'88 XR250R running lean

[colbystrong]

First of all, thanks in advance for any help for a rookie. I've searched around for several hours to find similar threads, but haven't found a silver bullet yet.

I recently inherited an '88 XR 250R from my uncle. Unfortunately, the bike has been sitting for a number of years. How many, I'm not sure. So far I've replaced the air filter (and removed the remnants of a couple nests), emptied the tank completely of the worst smelling gas I've ever run across, and taken off the carb - lots of gum and varnish so I let it sit in gas for a day, then carb cleaner for about a day to break everything up and clean it up.

The bike will run with half choke, but will die immediately without the choke. The bike also breaks up at higher RPMs and sputters under load riding it around. So, classic lean symptoms.

I took the carb back off, removed the bowl, and took out everything I could without disassembling the throttle valve assembly (it seemed fine and moved freely) and verified nothing had blockage.

The only service manual I could find was for the later year bikes ('96-04) so I was using the carb settings for the pilot screw (1 3/4 turns from seat) and the float (12.5mm). Are these also correct for an '88?

I also called my local Honda dealer and they can't order a carb rebuild kit because it's apparently not available (is this true?) so I'd have to order separately and I'm not sure where to begin with parts - likely all of the gaskets and o-rings. They seemed to be in good shape when I took the carb apart.

Before I do that, is there something I can try? I'm not sure the float is set correctly - could that be the cause of my problems? Is there a mixture screw I can play with to richen things up to see if that changes anything?

Thanks - I'm certainly not a carb guru by any means.

[Trailryder42]

The pilot screw IS the mixture screw. It's that brass screw at the front of the carb bowl, pointing down.

That pilot screw needs to come out and you need to clean out that passage. Take care to account for all its parts. Screw, spring, washer, o-ring. Goes together in that order. Make sure the o-ring is in good shape.

Without knowing the exact float level spec., setting it so the flat top side of the float is level with the float bowl mating surface should be pretty close.

[colbystrong]

Thanks very much for the quick reply. I'll pull the pilot screw out again and check to see if something got in there, but I'm 100% certain it's clean through all of the passages for the pilot and the o-ring looks pretty good. Always worth another look, though.

The float definitely is not level to the mating surface - it's probably about 8 degrees off or so (I remember it being closer to level before I pulled everything apart). I'll check that out too.

Thanks. It's supposed to be in the 60s this weekend, so I'd love to take this thing for a spin at more than 1/4 throttle.

[argclh6670]

12.5 mm is the correct setting for ur 88.

[e36graduate]

Colbystrong....where at in Massachusetts? I just got my 1990 XR250 running like a champ today after tearing apart the bottom side of the carb.....lots of gunk in that carb....can't believe how well it is running now.

[colbystrong]

e36 - I live east of Worcester, a few minutes away from where 495 and 90 intersect. If it's anywhere close to you I'd love to get a second set of eyes on this thing for sure...

[colbystrong]

Update:

Pulled the carb off again and the pilot passage is/was clear. I also bent the tang for the float so both sides of the float are parallel with the carb mating surface. For good measure, I shot carb cleaner into every single orifice I could find (main jet, slow jet, pilot hole, the other 3 or 4 holes, etc) and everything seemed to be fine. The bike still refuses to run without half choke.

Not knowing the history of the bike, I don't know whether or not it has stock jets. The exhaust looks stock. I replaced the air filter with a new aftermarket one a couple of weeks ago when I first tried to fire it up. Should I be worried about how much of a seal the filter makes with the airbox surface?

At this point, I'm going to replace the spark plug (seems unrelated, but what the hell) and order every gasket and o-ring on the carb... unless someone knows of a reputable aftermarket carb kit for the bike since Honda doesn't seem to carry one anymore.

Any other suggestions? I have about 20 hours into this now, and it's getting frustrating quickly.

[Trailryder42]

I have a .pdf shop manual for the '86-'87. Don't know if the '88 would be the same, but for those bikes stock jets were 125 main and 40 pilot.

[e36graduate]

Did you get the bike going? I was having similar issues and a good carb cleaning worked.....you will need to set the fuel/air mixture which is underneath the carb, on the bowl side that is closest to intake of engine....you will see it. Close it all the way, then open it 2 1/4 turns....should be bang on.

[argclh6670]

i think the diaphram bladder thing is bad, mine did the same. its behind that qurter size plate behind choke arm.

[colbystrong]

Did you get the bike going? I was having similar issues and a good carb cleaning worked.....you will need to set the fuel/air mixture which is underneath the carb, on the bowl side that is closest to intake of engine....you will see it. Close it all the way, then open it 2 1/4 turns....should be bang on.

I owe you a drink for sure - this fixed it. I gave it another half turn from where it already was (the manual I had for the next generation of the bike had his screw at 1 3/4 turns from seated) and it fired right up and ran like a champ.

I celebrated with a wheelie across the length of my yard.

Thanks for all of the suggestions, everyone!

[e36graduate]

That's awesome....I found that information in my owners manual....it too made my bike run well.

Now I need to find out why my bike will smoke once in a while when I start, cold starts....for about 10 seconds and then absolutely no smoke for the rest of the ride.