big bore

[seanca66]

what would be better a ice cube 276 or a 290 kit..what is the power on them?

pro/cons of each?

thanks

[nick bottino]

wont be a big diference with the 276 go with the 290,its much beter

[yamaha rider08]

i dont have one but i have heard that there worth the money. and the ice cube is the better one but it is less cc's. some people have given up there 290 for the ice cube. but like i said dont know from personal experence.

[Turismo]

what would be better a ice cube 276 or a 290 kit..what is the power on them?

pro/cons of each?

thanks

A 262 kit just ups the power everywhere, a 276 is much the same but loose a bit of over rev and the 290 kit is loads of torque, but loose over rev.

I would stick to the smaller capacities if you race, but the bigger kits are fine for trail riding.

[skidlid]

I have the 290 love the torque but did loose the overrev. On the track I have to be one gear higher in most sections. Might need to change gearing I have stock right now. Starts a little harder now.

[YZF25006]

I have a YZF250 06 and instead of getting an 07 am thinking of keeping it and fitting a big bore kit, Id like more power for jumps out of tight turns, tryed a 450 but found it heavy and hard work after a while of riding it. So what I need to now is what are the best make of kits and are there any other mods that require doing in order to release the kits full potental. Also whats the reliability like with one of these kits??

Many thanks Darren

[Turismo]

So what I need to now is what are the best make of kits and are there any other mods that require doing in order to release the kits full potental. Also whats the reliability like with one of these kits??

Hotcams and ported head for sure to get the most out of the increased capacity.

Reliability would be better as it is the rpm's that kill engines, not the hp as such.

I don't think there is a bad kit out there? I think that the RPM kits are way overpriced, but you can get them from Poeton over there in the UK.

Vertex make a 300 kit that looks interesting, I am looking at their 500cc kit for my bike at the moment.

The Athena 290 kits are relatively cheap and well made.

[oldnbold]

My opinion is your choice should be based on your usual place to ride. If trail ridng, I say the bigger the bore, the better as the torque is what you'd really enjoy. For track, my vote is still out. I had the chance to ride an 05' yzf290, built @ procircuit, on the track. while the power was awesome, many other things didn't set well with me and i don't know if i could have changed it enough for my liking. I'll make a disclaimer as the bike was set for a guy 25+ lbs heavier than me but I couldn't get the thing to turn with the gas on and when it did finally corner and hit the gas it would wheelie then blow thru 3rd way too quickly, run out of rev and then I'd grab 4th and blow thru it quickly then run out of rev. It had stock 13/48 gearing and it was wrong by a lot. 3rd was too low to corner and 4th was too tall. It may work better with the wr gear ratio, but in my opinion, the yz's ratio is too close. I'd also recommend running the axle as far back on the swingarm as possible to help with the instant wheelie problem.

After my recent upgrade, I'd recommend sending the head off to be flowed by Ron Hamp, add your choice of cam and high comp piston and maybe an ignition. this will work better with the gearing on the yzf. You should read some numbers Ron's posting from a crf250. Supposedly, he's done some headwork for Burned on a yzf with stellar results. all of the above for about the same money as a big bore kit. Just food for thought.

[motoman_87]

i read an article in a magazine and they said that it improved the wheelies out of corners and also the higher speed capability but said that it lacks the jetting setup for it so until then ill stick to the 250cc

[Revumhigh]

I have the 02 yz250F and i recently installed the Athena 290 kit. The bike was awesome to begin with tourque wise and now the low to mid power has definetly increased. As for the top end it does loose a little of the over rev so now it needs to be ridden like a 2 stroke ( short shifted) for the track its great but for the trails I will have to change out my stock cams for the Hot cams to gain back some top end.

I am still learning as I go.

Oh yea there are some threads about the Athens kit leaking oil around the gasket but I have yet to see this problem so far mine is good.

There is also a thread about hard starting when it is cold. This is true but it was mention to give your throttle two blips before kicking over and it seems to work like a charm.....

Good luck!

[CBDaddy]

290 or 300 for the torque.

262 or 276 + porting for the revs.

I run the Vertex 300 with Hotcams and Dr. D and I retarded the adjustable intake cam a couple of degrees to bring my revs back. I like it a-lot! ?

[owndjoo]

yea we sell both vertex and athena 290 kits. actually have 15 in stock for the CRF's right now! check out our ebay store ATV Unlimited.

[skidlid]

290 or 300 for the torque.

262 or 276 + porting for the revs.

I run the Vertex 300 with Hotcams and Dr. D and I retarded the adjustable intake cam a couple of degrees to bring my revs back. I like it a-lot! ?

What hotcam did you install? I also have an Athena 290 and have had problems adjusting to the powerband. I just can't decide if I should short shift all the time or try and rev it out some. Did you do any porting to the heads with the cam? I am running stock gearing now but it seems like I have to ride a gear higher than before in alot of sections.

[owndjoo]

gear higher is better, means you are carrying more speed and using the torque. I'll be running a 290 more than likely this winter, cant wait.

[CBDaddy]

gear higher is better, means you are carrying more speed and using the torque. I'll be running a 290 more than likely this winter, cant wait.

I run stock gearing 13-48. The torque could probably pull 13-47 or 14-48, and it might give you more speed. I have the Hot Cams. I think there was only one model for the YZ250f when I bought them a few years ago. They have an adjustable intake cam, so you can move the power band up and down the RPM range if you want. I have a bone-stock head. No porting.

[vetracer119]

I have a 2003 yz 250f with the athena 290 kit and the hot cams, any idea on jetting specs for this bike? I bought the bike with all this stuff and it just does not run right, wont idle, pops and just seem to not have power.

[Wheel]

None of these kits will give as much HP as a stock bore 250F that is properly modified with porting, cams, carb, and piston. Plus, none of these kits are legal for racing in an MX class that is limited to 250cc four stroke.

[CBDaddy]

None of these kits will give as much HP as a stock bore 250F that is properly modified with porting, cams, carb, and piston. Plus, none of these kits are legal for racing in an MX class that is limited to 250cc four stroke.

I'm not sure if you have anything to back that statement up with or not, but I find it very hard to believe that a 290 or 298cc kit properly jetted with a pipe won't make more power than a stock bore, even with a pipe, carb, and port work. Something else to consider is peak HP that you reach at 12K RPM is one thing. Broad, meaty, usable power from 3K-10K is another. The type of engine should be suited to one's riding style. Peak HP is not the best setup for every rider. Unless you are an expert or pro that keep it pinned and feather the brake all the way around a track, 90% of the time you will benefit more from torque than peak HP. Lastly, you can bolt on a pipe and big bore kit in your garage for $1000 or less. Good port work alone could cost that much, plus a piston, cams, etc. Getting peak performance out of a stock bore is far more expensive than bolting on a big bore and pipe.

Any overbores are illegal in 4-stroke displacement classes, but they are all legal in vet/age (non-displacement) classes.

[yz133rider]

262 is legal for 125 amateur events.

[CBDaddy]

262 is legal for 125 amateur events.

Not in the AMA its not. Check the rulebook. In the AMA displacement classes, the biggest 4-stroke you can run in the 125 class (called class 2) is 250cc's. You can bore 125's up to 144's, but you can't touch a 250. Only in the vet classes can you run over 250cc's, unless you want to race 450's. AMA Rulebook - go to page 34