XR250R tuning help please...

[gamorg02]

So i've been thru my carbs and started a discussion here on it. basically tried all of my jets and adjustments and still can't get it right. what i know:

1. i adjusted the valves. it was my first time.
2. i put a new air filter in.
3. oem snorkel was removed
4. unsure how bike ran before this season as i got it, make sure it ran and shifted then took it apart.
5. bike runs good 'til mid, even mid/high RPMs as long as the throttle is below 1/2 or 1/3.
6. after that with higher throttle positions at higher rpms shit goes downhill.

it almost seems like the choke is still on. so to try to help i've tried the following, and the symptoms are same. it pops (not backfires or anything) and just won't accelerate smoothly. sometimes it will pull thru but maybe 25% of the time.

tried to:

1. tape up most of the air box hole so its similar to the stock snorkel (richen it up)
2. remove air filter so it leans it out
3. tried mains 128 - 138 (stock is 130)
4. Tried all settings on needle (5 way adjustable).

all of those sometimes making the popping worse, but it will still bog down.


old plug looked wicked rich, not wet, but black. new plug after maybe 1/4 mile looks as it should. golden, maybe even a bit lean.

someone had recommended to check exhaust leak. i checked, couldn't feel any air, but the clamps were loose. tightened them down and it felt a tiny bit better but not great.

breakdirt916 came over tonight and we wrenched for a couple hours with no luck. since my exhaust has some aftermarket spark arrestor its hard to tell but it really does feel like his when the choke is still on.

if anyone has ANY ideas , please let me know. i'm at my witts end with the damn thing and would love some help. house calls will be provided unlimited beverages of your choice if someones willing...


my next idea is to try a very lean or rich jet and see if that helps at all.

the only other thing i can think of i know with vmax's if the airbox is off and the carbs don't have an air adjustment plug they won't rev past 4/5k rpms, and it almost sounds like that. i checked for intake leaks with carb cleaner too, nada.

anyways thanks in advance.

[breakdirt916]

gamorg pretty much got the major stuff, so the only thing I would add is how it feels: from idle to low/mid rpm's, the roll off is smooth. But once you get to a certain point, the bike hesitates (independent of throttle position) and the engine speed just won't accelerate. It does "catch" and continue through the power band occasionally, but for the most part it just hesitates when it gets to that rpm range.

Pretty much all the basics have been covered...any input here? fasteddie?

[gamorg02]

looks like similar symptoms here, huh bhavesh?

http://www.kawasakimotorcycle.org/fo...ccelerate.html

maybe a vent tube is partially blocked, and not letting enough fuel in at high RPMs? there is supposedly 2 of them on this bike, and one is attached to the drain hose.

[Cerberus]

every thing you describe indicates that it is too rich, but you want to go richer?!

a couple thoughts in no specific order;

(actually, check this first) try checking your float level (too high will run rich) and make sure your float needle and seat are clean, use an inline filter if there isn't one(personal preference there, but well advised i think)

try going down to a 126-125 and/or dropping the main needle (clip to top notch) and make sure it sits properly inside the slide so that is it down where it needs to be

if there is a low speed jet/needle, have you tried leaning that down a bit?

an exhaust leak could absolutely cause a high rev rich-out by causing a loss of inertial scavenging.. but its a bit or a reach i think, especially on a carbed engine.

lastly, since you did the valve adjustment, i have to ask, any chance of your valve timing being out of spec now? and are you sure the valves are adjusted correctly?

have you tried a new spark plug?

[Cerberus]

looks like similar symptoms here, huh bhavesh?

http://www.kawasakimotorcycle.org/fo...ccelerate.html

maybe a vent tube is partially blocked, and not letting enough fuel in at high RPMs? there is supposedly 2 of them on this bike, and one is attached to the drain hose.

those symptoms don't sound like they match yours.. especially with the spazzing tach.. (unless you have that symptom too and failed to state it?)

[Paul_E_D]

it almost seems like the choke is still on. so to try to help i've tried the following, and the symptoms are same. it pops (not backfires or anything) and just won't accelerate smoothly. sometimes it will pull thru but maybe 25% of the time.

breakdirt916 came over tonight and we wrenched for a couple hours with no luck. since my exhaust has some aftermarket spark arrestor its hard to tell but it really does feel like his when the choke is still on.

Well, I think you have answered your own question. Sounds like an obstructed exhaust to me. Take the sparky out and try it. I'm betting the packing is stuffed, or some kind of baffle has come loose in the pipe itself.

[gamorg02]

every thing you describe indicates that it is too rich, but you want to go richer?!

thats why i'm asking, maybe its too rich, its very difficult to tell to be honest, except the new plug was lean-ish. and with the mods done to the bike (how i got it) it SHOULD be lean if anything.

a couple thoughts in no specific order;

(actually, check this first) try checking your float level (too high will run rich) and make sure your float needle and seat are clean, use an inline filter if there isn't one(personal preference there, but well advised i think)

dry float level is perfect. no specs for wet level, so i can't verify it there, but that could provide insight as well.

try going down to a 126-125 and/or dropping the main needle (clip to top notch) and make sure it sits properly inside the slide so that is it down where it needs to be

needle is easy, jets not so much. only have a 128, and the symptoms follow with that. i can try running the leanest i have, but if i remember correctly it just caused more 'popping' during the symptom.

if there is a low speed jet/needle, have you tried leaning that down a bit?

slow jet, yes. its on the stock size right now with 4 turns out. 1-2 turns out and it doesn't like to idle smoothly.

