Did it.

I've heard about this and gas boiling and been a hard core doubter for the past 2 months. I swallowed my foot and half my ankle today.

Rode in the woods for an hour or so just making my own trails with my uncle and his 454. He wanted to ride mine, so we switched and rode around for a while. Well, they were getting fairly hot. It was 70 outside today, and a nice day to ride.

I wanted to show him the diff-lock so we went to this little muddy spot where the road is cut out from the side of the hill. There's a little 6ft. hill there that you can get a limited slip to spin out on if you don't shoot it fast. Steep but not long, and no traction. I shot it real quick on the 454 and spun, but made it. Got him up to it, made him lock it and put it in low, and he started up. Got halfway and the sucker totally cut out and wouldn't do a thing. I ran and grabbed the front end and he kept gassing it but it was getting nothing.

WTF?? Finally, he gassed it a few more times and finally it got some power and went on up. Ok, I was clueless, but all I could think of was Vapor Lock. We go on down the trail, cross a little stream and find another spot. I shot the hill on the AC and went up and parked it. Walked back down and got him lined up for another slow locked crawl and BANG!, same thing. He got in the middle of it where it needs power and the 660 cut out hard again. Just like it wanted to die, and got zero power. We fooled with it a while and finally got it to go on up. Drove to the house and it was hot as hell.

I could hear this wierd sound, but never saw the gas boiling (bubbling like water does). It was moving though some, and the motor had been turned off for plenty of time for it to settle. It wasn't calm though like water is when its just standing. I have no idea what it was doing inside the carb though, but it had definitely got hot and vapor locked.

I was pissed. A million thoughts went through my head. What could I trade it for? 650? no, I want the IRS. Rincon? No, I want the diff-lock. Sp700? maybe, but its too heavy. AC500i? No, no diff lock or speed. Finally I cooled down (the quad didn't) and decided that if this becomes a problem that reoccurs, I can wait for somebody else to make what I want. That or I can make a way to build a heat shield for the carbuerator.

Still, I feel like a complete Jackass for doubting people who have talked about the vapor lock. I never experienced this on my Arctic Cat, though a friend told me later today that he had vapor locked his Bayou 300 a time or two when riding extremely slow in the woods (making his own trail). I guess its not just a big engine thing after all

 

Andy~

Well, let's get our collective heads together and first call Yamaha. It's obvious that this shouldn't happen. Even though it's not happened to me, I guess I'll be sending my headers to Jet Hot to be coated, and perhaps even grab a jar of vasoline and buy Hifhlifters Heat Fighter Kit.

You know, I don't mind spending money on mods, if it's because I want to. I don't like it if it's to prevent a problem that shouldn't be there.

SilverBear

 

I wonder if you couldn't fabricate some kind of shield out of aluminum, and then back it with heat fighter tape on both sides. I'm going to take a look at mine and see if there is some place to mount something like that so it would shield the carb from heat. Also might look to see if I couldn't back the bottom of the gas tank with heat shield.

 

Actually Yamaha's fix for this problem is exactly what you described.

Take your quad to your dealer and explain the problem to him. He will then call Yamaha and they will send him the heat shield kit.

Yamaha is fixing them on a unit by unit basis. The same way they are handling the CV axle and floorboard problems.

Even if your machine is out of warranty, they will fix the problem. They are still issuing these kits to the early model 600 Grizzly owners. They had the same problem with the float bowl on the carb. collecting too much heat from the exhaust.

KNOWSALOT

 

I hope you do know a lot, cause I might just stop by there. Well, maybe Tues, cause most cycle shops are closed on Monday.

 

My grizz doesn't have this problem but should i take it in and tell them to put the shield on anyway??