2 Stroke 1988 CR250R Wont start / Wet Plug

[Stringer]

Yeah run it out for a bit and see what happens. should clear out in a couple runs.

Well I was finally able to take it out again, this time for 20 minutes or so. It started on the first kick. But ran the same. Black spooge out the exhaust, tons of hesitation, good amount of white smoke. It also wants to die unless I keep a good throttle on it. I tried to wheelie in first gear but there was too much engine hiccupping going on to manage anything like that. Possibly worth noting, the transmission oil I put in was belray gearsaver, and it was red like ATF.

Yours looks almost like mine did when i got it the summer of 88. I still have the rolling chassis.

If you are still getting the plug wet, set the float. If you are still getting a wet plug after running it awhile, try turning the idle control all the way down tight. you won't have an idle, but it makes it possible to ride it without fouling plugs. changing the carburetor out for a pwk is the best way to go, but may not be worth it to you moneywise.

the 88 was the bike to have for several years, but it wont run like the next series of engines did.

The float has been set to spec (16mm). Bike does not currently idle at all. I have to check the plug to see how it's doing I suppose, but I have had no hard starts yet.

What do you think I should do next?

 

[Nighthawk016]

check your mix screw, see how many turns it is out from gently seated. Then you need to decide if your carb needs to be rejetted or not based on the number of turns out.

 

[Stringer]

Its two turns out, per manual. Should I mess with that? Thanks.

 

[Nighthawk016]

manual is just a manual, not exactly how the bike should be, and jetting isnt a set it and forget it thing. turn it out to 2.5 turns and see if it runs better. if it does, you are running rich and need to lean out you jets, @Mihylo33 can help you with that!

 

[Stringer]

manual is just a manual, not exactly how the bike should be, and jetting isnt a set it and forget it thing. turn it out to 2.5 turns and see if it runs better. if it does, you are running rich and need to lean out you jets, @Mihylo33 can help you with that!

Ok I turned screw out to 2.5 turns, leaning it out. This helped with some of the excessive smoke. But all the other issues remain. Bike has lots of hesitation all over, and will not idle even with idle screw (part of the choke knob) turned all the way out. On the plus side the bike starts first kick, and transmission feels nice and smooth.

But this hesitation is awful, it is surely not running right. Any idea where to look next??

 

[Nighthawk016]

you need to work on your jetting haha

 

[SRAD97750]

Sounds like it needs some leaning out across the board.
I would drop a smaller pilot jet in and drop the needle down a bit. I would leave the main alone until you have the idle and mid-range sorted.
Remember to make only one change at a time so you can see the result.
-BIG DAN

 

[ossagp]

Well I was finally able to take it out again, this time for 20 minutes or so. It started on the first kick. But ran the same. Black spooge out the exhaust, tons of hesitation, good amount of white smoke. It also wants to die unless I keep a good throttle on it. I tried to wheelie in first gear but there was too much engine hiccupping going on to manage anything like that. Possibly worth noting, the transmission oil I put in was belray gearsaver, and it was red like ATF.



The float has been set to spec (16mm). Bike does not currently idle at all. I have to check the plug to see how it's doing I suppose, but I have had no hard starts yet.

What do you think I should do next?

If you are talking to me I would repeat what I suggested with the choke/idle knob. The purpose of that exercise was not to kill the idle. It is to keep that piece if junk from letting raw fuel dribble down the intake.

When you set the float, set it to where the tab just meets the extended needle tip at 16mm.

I quoted the wrong post.

 

[Stringer]

Yours looks almost like mine did when i got it the summer of 88. I still have the rolling chassis.

If you are still getting the plug wet, set the float. If you are still getting a wet plug after running it awhile, try turning the idle control all the way down tight. you won't have an idle, but it makes it possible to ride it without fouling plugs. changing the carburetor out for a pwk is the best way to go, but may not be worth it to you moneywise.

the 88 was the bike to have for several years, but it wont run like the next series of engines did.

Ok after I turned the knob the other way (I was curious if it would idle, and it did not) I turned it all the way in like you suggested. I guess I'll keep it there for now?

you need to work on your jetting haha

ok thanks lol. I was still worried I might have an oil crank seal issue. hope that's not the case.

