MM only runs on 2 cylinders please help?

av8er · Feb 28, 2014

tonite we put in new plugs, good spark on all 3 cylinders, pulled the carbs from the air box and cleaned the carbs, no issues found, put it back together, test rode it, still only running on 2, we will borrow a compression checker 2morrow, any ideas on what else to check or do,???? thank u !!

stingray719 · Feb 28, 2014

Sounds like a bad hole. If compression is good check crankshaft seal.

av8er · Mar 1, 2014

So today we checked compression

about 120- 125 across the board, the cylinder not running is closest to the clutch, pulled the carbs, cleaned all jets, checked fuel pump, good spark, not a coil issue, disconnected the Throttle position sensor. any Ideas???
also tried pouring fuel in the cylinder.

Scott · Mar 1, 2014

Pull the plug and put the cap back on it...and set it on cylinder head so it's grounded.
Pull the chord...does it get spark?

edit:: never mind...I think you did that.

Scott · Mar 1, 2014

Actually, I wanted to be a smartazz and say "Pull the third pipe & carb (shed the weight), plug the hole and run it that way." LOL

av8er · Mar 1, 2014

Scott

Thank U for all of your valuable Input:doh:

mike_s · Mar 1, 2014

How does the spark look? Is it red or yellow, or nice bright blue? Weak spark can be blown out once compression and turbulence is introduced. Check and make sure there is fuel getting to the float bowl, i have seen fuel lines colapse, and fuel pump outlets plug up. Is the plug wet? make sure none of the vent lines are restricted or plugged. Get the sled running and spray carb cleaner on the crankshaft in the seal area and see if that makes a difference in its behavior, could indicate a bad crankshaft seal.

mysledblows · Mar 1, 2014

What year is it? If it's a little older you can swap the plug wires from cylinder to cylinder as it fires them all at the same time. So if it runs on 1 hole and then you swap that wire to the bad hole and it runs you know it's a spark issue. If it doesn't follow the wire then it's a fuel or ?? Problem.

Scott · Mar 1, 2014

mysledblows said:
What year is it? If it's a little older you can swap the plug wires from cylinder to cylinder as it fires them all at the same time. So if it runs on 1 hole and then you swap that wire to the bad hole and it runs you know it's a spark issue. If it doesn't follow the wire then it's a fuel or ?? Problem.

Never heard of that.

mysledblows · Mar 2, 2014

Yepper. The 97 - ?? When they switched to the 300 watt ignition in 00 or 01 i think then each plug fired individually. The early ones fired them all at the same time.

av8er · Mar 2, 2014

it's a 2001

it had good spark, but not sure what color of spark it was, yes we pulled the carbs , then fired up the sled, and fuel was coming out of all 3 fuel lines, We also checked all of the fuel valves and t's to make sure they were unobstructed.

SRXSRULE · Mar 2, 2014

when you pull the plug on the cylinder that's not firing is the plug wet or dry?

If its dry you have no fuel, if its wet you have an ignition problem or mechanical issue. Whats the reeds look like on the cylinder? Does it have after market triple pipes on it? If it does and has three separate stinger mufflers make sure a mouse didn't build a nest up in there.

not very many things to check on a two stroke, just take your time. Eric

mike_s · Mar 2, 2014

Ah yeah, i forgot reeds. Does the non running cylinder seem to spit fuel and air backward through the intake? Worth pulling the reed cages and looking.

av8er · Mar 2, 2014

I didn't pull the reed cages,

but I looked them over pretty good with a flashlight, didn't see any damage or chips on reed petals,, spark plug looked dry. also stock exhaust

700redsled · Mar 2, 2014

pilot jet plugged does it run better with choke on

SRXSRULE · Mar 2, 2014

700redsled said:
pilot jet plugged does it run better with choke on

Seen that MANY times!

Check those tiny openings very close. Eric

av8er · Mar 2, 2014

after collaborating with my bro,

he says plug is wet, and we pulled all 3 jets and sprayed really well with brake clleaner, jet is clean, and good. WTF are we missing???

mike_s · Mar 3, 2014

If the plug is wet, chances are that cylinder is flooded, and the plug could be fouled. Pull the plugs, pull the engine over 10-15 times fast as you can (RPM wise) with the throttle held open, replace that plug and try again.

stingray719 · Mar 3, 2014

As I said earlier check crankshaft seal, especially if it is the PTO side.

700redsled · Mar 3, 2014

need to run wire or something through those pilot jets spraying them won/t do a good job owned lots of yamis had to do many times

MM only runs on 2 cylinders please help?

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