4 isn't firing

blackgpz at rochester.rr.com blackgpz at rochester.rr.com
Tue Aug 5 19:03:10 PDT 2008

I think a simple compression test is in order. It would have saved me a lot of diagnosis time when I lost a chunk off the head of an exhaust valve, in #4 cylinder BTW.


---- Dave Daniels <dwaynedaniels at sbcglobal.net> wrote: 
> Good idea! Thanks.
> schnowz <schnowz at localnet.com> wrote:  Sounds right - Easy enough to check. Put a clear piece of tubing on the bowl drain and form a U against the carb and open the drain. Level should be close to the joint IIRC (compare it to No 1)
> ----- Original Message ----- 
> From: Dave Daniels 
> To: schnowz ; gpzlist at micapeak.com 
> Sent: Tuesday, August 05, 2008 8:41 PM
> Subject: Re: 4 isn't firing
> I tried switching the wires between 1 & 4, as well as switching the plugs. When I pulled no. 4 plug, it was wet. Also, I looked down the well and you could see the top of the piston was wet. After switching the wires and plugs, the problem remained at no. 4. So, I'm thinking Dave Beard is probably right in that maybe a piece of grip got in the carb and is holding the float open causing no. 4 carb to flood the cylinder while it's running. By the way, I haven't put a fuel filter on yet. Doh!
> schnowz wrote: 
> Dave
> That would also be the case (2 cylinders not firing) for the wire if it 
> was a bad connection eg green snot at the end of the wires where the copper 
> wire used to be, because the 1 and 4 are in series. The only way it would be 
> one cylinder, would be if it was a bad connection and also shorting to 
> ground somewhere (bad insulation etc). You can also ohm out the leads and 
> caps - the resistance is in the book IIRC. Though this will only test 
> resistance of the wire/caps and won't necessarily tell you if you are 
> getting high voltage leakage on the insulation. Only way to do that is swap 
> the wires with a known good one and the cool header should move with the bad 
> wire.
> If it's doing it only at small throttle openings I would also suspect the 
> pilot circuit - carefully take out the pilot screw after putting a towel 
> over the engine. Make sure you get the o ring out too. Squirt some carb 
> cleaner in there and then follow with compressed air. You can get the screw 
> out by placing a short screwdriver bit in a socket and turn the socket with 
> your fingers (not a rachet - which is too big) Before taking it out screw 
> it in carefully and count the turns to bottom out - when reinstalling - turn 
> it to the same position as before.
> By the way a infrared thermometer fired at the exhaust headers are great 
> for checkin which cylinders aren't firing.
> Pete Staniforth
> > Start with coil, plug wire or faulty spark plug, although if it was the 
> > coil
> > you'd probably see two cylinders not firing.
> >
> > Bill in Yardley, PA
> > wkdenton at verizon.net
> >
> > ----- Original Message ----- 
> > From: "Dave Daniels" 
> >>
> >> So, it seems no. 4 isn't firing. Any ideas?
> >>
> >> Thanks,
> >> Dave D.
> >
> > 

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