XL250R Running hot

[Swaler]

Greetings. I have an '83 XL250R that I am having to run with the choke at stop lights etc to keep it from stalling. When I have it at decent speeds I can open the choke and it runs fine, but this threatening to stall at lights is a pain. Idle is high as well and doesn't seem to change when I back off the idle knob. Advice is appreciated.

 

Bill

[Trailryder42]

Sounds extremely lean in the pilot system. Usually, turning the choke on on a hot engine will kill it immediately. The fact that yours runs better with it on says it's needing more fuel.

How long has it been doing this? Just start?

If it just started, some culprits could be, a dirty fuel screw passage, plugged up pilot jet, air leak, missing or bad fuel screw oring.

If it's always done it, pilot jet size too small, fuel screw misadjusted, float level too low.

[Swaler]

It has only recently started doing it. It was horrendous to start...usually 25-35 kicks. I cleaned the carb then it started but began this process. I have a replacement for the pilot jet so I guess I will start there. I appreciate the feed back. Bill

[Trailryder42]

Ok, so you initially had a hard starting problem, for which you cleaned the carb to try to remedy. Did you remove the carb from the bike to do that or clean it place?

If you removed the intake manifold, it's easy to get its oring out of place and pinch it during reassembly. While bike is running, either use a piece of tubing held to your ear and probe the area listening for an air leak or spray the area with carb cleaner and listen for a change.

When you cleaned the carb, did that include removal of the fuel screw, spring, washer and oring and spraying out that passage?

When's the last time the valve clearances were checked/set?

Sounds like something you did or didn't do during cleaning and reassembly.

[Swaler]

I took carb off, cleaned bowl with carb cleaner and removed all jets and cleaned them with carb cleaner. Blew compressed air through the various holes for jets etc. I did spray out the pilot jet passage but I did not remove a washer and o ring. I did the valves about 200 kilometres ago. There is a bit of smoke coming back out the intake after I stop, and the odd hiss from the intake area when it is struggling to keep running.

[ThumperCurtis]

1 hour ago, Swaler said:

...the odd hiss from the intake area when it is struggling to keep running.

This sounds just like a air leak in the manifold. At idle you have to choke off the air from the carb to keep it running as its being supplied from the manifold leak. Then at speed you can un-choke and it runs fine because the amount of air through the carb is more than the leak from the manifold.

 

Get some starting fluid and spray around the intake manifold.  

[Swaler]

So, spent a couple of hours and pulled carb off, cleaned manifold. No gasket between engine and manifold...not sure if that is missing or there isn't one. Bike is new to new to me by about a year. Pulled out all the jets....and most interestingly the pilot jet had no washer, no rubber gasket and no spring. I have been adjusting it with great expectations and nothing seemed to change...no wonder. I had ordered new diaphragm for decal as well as new pilot jet kit. Put this in with the appropriate spring, washer and gasket....turned it out 1 3/4 turns as per manual...and voila!!!!! Started, ran without choke and pulled much better. Trying to garner a lesson from this experience unfortunately keeps coming back to my poor mechanic skill!!! Thanks for the ideas...I used both of your advice and am grateful. Feels like a brand new bike! Thanks. Bill

[Trailryder42]

4 hours ago, Swaler said:

I took carb off, cleaned bowl with carb cleaner and removed all jets and cleaned them with carb cleaner. Blew compressed air through the various holes for jets etc. I did spray out the pilot jet passage but I did not remove a washer and o ring. I did the valves about 200 kilometres ago. There is a bit of smoke coming back out the intake after I stop, and the odd hiss from the intake area when it is struggling to keep running.

The spring washer and oring are in the "fuel screw" passage. You seem to be calling the fuel screw the "pilot jet". It is not. The jet is inside the float bowl. Cleaning the pilot jet itself and the hole it screws into does no good if the fuel screw passage is dirty, blocked or has a bad oring.

You should check the valve clearances. As they wear, clearances get tight. If tight enough, it can partially hold open the exhaust valves and you'll experience this hissing and poor running.

Glad to hear you got it running better.

[Swaler]

Ahhh...my terms stand corrected. It was the fuel screw that was the issue....have added the spring etc and all well. I would hope I am a better surgeon then mechanic...usually o left o er parts then.

[Trailryder42]

3 hours ago, Swaler said:

 I would hope I am a better surgeon then mechanic...usually o left o er parts then.

Yeah, that would be bad. lol