Plug Shorting out, engine flooding... Gremlin?

[bmfouts65]

Recently picked up a 92 RMX250, very clean and well maintained. Ran great until the first outing. First, the idle screw did not affect the idle. Then, it started bogging at low speeds and dying when stopped. Suddenly it died, wouldn’t start. Dumped lots of fuel from overflow when trying to start. Went through carb three times, cleaned, adjusted floats, put in stock main jet, all looks good. Still dumps fuel after few kicks. Then found that the spark plug was shorted out. New one and it started right up. Thought it was fixed. Went riding, gas still dripping out overflow, won’t idle right (this may be due to the cable, though), started bogging, eventually died, won’t start, lots of fuel around the carb and the overflow. Took plug out, moderate to high carbon, but very oily and wet. Cleaned very well, put back in and it started!! Though not running well. Very weak spark. Old plug still won’t work. Other night, I realized that the vent house from the gas cap was stuck down the hole in the steering column and the column was full of water. At this point, it could be pressurized gas tank blowing fuel past carb, some unseen thing in the carb is flooding engine (only if I’m blind!!), or the spark is not enough to burn all fuel… or not enough air, but that’s doesn’t seem likely. Engine getting way to much fuel, but somehow plug is fouling and shorting out. Can too much fuel short the plug? Any ideas or suggestions or has someone experienced this before? Thanks!!

 

[Nathan Rubin]

Whats up dude.
It look like you've got the float problem or fuel needle problem.
Disassemble the carb.
Check the float level.
Check if the float not filled with fuel.
Check if the fuel needle sitting tight in the brass housing.

 

[bmfouts65]

I adjusted the float, actually made it higher (less fuel in bowl), checked floats for holes or fuel (they were fine), blew the carb out with air. I will definitely have to check the fuel/throttle needle, as I am having issues with the idle screw not affecting the idle and the throttle response being... strange. But would this fuel problem cause the spark plugs to short out? The whole spark plug shorting out is really confusing me. I put the plugs on a different bike to verify that they were shorted. So strange.

 

[nickyd]

how long was the bike running before it fouled the plug (when you put the new one in)....as for the fuel leaking - if the float is set, the float is set - it should not leak...if you are saying you tested the needle/float and it is correct, it should not leak fuel unless the drain screw is bad.

as for the fouling plug - any chance your clutch seal is bad? i have seen that eat plugs before (even on my bike) to the point that they would not start...brand new plug would fire though...

 

[bmfouts65]

Bike was running an hour and a half to two hours, maybe less. Drain screw is fine. Seems like something is forcing gas into the carb and the fuel is flowing out any place it can find, ie the overflow, carb seals, and the cylinder. As for the clutch seal, I am not sure what the conditions is. How does the clutch seal cause the plug to foul? I will have to look into that, would like to fix the tank first, then see if the plug still fouls. Thanks for the input!

 

[Nathan Rubin]

It is clear for me now what is the problem might be.
You are teling that the idle screw does no effect and plug fouled to soon, wright?
Check the choke system of the carb.
The choke system is leaking while closed.
Check the choke gaskets for wear.

Please send me picture of the worn pug of yours.
Closest zoom as possible.
I will try to understand what is the problem.
natan@givenimaging.com

 

[Colorado]

This might be a no-brainer, but I recently did the oops myself. Due to riding different bikes from different manufacturers, I reached down on the wrong side and played with my air screw meaning to adjust idle.

 

[bmfouts65]

The air screw can only be adjusted with a screw driver while the ildle screw can be adusted by hand. I also adjusted the air screw as recommended in the Shop Manual. Good idea though.

 

[bmfouts65]

I will send pics later today of the plugs. The seal seemed fine on the choke, but that doesn't mean that it's okay. If I operate the choke (open it) after the bike has been running for a while, it immediately kills the engine... if that means anything..? One thing about the plugs, they don't look that bad. I mean, they aren't all black and sooty, buy more oily/greasy than anything. And while riding, if I take one out, it's wet and the threads are oily black.

 

[nickyd]

back to what I was saying. if the clutch side crankshaft seal fails, the motor will suck tranny oil into the lower end and transfer up the transfer ports to the combustion chamber and voila - oily messy plugs....might not be your issue but just a thought - do you have excessive oil spooging out of the silencer? and does the bike puff white smoke?

 

[dirt bike dave]

I've heard that the carbs on some early '90s RMs are prone to microscopic cracks in the bottom of the venturi, just above the float bowl. Does not show up until the bike gets older. Under load the bike can suck excessive fuel through the miniscule cracks. I think the only solution may be to replace the body of the carb. Tricky to diagnose and a real PITA.

 

[Nathan Rubin]

Dear Bmfouts.
If opening of the shock leads to motor kill it means that the mixture is OVER-RICHED. There is many ways to check that.
1. Plug condition. (send me pics.)
2. Start and warm the engine for 5 minutes.
Make sharp opening of the buffle.
If you hear blah-blah-blah and the engine is about to stall,
the mixture is wrong. (weak or strong)
3. Start and warm the engine for 5 minutes.
Place clean white cloth at the muffler end.
And examine it at the different buffle openings.
0 to 1/4; 1/4 to 1/2; 1/2 to full.
On some opening you should discover exessive carbon deposits and even gasoline smell.
If you do, it is important on which stage the carbon appears.
KR and good luck.

 

[bmfouts65]

There is no oil coming out of the silencer, but it's aftermarket, all packing is new, and the bike has only ran for a total of about four hours since I got it. The bike does smoke quite a bit (as it is a 2-stroke), but when I start it up next, I will have to check the coloring. If I remember, it was blue and not white, but I will defenitely check it out! Thanks

 

[bmfouts65]

Nathan, I will run some of those tests, takes some pics, and let you know. Something has gotta be causing this!

 

[Nathan Rubin]

Just for your info.
Very cool place for knowing your bike.
http://www.alpha-sports.com/suzuki_parts.htm
:nod:

 

[bmfouts65]

Sweet, thanks. Last night, I think I found the issue w/ my bike. To test the float seals, I removed the bottom bowl of the carb, but kept the fuel line hooked up. While holding the float in the upper position, I turned on the fuel petcock, no fuel came out, so the float assembly appeared to be working fine. As I was doing this, I noticed that the throttle slide was way to high, hence the idle screw wasnt' even touching it. Following the line to the throttle, I realized there was too much tension in the line and it was holding the throttle slide way to high. I adjusted the line at the throttle, which dropped the needle down further into the main jet, hence stemming the massive flow of fuel. I haven't put it all together and started it, but it's looking promising. I can send pics of the plugs, but not sure how to post them?