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Author Topic: '76 CB750 overhaul question  (Read 1510 times)

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Offline SteadyRollin

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'76 CB750 overhaul question
« on: August 21, 2012, 10:13:32 AM »
hi gang,

i'm going to have a couple weeks off soon so i'm planning on overhauling some stuff on my bike. i have to replace the gasket on the valve cover, and i figure while im in there i might as well change the air filter and clean the carbs. i just got the bike and she was sitting for a while before that so she probably needs some other stuff too. i could use some advice on what other tune-up jobs i should tackle while im at it and what order to do them in. also, is silicone gasket maker ok for the valve cover? what other bits should i replace/adjust while i have the valve cover off? im confident i can do the work but im an inexperienced mechanic so im not sure where to start and how to organize the different tasks. thanks!  ;D
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Offline goldarrow

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Re: '76 CB750 overhaul question
« Reply #1 on: August 21, 2012, 10:22:28 AM »
First thing on your to do list is download the manual for your bike and do 3000 miles maintenance, focus on getting it back up and running. Don't worry about gaskets stuff just yet.

Welcome to the form.
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Offline MCRider

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Re: '76 CB750 overhaul question
« Reply #2 on: August 21, 2012, 10:33:46 AM »
Silicone gasket maker is the KISS OF DEATH for a CB750.  Many are the victims. The silicone dries hard, the part that squishes to the inside of the engine, breaks off and travels with the oil to the oil orifices in the head. Once they shut off the oil flow to the cam area, the cam seizes and breaks in half, taking a  lot of engine bits with it.

This I know first hand. Also, since I've been on the forum, at least 5 others have succumbed. There is a shop in Indy that has a broken cam mounted on a board hanging above the parts dept witha warning against silicone.

Use a non-hardening gasket sealer on a paper gasket.  GasgaCinch is a popular brand. But anyhting non-hardening is OK.
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Offline ekpent

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Re: '76 CB750 overhaul question
« Reply #3 on: August 21, 2012, 06:37:30 PM »
You do know that you need to pull the engine to do those repairs you outlined ?? You mention you are an inexperienced mechanic on these. Read up well and make sure you have the tools. Sure the leak is just the valve cover,they stay pretty oil tight and usually a leak is more around the head gasket area a little lower down or round sealing pucks under the cam towers. Final word---Impact Driver and heat gun  ;)
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Offline SteadyRollin

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Re: '76 CB750 overhaul question
« Reply #4 on: August 23, 2012, 12:32:05 PM »
well i got my clymer manual in the mail. just looking it over it seems like there is a lot to do! the bike starts fine and runs (pretty rough but it runs) it stalls out when i try to let it idle even after ive warmed it up. also, the cam chain is rattling like crazy. i tried the adjustment outlined in the manual but its still noisy as hell. i took off the housing for the springloaded tensioner and it looks ok not stuck or anything. there is enough oil in the bike.. the oil is a little dirty but not bad. to be honest im stumped on where to start here. feeling overwhelmed in fact...  :-\
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Offline Tugboat

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Re: '76 CB750 overhaul question
« Reply #5 on: August 23, 2012, 12:50:21 PM »
Start with the 3,000 mile tuneup. Valves, timing, cam chain.. then get your carbs off and clean them well and bench sync them. Sounds like your idle jets are clogged. Regardless, do all of that, and THEN see where you're at. Good luck!
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Offline elbowdeep

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Re: '76 CB750 overhaul question
« Reply #6 on: August 23, 2012, 05:53:49 PM »
old cam chain tensioner springs usually need some "assistance".  I like to put a tad extra pressure on the end of the plunger while setting the locknut.  Made all the difference on my bike - much quieter.  Accomplishes what a new spring would I assume
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Online Stev-o

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Re: '76 CB750 overhaul question
« Reply #7 on: August 23, 2012, 07:07:23 PM »
First off, welcome. Second, doesn't sound like you need an "overhaul".

A 3000 mile tuneup is in order, and probably a carb cleaning.

Did you just get it?
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Offline SteadyRollin

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Re: '76 CB750 overhaul question
« Reply #8 on: August 26, 2012, 10:52:01 AM »
first off, thanks for all the input, guys. i just got the bike a few weeks ago. before that she sat for over a year. as of right now i've got the airbox and carbs off. i got some rebuild kits for the carbs and i figure i might be able to salvage some of the old stuff for spares. as for the valves that looks like a pretty straight-forward job (feeler guages and an offset box wrench are in the mail). although im still a little fuzzy on how to position the engine to make sure the valves are in the right position. i know you have to turn that nut under the points cover clockwise but to which indicator? how can i tell its at the right spot?

also, the guy who owned the bike before me replaced the points with an electronic 'dyna s' ignition. how the hell do you adjust that thing?

MCRider, thanks for the heads up... potentially saved me a bad trip to yikestown. although now it looks like it'll probably be a while before i get to the gaskets.

ekpent, the impact driver was the first new tool i added to my kit when i got the bike and it has already come in mighty handy! im putting 'heat gun' on the list right now  :)
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