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crf250r engine mods

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Hi Im sure this has been beat in to the ground but here goes.

I have a 06 crf250r that I picked up cheap it has 25 hours on it maybe. Original tires graphics etc...

Looking for a bit more power. Put 1 tooth up on the rear sprocket. But looking for a bit more. I have rode 125's all my life. Had a yz250f and hated it. Seemed as if it would not rev very high at all.

Took the crf to the track and loved it stock(have never liked stock suspension)

The motor was really good. But after a few hours I found my self wanting a bit more.

Not sure if there is benefit from race fuel?

I have owned a 450 for years now tried race fuel in it but it was leaded 110 that made my 2 stroke scream but did nothing in my crf450r.

I do not want to change the cc or bore of the engine but would like a bit more.

port, polish, cam valve springs. I do not want a grenade.

Looking for dyno hp numbers, graphs etc.

And who can do the machining?

I am in San Diego CA.

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Ported head, 08/09 camshaft, 13.5:1 piston, AP mod and the right jetting. Personally, I'd rather see some good suspension on a bike. The bike is pleanty fast enough, the problem is you can't ride it to it's full potential. All the engine mods in the world with a goon riding it can't beat a stock bike with good suspension and a good rider.

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Ported head, 08/09 camshaft, 13.5:1 piston, AP mod and the right jetting. Personally, I'd rather see some good suspension on a bike. The bike is pleanty fast enough, the problem is you can't ride it to it's full potential. All the engine mods in the world with a goon riding it can't beat a stock bike with good suspension and a good rider.

Ding Ding.

If you truly are riding that thing to its full potential, well then you should have a contract and your own trailer. Very few of us can and ever will. Its not the bike that slows down, its the rider slowing it down.

Now if you just want a faster bike, well then dont tell folks your riding 100% out of it. Cause that just aint true:ride:

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That old of bike I would pull head and cylinder and look at it before spending a bunch of money on performance parts. Those origional tires should be about slicks if they have 25hours on them.

You may get all you need from making sure it is tight and up to spec and then making sure it is jetted properly. I have seen a lot of mod 250f's put together with a bunch of expesive cams, pipes, pistons etc that couldn't run with a really well prepped stock bike with good fuel and jetted really well.

It doesn't seem like people understand how improtant jetting is on carbed bikes. Every 250f we had was allways way to rich even for oxygenated fuels. Pull your carb and document what the jetting is. Do some research on what others are running in the 2006 crf250 in your type of climate. Then get you an assortment of leaner and richer mains, pilots, leaks and needles some good fuel and start testing jetting changes.

I remember yz250f's in 06 had I think a 178main and we ran useally 168-172 all over the country with MR9 fuel. Only time we came close to the 178 main was at Branson when the temp was freezing for the morning motos.

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guys I have owned 75 plus bikes in my life I am 40 years old. I never said I ride the stock bike at 100 % but who the hell does?

There is not much difference in a 2010 and 2006 I have backed to backed them on the track.

I have jetted rebuilt revalved etc bikes all my life. I have a small shop that I restore vintage 2 stroke street bikes and vintage cars.

I get it.

I know just what revalving a bike will do on the track.

I am not the average guy that is new to this whole thing.

That old bike was bought new in 08 the guy was in his late 20's he hurt him self and parked it. Its completely stock. The tires although old rubber are still in good shape, rims are straight, original plastics are fine very little boot rash etc you get the point.

I checked the valves and they are spot on. No tools were ever on the top end.

Now that I have explained that I don't need anyone selling me on doing the suspension here cause I understand what that does.

I am looking for dyno graphs or numbers for modded engines like I seek.

and who does good machine work.

as you can see the bike is in great shape. I'm done paying $7k for a new bike only to drop $2-3k in getting the thing to handle right. I will find bikes that guys were scared of never rode and buy them for $1800 like this one.

I put the bars and levers on it. It had the original stock stuff on it.

