Breaking up on the top end

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02RedWS6TA

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Did some top speed runs on GPS today to see what it would do and the MT V3 is breaking up on the top end. It's about 2 weeks old mods are ddm pipe, walbro 990, Ada aluminum intake, killer bee, and ngk plug. Running amsoil with 93 at 28:1


Plug gap set at .025 tuned to the darker (safe) side of brown. 2 stroke guy all my life so not new to tuning them.


Any ideas on why it's breaking up on top? Acceleration is nuts and it runs great until then. I haven't vented the cap but I loosened it all the way up for my last run and no difference. Only getting 29/30mph out if it each pass. Gearing is stock.


It sounds like it's running in to a rev limiter or the stator is garbage and it's losing spark up top. I can't imagine they have rev limiters built in but I couldn't find anything while searching. The only other thing I can think of is it is not ethanol free 93.


Ideas?
 
It's done it on 2 different ngk plugs and the stock plug.

It sounds like it's losing spark up top.
 
I've bumped the HSN up and it bogs more on top. It's about 1/16 of a turn rich now. Anything more and it loses speed. It went from 30 to 27 today with another 1/16 of a turn.

Killing it at wot it's darker brown. Safe with these crazy fluctuation on Temps lately.
 
talunceford said:
Look at gapping your coil.... Business card width between the magnet on the flywheel and the coil itself.
Click to expand...
Ok, will do that.

I am still running the stock filter oiled with belray oil I use in my dirt bike filter. Could it be starving for air? I wanted to run it a bit before ordering my next group of parts to get everything I was going to need in one order.
 
Last edited by a moderator:
02RedWS6TA said:
Did some top speed runs on GPS today to see what it would do and the MT V3 is breaking up on the top end. It's about 2 weeks old mods are ddm pipe, walbro 990, Ada aluminum intake, killer bee, and ngk plug. Running amsoil with 93 at 28:1Plug gap set at .025 tuned to the darker (safe) side of brown. 2 stroke guy all my life so not new to tuning them.

Any ideas on why it's breaking up on top? Acceleration is nuts and it runs great until then. I haven't vented the cap but I loosened it all the way up for my last run and no difference. Only getting 29/30mph out if it each pass. Gearing is stock.

It sounds like it's running in to a rev limiter or the stator is garbage and it's losing spark up top. I can't imagine they have rev limiters built in but I couldn't find anything while searching. The only other thing I can think of is it is not ethanol free 93.

Ideas?
Click to expand...
How is your filtration?
 
What speed are you expecting to get? 30mph sounds reasonable given the MT's very low gearing (1.4 ratio if I remember correctly). The Dunerunner has a ratio of 0.987 and it gets to about 44mph, seems like the correct difference given the gearing.
 
Ice_2k said:
What speed are you expecting to get? 30mph sounds reasonable given the MT's very low gearing (1.4 ratio if I remember correctly). The Dunerunner has a ratio of 0.987 and it gets to about 44mph, seems like the correct difference given the gearing.
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Only took speed readings out of curiosity. More concerned with the fact it's breaking up so bad on the top end. Resetting the speed after richening the HSN was also just done out of curiosity.

I did expect closer to 35/36 given the cool Temps and reading others posted GPS speeds with my same mods done.
 
02RedWS6TA said:
Only took speed readings out of curiosity. More concerned with the fact it's breaking up so bad on the top end. Resetting the speed after richening the HSN was also just done out of curiosity. I did expect closer to 35/36 given the cool Temps and reading others posted GPS speeds with my same mods done.
Click to expand...
Can you post a video? Actually seeing/hearing the issue might help diagnose the problem.
 
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