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90’s CB750 engine rebuild

amayhew

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Hello, I currently have a 92 CB750 Nighthawk . Needs rings. Looking for anyone who’s done an engine rebuild on this model to give me some advice.
 
That can easily be the valves rather than the rings. Could be a leaking head gasket too if the numbers are lower than 120. And be very quick to assume the test is flawed, bike testing using car testing tools is fraught with errors all over the place. I always test way more than once to be sure. The test can have issues using the bike battery as well, use a car one and test MUST be done holding the throttle wide open and all plugs out to be valid too. The test is a waste of time if using a tester that simply pushes against the plug hole.

If your skills are not way up there you will have hands full simply doing the head on one of those, hydraulic tappets can make all kinds of trouble if you don't know them.

Do a google search on the OEM service manual, it's out there and free if you find it.
 
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If it were a leaking head gasket wouldn’t the outside of the engine show signs of leaking near the head? I’m pretty skilled on rebuild, I’ve rebuilt the entire bike. Just never have done engine work on it. I have a service manual for the bike, just a little hard troubleshooting it without taking it completely apart...
So I’m guessing I probably did the test wrong. But even if I did, what makes me think it’s rings is that the two left pipes is that 1 and 2 are normal temp and 3 and 4 are not as hot as 1 and 2.
 
You can blow cylinder to cylinder at the gasket and not leak a drop.

Last sentence could be wrong, state of tune could easily do that by itself. Rings cannot fail or be worn without burning oil to get smoke. No smoke = not rings.

Honda rings are pretty good nowadays, more likely to have valve issues than rings at that mileage.

I'd be doing that compression test over.............
 
Thanks, didn’t know that. When I first start the bike up there’s a little bit of smoke but it useually goes away. Not sure if that just what the engine does or it it’s actually burning oil. If valves are more likely to go at that mileage how should I go about fixing that.
 
Compression test again to verify it.

Then head comes off to do a valve job. Engine likely has to pull from frame to do it.

If rings were a problem should have been eating oil too to have to add more. A bit of smoke at start may be oil or even choke when it's on until engine warms up.
 
Hey, hope you guys are still here, I have a similar issue. Same make, model, and year. Bluish-whute smoke, ornery engine. Compression test at a Honda powersports reported 40wet/180dry. Tips or suggestions? How difficult or expensive can I expect an engine rebuild to be?
 
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