Whats going on with brothers new yz250??

[jarrodking]

Last weekend my brothers new yz250 fouled its plug after its second ride, he cleaned the bike, started it up and rode about 10m then it fouled.

Just today same thing, i put a new plug in and we went riding, came home, he cleaned his bike and started it up, rode about 10m and it fouled again!

Whats the go???

[trailrider95]

Is the jetting set correct for elevation, temp, etc.?

[jarrodking]

yer he brought it from a very well known motorbike shop, Pro Griffin, and the motorbike mechanic set it up when he bought it. It seems to happen after he cleans the bike. And yes he puts a couple of rags in the airbox before he cleans so the filter doesnt get wet.

[RCannon]

If jetting is correct, I vote for water getting on the airfilter. Thats the most common way I have ever fouled a plug. The yz airbox flows a lot of air, and does not do much to stop water. A few drops is all it takes.

Also, if water got into the carb, same deal. To do it right, you just about have to tape the side vents shut as well as the space between the seat and fender.

[Dread]

I bet he left a rag in the boot

[jarrodking]

Nahh he didnt leave any rags in there, i double checked before he kicked it over. Wat do u mean if water is in the carb do it right? Do i need to take the carb apart or? Thanks for the brainstorming so far! Bit of a mystery :-(

[Superbike Mike]

The water in the filter gets sucked into the motor causing the conductor in the plug to crack like an ice cube tossed into a cup of coffee.

[Sam Hoffy]

I remember on my 2 stroke that I was fouling plugs when running too much oil with my fuel. Maybe put a little less oil in your fuel for next ride and see how you go. Good luck

[Fliip]

I remember on my 2 stroke that I was fouling plugs when running too much oil with my fuel. Maybe put a little less oil in your fuel for next ride and see how you go. Good luck

Don't use less oil... Mix at 32:1 (what I always use and always will) or 40:1. Pick a ratio and jet for it.

[charlevoixboy]

As a possibility, and this is a long shot, could water be getting into any part of the electrical system? Under the plug boot, harness, ect. I read about a case where, when using a powerwasher, water was blown past the stator cover and got the flywheel and stator wet. This lead to a weak spark and fouling issues. And since the cover is sealed the water wouldn't get out. It's worth a check at least.

[jarrodking]

I dont use power washers to wash the bikes, forces water into places where it shouldnt go, learnt that the hard way! But i checked the fly wheel, no water. Think we might just take it back to the dealer, they can sort it out!

[brentn]

Could be an incorrectly set float, cracking the throttle wide open allowing too much fuel and not enough air to go in flooding it.

My buddies bike is doing this right now, still not sure of the issue as we left it alone at the time and put it back in the shed.

[JFielder23]

My 03 YZ250 also fouled plugs like crazy when I first bought it. I was literally changing the plug every ride (and at 5 bucks per BR8EG that got expensive). I stopped using Yamalube 2-R at 32:1 and switched to Amsoil Dominator at 50:1 and I haven't fouled a plug since... I know I'll get tore up for this... but I'm still running my factory top end too, compression tested good every season. I'm not a shill for Amsoil or anything, just passing on my experience.

[SeniorYamahaRider]

Does he let it warm up before he takes off?

[rusky]

1. water in the intake (air filter, carb, etc)

2. incorrect jetting

3. Let your bike idle for too long before riding it - kind of goes hand in hand with incorrect jetting.

P.S. Never trust a dealer to work on your bike. For all you know all the mechanic did was adjust the air screw (unless you got a bill for different jets).

[RM125rc]

personally i have never fouled one but one of my friends has a yz125 and he ALWAYS fouls plugs. its because he never rides in powerband and when he starts it he dosent even touch the throttle or rev it he just lets it idle there and when he rides it he dosent ever get it into powerband. also you could have water in your fuel, just my 2 cents

[Fliip]

personally i have never fouled one but one of my friends has a yz125 and he ALWAYS fouls plugs. its because he never rides in powerband and when he starts it he dosent even touch the throttle or rev it he just lets it idle there and when he rides it he dosent ever get it into powerband. also you could have water in your fuel, just my 2 cents

Perfectly jetted will never foul plugs, even if you never see the powerband... But I jet my 250 rich, just because I like to run it hard... Richer never hurt.

[holland711]

id say ur using the wrong oil and the bike isnt jetted correctly, regardless of what old mate says, if the plugs are wet and black when they come out, its too rich!!

[Compton856]

im having similiar problems decided to drain my tank change my plug and try 40-1