1977 CB750 A Engine trouble.

[stallion]

Hello Honda CB Experts, I need your help. I just bought a 1977 CB750A. The bike runs great for the first 15min of riding it then it sounds like it is choking out, I loose throttle and it slowly dies.. I try to start it back up and I get white smoke from the carbs and the engine seems overly hot.. for back ground on the bike It sat for about a year but ran and had fuel preservitive type stuff in the fuel tank when i bought it. I decided it was a good idea to take carbs apart and clean them and check there condition. It looked  brand new when i took them apart and basically re-cleaned them and put them back. I also added an inline fuel filter under the petcock. I checked the timing and I can see that the points were brand new, and the timing "F" was right on the money. I changed all the spark plugs and they all spark but after one time of running them they developed black /burnt coal look. I checked compression and they all got about 60psi dry and 90psi wet. I have the pilots turned to 1 1/2 turns and the vaccum plugs closed. I also find my battery dies very quickly. any thoughts?

[shinyribs]

Those are very low compression numbers. Anything under 100psi is usually considered a non-runner. Between your compression numbers and your black plugs,it sounds like the piston rings are shot. Excessively worn rings such as those could possibly allow alot of the heat from the combustion process to enter the crankcase which would explain more than usual heat in the engine.

I hate to be the bearer of bad news.Sorry

[TOOLS1]

I have to Ditto Shiny. But on the plus side, it would be a perfect time to install an 836cc kit.
TOOLS

[stallion]

Thanks allot.. I suspected the same but didn't really want to believe it.. Lol. I am thinking of just replacing rings, lapping valves and honing  cylinders i don't know know if the cost benefit ratio pans out on the 836? .. thoughts? Is this something i could do myself with at home type tools.. I'll def google it. I am also having a heck of a time taking the three screws off from the side outside engine cover or alternator/magnito cover. Is it some sort of special Phillips head

On Oct 7, 2012 10:05 PM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

I have to Ditto Shiny. But on the plus side, it would be a perfect time to install an 836cc kit.
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 2
1977 CB 750-K
1981 CB 750
1995 KZ 1000 P-14
1981 KZ 750 LTD X 2
1973 CB 350
1979 CM 185 Twinstar
1987 Honda TLR 200
1982 Honda XL 80
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[Lucky 1]

When you checked the compression was the throttle wide open?

You can only tell the condition of the points with a dwell meter.
They might look ok but you cannot see electrons,you must measure them.

[Lucky 1]

You cannot lap valves that have worn out guides.

[Lucky 1]

Or the piston rings are glued to the ring lands.

[Lucky 1]

You can easily remove the screws with the proper tool.
If you bugger up the screws with the wrong size phillips bit then you will have hell to pay.

The Honda engine uses #2 and #3 phillips head screws.

Get an impact driver and use it correctly. You will not strip a screw.