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hondacb750f

finally

the video to show my progress. 1981 cb750f super sport.

https://www.youtube.com/watch?v=JwYXYSGgZ88

hondacb750f

Re: finally

I was just going thru some of the other threads here, and I noticed in one of hellbillys he has the same issues I had,

On your ride that you put the red glass pax on, you mentioned something about one and four not firing.

I just cleaned the carbs a week or two a go and have been running 87 gas,. So here goes, After letting the bike warm up, I heat tempted the exhaust and glad I did. I found out number one and four were the coolest temps. I pulled the plugs and they were fouled, I then sand papered them. witch helped number one. I had changed the number 3 plug with number 4, and this helped a lil bit. but after about 5 mins the number four exhaust was still cold enough to hold in my hand with out fear.

I will be getting new plugs on Monday but any other ideas? standing behind the bike the exhaust that is feed by 3 and 4 is blowing cold air, even thou number three has the hottest pipe coming from the jugs

and the exhaust that is feed by 1 and 2 is very warm.

carbs are vacuum synced, (trying to do the air is how I found this) the spark color on one bounces between white and purple, and the color on four is solid white.
Should I look at the timing or am I over thinking this,?

and again thankyou you every one

TOOLS1

Re: finally

Administrator

I would start with the coil since it fires one, and four at the same time.
TOOLS

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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
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hondacb750f

Re: finally

fair enough I will get my buddies muilty meter and go from there, thank you

hondacb750f

Re: finally

Merry Christmas every one. and a plenty full new year a head.

I am still starring down the barrel at this problem. I have new plugs, running wet and rich.

I have new wires.

The coils omed out good.

nice blue spark.

the fsm has suggestions for two or more not firing but not if only one is not firing.

I did put new crush gaskets on. however number four was difficult. should I try another set?

1983 cb750 number four exhaust running cold. that is my video in the top post, I make make another one if need be.

Thank you every one. for all the advice.

TOOLS1

Re: finally

Administrator

If it is only one cylinder not firing, and it has spark, then it would be either carburation, or an internal mechanical problem. Run a compression check, and clean the carb on that cylinder.
TOOLS

hondacb750f

Re: finally

thank you tools.

I will rent a compression tester next payday. the carbs are good. I did all three synchs.

happy new year.