Won't start and has black fuel in exhaust pipe...

[dinkyguitar]

Well, I haven't been able to start my 87 KX 250 since the weather changed.

I'm actually regretting having it since it's been giving me starting problems.

All my hard work down the drain since I can't start it.

Not sure what this means but, twice I took the exhaust pipe off and dumped 1/2 cup of looks like black fuel out of it

Definitely gas...my coolant is still there as well as my crankcase.

She has a good blue spark, and wet when I take it out.

Last time I dumped the pipe, I also flipped the bike over and spun the back tire. Maybe a teaspoon of this black stuff came out.

Today I dumped the pipe again, kicked it over, and I heard a small backfire in the pipe...almost like a fizz..

I'm using Amsoil 32:1....could this be bad fuel? I've had it for about 4 weeks..using 93 octane.

Can't seem to figure it out...and it gets me pissed when I see other bikes start 1 or second kick.

All I can say is that this sucks and is really taking me over.

dinky,

[alward25]

if you are mixing Amsoil @ 32:1 you may as well pour the oil straight in the gas tank.  Each oil manufacturer has their own mix ratio.  What the factory recommends is based on if you are running factory oil.  All that aside, it sounds like your needle and seat in your carb need some love, letting fuel keep running in your carb and never shut off.  Have you checked your reeds?  It can let  extra fuel in that you don't want and cause too much fuel to dump in and you would kick the crap out of it  or pull start it to get it going.

Good luck, try 50:1 on your Amsoil, it will burn much better.

[dinkyguitar]

if you are mixing Amsoil @ 32:1 you may as well pour the oil straight in the gas tank.  Each oil manufacturer has their own mix ratio.  What the factory recommends is based on if you are running factory oil.  All that aside, it sounds like your needle and seat in your carb need some love, letting fuel keep running in your carb and never shut off.  Have you checked your reeds?  It can let  extra fuel in that you don't want and cause too much fuel to dump in and you would kick the crap out of it  or pull start it to get it going.

Good luck, try 50:1 on your Amsoil, it will burn much better.

Thanks,

Just a little back ground. The needle and seat are new. I held the floats by hand and watched for leaks. I also checked the petcock and it's not leaking either. The reeds are new, and I checked to make sure there's no air gaps.

I do have a question....is it normal to hear hissing noises coming from the carb when you spin the flywheel by hand? Seems like air is getting blown back through the carb into the air box....and by spinning the flywheel I mean after the compression stroke when the piston is at BDT.

dinky,

[motopunk]

this noises are normal...  what you hear is the piston soaking air/fuel-mixture through the carb ...

hmm.. every time, you had this amount of fuel in the crankcase??  make sure, that the float valve in the carb willl be closed, when the fuel level is reached ...

 whats your actual jetting?

and you said the crankcasefuel is black, when you drain it out? ... that sounds like gearbox-oil in my opinion

[dinkyguitar]

this noises are normal...  what you hear is the piston soaking air/fuel-mixture through the carb ...

hmm.. every time, you had this amount of fuel in the crankcase??  make sure, that the float valve in the carb willl be closed, when the fuel level is reached ...

 whats your actual jetting?

and you said the crankcasefuel is black, when you drain it out? ... that sounds like gearbox-oil in my opinion

The fuel in the exhaust and crankcase only started when I couldn't get the bike running....When it was running in the summer (really just breaking it in after the rebuild) I didn't have this problem. Once the weather got cold is when I couldn't start it any more and I kept trying but it just didn't start. I think last week after I dumped the black fuel from the pipe I was able to start it...and it idled normal.

Mind you I never really got a chance to ride it since my yard is small....never got out of 1st and never ridden longer than 15 minutes.

Jetting was 350 main, 45 pilot. Today I set the float and changed pilot to 42.5 and main to 330.

I always check the gear box oil and it's as full as I filled it. Does seems to be missing any.

Like I said....it all started once it started getting colder.....

dinky,

[motopunk]

this noises are normal...  what you hear is the piston soaking air/fuel-mixture through the carb ...

hmm.. every time, you had this amount of fuel in the crankcase??  make sure, that the float valve in the carb willl be closed, when the fuel level is reached ...

 whats your actual jetting?

and you said the crankcasefuel is black, when you drain it out? ... that sounds like gearbox-oil in my opinion

The fuel in the exhaust and crankcase only started when I couldn't get the bike running....When it was running in the summer (really just breaking it in after the rebuild) I didn't have this problem. Once the weather got cold is when I couldn't start it any more and I kept trying but it just didn't start. I think last week after I dumped the black fuel from the pipe I was able to start it...and it idled normal.

Mind you I never really got a chance to ride it since my yard is small....never got out of 1st and never ridden longer than 15 minutes.

Jetting was 350 main, 45 pilot. Today I set the float and changed pilot to 42.5 and main to 330.

I always check the gear box oil and it's as full as I filled it. Does seems to be missing any.

Like I said....it all started once it started getting colder.....

dinky,

take a larger pilot jet to get richer ...  by cold weather is more oxygen in the air that needs also more fuel to have the right mixture...   

so why you go leaner with the 42.5..and 330. ?? this numbers are for the inner diameters in the jets... no wonder that your bike will not start...

  take a 50 pilot jet and a 360 main. needle in the middle and airscrew 1,5 turns open .. then try starting again...  in my bike is actual a 52 pilot for the cold german weather.

now i´m excited what happens next... 

[dinkyguitar]

I was thinking about that black oil in the exhaust, and probably the reason why it's black is due to the carbon in the exhaust. So that explains that...

