hey i own a new 420 honda and have had a bunch of trouble with it vapour locking when i work it hard at slow speeds i was just wondering if anyone has had a similar problem my dealer cant find anything wrong with it and yet every time i run it in say first gear over tough terrain for an extended period the engine starts to lean out and stops running if i shut it off and let it cool for awhile it runs again strange eh anyhow if you own a 420 maybe you could do me a favour and put it through a little test just so i know if it is just my quad or if honda needs to redesign there fuel delivery system a bit. to test do it on a warm day let it get warmed up by idleing or riding it around normaly then shift it into first gear and drive it slowly with a load on the engine a hill works great my quad will vapour lock within 15 minutes under these conditions none of the indicator lights have ever lighted on my bike good luck

 

does you fan come......and what kind of temps are we talking......its water cooled .......ive run mine in all kinds of weather and havent had a problem

 

I don't think you have a vapor lock problem. That would be extreamly rare on a electric fuel pump system that is soft piped.

I've been riding in the AZ desert, starting out at 88º at 5am and get back at 7am at 98º. I have riden a couple times at 105º. With 90 miles on my new machine, I don't have any type of fuel problem.

I ride about 15mph max then slow down to 5mph for 1-1/2hrs, then back to 15mph to ride back home. Alot of 2nd and 3rd gear usage.

However, the next trip I'm out, I'll try to duplicate your riding style then report back.

Could you have a suction air leak on your fuel pump, most likely a loose hose clamp? Or a piece of trash in the fuel tank that's floating over the tank drain ? A plugged fuel cap vent line?

 

I have been doing tight woods trail riding in the mountains. Highs are 85 degrees and above, and this is slow going...walking speed. Lots of nasty technical hillclimbs, etc. Fan comes on only rarely, and never any problems of any kind, no mater the heat or the load on the machine.

This is most likely something unique to your machine....

 

thats odd. i wonder if you have a loose air hose somewhere. is your radiator full? just wondering.

 

Try to loosen your gas cap next time it starts giving trouble, this will check for defective cap.

Next, switch over to reserve instead of "on" when it starts giving trouble, the reserve draws from another area of the petcock and that will show if the drawoff for the "ON" position is getting clogged.

Does the bike just stop running or does it kind-of power out? How long do you need to let it cool down for before restarting?

But I would check radiator fluid levels, and hose clamps as mentioned in a previous post.....

 

......check your airbox for leaks

 

find anything yet?

 

thanks for the ideas. i have checked all of the above. the other day i was out on a 07 rancher 400 and had it do the same thing under the same very slow hard work. a good mechanic friend of mine says it is vapor locking. i dont know, the last time i had it at the dealer they pretty much checked everything and it is all to spec. i am going to try rideing without the side panels to see if that makes a diffrence thanks again let me know if you have any trouble

 

The Rancher 400AT is gravity fed, so how in the world would it be possible to vapor lock it???? There are millions of gravity fed quads and bikes running around out there in hot weather, ridden slowly, under loads, etc., and you don't ever hear of any of them "vapor locking", do you.

I'm not sure where the fuel pump is on the Rancher 420. If it is positive pressure (pump is at the tank end) it should not vapor lock. If it is negative pressure, then it is maybe possible...