Pinched fuel tank vent line? As a test, try loosening the fuel cap a little and ride it.

 

the vent line checks out ok. i even took it off and blew through it.

 

After it runs for 5 minutes and then dies it has to sit for 10 minutes before it'll start right up again.

 

if the gas line is kinked maybe it is collapsing when it is running cutting fuel to the carb enough to cut off the bike and reopens when there is no pressure to fill up the bowl right

 

Maybe some crud in the tank broke free and is partially blockng either the fuel line or the petcock.
The carb bowl drains faster than it can refill, engine dies, bowl slowly refills over a few minutes, process repeats.

 

My brother in law said it may be the ignition coil overheating and malfunctioning causing bad spark. Then when it cools off it will work again until it gets hot it again. he told me how to test it, but for some unexplained reason i can't replicate the problem now and it ran all evening just fine. Gonna ride again in the morning and see how it does.

I hate gremlins.

 

Also it's a brand new fuel petcock valve and i cleaned out the tank real good before installing it just last week and a new fuel filter today too.

im happy it's now working fine but i feel like this problem may reappear.

 

well damn. I ordered a new coil. installed it and rode for an hour or so. figured i fixed it. then after a rest got back on it and it rode for 10 min and died. new coil, same problem. I don't think its a spark problem anymore. It still seems like something gets hot and causes it to die. Is there any use in trying a new fuel pump?

Any other ideas?

 

Sounds it is more than likely not getting fuel check for kinks and if you just replaced petcock, try going back to the old one

 

vacuum fuel pump?

 

yes. vacuum

 

Sounds like a fuel supply problem. I had similar with my 325, but it ran fine until the fuel in the tank was down to 1/2 or less. Fuel pump was the problem. You can take the line that runs to the carb off at the shut off. put on a length of tubing or fuel line and run it into a container. with the engine off and the fuel turned on, you should get a trickle of fuel, when you crank the engine or its running, the fuel flow should increase. If it doesn't, then you have a problem with the vacuum line or the fuel pump. These are vacuum diaphragm pumps and the smallest leak in the diaphragm will cause failure.

When I started diagnosing my issue, I found that the fuel shut off is just a small distance above the bottom of the tank. With a full tank, there was enough pressure from the liquid in the tank to keep the carb supplied. When the fuel level dropped, it was starving the engine. Let it sit and the trickle was enough to get it to run again for a short time.

Vacuum line on the 325 runs from the fuel pump to the top of the engine. I would have to guess the 425 will be similar.

Good luck with it!

 

pump may be issue

 

Look at the lobes on your cam

 

When I rebuilt the carb last week I put a new inline fuel filter on and it was different than the old one. It's metal and about 3x longer. also u can't see through it from end to end like the old one so it must flow differently internally. Not sure if that's the issue but we noticed it runs good if you just drive around for about 15-20min, but if you are going fast and hotdogging it will beginning hick-ups and then stall out when you slow down. Also it seemed like at night in the cold it didn't happen. I swapped the new filter with the old one and it did fine yesterday but it was really cold here. I will continue "testing" it all weekend.

I don't know anything about cams but it seems like if that was bad it would run crappy all the time right?

 

Wrap your fuel line from carb to gas valve with heat reflective tape, Ive seen them boil gas in line and vapor lock.

 

Thanks. I may do that if it reoccurs but so far it has been good these last 2 days. Maybe the cold weather is helping. It seems to like running when it's cold outside.

 

well today we were able to get it to die again. i'll try the tape first and then if that doesn't fix it i'll order a new fuel pump.

less wrenching, more riding would be nice.

 

It's seems like we've fixed the problem by simply lowering the float level. Which I thought was weird, but now she purrs all day.

I had set it to be parallel to the bottom of the bowl like i read somewhere but turns out it needs to hang a little lower apparently. Oh well rookie mistake I guess.