Gas additives causing build-up and plug fouling?

[Blisterphish]

I have two bikes, 96 YZ250 and a 00 PW50. Both ran great then began to lose power and idle poorly. Then they began to not start at all and oil-foul plugs.

I had this problem before with the YZ, the Yami shop said it was bad jetting and changed them out (okay whatever, I can't argue with results) Two weeks later the same thing is happening to the PW as well.

The only thing in common with these bikes is the gas and the Yamalube 2-stroke oil. I drained the fuel and the oil from the PW and replaced with new Yamalube and high octane from a different gas station but still won't start.

Is it possible that the gas from the original station has caused a build-up in the jets that I can't see? This is not a single bad batch of gas either. I've had several cans of gas from this station. I noticed that any spilled gas from station A leaves a sticky film on the garage floor while gas from station B evaporates cleanly. Is this possibly an additive at station A that the bikes don't like?

If it is a build-up from the gas what the heck do I do to get the bikes back to running condition?

 

[DLHamblin]

Put a new spark plug in each and try starting them.

 

[trial_07]

Clean your carb jets if necessary and check for sticky residues stuck inside the carb bowl. With new spark plugs like hamblin mentioned it should start. Then pin the throttle a couple of seconds to clear out anymore ****.

 

[Blisterphish]

I've replaced the gas/oil and plug in the PW but it will not start at all
The YZ's plug still looked good so I just changed out the gas/oil mixture. It backfires and will not start.

This is friggen killing me!
I have not pulled the carbs and cleaned them but I'm not convinced that there is a problem with the carbs at all.

Just take the symptoms - If they were your bikes what would you look at?

 

[ComradeMikhail]

If they were my bikes, replace the plugs. If it still refused, air filter. If it still refused to start, clean carb. You may not think it's the carb, but it very well could be. Bikes are weird sometimes. The only way you're ever gonna find out what it is is to go through everything that has to do with the ignition/fuel delivery on the bikes. My first choice would be the easiest/cheapest. Usually being cleaning out the carb.

 

[Blisterphish]

What do you suggest cleaning the carb with? Just spray carb cleaner? I've heard it can damage the plastics and rubbers.

 

[DLHamblin]

What do you suggest cleaning the carb with? Just spray carb cleaner? I've heard it can damage the plastics and rubbers.

I'd take the carb off, take the bowl off the bottom and spray cleaner through the pilot and main jets at the least ,if worried, take the jets out, soak in carb cleaner and then blow some compressed air through them (just hold them well so they don't go shooting off somewhere). If you are careful you can use a piece of thin wire to push any stubborn crud out but be careful not to scratch or gouge the inside passage.

Plus; with the bowl off you can see if there is any crud left in it.

 

[Blisterphish]

This happened a few weeks ago to the YZ and I took the carb completely apart and cleaned it like you suggested but never did see anything that stood out as bad. I took it to the shop and they had it running in two hours. Said they had to change the jetting. I have a hard time believing it though because it was running fine for months then died and the jetting was suddenly off??? Now the PW that was running fine is doing the exact same thing.

 

[husabutt]

Carburetor needle jets are a often overlooked wear item. As they wear the jetting will get richer. A smaller main jet and lowering the needle will help compensate for wear but a fresh needle and needle seat may help if your jetting is getting richer on you.

 

[Blisterphish]

good advice hasabutt.....thanks.

All: I changed out the plugs on both bikes, drained the gas/oil and they fired up. They ran like crap but they fired up. I'm pretty sure the gas from station A has some sort of additive that goobers up the bikes and hopefuly it will clear out with the high octane from station B. I'm going to OK for the weekend to tear it up with some friends so we'll see how she holds out. Fingers crossed that I don't just foul another plug(s) and end up sitting at camp with the ladies. :cool: