still can't ride

if you might have seen it, i wrote in before that my VERY new 426 was just dumping fuel straight out the bottom of the carb. i took the float bowl apart & checked for debris - none there. I put it back together and changed the plug which was fouled/wet, and it ran fine for about 3 hours of riding. Then sunday it just started dumping fuel again, I rode it back to the house wide open for about 1/2 mile, it ran fine but dumped fuel the whole way. If anybody knows what the cause might be or had similar problems i would sure like to hear from ya. thanks.

is it comming from the overflow vent hose? or maybe the bowl plug is not tight/gasket damaged? did you check if the float needle shut off the fuel flow when you had it apart?

If it's a new bike I'd try your dealer, if he should help you out on a new bike!


Chris in the Mojave

'98 YZ400F

I'm taking it to the dealer on Thursday ....but they didn't seem too helpful over the phone. Fuel's coming out the vent hose, the gasket is fine. One of my buddies thinks it's a metal shaving stuck in there somewhere he said he had the same problem with a new banshee quad, so i might take the carb totally off and clean it out, but there weren't any shavings in the bottom of the bowl at all, so i don't really think that is the problem.(Chris - good Yamaha dealers are a rarity in Western PA from what I've seen)

Good dealers are few and far between, period.

I've found that you seem to get better "service" if you hang out on the sales floor looking at the new bikes, striking up a conversation with any of the guy's looking at new

bikes, while yours is being worked makes dealers very nervous. If they are looking at one like yours be sure to throw out "I just bought one of those here". You

know and the dealer knows the next question will be " how do you like it?"

It's amazing how fast a mechanic gets "freed up " to take a look at yours :)


Chris in the Mojave

'98 YZ400F

I was reading on the WR page and i think they solved my problem. I can't remember if anybody wrote in on this page about their fuel tank being pressurized (hissing out of the vent hose), but anyway my tank does seem to build up pressure, and if i don't take the lid off for awhile it gets so strong I can hardly get the lid off. After taking my carb & float bowl apart for the third time to look for debris or some kind of hang-up and finding nothing I am starting to agree with the WR page that the only way for the fuel to escape when under pressure is through the carb's vent hose and that's what is messing up my float. I am pretty sure the problem is with the float because it stopped after taking the gas tank lid off and tapping on the float bowl. I ran it for like 3 hours after that and it was fine. I'm thinking about unbolting the valve on the tank lid and just running a straight hose....any suggestions?

I have noticed the tank pressure problem before as well. It only happens to me on really hot days in slower riding conditions. One time it flooded my bike and pissed fuel out of the carb until I remembered reading about the problem on this site. The other couple of times I noticed my bike "loading up" and just loosened the fuel cap while riding. Once while riding I could smell fuel and looked down to see that my vent hose had come off. Not sure if pressure did this or not but it was hot out that day. Has anybody removed the valve in their gas cap??


99 YZ400 Stock!!

My 400 was doing the same thing. I found that I had put the plastic spacer in wrong. It was touching the float. I dropped the bowl put it in right and it worked fine.


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now