2001 cr250r takes a little bit to hit powerband

[chanlarius]

So i got this cr250r and ever since i got it, it wouldnt get those high pitch 2 strokes revs, and it requires me to pin the gas for like 5 seconds, and then itll finally hit powerband. I'm about to buy a new carb for it but i'm thinking it could be the reeds. Any ideas?

[KillerK]

Sounds like the powervalves are hanging up.

Any idea when they were serviced last?

There shouldn't be a need for a new carb. It may need to be gone through though.

[chanlarius]

No clue, i bought the bike used

[chanlarius]

I also already put a carb rebuild kit in and it did nothing what so ever.

[KPRacing]

As previously stated, look into the powervalve.

It's a process of elimination.

[chanlarius]

Should I just look for any unusual play and gunk build up? Would that fix the way it hits powerband?

[callen8365]

Have you done a compression test yet, or a leak down test? I would check the health of the engine first because it's free unless you don't have the tools, before buying new parts. If both of those check out, you can check the power valve to ensure its functioning properly by opening up the left side of it. I forget the exact process but it's in the manual and pretty simple to do. The other thing I would suggest is checking the reeds for any cracks and cleaning the carb and make sure it's jetted and adjusted correctly.

Hope this helps,

Chris

[yzmxer12]

Make sure the powervalve is installed correctly. Had a cr that had the powervalve in the wrong position. Made the bike super mellow.

[chanlarius]

I just did a new top end on it and rebuilt the carb. Everything is good, i think you guys are right about the powervalves

[chanlarius]

Make sure the powervalve is installed correctly. Had a cr that had the powervalve in the wrong position. Made the bike super mellow.

I think that my powervalves just need a nice cleaning. It does run rich

Have you done a compression test yet, or a leak down test? I would check the health of the engine first because it's free unless you don't have the tools, before buying new parts. If both of those check out, you can check the power valve to ensure its functioning properly by opening up the left side of it. I forget the exact process but it's in the manual and pretty simple to do. The other thing I would suggest is checking the reeds for any cracks and cleaning the carb and make sure it's jetted and adjusted correctly.

Hope this helps,

Chris

I appreciate your input Chris, that helped a ton

[seer]

Jetting.

[KillerK]

I got your pm

Power valves will be all or nothing effect. Meaning if stuck you will have great bottom end and no top end or vise versa.

As said, sounds like possible jetting.

What you described sounds rich.

Check plug, possibly partiality fouled. Check jetting. Air filter.

Then look into reeds/power valves.

If you just rebuilt it you would have had to time the power valve fork when installing the cylinder. You also would have noticed the flapper valve and transfer barrels. (power valves)

Did it run gud before the rebuild?

[chanlarius]

I got your pm

Power valves will be all or nothing effect. Meaning if stuck you will have great bottom end and no top end or vise versa.

As said, sounds like possible jetting.

What you described sounds rich.

Check plug, possibly partiality fouled. Check jetting. Air filter.

Then look into reeds/power valves.

If you just rebuilt it you would have had to time the power valve fork when installing the cylinder. You also would have noticed the flapper valve and transfer barrels. (power valves)

Did it run gud before the rebuild?

It ran about the same before the rebuild. The rings were paper thin. I have no idea how to adjust the power valves. I honestly didnt know they were that important

[chanlarius]

[chanlarius]

But the thing is, once i pin the throttle and open up the powerband, it's good for the rest of the ride. Also it has tonnnnns of power, i can give it little to no gas and itll lift right up, i'm thinking it's just reeds since i already did a top end and carb rebuild and air filter and spark plugs.

It ran about the same before the rebuild. The rings were paper thin. I have no idea how to adjust the power valves. I honestly didnt know they were that important

Forgot to tag you in the previous statement ^

[KillerK]

Try adjusting the air screw. (turn it counter clockwise) that will give the low speed circuit more air. (leaner)

Don't turn it out more than 2 1/2 turns from fully seated.

If that's not enough then check needle position.

[chanlarius]

Try adjusting the air screw. (turn it counter clockwise) that will give the low speed circuit more air. (leaner)

Don't turn it out more than 2 1/2 turns from fully seated.

If that's not enough then check needle position.

I run a pro circuit silencer and gold series fatty, with a 400 main and 30 pilot, i havent messed with the air screw or needle position, that could be it.

[ByronK]

i do not think your carb is the problem, if it was a carb issue the engine would either cut out (lean) or would not clear up because of rich jetting. as you described the pitch noise comes into play after 5 secs or so, this means that the PV does not open, when PV opens the engine sound changes and it screams!

 

before doing anything else check your powervalve operation, open the left PV cap and with a flat screw driver try to turn the PV barrel anti clockwise, it should turn smooth without clogging just by its normal spring tension, if not then they must be cleaned from carbon deposits - oiled and reassembled.

then bring the engine to operating temp, remove the left PV cap and rev the engine, then check that the barrel mark goes from "L" to "H" (it should from mid-top rpms), not wait 5 secs though it should open right away. If the PV opens partially then either it is clogged or needs adjustment, adjustment is easy, do these two simple steps first and then we will go into adjusting it.

 

if you could post a picture of the valve if you remove the exhaust get a close up of the PV barrels from the exhaust port to see if we can help you out.

[chanlarius]

i do not think your carb is the problem, if it was a carb issue the engine would either cut out (lean) or would not clear up because of rich jetting. as you described the pitch noise comes into play after 5 secs or so, this means that the PV does not open, when PV opens the engine sound changes and it screams!

before doing anything else check your powervalve operation, open the left PV cap and with a flat screw driver try to turn the PV barrel anti clockwise, it should turn smooth without clogging just by its normal spring tension, if not then they must be cleaned from carbon deposits - oiled and reassembled.

then bring the engine to operating temp, remove the left PV cap and rev the engine, then check that the barrel mark goes from "L" to "H" (it should from mid-top rpms), not wait 5 secs though it should open right away. If the PV opens partially then either it is clogged or needs adjustment, adjustment is easy, do these two simple steps first and then we will go into adjusting it.

if you could post a picture of the valve if you remove the exhaust get a close up of the PV barrels from the exhaust port to see if we can help you out.

So what you're saying is that since it takes a little bit to get the high pitch noise, that means that my pv are not opening from all the carbon gunked? That means all i gotta do is clean em and grease em back up, and i'm all set, correct?

[ByronK]

probably yes but firstly follow the steps i've mentioned above then move onto the next step, also NEVER put grease on the PV barrels just 2T oil, disassembling and installing them will also need to adjust them too.