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CRF150, it is finished.

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My over the winter project was to add, or try to add, 4 to 5 horse power to my 2003 CRF150F.

I am pleased to say the project is finally completed!

I added the following performance parts. Price of each in [ ] at the end.

Bore / hone. [$50]

JE Piston and rings, 12.5 to 1, with the dome milled down to make it 11.5 to 1. The .050 over piston makes the displacement 159.6 cc's to run in a class with max displacement of 160cc. [$180]

Ported the head. I didn't really make the ports larger, I just cleaned out the casting flaws and lines, and matched the intake manifold to the port. [$50 for the Dremel tool]

28mm Mikuni flat slide carb (TM28). This was a bear to get jetted, but after countless hours of trial and error, I finally got it. [$120, used]

Powroll performance camshaft. This cam has just a little lift, but quite a bit of duration, just what I wanted for the high rpm / high speeds of flat track racing. [$150]

Powroll Thrust Nozzle exhaust. [$30]

Various required gaskets and o-rings. [$50]

Total cost, $630. Would be about $700+ with a new carb.

But was it worth it? I believe it was. This little bike really came alive. Yesterday, after getting the jetting problem ironed out, I took it out onto a 1/4 mile oval short track to see what she'd do. I was running at about half throttle for a few laps, just to get things warmed up. My nephew pulled up along side me on his stock CRF150. We looked at each other and smiled. We boh twisted the throttles open at the same time, and by the time we reached the next turn 70 or 80 yards down the straight, I was at least five bike lengths ahead of him. After the next straight, I was 10 to 15 bike lengths ahead. What makes it better is that I weight 165 pounds, to his 100 pounds. So my little 150 really came alive with those $630 worth of mods. I then let my Nephew ride my bike, heck, I had a hard time getting him off of it. He was turning lap times 3 seconds faster on my bike as he was his, and a second faster then I was, probably because he weighs 60 pounds less then me. (I sure ain't going to admit he's a better rider then I am, even though he is). So ... if you have an extra 6-700 dollars, and enjoy making slow bikes go faster, I would suggest giving it a try.

Next on the list. Powroll oversized header pipe, and maybe, just maybe, mods to the CDI box (incorrectly called the rev box). If I can make or have someone make a CDI box that keeps the RPM below 10,000 but still have the advantage of the better ignition curve, I'm going to give it a try. If there are any after market ignition companies reading this that can make a CDI box do what I want, send me one, I'll test it out for you.

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Sounds sweet, you dont have to run a race gas blend do you????

Yes, the engine knocked a bit with 93 octane pump gas, so I'm using a 50/50 blend of 93 and 110 race fuel.

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160 is legal in the 80/85 class isn't it??? making sure before i do anything to mine

I'm not sure about the rules in Indiana, but here in Illinois District 17, there is a class in flat track called the "86 to 160cc single cylinder four stroke only class". The CRF150 is the bike to have for that class.

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Hey Mike,

I have the 26mm carb on my 150, and the jetting has never been right. I ride Occatilla wells, and motocross tracks. It's great off the start, and full throttle, but if you back off the throttle, then put it on again it dies! Those are the simptomes! Any Idea's. The guy who tricked out my bike seams more than clueless. I have a 175 kit, the cr85 front and rear suspension all revalved. It just has that mid throttle bog!

todd

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toddadam7...

If you are talking about the roundslide 26mm mikuni it is a totally different ballgame... I have had several people with that carb who would like to throw it away... honda 150 and ttr125 users alike... the 28mm mike38 has is a flatslide...

Good luck!

Mike38

I am so happy you are happy with the bike... I have one more of those pistons sitting that I cannot decide what to do with... we will see!

See you in a few weeks!

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How much is your race gas????

I bought two gallons of Polaris snowmobile race fuel for $8 / gal. :thumbsup: I'm looking for something less expencive asap.

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Turbo blue 100 or 104 is fine.. your not running that high of compression... it should be around 4 bucks a gallon...

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Sounds great... I'm actually looking to do something similar. Any intention of dyno'ing it to see how close you got to you HP goal?

One question... Where did you source your piston?

Thanks,

--Fillmore

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Mike got that piston from me... I had the pistons custom made... I have a guy I work with that worked at JE... he designed them...

I have one left... not sure what I am going to do with it yet...

If I could get enough interest I could make another batch order... I need 4 people minimum...

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What are we looking at price-wise?

I don't think that it'd be too hard for me to come up with an order for four just from my circle of local friends...

--Fillmore

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lets see some pics man
pics?

Sorry, no digital camera. Picture if you will, a CRF150 with flat track tires, 428 conversion, no front fender, no air box, and Flander's Number 10 handle bars. That's about it. The rest looks like a stock bike.

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toddadam7...

If you are talking about the roundslide 26mm mikuni it is a totally different ballgame... I have had several people with that carb who would like to throw it away... honda 150 and ttr125 users alike... the 28mm mike38 has is a flatslide...

Good luck!

Any word on why the 26mm sucks so bad? I'm seriously considering an 26mm XR200 carb for my wife's 175cc.

Tanks :thumbsup:

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