Cr250 Low torque on low end

[Race_Bennett]

Hi, I have 1997 Honda cr250. And I thought it had pretty good power. But I nottice that when I gas it from idle , it speeds up but not anyware close to spin tires or anything. It will speed up and eventually 2-3 seconds afterword lift up the front end. Now i would have not paid attention to that accept my brother also has a cr250 which is a 99, but is strong from the start. I have a bigger pipe than he does, and also a fmf muffler (he has a stock) It had a 180 main jet which i recenty changed to a 178 because it was lacking gas in the top end and the floats were already set to high. I checked the air/fuel ratio, air filter, compresion (150, same as bros), Spark plugs brand new. It runs fine in the Top end. Any suggestions? Maybe becasue they switched carbs in 99 my brothers is more peppy in low end?

I broke the 2 top engine mounts recently so I am taking everything off, so it would be a good time to look into this.

 

[dirt bike dave]

The main difference is the cylinder porting. The '99 has more mild porting which is better for low end. It's also good for longer ring and piston life, and better fuel range. The stock '99 pipe is good for low end. Many riders prefer the '99 cylinder, especially for trail riding. The '97 may make more peak power, though.

I had a '99 that was set up by a top enduro racer (former district champ). He had put on the '97 carb (with a 165 main for 4,000 sf elevation) and '97 ignition. The bike had a v-force reed block, e-line lighting coil (acts like a flywheel weight), FMF spark arrestor but stock pipe and porting. It made outstanding low end power for a 250 two stroke. The '99 motor with the minor mods felt nearly identical in power and delivery to my buddy's 2005 KTM 250 exc.

You could try swapping pipes with your brother. If you like the stock '99 pipe on your bike, see if you can find one used. I've seen them for sale around $50 before.

 

[Race_Bennett]

My brother has a big pipe to just maybe 1/2"-2"smaller. The Bike has been raced-rebuilt-sold to a dentist-then sold to me. I bileve the back sprocket is bigger on mine which makes me even madder. Because that SHOULDgive me more torque. My brothers bike was from some druggy who never rode it and was owned also previously. Mine was used for a trailriding, and he wanted a 4 stroke.... go figure... I have thought about a rebuild 285 bore :) but my uncle who has a bike shop said its nikel plated therefore unless i buy a sleeve i cant bore it out. I have thought about a new piston + rings or new rings, but usualy they seem to be pricey? When i tear this thing apart (tommorow) Should i try to pull the piston out? i could post it here and also show my uncle and see what to do. How much do you guys think a re ring kit is and ow much for piston + rings? ive got 1000$ but i really need to put it into my jeep to make it road worthy in a year. i really want to spend a max of 150$ as i dont NEED to have that urgently. But for 1300$ + extra new clutch and sproket i cant complain.

 

[dirt bike dave]

Service Honda has good prices on parts. Also, Mach 1 Motorsports, a dealership in California, used to sell top end kits (Honda parts) for around $120 for your bike. This would include a new piston, wrist pin, wrist pin bearing, circlips, rings, head gasket and base gasket.

Piston replacement and powervalve service is very easy on the CR250. The only tricky part is when you are putting the cylinder back on the cases, you have to make sure the fork that actuates the powervalve is lined up propertly with a pin in the cases. If not, the powervalve won't work and you will have to pull the cylinder again.

You and your brother should get a FACTORY service manual (not a Clymer or Haynes manual). I think they cost $50+- but it is well worth it and it covers both your '97 and his '99. The US publisher is at www.helminc.com It might take a few weeks to ship, though.

 

[Race_Bennett]

We have a Clymer manual, I got it with my bike :) ITs pretty good accualy and its 97-02 so we can both use it. What will be different in the honda manual?

 

[cnielse5]

Have you checked to see if the power valve is moving correctly? I have a 97 that rips on the bottom, the 99 porting is smooth all over the 97 is a more violent hit to it. but that bike should be more prone to wheel spin on the bottom end than the 99.

 

[dirt bike dave]

We have a Clymer manual, I got it with my bike :) ITs pretty good accualy and its 97-02 so we can both use it. What will be different in the honda manual?

Never seen the Clymer for that bike, but I had the factory manual and it was great. Excellent diagrams and instructions for anything you would ever want to do, plus tuning and troubleshooting guides.

Worth the price difference IMO if you were going to have to buy the Clymer. Since you already have the Clymer and you like it, that's a different story!

 

[CACRanger]

Have you checked to see if the power valve is moving correctly? I have a 97 that rips on the bottom, the 99 porting is smooth all over the 97 is a more violent hit to it. but that bike should be more prone to wheel spin on the bottom end than the 99.

I agree...my 97 will spin the tire and/or lift the front wheel right off the ground ass soon as the throttle is touched and that is with my ~250 lb. butt on it. Sounds like something is wrong with your bike.

Chris

 

[dirt bike dave]

Maybe his jetting is way too rich or the top end is worn out.

If the PV were stuck closed, it would run OK on bottom but bad on top. If open, it would run bad down low but strong up top. It is very easy to check PV operation on the CR. Pull the inspection cover off the left side of the cylinder and start the bike. If should rotate 90 degrees as the rpm goes up.