1979 CB750L. My first cafe/brat project. Denver Area

V10Pilot

Member
I picked up this '79 Honda CB750L for $200 in non running condition. I don't have an exact plan just yet but I am going for a cafe/brat setup for sure. I want to be able to get a passenger on the back from time to time so I'm probably leaning towards brat at this point. I am by no means a professional builder/fabricator/mechanic but I'm not completely new to basic mechanical work. I've done motor and suspension work on my 2000 Viper and rebuilt a 2001 Kawasaki ZR-7S back to showroom condition. I'm learning as I go but reading other pages shows me I'm in good company and you guys and gals have a tremendous collective knowledge here.

A few quick points I can think of while I'm writing this first post:

-I bought a set of spoke hubs because I'm not a fan of the Comstar wheels
-The tank is pretty bad but I'm going to try and save it. In the video link you'll see my Fiji bottle tank hanging off the left side.
-The carbs seem to have come from a CB750F. They have VB42B stamped on the side and all the docs I've seen say I should
have VB42A or VB42C. I don't know if there are major differences between A,B, and C carbs or if they just came from the
factory with different jets and needles. I'm not sure if running these carbs will make much difference with the (presumed) stock
motor.
-I'd like to do a full engine tear down and rebuild.
-The electrical and charging system works great at this point but I may upgrade to electronic ignition before I rebuild the bike. (possibly even go with an M-Unit but I'll decide that later)

Is there anything I should measure or check that is easier BEFORE taking the bike apart for the build?

I cleaned and replaced soft parts on the carbs and it seems to be running great for a bike that hasn't been on the road in 10+ years. I bought it from a guy that used to ride it when he lived in Indiana. He brought it with him here to Denver and that's where the bike will live now. I only turned the pilots out two turns to start and it seems to run great. I am however NOT an expert when it comes to carbs so I'll rely on as many sources as I can to figure out the correct setup later.

Link to a video of it running after the carb cleaning and rebuild.
https://youtu.be/347tfYIeaXk
 

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V10Pilot

Member
Quick link to a few of my first posts on here.

New member in Denver, CO 1979 CB750K
http://www.dotheton.com/forum/index.php?topic=74981


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farmer92

Member
Why would you pull the motor apart if it was running?
Was it running badly?
Seals leaking?
Bearing finished?
 

V10Pilot

Member
Seals and gaskets leaking, compressions was 125 across all cylinders.


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V10Pilot

Member
Head is off and time to clean and lap the valves. There is so much crap in the seats it’s no wonder the best I was getting was 125psi. The tensioners still have a little flex but may as well replace the 40 year old plastic while I’m in there. Are you Honda guys using factory gaskets or going with a modern brand during reassembly?


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Maritime

Active Member
OEM for head and base, aftermarket for all the rest is usually fine. That's the rule on liquid cooled anyway like my GL1000. I paid the price for Honda Head gaskets and bought a full gasket kit to get all the o-rings and valve cover gaskets and seals needed.
 

V10Pilot

Member
Maritime said:
OEM for head and base, aftermarket for all the rest is usually fine. That's the rule on liquid cooled anyway like my GL1000. I paid the price for Honda Head gaskets and bought a full gasket kit to get all the o-rings and valve cover gaskets and seals needed.
Thanks for the input.


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V10Pilot

Member
Engine cleaned, soft parts replaced, tolerances checked, primed and painted. About to make the case whole again. I’m tired of seeing factory silver or black motors so I went with Cast Iron paint. I think I looks pretty damn nice.


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pidjones

Active Member
Careful with the valve lapping. At least on the GL1000, the valves have Stellite faces that are very thin. If there is pitting, best to replace (for the GL1000, they were just $10-15 each). Seats could be ground and lapped (with old valves) however. I love going to other colors on the cases if not a resto. I did POR15 MG Maroon on mine.
 

V10Pilot

Member
pidjones said:
Careful with the valve lapping. At least on the GL1000, the valves have Stellite faces that are very thin. If there is pitting, best to replace (for the GL1000, they were just $10-15 each). Seats could be ground and lapped (with old valves) however. I love going to other colors on the cases if not a resto. I did POR15 MG Maroon on mine.
That motor looks great. More than a 10 min polish job too I’m gonna say! Thanks for the advice on the Stellite. I’m going to have to find out whether or not my valves have the coating.


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cxman

Active Member
make sure that you have locktited and torqued the hell out of those prone to work loose and make the motor sound like a rod is knocking

starter clutch bolts
 

V10Pilot

Member
cxman said:
make sure that you have locktited and torqued the hell out of those prone to work loose and make the motor sound like a rod is knocking

starter clutch bolts
I plan on it. I still need to rebuild the starter clutch. It made a horrible sound when I would engage the starter but sounded fine after it was running.


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cxman

Active Member
make sure you put in oem honda starter clutch springs

use the real deal i have tried some aftermarket and ebay kits and they fail early
 

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