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reece12345

klx300 cylinder

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will the 300 cylinder go on the 07 klx250 ive been reading and the stoke is the same just biger bore

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To go 292 cc on the KLX250, just add the following:

1 x barrel part number - 11005-1983

1 x piston pin part number - 13002-1109

1 x set piston rings part number - 13008-1071

2 x piston pin clips part number - 92033-1054

1 x Head gasket part number - 11004-1314

1 x cylinder gasket part number - 11060-1740

1 x Piston p/n 13001-1463

At Ron Ayers, the cost is right at $500.

However, Bill Blue puts out a "Big Bore Kit" for the bike that produces 331 cc on the KLX250. It is a 9 mm overbore. My bike is equipped with this upgrade and I'm very happy with the performance.

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There is a guy named Harold on planetKLX that put a 300 barrel on his (94?) 250. He had to have Jerry at FSW machine down the spigot on the cylinder. He said that mod also ups the compression ratio to 12-something.

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for an 07 klx 250 the 300 cylinder is a perfect fit, no mods needed. just rejetting.

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Nope, just lift your stock head up, slip in the KLX300 cylinder, piston, rings, pin, circlips and gasket then lower your stock head.

Voila! 292 cc motor! All Kawasaki parts.

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However, Bill Blue puts out a "Big Bore Kit" for the bike that produces 331 cc on the KLX250. It is a 9 mm overbore. My bike is equipped with this upgrade and I'm very happy with the performance.

With this mod, what do you compare the performance to?

Compared to stock with free mods/jetting?

Compared to a drz400?

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I've not had the bike on a dyno yet. However with my setup, 331 cc, Yosh cams, no backfire screen, no airbox lid, aftermarket can and a modified TM33 carb, I'm expecting around 29 to 31 horses at the rear wheel.

Compared to 18 stock, I think this is quite an improvement.

All I know is that I'm very happy with the results.

One of my friends has asked me to "upgrade" his KLX250 to a KLX331. We're going a different route.

Stock carb, jetting changes, drilled slide, aftermarket exhaust , removal of airbox lid and backfire screen. His bike will probably be down a couple of horses as the cams are stock.

I'll let you know.

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what is the % chance of the airbox catching on fire w/out the backfire lid, i heard its dangerous to keep off, thanks.

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Also- I'll be real interested to hear about high miles 331 bikes (how they hold up for 10K miles, etc).

Sounds cool!

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what is the % chance of the airbox catching on fire w/out the backfire lid, i heard its dangerous to keep off, thanks.

Chances are slim - really slim, but there's always a risk. Haven't got a %'age for you, but I've never heard of someone catching their bike on fire from removing the backfire screen. The screen won't prevent backfires, it just dissipates the flame somewhat. I've backfired a throught the carb few times when kicking over, but never seen any scorch marks on the filter.

No doubt somebody(s) in the TT forum has an interesting bike-burning story to tell, but I think the risk is worth it if your bike is tuned well. Your call.

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Remember, while I have removed the backfire screen from the intake tract, I have also changed my air filter out. Twin-Air makes a "Replacement Backfire Filter" for the YZ450F. I guess that is their backfire dissapation. It will fit the KLX250. Just have to turn it a bit. You can't read "Twin-Air" horizontally, but the filts fits and works just fine.

Yes, I would love to tell y'all about 10,000 miles on a 331 motor. I've got some riding to do.

However since this is basically the same thing as the ATV guys do on their Mojaves, and I've never heard of catastrophic failures, I'm not concerned.

While this is a motorcycle engine, when I was running a Super Pro NHRA bracket car, I had a 500 cubic inch big block V-8 engine that ran sleeves in all the cylinders. Never had an issue with that motor and it was a very stressed situation!

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I've not had the bike on a dyno yet. However with my setup, 331 cc, Yosh cams, no backfire screen, no airbox lid, aftermarket can and a modified TM33 carb, I'm expecting around 29 to 31 horses at the rear wheel.

Compared to 18 stock, I think this is quite an improvement.

All I know is that I'm very happy with the results.

One of my friends has asked me to "upgrade" his KLX250 to a KLX331. We're going a different route.

Stock carb, jetting changes, drilled slide, aftermarket exhaust , removal of airbox lid and backfire screen. His bike will probably be down a couple of horses as the cams are stock.

I'll let you know.

Is that you, Marty?....it's gotta be!

It will be very interesting to see your dyno results. We just had a guy at Kawasaki Forums run a 331 with mikuni 34, Muzzy, Webcams Larry Roethsler (sp?) grind cams and chamber/port work and got a little over 28HP and about 19lb/ft torque. He was running a pretty aggressive Kenda knobby on the rear, so I'd suggest trying to find a smoother tire that will hook-up better with the dyno drum. I would guess that he was putting-out over 30hp, but just needed the right rubber to hook-up.

We all saw the difference that made with Nobrake's dyno run.

Cheers!

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