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Makotosun

DT400 Engine miss above 5000 RPM under load.

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Replied by Gr8uncleal on topic DT400 Engine miss above 5000 RPM under load.

Had it been bogging down or felt wheezy, I might have suggested the air filter lid, but I've not seen it cause symptoms like you were having.
The following user(s) Liked this Post: Eflrr96
03 Jul 2024 09:50 #11

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Replied by MarkT on topic DT400 Engine miss above 5000 RPM under load.

Congratulations!

Uni filter for the 400 and "sticky" air filter oil are both known to be a problem.

Stock Yamaha filter and Twin Air "dry" filter oil works wonders.  Some trim the Uni to be more like original and not two full layers.

 
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
The following user(s) Liked this Post: Ht1kid
03 Jul 2024 11:27 #12

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  • RT325
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Replied by RT325 on topic DT400 Engine miss above 5000 RPM under load.

Oh wow, thank goodness for that, even if i failed to pin it haha. That's another odd happening to remember.
Thanks for the update & best bit is "you sorted it".
Have actualy had that before on a customers bike about 50 years ago where i think either seat was collapsing or he'd stored something under the hinged seat on whatever bike it was although totaly choked it so easier to go looking.
03 Jul 2024 16:57 #13

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Replied by Eflrr96 on topic DT400 Engine miss above 5000 RPM under load.

THANK YOU!!!  I appreciate all your help and patience! 
I’m either livin’ the dream or dreamin’ of livin’!
The following user(s) Liked this Post: RT325
03 Jul 2024 20:25 #14

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Replied by Eflrr96 on topic DT400 Engine miss above 5000 RPM under load.

Everything ran well up to a rev with load. The running rich definitely revolved around load in the engine. 
I’m either livin’ the dream or dreamin’ of livin’!
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03 Jul 2024 20:27 #15

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Replied by Eflrr96 on topic DT400 Engine miss above 5000 RPM under load.

THANK YOU!!!  I appreciate all your help and patience! 
good to know about the uni filter! Stroke of luck (bad luck) that I’d pick a uni! Lol!!! 
I’m either livin’ the dream or dreamin’ of livin’!
The following user(s) Liked this Post: RT325
03 Jul 2024 20:28 #16

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Replied by Eflrr96 on topic DT400 Engine miss above 5000 RPM under load.

THANK YOU!!!  I appreciate all your help and patience! 
good to know about the uni filter! Stroke of luck (bad luck) that I’d pick a uni! Lol!!! 
Oh, and another slight benefit of the struggles I’ve had with this thing is as hard as it was trying to get air from anywhere it could it sort of confirms it wasn’t sucking it from a crank seal or the O-ring/transmission gig! Bonus!!! 
I’m either livin’ the dream or dreamin’ of livin’!
The following user(s) Liked this Post: RT325, Gr8uncleal, Ht1kid
Last edit: 03 Jul 2024 21:03 by Eflrr96. Reason: Misspelled word
03 Jul 2024 20:45 #17

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