Sounds like it needs some leaning out across the board.
I would drop a smaller pilot jet in and drop the needle down a bit. I would leave the main alone until you have the idle and mid-range sorted.
Remember to make only one change at a time so you can see the result.
-BIG DAN

Ok no prob I can do this. Ill just have to figure out what kind of pilot jet to order? What size should I get? I know right now I have stock everything. Im also curious why I am running this rich to begin with, I am 65ft above sea level.

If you are talking to me I would repeat what I suggested with the choke/idle knob. The purpose of that exercise was not to kill the idle. It is to keep that piece if junk from letting raw fuel dribble down the intake.

When you set the float, set it to where the tab just meets the extended needle tip at 16mm.

Yes I have left the choke knob turned all the way in like you suggested. And yes the way you describe is the way I have set the float height. I measured from the gasket surface to the very end of the float bowl, just as the tab hits the needle.

 

[Mihylo33]

With 2.5 turns out on the air screw you may need to drop one or 2 down on pilot. If it's gurgling you may need to do the same on the main jet.
I don't think you have a bad main seal yet as I have not heard you complain of excessive smoke or a foul smelling smoke.
I assume you cleaned the carb atleast 2 times and then once more just in case?

 

[ossagp]

Your question about why it is running that rich to begin with is very appropriate. Jetting when stock, or in the neighborhood, isn't the culprit when you are at sea level.

Obstructions from either intake if exhaust don't seem to be the problem. If your carburetor isn't leaking fuel when the engine is off, and the fuel is on, I don't think you missed a leaking needle or the sleeve the needle rides in.

If you have the choke screwed down hard we eliminated that as a source.

If you think that spring loaded tip on the float seems a little soft you may want to try setting it at 17 or 17.5. Fast and free way to lean it out across the board.

 

[Stringer]

With 2.5 turns out on the air screw you may need to drop one or 2 down on pilot. If it's gurgling you may need to do the same on the main jet.
I don't think you have a bad main seal yet as I have not heard you complain of excessive smoke or a foul smelling smoke.
I assume you cleaned the carb atleast 2 times and then once more just in case?

Yes at least three times it has been cleaned. Rebuilt with new jets and gaskets.

Your question about why it is running that rich to begin with is very appropriate. Jetting when stock, or in the neighborhood, isn't the culprit when you are at sea level.

Obstructions from either intake if exhaust don't seem to be the problem. If your carburetor isn't leaking fuel when the engine is off, and the fuel is on, I don't think you missed a leaking needle or the sleeve the needle rides in.

If you have the choke screwed down hard we eliminated that as a source.

If you think that spring loaded tip on the float seems a little soft you may want to try setting it at 17 or 17.5. Fast and free way to lean it out across the board.

This is what I was worried about. Im near sea level and everything is stock so I shouldn't be this far off with jetting but it is. This tells me it may be something else, and jetting to compensate might be the wrong way to go about things.

When I got the bike it was set two needle clip positions leaner, float was at 18.25mm, screw was 2 turns out, and main was a 175 instead of the OEM 185 I put in there. And the bike ran ultra rich spitting black shit everywhere.

I have no problem digging into the carb again but something is telling me I'm not addressing the root cause. Then again I could be wrong too.

Not sure exactly how to proceed here. Bike should be running great but it's not.

 

[Mihylo33]

Change the jetting back and see if it clears up. Hell my bike is 3 sizes leaner on the pilot and I'm at sea level.

 

[Stringer]

Change the jetting back and see if it clears up. Hell my bike is 3 sizes leaner on the pilot and I'm at sea level.

Ok I will dig into the carb again. Though should I just change float level? Or just change clip position? Both? Maybe go ahead and order a leaner pilot jet? If so what size? Right now I have the stock 62. Also how do I know what pilot jets fit in this carb? Is there a certain style or something? I will take this carb apart but need a plan of action. What do you think? Thanks!

 

[Mihylo33]

Ok I will dig into the carb again. Though should I just change float level? Or just change clip position? Both? Maybe go ahead and order a leaner pilot jet? If so what size? Right now I have the stock 62. Also how do I know what pilot jets fit in this carb? Is there a certain style or something? I will take this carb apart but need a plan of action. What do you think? Thanks!

There aren't many different styles of jets in a bike. You do need the carb make and model in most cases to get the proper jet but big you go to a dealer they'll just look up the bike model and find what series.