80 Trailfire 340 won't rev up, high rpm troubles...

Technical topics related to machines powered by Kasasaki motors
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xjfish
Posts: 16
Joined: Tue Jan 05, 2016 8:32 pm
Real Name: Nick
Location: Brainerd, MN

80 Trailfire 340 won't rev up, high rpm troubles...

Post by xjfish »

Hi guys. It has been awhile since I have posted, have an issue with my 80 Trailfire. Any input or suggestions greatly appreciated. :beers;

End of last season I noticed the sled was running crappy at high rpms only. I had very little time to look into it last year but did do a bit of a stress test on the coil with a spark tester and found one of the spark plug wires out of the coilpack was leaking and arcing to the block. Kinda figured that was the problem, ordered a coilpack (aftermarket Taiwan) and put the sled away. Yesterday I drug the sled out of storage and installed the coil/secondary wires reusing original plug boots. Sled started 2nd pull and runs perfect until after "mid rpm" (no tach). Both plugs have good blue spark when pulling over. No real change.

"Crappy" details: Engine really feels/sounds like it is hitting a rev limiter at high rpms only. Does not feel like it hits that sweet 2 stroke powerband like it used to... Does not backfire. Spark plugs indicate one side slightly drier or leaner than other side, low miles hard to read. Sled seems to have issues with high rpms with the track off the ground...

Could a failing cdi or stator possibly cause this? Can anyone please tell me the resistance and wire colors for stator coils? I tried using my cheap digital DVOM to take some readings but I just don't trust them. I will grab my Fluke from work and decent compression tester Monday...

Fueling? Carb "should" be clean. If the main jet was partially plugged or choke not seating I can see a problem. Checked last year and was very clean, i guess i may need to reverify... Needle height setting?? I did replace throttle cable...

I REALLY appreciate your reply and will post findings in hopes to help someone in the future. 8)
xjfish
Posts: 16
Joined: Tue Jan 05, 2016 8:32 pm
Real Name: Nick
Location: Brainerd, MN

Re: 80 Trailfire 340 won't rev up, high rpm troubles...

Post by xjfish »

Also: Is there any difference between the 340 and 440 ignition systems at all same year for these sleds?
xjfish
Posts: 16
Joined: Tue Jan 05, 2016 8:32 pm
Real Name: Nick
Location: Brainerd, MN

Re: 80 Trailfire 340 won't rev up, high rpm troubles...

Post by xjfish »

Compression is 150 PTO 145 MAG

Swapped plugs and boots. After some WOT pulls: PTO side plug dry/MAG side wet. Same with previous plugs. Something must be different from side to side.

I don't really suspect an ignition issue would cause a spark difference side to side unless it was the coilpack.

I suppose it is possible a crank seal is leaking/sucking air at higher rpms? I changed them a few years ago. Any thoughts?
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Hec In Omaha
Posts: 63
Joined: Sat Jan 23, 2016 9:52 pm
Real Name: Hector
Location: Beaver Lake NE

Re: 80 Trailfire 340 won't rev up, high rpm troubles...

Post by Hec In Omaha »

xjfish,

If you suspect a leaking crankshaft seal, try this. Fire up the engine and and spray carb cleaner right at the PTO crankshaft seal. If you notice a difference in the engine rpm when you hit it with carb cleaner your shaft seal is leaking and sucking air. This is what I did to confirm I had a leaking crankshaft seal. I just rebuilt my engine and both my seals were bad.

Good luck!

Hed
1981 Trailfire 440
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