just picked up an 83 honda xl250...and it's already driving me crazy

[Dr Rockso]

hi , i just picked up this 83 xl250r and i've been trying to get it running right , i've cleaned out the carb (3times to be sure) , it has the stock jets , they're clean as new , the float isn't adjustable in these 83's so i'm sure thats where it should be . the bike starts up first kick and revs just fine and has plenty of power , but when you rev it up and try to let it go back down to idle it hangs up . if you let it sit for a while the rpm's will drop back down to normal . sometimes it does it worse , sometimes it barely does it , but it seems to always do it a little . i got a new air filter and that solved the problem with not being able to cut the throttle wide open quickly . and i bought a can of starting fluid so i could see if the carb boot is leaking .... it's not . it's running hot too , so hot that it just dieseled after i turned the bike off . does anyone know the factory position of the mixture screw ? this is driving me crazy , i'll be sitting there and the idle will be fine , i'll blip the throttle and it'll rev up and then continue to hold higher rpm's after i let go of the throttle , sometimes it'll come back down , sometimes it'll just stay revved up . when i mess with the idle screw it'll come back down , but then i'm idling really low , almost to the point of it konking out . i've tried different positions of the mixture screw and it doesn't seem to change much , if any of you guys know what i should check please help me out .

 

[groundeffect_db]

Sorry, I'm a newbie and not sure I can really offer anything here, but I'll give it a try:

Well, if you are running too hot like you've mentioned, perhaps the carb is getting too much air and not enoug gas to cool it and burn at normal rpms. There may be an air leak in a hose to the carb, or fuel line etc...

I'm not sure, but I hope that helps.


But please let me say, wow, that is a good looking bike! 1983, that's pretty cool stuff. I had no idea bikes could be around that long and keep running.... I'm just getting started in the sport ( at 29 ), finding it alot of fun so far and I was wondering how long I could possiblely have my bike. I thought a couple years, but it sounds like if it well taken care of I could have if for a few more then 3-4 years.


thanks.

 

[Dr Rockso]

my last bike was a 1972 , so yeah , if taken care of they can last forever ....well maybe not the new ones , the new 4 strokes need just as much work as the 2 strokes . i just wish i knew what was going on with this one . i just pulled the plug and it was dry and sooty black , which doesn't really go along with my initial call of it running too lean . the real question is if it's not running lean , and the carb boot isn't leaking in air then why does my idle hang ...and why in 20 minutes of riding did it get hot enough to diesel after i turned the bike off . i'm really starting to get pissed at this thing .

 

[Dr Rockso]

i just looked on the parts diagram and noticed there's an ignition advancer under the clutch cover , do you guys think that if that was stuck , or sticking that it could cause my weird idle and make the bike run hot as hell ?

 

[Dr Rockso]

i just made sure the throttle cable was routed properly and it is , i tried messing with the mixture screw and it doesn't seem to help it , i can have it turned all the way in , or so far out it's about to fall out and it'll still do it . nothing seems to stop it from hanging up . i've been thru this carb more times now than i can count , anyone have any other ideas before i sell this dumb thing to someone else and let them deal with it ?

 

[groundeffect_db]

Sounds like you've done a lot of work like reset to factory settings( if you know them? ). Good to see the throttle cable is routed propertly and likely nothing to bind it or hang it up.

Does the carb stick when the cable is pulled at all?

Have you replaced all of the tubing?

replaced the plug?

check wiring on the plug cap?

just tossing out ideas.... ?!?!?!

 

[Dr Rockso]

yeah , all that stuff works fine , the funny thing is no matter how rich i make it or how lean i make it it still hangs up , it does seem to do it worse the warmer the engine gets , but sometimes it doesn't do it at all . you'd think if i had a lean condition (which there doesn't seem to be from looking at the plug) it would always do it . the other thing i'm thinking is this is one of the first years for the electric ignition on these , but honda still used a spring loaded ignition advancer (conviently located behind the clutch cover ..yay) if that was sticking then it would have the ignition advanced when it shouldn't be , that could cause the weird high idle that sometimes goes back to normal couldn't it ?

