Problem with my YFZ!! HELP!!

[raptor_02]

The last couple of times I rode my YFZ at the local MX track I could go a few laps and then all of a sudden it appears like the quad won't take gas. It will start cutting out real bad for a minute and I will have to stop. I let it sit there and idle then I occasionally rev it up and after about a minute it gets back lined out. Well I drained the gas out of the tank and inspected the carb real well. Didn't find nothing. Took some torch cleaning tips and made sure nothing was in the main jet or pilot jet and everything appeared to be fine. Well the next day with a clean carb and a new tank of fuel it did the same thing again. This is a big problem cause it did this on the face of a jump and almost caused me to indo. We think it may be the accelerator pump in the carb but we are not for sure. Any advice by you smart mechanics out there would be greatly appreciated.

[Bill Fuller]

Is it possible since the cool weather that it could be to rich?those damn FCRs are tempermental.

[Southtown00]

Did you try checking the actual gas line that runs to the carb? How about the gas tank vent hose. It will do that if it gets stopped up.

[dhines]

It's likely either jetting or an electrical problem. A number of folks have had problems with their machines cutting out due to a bad rectifier (I think). Try turning on your lights when it cuts out and see if it improves.

[Jekyl_22]

I have heard about lots of problems like this with the YFZ.

Some solutions I've heard/done:

1) If it runs fine when your headlights are on, then you can either run it with your lights always on, have your stator rewound, or buy a new stator from Trail Tech for about $200.

2) Maybe it's just the temperature changes. The FCR carbs are suppossedly sensitive.

3) Clogged fuel filter... take apart your petcock and clean both your RESERVE and ON filters.

4) Take off your carb, remove the float bowl, and take out the torx bolts. There is suppossed to be a little O-ring in there that can swell up when not tightened down enough. I've heard that lots of the carbs are like this...in which case you will have to order a new O-ring.

I had the same problem that you are talking about. It kept getting worse and worse until it just ran like crap. I tried everything I could think of until I decided that it MUST be jetting. I know that my jetting is much more rich than anyone I have heard of, but it runs awesome and better than it ever did. I'm not positive what jets I'm running (I'll check for ya today).

I have to tell you though that I haven't tried the O-ring in the carb thing yet. I just heard about it today and plan on checking it out tonight. Although my quad runs good, I find it hard to believe that I would need such big jets. So I'm going to look into it...

Hope some of this helps ya!:)

[Jekyl_22]

Ok, last night I checked my O-ring in my carb and the filters in my petcock, they were both fine.

As for my jetting, I am running a 190 main, 50 pilot, a NCVQ needle on the 6th clip, and I'm not sure about my airscrew (forgot to check). I have never heard of anybody with a 450 with such big jets, but it certainly runs great. All that I have done to it is removed the airbox lid and heavily modified the stock exhaust pipe.

I'm not sure exactly why I have to run such big jets, but they work awesome for me. I spent about a week jetting it. It will pull wheelies in 5th gear very easily... whether it be gravel, sand, dirt, or pavement. And it also has awesome throttle response.

Oh, and my elevation here is about 800ft. above sea level and temps are from 60° & 80°.

Sorry, I know it's frustrating when your quad doesn't run right. I don't know if any of this helps, but I hope it does.
:(

[caseMN]

I had a similar problem with mine. The motor would cut out after it warmed up, and I only felt it during hard acceleration. It felt like it was hitting the rev limiter about 2000 grand to early. I went through the carb and unplugged the TPS, they were fine, and the problem still presisted. So I took it to the dearship and they found that the CDI box was shorting out when the engine would rev up. They replaced it and i haven't had problem since. The mechanic there also mentioned that he has seen the coil arc to the engine causing a similar problem. Overall its bean a good machine with some small electrical problems. I was also given some other advice to change my oil every 5-10 hours depending how hard the machine is ridden, and to clean the air filter every week. It is a race machine and the maintaince should reflect it.

[quadnice]

Both my YFZ's have had similar problems.
The float needle got stuck, limiting the fuel to the bowl.

-Went trail riding 1 day, & my 04 quad would not start.
----cleaned float needle & fuel supply intake @ carb

-On my 05, it sounds similar to what raptor_02 is describing.
I believe the fuel may have gummed up from sitting for longer periods of ride time.
----cleaned float needle & fuel supply intake @ carb