Can't figure out missfire

[tkos115]

I did swap swap plugs too, no change. I haven't had a chance to pull the head yet or do a leak down test. Hopefully today or tomorrow I'll be able to.

 

[StarTech]

I know this will a pain but have swap the twin carburetor around?

 

[slomo]

Pull the carbs and "Bertsmobile1 boil clean" them. Sounds like either a vacuum leak or dirty carbs.
Valve clearance check would be nice.
Clean the cylinder cooling fins yearly.
Pull the ignition coils and clean slash polish the mounting surfaces. Provides proper ground for coils. Load test your coils.

 

[tkos115]

So I did a leak down test, didn't really drop more than maybe 15%. Didn't really hear any air coming through the intake or exhaust valve. But I decided to pull the head anyway. I found that the exhaust valve guide is worn. But the valve seat and face look perfect. No abnormal wear or pittin, totally clean. I posted the link below of the guide wear. Could that still cause an issue with it?

 

[tkos115]

Here is a picture of the seat

 

[slomo]

That valve guide is shot.

 

[slomo]

Is she drinking oil on the job?

 

[tkos115]

It actually doesn't smoke at all, not even a tiny bit hah. So I did some more digging and found that the intake valve is leaking by the seat. It doesn't always do it but if I push the valve down and release it sometimes it will seal. I tried lapping it in several times and no difference so I'm gonna replace the head. I filled with intake chamber with WD40 and pressurized it. As you can see the bubbles. The valve seat in the head looks like it might be the culprit. There was a black stained area where it looks like compression was blowing by the seat on the inside where it's pressed in. Everywhere else around it was nice and clean.

 

[slomo]

She's a leek-a' ma-ma she's a leek-a'. Steve Lav on YouTube.

 

[sgkent]

what valve guide? All I see is a big hole with a valve stuck in it,