250 1988 yz250 build

L

Lovespeed

Ok I finally got everything I needed to make it run and put in the new spark plug, carburetor, and gas tank and set everything up. I cranked it and it ran!.... Except I'm seeing more issues. First problem: black stuff is shooting out the exhaust and it smells bad. I'm pretty sure it's just old build up that's never been cleaned out. Could that cause any problems? I tried to get the exhaust off but it's attached by springs and I could only get one off the rest feel like they're impossible to get off so if anyone knows a way that would help I would appreciate it. Next problem, it's idling very high!! As soon as I crank it, it sounds like I'm revving it almost full throttle and I cut it off because I felt like I was gonna damage it. I have no idea why it's idling so high. I didn't adjust the fuel or air screw so do you think it might be that? Let me know which ways to turn which screw to lower the idle. If it's not that then does anyone have any other suggestions on what could be the problem? Thanks in advance.
 
L

Lovespeed

Alright I'm pretty certain that the cause of the high revving is an air leak. I read that on 2 strokes an air leak can cause engine seizure which is DEFINITELY not something I need to deal with right now so I need this problem fixed. I heard it might be the boot between the carb and engine but I doubt that since I checked it so I'm gonna go with the crankcase. Should I just buy an all new seal or something? Anything else I need to check?
 
SRAD97750

SRAD97750

Moderator
Staff member
A screaming engine from start is one of a few possible things.
Choke is on
Throttle slide in backwards
Throttle cable mis-adjusted
Throttle adjusted too high
Air leak
 
L

Lovespeed

I'm just going to play it safe and go ahead and replace things associated with an air leak. What all gaskets should I replace? So far all I know to replace is the ignition cover gasket. Anything else I should replace?
 
Mihylo33

Mihylo33

Oh man. Make sure the slid is in correctly. I don't know how many times I fixed bikes that kids dropped the slide in and didn't align the guide pin. Sucker would hang wide open!
 
L

Lovespeed

Yeah I made sure it slid in all the way but I'll double check to be sure. Also now I haven't got any new gaskets yet. I'm trying to figure out what all I need and then I'll buy it all at once.
 
O

ossagp

The screw turns counter counter clockwise to lower the idle. you should hear a good solid click when you roll the throttle shut. A quarter turn of smooth even throttle pull and a good click as above upon closing.

Remember to test and not guess.
 
Redordead89

Redordead89

If you're going to replace gaskets then you should probably get a new seal kit for the carb and strip it clean it with carb cleaner and reassemble it to rule out any carb issues too!
 
O

ossagp

Lovespeed:
Yeah I made sure it slid in all the way but I'll double check to be sure. Also now I haven't got any new gaskets yet. I'm trying to figure out what all I need and then I'll buy it all at once.
Click to expand...


Good idea to check it since if the slide is hanging open it will make serious horsepower should it ever do it when you are riding. The air leaks are pretty much limited to just causing the high idle, but are not so serious from a safety standpoint.
 
L

Lovespeed

Redordead89:
If you're going to replace gaskets then you should probably get a new seal kit for the carb and strip it clean it with carb cleaner and reassemble it to rule out any carb issues too!
Click to expand...

I already completely cleaned the carburetor so there should be no issues there. I'm 99% sure it's one of the seals I just gonna check them to see exactly.
 
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