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MSGT Luttrell

Brute Force 300 Top Speed Way Down

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I have two Brute Force 300 ATVs that I maintain, my brother's little Brute had a carburetor issue after sitting up all winter with no stable in the fuel. It was acting like the main jet was clogged, it idled and ran at low speed well, but bogged real bad at higher rpms.  I replaced the carb with a brand new carb, I made sure it had the correct size jets, needle valve and that the mixture screw was adjusted the exact same as the one it came from the factory with.  Anyway, after I got it back together my brother test rode it around the farm and said it was good as new and no bog.  Fast forward a week or two and his wife rode it down the road to get some fuel and brought it back saying that it had no top speed.

I hopped on it and went down the road and sure enough it tops out at 36 mph and it should run up to around 46 mph in high gear.  It runs and idles great, just seems down on top end power and not quite as peppy as it should be.  I can't see it being the carb after all I did to assure it was right when I installed it.  Any ideas?  Belt pulley governor? I already checked for dragging brakes and they were good.

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Posted (edited)
7 hours ago, MSGT Luttrell said:

I replaced the carb with a brand new carb,

Brand new genuine OEM carb ($$$) or, a cheap Chinese clone?

Most China carbs are hit-or-miss quality wise.

Throttle cable adjusted properly, does it open the slide all the way?

Edited by mlatour

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It a clone, but this isn't my first rodeo with them, I tore it completely down and yes, it does open the throttle all the way.  I'm thinking there's maybe another issue going on not carb related.

 

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Posted (edited)

Aside from the carbs, was anything else changed, adjusted on the slower quad?

(different rear tire size installed, stator plate/timing moved etc.)

 

Just a thought but if the main jet was clogged, inspect the fuel line for internal degradation (ethanol eats away at older fuel lines)

which will constantly block your carb's internals until the line is replaced.

Edited by mlatour
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Posted (edited)

No, nothing else was changed, the ATV is all stock.  I guess, I'll make the time to ultrasonic clean the factory carb and reinstall it just to rule out any differences between the two carbs.  I did check the fuel lines, they all flowed freely at a very good rate.

 

Edited by MSGT Luttrell

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