82 Maxim 550, one cylinder not firing.

Hey Guys,

New to the board, new to my 82 Maxim 550. I usually ride an 01 Ninja 600 so this thing is very different

Background:
I picked this bike up for $300.00 with 20,000 km on it, looked in decent shape. Had it fired up the first night except it was pissing fuel out of the exhaust. Tapped the carb a few times and it stopped pouring fuel out the exhaust but now is leaking out of the intake side of carb#4. Cylinder 4 appears like it is not firing at idle. The reasons I think this are:
- Spraying carb cleaner into the other 3 carbs causes the bike to stall, I can empty an entire can into carb #4 and it does nothing.
- Header pipe is barely warm.
- I can pull the wire and it runs the same.

After quite a bit of research, this is what has been done:
- New plugs
- Carbs taken apart and cleaned - floats freed up, jets cleaned, everything was pretty much removed and cleaned spotless. Floats appear to be synced as far as I can tell. Carb's were bench synced. Diaphrams have no hole.
- Compression tested - approximately 160PSI across all cylinders.

I put it back together, fired it up, same issue. The header pipe is stone cold at idle. Also, if I cover the intake side of any other carb, the bike wants to stall. If i cover the intake side of carb#4, the idle increases dramatically and the engine races. (air leak somewhere?)

It seems like when I bring up the RPM, I think the cyliner is firing as the header pipe starts to get hot.

I'm out of ideas, anybody have any suggestions?

Cheers,
Nick

 

Let's start with a valve adjustment, or at least a clearance check.

Then unscrew the plug cap off the #4 wire, cleanly lop about 3/8" off the end of the wire, and screw the cap back on.

Do those two things, report back.

 

Thanks for the tips.

I actually ordered a new plug wire that I will splice in or change the cap if I can.

Would valve clearance be an issue when compression seems fine? To be honest, I'm technically minded and capable but never played around with valve clearances before, it doesn't look that hard to check but adjusting might be a different story.

 

Valve clearance check and adjust: http://xjbikes.com/Forums/viewtopic/t=14827.html

a tight valve might not begin to affect compression until the motor gets fully warmed up.

the caps unscew off the wires, there is a "spike" inside the cap that screws into the center of the wire. which is why I suggested the "cutting a new end" trick.

if you have never done your valves and don't know for sure when it was done, remember that the inital adjustment interval was 3000 miles and then every 5000 thereafter.

how many miles on your bike and how many have you put on?