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

[Ol'89r]

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 ?

That is normal. Don't try to adjust the idle until the bike is fully warmed up. If you adjust it when it is cold, it will be too low when it warms up. Japanese bikes are very cold blooded, especially Hondas.

Your feeler gauges don't make sense, 2.54mm is .100 thousands and 1.27mm is .050 thousands. That is too much clearance. If you have a .004 thousands feeler gauge, you could use that on both valves and just for testing purposes, you would be in the ball park. Set the intake with a little drag on the feeler gauge and set the exhaust without any drag. You should be able to hear and feel a slight click on the rocker arm.

I would reset the valves using the proper gauges and then check your compression. If the valves were tight and ran for any period of time, you may have a burnt valve. A burnt valve will also cause an erratic idle. Your carb depends upon a certain amount of vacuum to work properly. If the engine is worn, (bad rings or valves) you won't have enough vacuum for the carb to work properly. If when you check your compression the reading is low, squirt a little oil in the cylinder and check it again. If the pressure comes up you have bad rings. If the pressure doesn't come up, you have bad valves or both. Be sure to hold the throttle wide open when you do the compression check.

You can tune on your carb all day long but if the engine isn't tight you are wasting your time.

 

[Dr Rockso]

i'm going to go get another set of feeler guages today , my compression tester is dead , but the bike feels like it's got plenty of compression , and it doesn't smoke , it actually sounds really good . it's impossible to set the exhaust on this one with no drag because they put a spring on the rockers for the exhaust valves that keeps the rockers down , when i did them i just tightened the adjuster untill i could still slide the feeler guage around and then tightened up the nut . i'm also going to buy a can of carb cleaner with the little straw and give the carb another go , it's getting better , so maybe there's still some junk in the pilot circuit somewhere .

it's that normal to have to adjust the idle all the time ? i mean when it starts the idle is way high and once it's warm it's super low . all of this is without the choke on . all my other bikes idle like crap untill they're warmed up , this bike seems to be the complete opposite .

 

[Dr Rockso]

ok , well today i went and got a new set of feeler guages , set the valves . i also bought a can of carb cleaner and went crazy on the carb for a few hours . from this point on it is %100 not due to junk in the carb , you could eat out of that thing now .it's too late to start it right now so i'll post the results tomorrow but if this doesn't do it i don't know what will . here's hoping .

 

[helio lucas]

what about a blown head gasket???
the engine is air cooled so it could be sucking air...
look for blown spots around the head... or start the engine and spray something like wd40 around it and see if makes bubbles (or the idle speed changes)...

 

[anthonysimo]

Two things I'd like to offer up as potential causes 1. very small hole in the carby float which may cause changes in fuel level in the carb depending on temp. Take the float out and hold it under fuel in a glass and see if any bubbles appear. if not leave the float there for say 10-20mins and then release it from under the fuel and see if it floats evenly , take the float out dry it off and shake it to see if you can hear fuel inside the floats. If in doubt replace it. 2. Do you have good consistent fuel feed from the tank as a partly blocked tank filter/line may restrict the fuel and lean the bike out just enough to cause fuel level problems in the carb which resolve themselves when you stop the motor but return as soon as you run the motor fast enough to use more fuel than can be supplied through the retricted filter. Finally any breather tube to the carby should be removed and checked for free flow in both directions. Good luck.

 

[ZOMBIE666]

thats guys for helping him out, he ended up selling the XL last night. :cool:

 

[oscaman]

I have an xr350r and the only throttle trouble I have had is when the twist grip gets dirty enough it will hang a bit and make the cable slow to let the slide return all the way down to the idle screw. The cable could also be kinked or dirty enough to do the same thing. Hang in there , they are bulletproof in general !!

 

[schmanman]

somtimes the simplest thing are the problems....

my old kawasaki did this now and then...


lube the throtle cable, and the carb slide. since you've already cleaned the carb numerous times, I would concentrate more on the throttle cable.

I'll bet that's the problem. just a can of wd-40 will work.

unscrew the throttle cable all the way at one of the adjustable parts (circled in red in the picture in the link below), and spray lube into the cable, and twist the throttle for a while, to work it down the cable. (with the bike off obviously)

http://i343.photobucket.com/albums/o442/schman-man/untitled.jpg