Only running on 3 cylinders

[85Max]

Okay here we go again. My 85 max is only running on 3. The front right one is not fireing. Noticed when I was trying to sink. Took of the vacuum cap to hook up the syncronizer while running and the engine didn't drop. Set and unset mixture screw, no engine change. Disconnected spark plug while running, no engine change. Took out the spark plug, it was not wet and it had spark. I've rebuilt these damn carbs 2 or 3 times. It seems like this one is not getting fuel to the cylinder. Any ideas guys?

Jake

 

[maleko89]

Try draining the float bowl, anything come out?

 

[lankeeyankee]

Okay here we go again. My 85 max is only running on 3. The front right one is not fireing. Noticed when I was trying to sink. Took of the vacuum cap to hook up the syncronizer while running and the engine didn't drop. Set and unset mixture screw, no engine change. Disconnected spark plug while running, no engine change. Took out the spark plug, it was not wet and it had spark. I've rebuilt these damn carbs 2 or 3 times. It seems like this one is not getting fuel to the cylinder. Any ideas guys?

Jake

Jake did this start right after you broke your carbs down and re installed them since you are re synching them

 

[85Max]

I drained the carb, it had plenty of fuel. Looked clean.

 

[85Max]

YES it sure did! Have you run into this? Rebuilt them because the previous owner let it set for over a year with no stabilizer. Jet block was full of a rust colored residue. Put them back on sparkling clean, now the one cylinder does not fire.

 

[85Max]

d

 

[85Max]

Jake did this start right after you broke your carbs down and re installed them since you are re synching them

YES it sure did! Have you run into this? Rebuilt them because the previous owner let it set for over a year with no stabilizer. Jet block was full of a rust colored residue. Put them back on sparkling clean, now the one cylinder does not fire.

 

[maleko89]

Did you put the rubber caps in the right places in the jet block? Did you use compressed air and make sure every hole in the jet block and float bowl orifices was clear?

 

[85Max]

Did you put the rubber caps in the right places in the jet block? Did you use compressed air and make sure every hole in the jet block and float bowl orifices was clear?

Yes sir. The rubber caps are getting hard though.
I just started it and put my had over the carb (#4) while it was running and my hand got wet with fuel. Could it be that out of sink as to not fire on that cylinder? The plug had spark. Checked the resistance on the plug wire, it was 10.63. Also I noticed the carb (#3) behind the one not firing was smoking more than the rest when I shut down.

 

[lankeeyankee]

Yes sir. The rubber caps are getting hard though.
I just started it and put my had over the carb (#4) while it was running and my hand got wet with fuel. Could it be that out of sink as to not fire on that cylinder? The plug had spark. Checked the resistance on the plug wire, it was 10.63. Also I noticed the carb (#3) behind the one not firing was smoking more than the rest when I shut down.

Pull the carbs back off and remove every float bowl and compare the carb that is messed up with the others and look for the difference.

 

[maleko89]

Compare the butterfly valve for the #3 carb with the others. If the valve is closed too far vacuum should be higher than the other carbs. The valve would be closed if that cylinder is way out of sync.

We had this issue on the forum before where the vacuum was off the chart due closed butterfly valve. Pilot mixture isn't enough to fire the cylinder with the butterfly valve closed. It needs some of that air to get by in the main carb bore.

 

[85Max]

Valve appear to be about the same

 

[maleko89]

Could have an air leak. Check all the boots. Spray WD-40 around the joints and listen for tone change. Check for cracks on the manifolds too.

 

[lankeeyankee]

This problem was induced by him maleko. He doesnt have a cracked boot or a stuck butterfly. I asked if this problem started after his rebuild and he replied "yes"
Its something he did or didnt put back together properly. He could have put the PAJ jet in the main jet vice versa. Thats why I asked him to pull the carbs and compare everything with the carb thats messed up.

 

[maleko89]

Good advice Lankee.

Sometimes problems start by just removing the carbs, especially worn boots. I remember someone using a impact driver to loosen the manifold cover screws and cracked the manifold. Sometimes the air box doesn't get put back on right and a boot is pinched.

 

[lankeeyankee]

I am betting he either has the fuel block 180 out, or a PAJ / Main reveresed. Something.
Those are good troubleshooting tips MALEKO if the bike dont this before he pulled the carbs

 

[maleko89]

Even if it didn't do this before I would still check it. Maybe they were installed wrong? Not seated in boots correctly?

 

[85Max]

Just to clairify, the bike didn't run at all before I took the carbs off. Then it ran for a few short trips and started spitting and coughing and would only run on choke. So I cleaned them again, runs now, just on 3 cylinders.

 

[85Max]

Well I found the problem. When I took off the plug wire to look at it, it seemed like it wasn't pushed into the coil far enough. I cut a 1/4" off to get a better connection and pushed it in better and now it fires on all 4. Unfortunately my battery is now dead and the baby's asleep, so I have to wait to sync it. I'm going to buy new plug wires too, these are probably 23 years old. Where do you get good plug wires, other than the dealer who sticks it to you when you buy from them.

 

[maleko89]

Great news! Man, you tease....you said that you had spark. ;-)

Go to any powersports shop and ask for copper core spark plug wire by the foot. Get new NGK spark plug boots too. I think I bought 3 feet of wire and four new boots for under $20.