer]

Absolutely, no question.

Also, the new 17T front sprocket arrived today with the new chain. I put everything on, but in the excitement forgot that the link supplied with the chain is a rivet style link, and I had ordered a clip on link which is being shipped separately. Will have to wait for that before closing everything up. This is a RK RX-ring 530XSOZ1 racing chain that I put on. I made sure to get a lubricant that was O-ring friendly.

In the meantime, when I put on the outer nut on the final drive shaft, I lightly tapped the tabs of the washer that grips the outer nut into place, and when I did that, I noticed one of the tabs developed a scored wrinkle.. is this okay? Or should I replace this washer?  Only three of those tabs fit in place, the others were not aligned. If you blow up the last picture, the shiny line on the tab below and to the left of the sun symbol is the wrinkle itself.

[CB_Jeff]

Looks good. What is the final config.? 17 up front and 48 rear? JT Sprockets?  And on the chain, how many links? I have a '77 750 k and the 630 needs to go.

[deafcaferacer]

Yes, 17/48 is the final configuration, and yes, the 17t is a JT sprocket which was recommended to me, and it is a high quality product. I think the final link count was 102, but I'm sure every bike is different.

I feel that getting rid of the 630 is always a good call. It is way too bulky, and today's 530 has much more tensile strength and is of  superior design anyway.

[CB_Jeff]

One you get it back on the road I would be interested to see if you note any changes as well as your thoughts on the gearing.

[deafcaferacer]

One you get it back on the road I would be interested to see if you note any changes as well as your thoughts on the gearing.

I definitely will. I am keeping the 18T in case the 17T turns out not to be a good fit.

[deafcaferacer]

Clip-style chain link arrived today and I put it on, but not without plenty of cussing which the neighborhood kids overheard, unfortunately. It was hard to compress the o-rings to the point where I could slide on the clip.

So she is almost back to normal except for the transmission shift cover (I am waiting for a new gasket to arrive).

The sidecovers FS sent me are very good, easy to work with in terms of cutting and sanding. It probably will offend some of the purists here but I cut off the airbox extensions for a better flow look, painted a 7 on, and slapped them on.

I sent off the muffler, chain guard, and front fender to be sandblasted. They all had extensive rust and this gives me a good excuse to have more stuff de-chromed, for that industrial machine look.

[Elan]

The clip must face a certain way, too. Pretty sure its the open end facing back.

how are you going to coat the muffler afterwards?


must be nice to be back on the road!

[deafcaferacer]

Yes, the open end of the clip faces backwards.

Not quite on the road yet and apparently not for another week.. the guy doing the sandblasting is apparently backed up. I don't dare run the engine without the muffler for fear of damaging the valves.

Question: for the transmission gear cover gasket, should I appeal gasket sealant? Or should it go on bare?

[Stev-o]

No sealant is necessary or recommended. Be sure to fully clean both surfaces...

[deafcaferacer]

No sealant is necessary or recommended. Be sure to fully clean both surfaces...

Thanks, what is the best way to clean them?

[Stev-o]

No sealant is necessary or recommended. Be sure to fully clean both surfaces...

Thanks, what is the best way to clean them?

I use a sharp paint scraper but a putty knife will work too. Surface should be smooth to the touch all the way around with no gasket or sealer residue to ensure a good seal.

[deafcaferacer]

Thanks Steve-o.. I did that.

New gasket arrived today, put it in and put tranny shift case back on and found to my horror that one of the screws just wouldn't tighten.. apparently the interior thread had been completely stripped. But very fortunately, it was the one screw that came out the back end (unless it was not supposed to?) so I went to the hardware store and found the exact same screw but 1/4" longer, got a split washer and nut and put that on and carefully tightened it so as not to squeeze the gasket too hard and create an imbalance in the seal.

In the pic it is the hole right above the shift hub.

[deafcaferacer]

Ok.. frustrated here. What on this dipstick constitutes "full"?

Looking through the manual I only saw a brief discription- a "lower line" and "upper line" and I can't see it on this dipstick which comes off a '73 oil tank. Any clue??

[SOHC4 Cafe Racer Fan]

The top end of the hexed xxxxxx portion.

[deafcaferacer]

Thanks.. a lot of beginners questions, I know.

At the risk of cluttering up this thread, I have to bring this up. When putting everything back together, putting the gas tank back on and plugging the fuel tube back on, I noticed that the tube was nearly folding over itself and that it was contacting the cylinder case. Should it even do that? I would imagine that the tube should curve naturally to aid with fuel flow, but it doesn't seem to be doing that here. I could make it shorter so as to promote a more gentle curve?

[Stev-o]

Looks too long