Had my 97 MXZ out yesterday, just bought it a few months ago. Supposedly the carbs had just been gone through and cleaned last fall. I put in new NGK plugs and took it for a spin. Runs great from idle when you hit full throttle, but cruising along at about 3500rpm, hit full throttle and most of the time it bogs. Go back to idle and go full throttle and it pulls hard for about 3 seconds and then starts to bog once again. Still great fun to ride, I just wish it would pull hard on full throttle. Looking for ideas, was thinking either a hotter plug or smaller jets???

are the plugs gapped correct? if they are then check to see on the plugs which side is causing the problem.

I would clean the carbs again yourself,look at the pilot jets to make sure they are clean.Sounds to me that it's in the fuel system. Check your rubber boots on the carbs for cracks. Then I 'd look at the fuel pump and or pulse line going to it. It seems that gets enough to idle and one hard charge before it's running out of fuel.hotdoo

Had the same problem with my sled last year. Cleaned the carbs and one of the jets was packed full. Let it soak for a long time then popped it out. Havent had a problem since.

I'd change your primary spring, if it is original it is probably worn.

3500 is a bit low so the weak spring is probablely allowing lower engagement


also check your belt for wear(1/16 above the secondary when stopped)

First of all, gapping the plugs will not increase performance. It will only increase the life expectancy of the plug. As long as they're not completely closed or way too far open, they'll work all the same.

Second, the pilot jet does not control the fuel at 3500 rpms. About 1/4 to 3/4 throttle is controlled by the needle and main jet.

Third, NEVER put a hotter plug in your sled than recommended by the manufacturer. That's a good way to burn down your engine.

I'm going to have to agree with mmgg on this one. Sounds more like a clutch/belt issue than a carb issue. I'd still clean the carbs first to be sure, but I'd guess that your belt is slipping or a weight is sticking. You can clean the primary by spraying brake cleaner in the opening on the outside and blowing air, other from compressed air in a can or a compressor, into the hole. Then use fine grit sandpaper to clean off the sheaves. If none of this works, I'd change the spring.

Hope this helps.

CLEAN THOSE CARBS!!!!! pilots are plugged.
Always clean them before season starts .

Plug gap is important ! so make sure they are right.

AT 3500 your still in the pilot curcuit..and do flow all the time , even at wide open.
Air and fuel mix has to vaporize to ignite. Any one of them is off and it will stumble.

mutt