1999 XR250R help please...

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gamorg02

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having some problems with my newly aquired '99 xr250r. posted this on a local forum here too but u guys know your shit, so please if anyone has an idea lemme know!

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
idea.gif
, 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.

-------------------------------

a guy came over to help me with it tonight and he added:

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.
 
Sorry G, no help here. If you figure it out, please post it up. I have a similiar issue with the PW80 I rebuilt earlier this year. The kids are still a bit yound for it so I haven't bothered pissing with it. It was a basketcase when i got it. It will run now. Its fine in the low end but like you, once you get to mid range and above it feels dead.

The stock airbox and snorkel were gone when I picked it up so I just bought a clamp on dual stage, foam, uni filter. I've heard others have gottten this setup to work but it ain't working for me!
 
Sorry G, no help here. If you figure it out, please post it up. I have a similiar issue with the PW80 I rebuilt earlier this year. The kids are still a bit yound for it so I haven't bothered pissing with it. It was a basketcase when i got it. It will run now. Its fine in the low end but like you, once you get to mid range and above it feels dead.

The stock airbox and snorkel were gone when I picked it up so I just bought a clamp on dual stage, foam, uni filter. I've heard others have gottten this setup to work but it ain't working for me!

will do brotha..

Not sure if you have a manual for it, but if not, here's a link that may help,

http://abhibeckert.com/downloads/Honda-XR-250-R-96-04.pdf

Sounds like it is running rich or poor spark. Is it just happening under load or even when you the bike is being reved in neutral?

Good luck


Mike

i do have the manual, so i know where everything is and how to get to it. i appreciate the link tho man! the guys at thumpertalk didn't really point me in any good directions, the jets i have SHOULD work, as per everything i read.

now, moving away from it being an a/f ratio issue, i haven't ruled out mechanical (altho I think it would show at all RPMS, if a valve or the top end was shitty), but could be electrical?

guy before me replaced the stator. thought it was bad b/c the kill switch got shorted to always on. i can do it in N or under load though.
 
I had a spark issue with my Honda CR5 last year. Different symtoms though. Real easy and free fix so it might be worth a shot. I just removed the coil from the frame (it grounded to the frame) cleaned everything up and put on something similar to dielectric grease and my spark issue was gone. Doesn't sound like the same problem but figured I'd throw it out there
 
i found a coil, plug, cdi for $90 on ebay with 14 and 7 day refunds. maybe pick it up and try, no easy way to bench test the CDI i guess. such a simple damn system this should be easier, heh.

can valve problems only show at high RPMs?
 
Did you verify that the timing is spot on by checking the marks on the cam gear and flywheel? Perhaps you jumped a tooth.
 
First off, did you do a compression test yet? a leak down test?

I beleive those bike have a decompressor on them - if so, they can "leak" at higher rpms and cause symptoms as you mentioned. Can check this with bike in neutral, gradually increase rpm while listening/watching decompression valve to see if it "pops off".

Next, warm bike up with old plug in, than put in new plug, start bike, leave in neutral, rev bike till she starts to crap out, kill engine, take plug out and check to see how it looks. Should give indication if rich (wet/carbon), lean.etc...

I know you did work on carb, is the float height spot on, makes a big difference on these one lungers.

Mike
 
First off, did you do a compression test yet? a leak down test?

I attempted to. Couldn't get my damn compression adapter down there. the angle and the length of the adapter is all messed up. so no, not yet.

I beleive those bike have a decompressor on them - if so, they can "leak" at higher rpms and cause symptoms as you mentioned. Can check this with bike in neutral, gradually increase rpm while listening/watching decompression valve to see if it "pops off".

there is a manual (and i think auto when using kick starter) decompression. I have not adjusted it yet and have been trying to read up on it as the 'free play' thing was mind boggling but i think i have it down now. I can also take a look at the 'pop off' thing.

Next, warm bike up with old plug in, than put in new plug, start bike, leave in neutral, rev bike till she starts to crap out, kill engine, take plug out and check to see how it looks. Should give indication if rich (wet/carbon), lean.etc...

when i do this the plug looks lean if anything.

I know you did work on carb, is the float height spot on, makes a big difference on these one lungers.

yes. spot on. only can do a dry set tho, so thats assuming the needle valve is closing when it should, wish i could get a wet reading.

Mike

:bang head::bang head::ummm:
 
figured it out. bad ground. cleaned it and put ti back together and she runs great! re-jetting to the 'recommended' for my mods and good to go!
 
Glad to hear that you figured it out. Goes to show us that sometimes it could be anything causing the problem. Persistence is the key.

I'm working on my son's 2002 Honda CR125R, that has a carb that keeps on leaking from the overflow. Had it apart a half dozen times, with no luck and tonight I just read on another forum that the spec for the float height in the manual is wrong, readjusted to what they recommended and no more leak :confused2:

Mike
 
it was annoying. to say the least. tough to troubleshoot a bike with no battery either (as far as electrical). the bench tests were non-existent or you needed like some special tools. My electrical tools consist of a 4$ meter and some heat shrink tubing basically. my expertise is not much more impressive either.
 
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