As to the jets....I had the bike running after the rebuild in the summer with stock jets, but it took several kick to always start it....and it would backfire before it started. Each time I would check the plug and it was wet, so I assumed it was running rich.

I bought leaner jets thinking it was fix the problem but never did. My plug always looked clean and tan in color why it did run...

Now I have the fuel in the exhaust so again I'm thinking a rich condition....

Today I'll try to get some of that excess fuel in the crank case out by kicking it over without the plug and exhaust. Last time I did this I was able to get running (on stock jets). Took a lot of kicks but she started....then the following day I had issues.

dinky,

[Foxx4Beaver]

I was thinking about that black oil in the exhaust, and probably the reason why it's black is due to the carbon in the exhaust. So that explains that...

BINGO!!

and I don't buy the "too rich" gig either, especially since you already stated you had it running in the summer with a "clean tan plug".
I would go back to alward25's post, and start there...just because things are new, does not mean they're "good"...where did you get the float valve from?...cheap ones don't last!!
Re-check your float height while you're at it!
Does it have brass floats?...they can become corroded and get pin holes in them, creating your fuel to constantly flow.

if all this checks out...then you should start thinking about cleaning your electrical grounds on the frame and the plugs.

[dinkyguitar]

I was thinking about that black oil in the exhaust, and probably the reason why it's black is due to the carbon in the exhaust. So that explains that...

BINGO!!

and I don't buy the "too rich" gig either, especially since you already stated you had it running in the summer with a "clean tan plug".
I would go back to alward25's post, and start there...just because things are new, does not mean they're "good"...where did you get the float valve from?...cheap ones don't last!!
Re-check your float height while you're at it!
Does it have brass floats?...they can become corroded and get pin holes in them, creating your fuel to constantly flow.

if all this checks out...then you should start thinking about cleaning your electrical grounds on the frame and the plugs.

Thanks for the suggestions...The needle & seat are literally new. Float height checked yesterday. A few weeks ago I submerged the floats in a jar of premix and they were fine. I shook them just to see if I could hear fluid, but nothing in there.

The other thing I want to replace is the intake boot which on the outside shows cracks, but on the inside looks sealed.

Boyesen has a one piece reed cage/intake I was looking at. And although I checked my reed cage/reeds they looked good without any visible gaps...the new Boyesen intake might have better sealing which might boost my compression level.

I was also entertaining the idea of buying a new Mikuni VM38....I've always had a feeling about my current carb....just something about it.

Oh, and 1 last thing....I going to get fresh gas and mix up some fuel just to see if that's the problem.

dinky,

[Foxx4Beaver]

The needle & seat are literally new.
the other thing I want to replace is the intake boot which on the outside shows cracks, but on the inside looks sealed.
dinky,

if they're aftermarket, don't have high hopes!...been there, done that....that's why I bought a completely brand new carb...aftermarket replacement parts for carbs are garbage.

Sandblaster has a good thread on how to seal up old intakes.

[alward25]

all of the intake boots are cracked, even new they look like trash.  But it does not hurt.

[dinkyguitar]

Well, I got fresh gas mixed 50:1....

Still no go. Funny thing is, after draining the carb, opening he petcock, choke on, and first or second kick I could hear a little backfire in the exhaust chamber...almost like a fizz.

I just think somehow fuel is going straight from the carb into the exhaust....snuffing out the spark.

Today I kicked it about 10-12 times, pulled the exhaust off and a table spoon or two dripped out of the pipe...granted some could have been left over from me dumping it yesterday but it seems like it's loading up.

I have a new air cleaner, reeds. When I have the carb apart I can see it's clean inside. I check all the jets, shine a light to see if anything is plugged. I set the float, make sure the needle & seat didn't leak etc....

I have an blue consistent spark, new coil, stator.

Only thing bugging me is the compression is 140psi after a complete rebuild. After 10 or so kicks...not sure how many kick I should do. The guy I brought it too honed the cylinder and it still had honing marks from 8 or so years ago. Maybe I should have bored it out...or re-plated....did 87 KX 250's have plated cylinders??

When I get it started it runs normal....the idle does wonder up and down every now and then, nothing drastic...but it has power in 1st, kicks up the dirt.

It's a mystery..

dinky,

[sandblaster]

When doing a compression test are you holding the throttle wide open and kicking it?

[motopunk]

"Now I have the fuel in the exhaust so again I'm thinking a rich condition.... "

this fuel in the exhaust is unburned fuel and comes from the many trys to start the bike with the to lean jetting!!!

  you said it was running in summer but with also many kicks. so i know, that your pilot jet was in summer a little bit to lean too!!
now we have winter: colder temps= more oxygen in the air, so you need the richer jetting for right mixture and the bike runs.. what you did was leaner jets instead of richer jets...

make sure that the float valve could close and that the floats are moving freely up and down . now we closed the circle with your bike-problems...
dry your crankcase and exhaust, then try this jetting :

 pilot 50 , main 360, needle in middle , airscrew 1,5 out ... 

dont think to much about other things, do it...    or let it, come to me to germany and i make your bike running in 30 minutes 

[Foxx4Beaver]

Only thing bugging me is the compression is 140psi after a complete rebuild.

When I get it started it runs normal....the idle does wonder up and down every now and then, nothing drastic...but it has power in 1st, kicks up the dirt.

It's a mystery..

dinky,

140 is a touch weak for a fresh rebuild, if you're doing the test correctly.
if your idle is fluctuating...then a leak down test should be your next step...or you'll be just pissing into the wind messing with jetting if you have an air leak.