The last 2 times I have taken my Raptor out to Pismo Beach it has popped off the carbs from the intake boots. I have about 25-35 hours on the motor and I always ride at Sea Level (Glamis, Pismo). I have heard that reason why it does this is because the valves are too tight and need to be adjusted. I have given the Yamaha dealer that I bought the bike from a couple of calls to try to figure this out but they just want me to bring it in and dont want to discuss any problems/symptoms. This is my first 4-stroke so I am somewhat unfamiliar with the mechincal intrcacies of these motors.

Also, my Raptor has made a strange squeaking noise. It only does this when I apply any throttle to the motor. When I let off it doesnt make the sound, but as soon as I resume the acceleration the squeaking returns. It sounds like rusty hamster wheels turning, at least thats what my friends say when I pull up to them.

 

Mine hasn't popped off yet! I have 31 hrs on mine. When I purchased mine, Early May, the dealer told me to bring it back around when I have run aprox. 5 tanks of fuel through machine to adjust the valves. I had it done. Seems to run fine and no popping yet. I did tell the dealer that the carbs seem to move around alot at idle just because of what I have read on the forums. They said this is normal because of rubber boot. From what I read on forums this is caused by a lean condition/backfire that pushes carbs off. I did raise my idle ever so slightly and marked it so I can put it back to same position if needed. I also read that you will hear the pop before they come off. Do a search on (raptor problems) lots O info. there.

 

I also heard a good set of heavy-duty hose clamps help to hold the carbs on even though your problem is carb related.

 

You need to adjust your valves for the hamster noise (You get this when reving up) and have the carb adjusted if your blowing them off

 

my carb screws were adjusted, and I took some clamps off of an old junk ninja intake and havent ahd any trouble since, and mine does do teh back fire through the intake, and i feel it through the seat kind of annoying type thing.

 

The backfire comes from head intake pressure being off balanced. The left side carb feeds 2 intake valves and the right side feeds 3. If you took some duration out of the cam, this would be eliminated, unfortunately so would peak performance. Yamaha is aware of the problem. Keep your dealer notified if you are having this problem and if and when they come out with a cure you will be on the list. Don't hold your breath. For the mean time clamp the crap out of the intake boots.

 

I talked to the Service Manager at the dealer where I bought my Raptor yesterday. He said the only problem that Yamaha has admitted to with the Raptor is this one (Carbs popping off). He said that the reason they pop off is due to: #1. A faultly boot and #2. Engine jetted too lean. This would cause the engine to backfire and pop the boot off. He said about halfway through the production year they changed the boot, and started jetting them a little richer. So, if you have a later model year you should be ok. If not, I'd be going into my Yamaha dealer and having them replace that boot.

2001 Yamaha Raptor (GYT-R bumper, DG Skid Plates, Pro Design Kill Switch)
1988 Yamaha Warrior (too many mods to list)

 

Yamaha has only ever offered 1 part number for the intake boot, and the jetting has been a standard 140 on the left 145 on the right and 22.5 pilots from day one. If you run a bone stock raptor on a dyno and utilize an exhaust sniffer you will find an almost perfect jet ratio (sea level test). We tried to increase the pilot size in the beginning and it only made the problem worse (unburnt fuel being ignited boom backfire). It is honestly a very isolated issue right now and this is why Yamaha has not acted yet.

 

Thanks guys for the great information.

I think I need to give my Yamaha Dealer a call to make them aware that I am experiencing this problem and also I need to give Big Gun Exhaust a call because I am running their recommended jetting changes on my carbs.

My bike was backfiring after I would shut it down, it looks like it just needs the valves to be adjusted and hopefully that gets rid of the "hamster wheel squeak" when I hit the throttle.

Also, my Raptor stalls frequently when I stop abruptly or when I have a rough landing. I hear this is because of automatic decompression,... Does this happen to anyone else?

 

Have the dealer install the new intake manifolds (that's all they can get now) which will hold the carbs better. Don't overtighten the carb clamps because it will help push off the carbs. Adjust the idle mixture screw (turn out) to prevent lean misfire. This will solve your carb blowing off problem.

As for stalling after landing, it's not the decompression. It may be the jetting which came with the pipe or the fuel level in carb is too high. Did you modify your intake system (airbox, filter)? Just piping it shouldn't require jetting change.