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Engine cutting out after peak rpm

Engine cutting out after peak rpm

Old 05-30-2014, 01:37 PM
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Default Engine cutting out after peak rpm

So recently i got a used mugen mbx6 with a ninja bo1a and 2062 hong nor pipe, both in pretty good condition, while tuning the engine i found it that it would die just after i applied full throttle, so you got to the peak rpm and then when returning to idle it would die. Any ideias as why this might be happening? The spark plug is a #6 and im running 20% moddeltecnics fuel.
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Old 05-30-2014, 01:41 PM
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Is the bottom end too lean? How does it do from a dead stop to wide open? How does it do when it's at peak RPM?
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Old 05-30-2014, 01:56 PM
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Goes up pretty well, plenty of smoke and such, and its getting pretty high rpms and power. From a dead stop to wide open also no issues, no cogging or anything similar. Tried richening up the top end but didnt do anything!
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Old 05-30-2014, 02:01 PM
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How's your idle? Is it 2 staging or very steady?
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Old 05-30-2014, 02:03 PM
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Sounds like you LSN is to lean. I had an issue similar last year. ON a larger track with a long straight into a sweeper followed by another straight. I would let off the throttle at the sweeper and when I got back onto the throttle for the next short straight it would die. Your really leaning on the engine so its starting to lean out at WOT, then returning to idle its out of fuel because you burned it all off on the straight. Fatten up you LSN 1 to 2 hours and try again. It should solve your problem.
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Old 05-30-2014, 02:05 PM
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Originally Posted by beidle99 View Post
Sounds like you LSN is to lean. I had an issue similar last year. ON a larger track with a long straight into a sweeper followed by another straight. I would let off the throttle at the sweeper and when I got back onto the throttle for the next short straight it would die. Your really leaning on the engine so its starting to lean out at WOT, then returning to idle its out of fuel because you burned it all off on the straight. Fatten up you LSN 1 to 2 hours and try again. It should solve your problem.
That was my thought as well...
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Old 05-30-2014, 02:20 PM
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Will try tonight and report back, wasnt two staging the idle, just seemed high, but then again i was indoor running a nitro( at night so i need some light) so it may be just my imagination
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Old 05-30-2014, 02:23 PM
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This could be so... many... things...

Leaky front bearing, mid needle out of whack, bad CB bearings, bad plug, torn pressure line, leaking fuel tank...

I'd change bearings and plug before I started messing with needles. Then check line and tank, then think about tune.

Once tuned, these engines don't suddenly become un-tuned for no good reason. Sure, some tweaking here and there might be needed depending on conditions, but if an engine just all of the sudden starts acting like the tune is way off, chances are you have another issue.

I would think about putting a 2 needle carb on there too, save yourself a lot of headache.
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Old 05-30-2014, 04:45 PM
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Thing is Billy, i just got this engine, it wasnt tuned at all ( the owner said the same himself) so it just wasnt an engine getting out of tune, it was a engine who wasnt tuned at all.
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Old 05-30-2014, 08:15 PM
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When my engine was dying at full throttle today it was too lean on the HSN. Richened it by 1/2 a turn and it started working a lot better.
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Old 05-30-2014, 11:17 PM
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Originally Posted by frewster View Post
When my engine was dying at full throttle today it was too lean on the HSN. Richened it by 1/2 a turn and it started working a lot better.
+100

Remeber if the engine is too hot, you wont notice the richer HSN seting until the engine has gone down in temp. Normally I would stop the engine and restart it after a minute or so.
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