an exhaust leak could absolutely cause a high rev rich-out by causing a loss of inertial scavenging.. but its a bit or a reach i think, especially on a carbed engine.

any good ways to test aside from feel for air?

lastly, since you did the valve adjustment, i have to ask, any chance of your valve timing being out of spec now? and are you sure the valves are adjusted correctly?

timing could definitely be it, would that show only at higher rpms? valves coudl DEF be off, i double/triple checked them, but triple checkign the wrong work when you don't know any better is not good either. they didnt' seem that hard tho, so i do doubt it. plus it starts pretty easy, and i've heard if valves are off, [kick]starting can be a biatch.

have you tried a new spark plug?

yes.

those symptoms don't sound like they match yours.. especially with the spazzing tach.. (unless you have that symptom too and failed to state it?)

the spazzy tach was mentioned by another guy, but the original poster sounds very similar to mine..

Well, I think you have answered your own question. Sounds like an obstructed exhaust to me. Take the sparky out and try it. I'm betting the packing is stuffed, or some kind of baffle has come loose in the pipe itself.

i can try that tonight. thats an easy one. i may also try taking the tubes off the carb vents just to see what happens.


thanks everyone for the replies so far

[Paul_E_D]

Don't go too crazy with jetting. This is NOT a jetting symptom for a 4 stroke unless the main jet was just rolling around loose in the carb. How old is the bike?

[gamorg02]

Don't go too crazy with jetting. This is NOT a jetting symptom for a 4 stroke unless the main jet was just rolling around loose in the carb. How old is the bike?

i was starting to think the same thing. bike is a 1999 so not crazy old, but i'm at least the 4th owner. i know it was used as a legit road bike not so long ago (2007/2008) maybe..

i've put a lot of time and parts into it (not related to this issue), so aside from this its running/turning/moving well, so hopefully its the last hurdle. went through just about everything but the engine internals.

i know the Previous owner replaced the stator thinking itw as bad (ended up being kill switch short circuited always on), so its not the original (which I do have) if anyone starts thinking it might be electrical.

[Paul_E_D]

The motor runs, so it's not likely mechanical. It could be a fuel blockage, airleak/blockage, or electrical. Have you tested the coil yet?

[gamorg02]

The motor runs, so it's not likely mechanical. It could be a fuel blockage, airleak/blockage, or electrical. Have you tested the coil yet?

doubt its airleak, as i couldnt' get the idle to change, dousing the intake boots in cleaner, but it could be.

blockage -> doubt it in fuel line as i have new hosing on there with an in-line filter, but it still doesn't rule out the vent tubes. haven't looked there yet.

have NOT tested coil. I'll be honest, electrical is my weakest area of expertise. It looks like I need to do some tests to see if the minimum voltage is 100V. but i need a 'peak voltage adapter', is that right? or is there an easier way to test the coil?

could a coil only show at certain rpms and above?

[gamorg02]

so i figred it out. FINALLY. it was bad ground. cleaned it, put it back together, ran great. rejetted based on recommendations for mods, ran better. took her out today and no problems what so ever.

[breakdirt916]

I will also add that the XR250R is a fantastic woods bike...saw this thing in action yesterday and it definitely rocked out!

[gamorg02]

yea it worked out real well. looking into bark busters now tho! that tree was not happy to see me.

u get my text on risers?

[breakdirt916]

yeah, those trees are tougher than they look

round 2 tonight?

[gamorg02]

yeah, those trees are tougher than they look

round 2 tonight?

can't tonight. brett and i were thinking tomorrow or maybe thurs pm. i will keep you informed. love to hit up the beaver loop again.

[breakdirt916]

can't tonight. brett and i were thinking tomorrow or maybe thurs pm. i will keep you informed. love to hit up the beaver loop again.

I'm working nights tue/wed/thu, but let me know in case something opens up!

[gamorg02]

will do man.

[gamorg02]

so the issue came back (not nearly as bad) a few days ago and got to dig into it last night.

i think the ground still could have been the culprit but i also found a coil wire thats female connection was a bit loose. crimped it down and all is good again. wondering if when i 'fixed' the ground, unplugging and re-plugging in the coil seemed to fix the problem but i really just disloged dirt and then when iput the dieletic grease in, that helped 'solve' the problem. now over time, the grease has worn away so the issues started coming back. we'll see in a few weeks!

[breakdirt916]

hopefully that'll be the last of that!

it randomly happened on the trail?

[gamorg02]

nah started happening again the other day.

[Paul_E_D]

Well, You know its electrical. I would just start by cleaning baterry post and all ignition related contacts. Tighten them up and slather em with dielectric. Possibly get a new ground strap. If the problem persists after all that, then I'd look into the coil and or points/ignition module (depending on year of the bike). Also inspect the stator wiring. These often crack where the wires leave the epoxy. You can resolder and seal back up with liquid tape.

[gamorg02]

Well, You know its electrical. I would just start by cleaning baterry post and all ignition related contacts. Tighten them up and slather em with dielectric. Possibly get a new ground strap. If the problem persists after all that, then I'd look into the coil and or points/ignition module (depending on year of the bike). Also inspect the stator wiring. These often crack where the wires leave the epoxy. You can resolder and seal back up with liquid tape.

no battery on the xr! all the cdi and coil contacts are cleaned and have the grease on them. after crimping down the female coil plug piece it runs well, and ran good for the 2-3 miles I did yesterday.