 

[Dr Rockso]

hmmm , well i just pulled off the side cover for no reason ....seems 83 was a transition year , mine didn't have the advancer (17 in the diagram) , it just has the rotor (16 in diagram)

here is some real pics

so i guess that wasn't it , i guess i'll check the carb again , i could have sworn everything was clear in there.

 

[groundeffect_db]

thanks for sharing the pics, you'll get it, you have to, you're trying everything! :)

You can also look at this troubleshooting like this - you're getting to know that 83 honda really well! :)


Hope that helps and good luck with the rest of your research! please continue to keep us posted, this is some great information and proceedure you're doing here.


Cheers

 

[Ol'89r]

yeah , all that stuff works fine , the funny thing is no matter how rich i make it or how lean i make it it still hangs up , it does seem to do it worse the warmer the engine gets ?

Your air screw should be adjusted from 1 1/2 turns to 1 3/4 turns out from the seated position.

Check your valve clearance. Should have approx .002" on the intake and .003" on the exhaust valves. Tight valves will cause your bike to run hot. The hotter the bike gets the worse it will run. Check the compression after adjusting the valves. Should have at least 120psi.

Check your intake manifold. Especially at the area where the rubber is bonded to the aluminum mounting plate. On the older XR's/XL's, the rubber can separate from the plate and it is hard to see unless you remove the manifold or try to pull it back away from the head.

When you cleaned your carb did your remove all of the jets and blow air through the orifices? Especially the pilot jet and pilot air orifice. Remove the pilot jet and the air screw and make sure air comes out of both holes. Make sure you can see daylight through the hole in the pilot jet. A bent slide needle will cause a bike not to idle down correctly. Remove the needle from the slide and roll it on a flat table. If it is bent, replace it.

With the electronic ignition your bike does not have a mechanical advance. It is done electronically.

If the bike is running so hot it diesels then something drastic is wrong with it and you should not try to ride it until you find out the problem.

 

[Dr Rockso]

oh ok , 1 1/2 turns out was what i had it at originally . i haven't checked the valve clearance yet but i will now . the manifold is good , i sprayed starting fluid everywhere , didn't raise rpm on me at all , even wiggled the carb while spraying to make sure there were no hairline cracks i wasn't seeing . i'm going to clean the carb yet again and see if that does it . i realize now that the ignition advancer i saw on the parts diagram is right next to the electronic ignition rotor , mine has the electric , i thought it was strange that an electronic ignition needed an advancer . i've got the bike all torn down now so hopefully i'll find whatever the problem is .

 

[Dr Rockso]

hmmm , ok , well i adjusted the valve clearance to stock spec (the sticker on the bike said intake is 0.05 and exhaust is 0.10 so thats what i put it to) ,and cleaned the carb again . so i went out and started it to see if i fixed the problem and it doesn't seem that i have . from when you let go of the throttle there's the normal decel but then right before it gets to idle speed it stays a bit revved up for about a second or a second and a half then it goes back to idle speed . right now i have the air screw on the carb 1 1/3 turns out . also for some reason now i can't crack the throttle all the way open without it trying to die . i went all thru the carb today , for hours , it's clean , every passage allows compressed air thru it ....i'm really starting to hate this thing . is 1 1/3 turns out on the air screw correct ? i don't have a manual yet so i don't have any of this information .

 

[2strokerfun]

Just double checking to make sure you set valves at mm, not inches, from the numbers you used.

 

[Ol'89r]

Just double checking to make sure you set valves at mm, not inches, from the numbers you used.

Good catch 2stroker. :cool:

The specs given on the sticker 0.05mm is the same as .002" and 0.10mm is .004" thousands of an inch. Also make sure your piston is at top-dead-center when you adjust the valves.

On the air screw adjustment, 1 /13 turns out should be in the ball park.

What happens when you turn the idle adjustment screw, (not the air screw) all of the way out? Does the idle drop down then?

