why is 1 cylinder running hotter than the other on my RMK?

[Bocephus]

98 RMK 700. i purchased it knowing something was wrong with it. the guy i got it from didnt know much about the mods as everything was installed before he bought it. this is what i can see on it so far....

SLP BOOST BOTTLE
HOT SEAT HEAD
GUTTED AIR BOX
STOCK PIPE
AFTERMARKET CAN (took it off, but cannot see a brand name on it)
STOCK CARBS KEIHIN PWK’S

-JETTING- (im not sure how accurate this is, but its what was installed when i purchased it)

i am at 1500' ASL
175 MAINS
42 PILOTS
R1371G NEEDLES

i have cleaned the carbs and made sure the jetting is the same on both carbs. the compression on both sides is right at 125. watch the videos of my egt gauges. you can see it is 150-200 degrees cooler on the LH side compared to the RH side. this temp difference stays consistant throughout the RPM range. it even gets a little more than 200* difference at 3/4 throttle to WOT.

something else iv noticed..... it will not run solely on the LH cylinder (while the RH spark plug wire is unhooked). it will pop a couple times and try to stay running, but it wont. however, it will stay running solely on the RH side while the LH spark plug is unhooked (obviously it runs rough because its on firing on one side, but it does stay running)

so, whats going on with my LH cylinder? any ideas? i just bought this sled and dont know a whole lot about it.....or it's history. when i 1st brought it home it wouldnt idle without fouling plugs. iv played with the carbs and it seems to be mostly over that problem. also, if anyone knows anything about the hot seat head, any info is appreciated. i see they have 3 different heads on their web site, but i do not see any markings on this head to signify which one it is.

at an idle




1/4 throttle

 

[6zigz9]

Did you check your chokes too? Mine was getting hot on one side and it was opposite side of the stuck choke.

 

[retiredpop]

I suspect the carburetors are not synchronized.

 

[4GR8X]

Greetings Bocephus660,

Your note reads like currently your sled is running fine, but you’re concerned about your EGT temperature differential...?

Offered for your consideration.

Verify the accuracy of your EGT numbers.
Flip flop your EGT probes at your y-pipe see if your hot side jumps to the other cylinder. If so maybe an issue with the EGT gage

Do your (new?) spark plugs also show a dark plug on the cool side and a lighter colored plug on the hotter side? Usually your spark plug wires are long enough you can hook then up backwards, see if that changes your hot and cool sides. If so maybe an electrical/ignition issue.

I have experienced a wide temperature differential traced back to my reed valves. The peddles had worn and no longer sealed properly. Ordered a rebuild kit for the reed valves.

Good luck.

Craig.

 

[sled_guy]

Polaris twins run hotter on the mag side than the PTO side. That's why a lot of people go 1 jet size bigger on the mag cylinder. It's because of how the coolant flows in through the motor and out the head.

It's nothing to be worried about assuming the carbs are clean and synced. If it is 200 degrees hotter at WFO then step that side up 1 jet size and see if that brings your temps back down.

Also, if the probes aren't positioned exactly the same in relation to the piston face you can get a different temp reading from side to side.

That's why you should tune with plug/piston reading not, EGT readings.

sled_guy

 

[lurker]

I gave you the same answers as above on HCS, only thing missing is change your plug cap's. They have a tendancy to gain resistance over time and you may have a bad one. Cheap and easy to change.