Bike is going well, accelerates fine up to 13,000 but when I accelerate to a decent speed, say 160 or 180 and back off on the throttle to just cruise and maintain the speed the bike just dies off. Even changing back down a gear and getting it back into it's power range won't help, it just won't accelerate again or maintain the speed and just dies. Any ideas? The bike currently has NSR300 barrels and TYGA pipes and has been derestricted.
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MC21 Honda NSR250. TYGA 300 conversion.

Hey mate.
Can you describe how it dies.
IE - does it cut out like its out of fuel ?
If it cuts out at 180, what does it slow down to before it fires up again ?

It might be running out of fuel.
Next time it does it, shut the fuel tap off, pull the clutch in and switch it off. Come to a stop and crack the carbie bowl drains. If nothing comes out, its got no fuel. If it pisses out fuel, you can cross that off your list.
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Winning isn't everything, but loosing isn't anything

It dies more as if there is no ignition - as if the kill switch has been flicked. Last time it came back on about 130 and started to accelerate again. I don't think that it's fuel as if the throttle is held on and it is taken up to 13000rpm in each gear it doesn't die - not until you back off slightly to cruise.
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MC21 Honda NSR250. TYGA 300 conversion.

When my floats were set too low, after heavy acceleration and then constant 130kms+ the carbs would drain until I dropped back to around 100kms
It might also be worth checking the fuel's flowing properly to the carbs from the tank
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Why do things simply when you can complicate them

Will check the fueling, however it seems unlikely as it is fine when accelerating, which would use more fuel then merely cruising. Unlikely it is the float level or anything to do with the carbs as the bike was tuned on a dyno and I asked the tuner whether he checked the float levels and he did. He did mention that he thought it sounded like the crank seal, especially after I told him that sometimes when I accelerated it would hit 11,000rpm and just stop, although a new plug has seemed to fix that. Doubt it's the crank seal either as I just had a new one put in 2,000km ago. Any other ideas? Ignition system?
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MC21 Honda NSR250. TYGA 300 conversion.

I have the same problem with my mc21.
Do you already know what the problem is?

im no expert when it comes to NSRs (thats way im on here to learn) other than knowing there a right laugh to ride

but 13,000 rpm ,that can be doing it anygood

take mine to about 11,200 then its time for another gear ,if theres no gears left ,then just tuck in and smile

as for as my 21 goes theres no point in reving it above 11,500

if his is anything like my 300 then the power only really tales off above 12,250rpm (ish) and it keeps going to 13,000 if you let it - even on 16/40 gearing. It gets there FAST too - mine achieves that speed in 6th well within the length of the back straight at Taupo here in NZ.
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After years of moaning about immigrants now i am one...

Problem turned out to be a combination of a faulty coil and the needle being too rich. Lowered the needle and put a new coil on the front cylinder and it goes like a dream.
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MC21 Honda NSR250. TYGA 300 conversion.

yeah, nice one. I found my lower coil was a bit corroded on neg. contact. i swapped em round and seems to be going better
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