I really just want to build a pretty sick bike before I'm to old to ride LOL

As for jetting I did pull the plug and it looked a bit rich. I installed a new plug and will read it. (can't really go off of the original plug cause I'm sure the last owner had no clue how to ride and was riding it like it was a xr100) As for the throttle response it was bad when I got it chopping the throttle quick was just a big bog which I cant stand. I know that this is caused by the AP not tuned correctly so I took the carb linkage cover off and sure enough when you twist the throttle there was a lag. I just safety wired the cam together. It has no bog at all now.

1-1.jpg

photo-3.jpg

Edited by limp1969

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Well now that we understand where you're coming from, we get it! You have to remember, the majority of the people that ask this question are usually young kids that are not real good riders and thing that the only way to win a race is to mod the bike. I have guys bring me brand new engines because their kid gets his ass whipped in the C-class and thinks that adding $2k worth of parts are going to get him that ultimate $10 1st place trophy.

Now there's only a few guys on here that would be able to show you a dyno graph of the upgrades that they've done. Ron Hamp is one of them with tons of research and graphs to back up what he's done. I can only give you the real life experience that I've had with these machines. I'm not a rider anymore, but what I replied with above has been overwelmingly the best engine mods I've made that is reasonably in terms of $$$ that everyone has been very happy with. With the addition of an aftermarket exhaust will only enhance the items I've mentioned. As you know, what you want out of it in terms of bottom end, top end, etc is going to determine the type of camshaft and other components you install in the engine.

I think I speak for everyone that replied to this thread, the last bit of information you provided would have been nice to know from the beginning! No disrespect my friend!

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HAHA

I know there are a bunch of guys on here that are just what you said, so sorry about the lack of info.

As for a 08/09 cam is the bleed of better for a high comp piston. Where will the 08/09 cam move the power too in other words what is the difference?

vs a after market cam? I am sure they do but is a custom cam way to much $$ or is it worth the money?

Valves, springs and gaskets would be the next ?

I m not trying to reinvent the wheel here Im sure the spec build you stated is just what I am looking for. I just dont know anyone that has built this.

The things I like about the honda over the yzf is how it revs and does not fall flat. My buddy has a broc tickle yz250f no clue what was done to it but it is fast and handles nice. But still falls flat up high. It's a short shifter.

He has a power bomb some sort of pipe, Hinson clutch basket suspension work 1 tooth up in the back. never been in the engine to see what it is. They removed the sump. I guess for weight.

You can see it sitting behind my crf.

If I could take what the bike does now and add a few ponies I would be happy.

Will u4 gain me anything?

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RHC 5 cam and valve springs with a wiesco piston pump gas .

Hi Ron

Piston change for compression or valve clearance?

Thanks to all

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high comp piston and rejetted a nice exhuast system and nitro will go along way. just cut theheader itll back fire when your deccelerating...thats you bike telling you to go faster. haha im just playing honda as is is a better bike then all the other250s rev higher faster lighter more comfortable. i think just get another 450 unless you want a 14k rpm boom

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high comp piston and rejetted a nice exhuast system and nitro will go along way. just cut theheader itll back fire when your deccelerating...thats you bike telling you to go faster. haha im just playing honda as is is a better bike then all the other250s rev higher faster lighter more comfortable. i think just get another 450 unless you want a 14k rpm boom

Ha ha

Well not looking for a bomb. And a 450 is just to much. I will only ride the 450 in the desert pole line road. Where you really need the power or a bigger sandy track.

My main track bike is a 05 yz125. It has engine work,reeds, vortex,dep pipe, excel wheels, clamps,suspension work.

It's the one in the middle not a great picture. At 39 years old I can go around the track 4 times as much charging vs a 450. It is a physical thing riding a 450. If I was 21 again that is all I would ride. LOL

getting old sucks!

photo-4.jpg

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if you want to run race gas drop a high comp. piston in it to get your performance out of it. youll love it!

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maybe a stroker crank too they are basicaly bolt on hot rods makes a nice one you may need to shave the webbing in the bottom of your piston depending if you run a stock piston or aftermarket. huge power gains with the hot cams one! but had to adjust jetting to gave the motor more vaccume but still wanted more petro.

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