01 YZ426 Won't stay running

My riding buddy has an 01 YZ426F that won't run for crap. The funny part is that he rode is last weekend, washed it, and parked it until today. We went to ride today and the bike wouldn't run. Both of us now have sore right feet from working on this thing today.

Here's the deal. When we get lucky, it will crank and idle with the choke OFF for about two seconds and die. If you try to turn on the choke or give it any throttle it dies. There was about two times where we got it up over idle in which case it seemed to run ok with the throttle at about 1/4. Then we closed the throttle and it died after about 10 seconds of idling. Then it is a real bear to get started again or even to get it to pop off. A couple of times we checked the plug after beating our feet to death to see if it was wet and it was not so I'm leaning towards lack of fuel, but not really sure since it starts with the choke off and will never start with it on.

We took the carb off twice and cleaned it with carb cleaner and blew it out with compressed air with no change. As best I can tell air and carb cleaner were coming out where they should have been so I don't think any passages were blocked. Also, we checked for water in the gas by draining some gas into a clear cup and letting it sit to see if any water droplets formed in the bottom. No water. Tried fiddling with the mixture screw some and that didn't seem to do much either.

Like I said, this happened very suddenly, and at the moment I'm not sure what to check next. I have been looking through posts for about an hour now and most seem to point to a dirty carb but after cleaning it two times I'm starting to look for something else.

Sorry for being so long winded, but I was just trying to get as much info in here as I could.

My riding buddy has an 01 YZ426F that won't run for crap. The funny part is that he rode is last weekend, washed it, and parked it until today. We went to ride today and the bike wouldn't run. Both of us now have sore right feet from working on this thing today.

Here's the deal. When we get lucky, it will crank and idle with the choke OFF for about two seconds and die. If you try to turn on the choke or give it any throttle it dies. There was about two times where we got it up over idle in which case it seemed to run ok with the throttle at about 1/4. Then we closed the throttle and it died after about 10 seconds of idling. Then it is a real bear to get started again or even to get it to pop off. A couple of times we checked the plug after beating our feet to death to see if it was wet and it was not so I'm leaning towards lack of fuel, but not really sure since it starts with the choke off and will never start with it on.

We took the carb off twice and cleaned it with carb cleaner and blew it out with compressed air with no change. As best I can tell air and carb cleaner were coming out where they should have been so I don't think any passages were blocked. Also, we checked for water in the gas by draining some gas into a clear cup and letting it sit to see if any water droplets formed in the bottom. No water. Tried fiddling with the mixture screw some and that didn't seem to do much either.

Like I said, this happened very suddenly, and at the moment I'm not sure what to check next. I have been looking through posts for about an hour now and most seem to point to a dirty carb but after cleaning it two times I'm starting to look for something else.

Sorry for being so long winded, but I was just trying to get as much info in here as I could.

take off the gas cap and try it. if it runs your vent is pluged. Next check the pilot screw is turned out about 1.5 to 2 turns.. I just went thru this same thing with my bike this week lol.. check my thread for what others said to me

I have seen water in the fuel due to pressure washing, especially around the gas cap. Drain the fuel tank and the carb. See where things go from there.

take off the gas cap and try it. if it runs your vent is pluged. Next check the pilot screw is turned out about 1.5 to 2 turns.. I just went thru this same thing with my bike this week lol.. check my thread for what others said to me

We checked the gas cap yesterday while we were working on it and it seems to be fine. Also, we have tried setting the mixture screw at many different places and nothing seemed to help. It only made things worse.

I have seen water in the fuel due to pressure washing, especially around the gas cap. Drain the fuel tank and the carb. See where things go from there.

Checked the gas too. Seemed ok. He didn't pressure wash the bike, he just used a hose. May change the gas anyways though. Carb has been cleaned twice with no luck. Probably going to clean it again today.

Did you ride through some deep water where the valve cover vent tube could have maybe sucked up some water ? Just a thought. Or even maybe water go into the exhaust when you were cleaning the bike.

sounds like it's running too rich? orr maybe a vaccum leak somewhere?

Did you check the accelerator pump diaphram for damage when you took the carb apart ?

Well......after working on the bike for most of the weekend, we found the problem. Put a new plug in the bike and it runs like a champ. Dooooh!!!!:worthy::eek::smirk::banana::lol:

Well......after working on the bike for most of the weekend, we found the problem. Put a new plug in the bike and it runs like a champ. Dooooh!!!!:banana::eek::worthy::devil::lol:

:smirk: you know whats worse when it wont start and you scream and curse at it for ever and realise the gas was off...

:eek: you know whats worse when it wont start and you scream and curse at it for ever and realise the gas was off...

Lol or an idiot on a kawi kicks forever only to find out after 15 minutes that the kill switch was set to off :smirk:

Well......after working on the bike for most of the weekend, we found the problem. Put a new plug in the bike and it runs like a champ. Dooooh!!!!:worthy::eek::smirk::devil::lol:

When I first got my bike in 2001, (YZ426F) I did the exact same thing, always plug the holes in the side panels and exhaust. Never spray water at the carb boot and the back of the seat where water could get into the air filter. Run the bike for 5-10 minutes after washing it and you will never have a problem. I learned this the hard way also!!!!:banana:

Run the bike for 5-10 minutes after washing it and you will never have a problem.
It's also a good idea when doing this to raise the idle and open the hot start for 30 seconds or so to draw off any water that may have collected in that bore. This is especially important for any 400/426 with a thumb lever conversion kit on the hot start. Failure to do this can result in a frozen plunger.

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