250 Yz250 Issues

So Let me start off giving you some background info, I bought this bike as a basket case and entirely rebuilt it. New crank, gaskets, bearings, and pistons, I cleaned out the carb with some carb cleaner and checked for spark and It had spark. So came today when I tried first starting it. Nothing happend but the bike started pushing my leg up and my plug was sooty and black so I sprayed carb cleaner down the into the air tube(with air filter off) and it started and ran for 30 or so seconds and the idle was really high couldnt adjust it with the idle screw. So I tryed again put some carb cleaner in the air intake again and it was just pushing up my leg when I kicked down and yes there was spark... So Im lost on what I need to do HELP! Thanks!
 

SRAD97750

Moderator
Staff member
Sounds like the throttle cable needs adjustment, the slide is not seating correctly, or your carb is not getting enough fuel.

If the cable is too tight or caught on something along the path, it'll hold the slide open and cause hard starting, when they do start the idle is too high and not touching the adjustment screw to make a difference.

A backwards slide can cause hard starting in a VM (round slide) style carburetor, when they do start, they idle really high (screaming) and is not adjustable.

A lean condition will cause high idle, surging, and inability to adjust idle speed in a 2T. Check the float setting.
-BIG DAN:thumb:
 
Sounds like the throttle cable needs adjustment, the slide is not seating correctly, or your carb is not getting enough fuel.

If the cable is too tight or caught on something along the path, it'll hold the slide open and cause hard starting, when they do start the idle is too high and not touching the adjustment screw to make a difference.

A backwards slide can cause hard starting in a VM (round slide) style carburetor, when they do start, they idle really high (screaming) and is not adjustable.

A lean condition will cause high idle, surging, and inability to adjust idle speed in a 2T. Check the float setting.
-BIG DAN:thumb:

I have loosened the throttle cable completely so there is no chance it could be that good thinking though, But it almost seems as if the engine is flooding when I am kick starting it, it will want to somewhat weakly kick my leg up. and When I kick the bike over it uses up fuel I believe this is normal? Also the bike is near impossible to start...Im almost certain it is fuel related as everything else checks out fine... Hopefully I can hear from you again and in the mean time Ill try adjusting the float settings Thanks!
 

SRAD97750

Moderator
Staff member
I verify the slide is hitting bottom on the carburetor body/adjusting screw when adjusting the cable.
It can seem close, and the cable loose, but not bottom out on the screw.
This is far more common than you'd imagine. -BIG DAN:thumb:
 
I verify the slide is hitting bottom on the carburetor body/adjusting screw when adjusting the cable.
It can seem close, and the cable loose, but not bottom out on the screw.
This is far more common than you'd imagine. -BIG DAN:thumb:
Okay thanks Ill check It out
 
What does "pushing my leg up" mean?
If it means that its hard to kick, then you probably have good compression, yes?

Add question - how old are you?
 
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What does "pushing my leg up" mean?
If it means that its hard to kick, then you probably have good compression, yes?

Add question - how old are you?
Yeah great compression, it has a slight kick back like when the kickstarter pushes your leg back... and 18
 
But it almost seems as if the engine is flooding when I am kick starting it
Is the plug wet and smells like gas? If so, it sounds like you are flooding the cylinder (with gas), and you're extinguishing the spark (flame) and the spark plug may not be re-usable at this point. This is called a fouled plug. If you have a fouled plug, and you keep trying to get the bike running, you are chasing your tail, and typically aint gonna happen. So start with a new plug.

This could be caused by a leaky float valve, allowing way too much fuel into the float bowl, and into the jets/venturi. If you dont know what this is, you need to do some basic research on this, its not complicated, and works just like your toilet in your bathroom.

There are two (3) conditions in ANY vehicle that uses a liquid gas - you are either running rich (too much gas) or running lean (not enough gas) to sustain engine performance. Right in the middle is the 3rd, and its the sweet spot that we all strive to achieve, but more often than not, we are not there, and are either rich, or lean. This is why computer controlled fuel injection is best, but I digress...

The condition of your spark plug is the best way to determine where your engine is at; wet = rich/flooded/not running. Dry = running, and a good start to diagnosis.
 
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Is the plug wet and smells like gas? If so, it sounds like you are flooding the cylinder (with gas), and you're extinguishing the spark (flame) and the spark plug may not be re-usable at this point. This is called a fouled plug. If you have a fouled plug, and you keep trying to get the bike running, you are chasing your tail, and typically aint gonna happen. So start with a new plug.

This could be caused by a leaky float valve, allowing way too much fuel into the float bowl, and into the jets/venturi. If you dont know what this is, you need to do some basic research on this, its not complicated, and works just like your toilet in your bathroom.

There are two (3) conditions in ANY vehicle that uses a liquid gas - you are either running rich (too much gas) or running lean (not enough gas) to sustain engine performance. Right in the middle is the 3rd, and its the sweet spot that we all strive to achieve, but more often than not, we are not there, and are either rich, or lean. This is why computer controlled fuel injection is best, but I digress...

The condition of your spark plug is the best way to determine where your engine is at; wet = rich/flooded/not running. Dry = running, and a good start to diagnosis.

Yeah I understand though does a fouled plug completely eliminate spark? Because when I ground the plug and kick it over It still has spark anyways yes the plug is black and wet so I will try to diagnose
the carb... Thanks
 

SRAD97750

Moderator
Staff member
Blue spark is all you need. Looking at the plug is usually a waste unless the bike has been running. Trouble trying to start a bike from a rebuild (or box) is carburetor related 99% of the time. Of the 40+ bikes I have reassembled from literal piles of parts, fueling was always out of wack the first attempt. Even on Fuel Injected models.

Your high idle and described symptoms of hard starting are a lean fueling related issue. The carburetor cleaner is acting as the fuel, allowing it to run shortly.
Keep it simple, follow the symptoms. You've already done the hard parts!
-BIG DAN:thumb:
 
Start with the float height setting. If you want to try something first, tip it over until fuel runs out of it then stand it up and kick it and see what happens. That will temporarily override a low float height condition. If that doesn’t work, turn on the fuel valve for 30 seconds, then turn it off, tip it over and let a little fuel run out then stand it up and try to start and see what happens.
 
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