Topic: cb750 cylinder NO 1 puking oil not firing with fresh rebuild arrrgggg

[cbfreaky750]

hi my newly restored cb750 is not firing at cylinder no 1 the compression was normal and it has new valve guides spark plugs but it just does not get hot i can still touch it with my hand 5 minutes later. there is black oil is coming out of the exhaust around the header and splattering all over the engine also the oil gets dirty real fast what could be the problem   

[cbfreaky750]

here is a pic of the oil

[hcritz]

Hey CB...
Is it actually oil or could it be fuel?

[cbfreaky750]

it could be a mix of both but i would say its mostly oil

[Bob Wessner]

I would think that if that much oil (or mix) is getting into the cylinder and to the exhaust, the plug is fouling and that's why it's cold. The lack of fire could be a symptom. I would focus on how all that is leaking in there.

[cbfreaky750]

I dont understand where the oil is or mix is coming from i was thinking a rings could be stuck. The compression of is 150psi though and the valve seals are brand new also the carbuerators are completley rebuilt i did however tighten the air screws becouse of the drag pipes made it lean could it be way too rich??   

[Bob Wessner]

i did however tighten the air screws

By tighten, do you mean fully seated??

[JHansen]

Only a theory, but perhaps a leaky head gasket? Oil getting into the cylinder, fouling plugs, then mixing with unburned gas and leaking out? Are you sure the head was torqued down properly?

[hcritz]

I would make sure that it's not mostly fuel...that could wash down the cylinder and ruin your fresh rebuild on that cyl.
The floats seem to be notorious for sticking! Normally that would run out the overflow...pinched tube???
Have you tried a fresh plug and check for fire on that cyl.?

[cbfreaky750]

Well I must have fully seated the air screw too much i backed it out 3/4 of a turn and now its gets hot enough to burn my spit off hurray the plug is a little oil fouled now but its not too bad i put a set hotter plugs in becouse all the plugs are a little oily it seems to help alot also the head was properly torqued down in sequence. i have a clymer manual with the torques   

[dusterdude]

groovy

[hcritz]

Good Deal!

[Bob Wessner]

Glad to hear it was that simple. Good riding. 

[cbfreaky750]

thanks alot for your quick suggestions im glad its runs after all its been through

[Big Jay]

Were both of the tiny oil jets still in the head when you put the rocker stands on? If not the head will fill with oil and go down a valve stem, new seal or not.