 

[Dr Rockso]

the feeler gauge i have has 2 numbers per feeler , but they're kinda hard to read , mainly it's hard to see the decimal points .

the one i used for the exhaust reads
010
254
mm

for intake i used
005
127
mm

both of those feelers are on the small side as the feelers get much bigger , the smallest feeler says 004 102 mm. i did make sure i was at tdc on the compression stroke . when i first opened up the rocker covers i couldn't get the small click in any of the rockers so i'm assuming the valves were tight . now there's the slightest little click in each rocker when you grab one and try to lift . i think i did it right , i've always used the 008 feeler for setting the valves in my old vw . the weird thing is that it still does the idle thing even after the valve adjustment and tons of carb cleanings . the idle adjuster does work , and when the idle starts to hang if i turn the idle screw the idle will come back down most of the time , but it'll be way lower than it should be . there's slack in the throttle cable so i know it's not sticking . i think this might be my offroad curse , i can have as many street bikes as i want and i never have a problem , but every single dirtbike i've ever had always has some impossible to figure out mystery problem that eventually causes me to sell the dirt bike .

here's a few other notes on the bike that may help you guys figure it out because i'm at a loss

the carb has one of those air cut off valves , but the diaphram is good with no holes

the decompression system is busted and no matter which way i turn the little lever on the cylinder head it feels the same to me at the kick starter (not that i need it on a 250)

when the idle does hang up if i roll almost to a stop before pulling in the clutch it'll hold a regular idle untill i blip the throttle again

sometimes when the idle hangs up it'll stay raised untill i blip the throttle a few times

it seems to get worse the hotter the engine gets

most of the time when i blip the throttle it'll rev up , the rev's will come back down and right before it gets to idle it'll hang for a second and then go back to idle .

 

[Dr Rockso]

here is a video , maybe it's just me and thats how it's supposed to run , but i doubt it , you guys be the judge .
<object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/P8-g6fAPjbA"> </param> <embed src="http://www.youtube.com/v/P8-g6fAPjbA" type="application/x-shockwave-flash" width="425" height="350"> </embed> </object>


note , i just uploaded the video so if it says it's not there then youtube hasn't approved it yet , it'll work soon

 

[sick 96 250]

just an idea but make sure your throttle tube isn't sticking a little causing it to hang up and maybe check to make sure you needle for the carb isnt bent. Just ideas since you seemed of tried everything else. In the vid it really doesn't sound all that bad on decel.

 

[Dr Rockso]

the needle isn't bent and the throttle tube isn't sticking . i couldn't really get it to hang at as high rpm or as long as it does in the video as it does sometimes . it also seems to do it more it i just give it enough throttle to rev , if i open it up and then let it come back down it normally gets back to idle quicker . i know this has the air valve thing which if i read right is supposed to lean the bike out some on decel so you don't backfire out the carb or anything so what little of the problem i have left may just be that , but it still doesn't seem right to me . tho i guess i need to adjust the valves again once i find a set of feeler guages that go down to 002 .

 

[Dr Rockso]

i just went out and rode it again and now it doesn't seem to be doing it really at all , tho i'm sure it'll do it again as soon as i say i fixed it ...i still have to mess with the idle every time i start it tho , it's always too high when it first starts and then way too low once it's warmed up . i still need to re-adjust the valves .

 

[Dr Rockso]

man this thing is annoying , i just messed with it some more and now it goes back to idle pretty quickly , but i shouldn't have to constantly need to adjust the idle . i had it somewhere good , rode around the house 4 times and when i pulled back up the idle was very low , then when the bike cools off and i start it the idle is way high , what could be causing this ?

 

[snb73]

Have you tried a new throttle return spring? After 25 years it may have lost some of its tension.

 

[snb73]

Have you tried a new throttle slide spring? After 25 years it may have lost some of its tension.

 

[Dr Rockso]

it has nothing to do with the slide , it snaps back just fine . it acts more like the bike is constantly changing it's own jetting . i keep taking the carb apart and every time the jets are clear , all the passage ways allow compressed air thru them . yet i every time the engine starts the idle needs to be adjusted . every dirtbike i've ever owned has done stuff like this to me , it's always something stupid and it's always impossible to diagnose .

 

[dirt bike dave]

A worn slide and weak return spring can snap back fine when the engine is off. But when the motor is generating vacuum (such as when it is de-celerarting), a worn slide can get c*ockeyed in the carb bore and not return to full closed as quickly as it should. If that is the problem, a stronger spring could help.

 

[Dr Rockso]

mine is the kind with the arm that raises and lowers the slide , the spring on it is pretty big and very strong . the slide and bore looked great , i don't think there's very many miles on this bike , it's just been sitting .