82 cb750 "cafe" project

[liverpoolphil]

Hi all...... My first post here, I've already spend some hours trawling a load of forums, and kept coming back to this one so thought I'd register and share my build, hopefully getting some good advice and guidance along the way

The bike is a 1982 cb750k (RC01 engine) with £37k on the clock, bought as a winter project and opportunity to develop my motor skills (had bikes all my life, not very experienced mechanically and always wanted to be... Got some great contacts for the specialist stuff). I want to end up with a rideable (Im a fair weather rider) good looking / good moving "keeper"

We collected the bike on Thursday...the guy who came with me is an experienced mechanic. He confirmed the engine wasn't seized and the bike seemed good and straight. What I like about it is, considering its age, how little it's been fettled with. All the fastenings are stock and in good condition, the tank has a pin hole in but apart from that is in good order (after a good service / clean / polish)

A little investigative work has concluded the start motor is finished (I stripped it this morning and it's past repair in my opinion) some further observation shown the spark plugs are good, the engine oil was in reasonable order (although I definitely smelt fuel when I drained it) plugged in a battery and all electrical parts work, which made me happy.

To my first dilema...as I've ordered and replacement starter and my investigations give me confidence the motor will run.... I'm keen to continue the strip down, but all my research tells me I should leave the bike and get it running before going any further

Shall I go fishing for the weekend (wait for parts to arrive) or continue in the shed?

 

[Avidtraveller]

Mostly depends on any known issues, and how far you want to dive into it right away; if the electrical is testing OK, aside from any routine maintenance like checking brakes, there's not much more diagnostic things you can do until you get it running. Did the previous owner include any maintenance records?

 

[liverpoolphil]

Thanks for your response.... No history (although the milage checks out as accurate) I'm willing to go as deep into the engine as I need / have to I've decided to focus on some other things (brakes etc) until I can get it running

 

[Chris in Dorset England]

Hi all...... My first post here, I've already spend some hours trawling a load of forums, and kept coming back to this one so thought I'd register and share my build, hopefully getting some good advice and guidance along the way

The bike is a 1982 cb750k (RC01 engine) with £37k on the clock, bought as a winter project and opportunity to develop my motor skills (had bikes all my life, not very experienced mechanically and always wanted to be... Got some great contacts for the specialist stuff). I want to end up with a rideable (Im a fair weather rider) good looking / good moving "keeper"

We collected the bike on Thursday...the guy who came with me is an experienced mechanic. He confirmed the engine wasn't seized and the bike seemed good and straight. What I like about it is, considering its age, how little it's been fettled with. All the fastenings are stock and in good condition, the tank has a pin hole in but apart from that is in good order (after a good service / clean / polish)

A little investigative work has concluded the start motor is finished (I stripped it this morning and it's past repair in my opinion) some further observation shown the spark plugs are good, the engine oil was in reasonable order (although I definitely smelt fuel when I drained it) plugged in a battery and all electrical parts work, which made me happy.

To my first dilema...as I've ordered and replacement starter and my investigations give me confidence the motor will run.... I'm keen to continue the strip down, but all my research tells me I should leave the bike and get it running before going any further

Shall I go fishing for the weekend (wait for parts to arrive) or continue in the shed?

Hi and welcome to the site.

This is a copy/paste from a post of mine to some one else. Just being lazy
Apart from oil changes/air filters etc. etc check out below.
It's an awkward job but check your valve clearances. Very often they have not been checked for years and will have closed up. It's a known problem, DO NOT set them to the clearances in the manuals, set them between 4-5 thou. You may find they are less than 2 thou. Honda knew about the problem but did nothing about it. The manuals clearances will cause valve burn out. Check your compression pressures first. They should be 170-150 psi. Lower than that check those valve clearances BEFORE ripping the carbs off and/or the cylinder head.
Something else, do not use pod air filters they will give you unlimited problems. The carbs were designed to work with the standard air box, and will not work correctly with pods. it's all to do with internal aerodynamics in the air box. Leave the air box on if I were you with the standard filter.

 

[liverpoolphil]

Valves next on the list..... Massive bonus yesterday after fitting the replacement starter motor, the bike fired right up! Sounded a bit rough, but it's a runner! Now for the complete tear-down

Done a fair bit of research and not come across the issue Chris mentioned about not following the valve specs from the manual so cheers for the heads up

 

[liverpoolphil]

Thought I'd do a bit of an update on this thread. Valve clearance was "OK", couple of them were marginally out of spec but I decided to tear down the top end and treat her to some new piston rings. I've attached some pics of the top end, all looks OK IMHO but I'm not very experienced so if any of you see anything I should be aware of, please do let me know.




In the meantime, I'm polishing aluminium ��

 

[Chris in Dorset England]

Thought I'd do a bit of an update on this thread. Valve clearance was "OK", couple of them were marginally out of spec but I decided to tear down the top end and treat her to some new piston rings. I've attached some pics of the top end, all looks OK IMHO but I'm not very experienced so if any of you see anything I should be aware of, please do let me know.
View attachment 8642
View attachment 8643
View attachment 8644

In the meantime, I'm polishing aluminium ��

As regards the pistons and bores, best thing is to get them checked for ovality and taper A local engine shop should be able to do that for you if you don't have the gear to do that. When you refit the engine to the frame. The books say fit the carbs with the engine in place. Not forgetting to loose fit the airbox 1st. In the frame that is! It's one hell of a fiddle to fit the carbs and line them all up with the airbox, carb intakes and cylinder head. Don't ask I came to the conclusion that on the production line the engine was full assembled with carbs airbox etc then fitted to the frame. There just too much fiddling about for a production line. You might like to try fitting the whole thing in one piece. Should I need to remove the engine in the future, I will attempt the 2nd way. If you try that and succeed let the world know! Fit the carb bank from the left side if the engine is in the frame.

 

[Wez_]

The tear down is somewhat straight forward. Reinstalling the camshaft chains will cause some questions. Valve clearances are major from what I found out here also. Take the advise about running the extra valve clearance serious and do it. As far as pods go, they are really cheap and look great, but your motor will max out around 7K RPM and will also be low on power. I went from pods to air box and I'll never forget how the bike almost jumping out my hands! Aside from that, these bike are extremely reliable.