MM700 problems at 3/4 throttle

E

ErikBerg

New member
Joined
Apr 23, 2009
Messages
40
Age
50
Location
Northern Sweden
My Mm700 gets to much fuel at 3/4 throttle. At every other throttle position everything is fine, including full throttle. Only when engine is warm, it seems.
- I have tried 3 different carb setups, Yamaha spec.
- Fuel pump is new.
- Hoses are inspected.
- Tank gets air.
- Carbs are clean.

I simply can't run at 3/4 throttle. Quite disturbing. What might be the problem?
 

Main: 143,8/142,5/142,5
Pj 45
Needles 2,5

Yamaha spec for 100-500 metres, -7 - -18 degrees C.
The weird thing is that this is the 3rd setup, and the problem remains.
 
info, info, info

What exactly does it do. It may not be what you think. Possibly your clutch is hanging up and bogging the motor. Have you hit the choke when this is happening? If it gets better your too lean worse your too rich. Need an exact description of what it sounds and feels like for better help. Just my 2 cents
 
It sounds exactly like it does when you hit the choke. In swedish it's called "bluddra", in english...choking, misfiring?
When I hit the choke it sounds the same, just even more.

Thanks! :)
 
have u pulled the needle and seats the rubber seal on the seats could be leaking causing more fuel than is needed , 3/4 throtle and above is ur main jetting but ur jetting is correct , putting the chock on in this postion loads it up more tells me ur getting enough fuel. did u chk float levels may be they are set to high.
 
ErikBerg said:
It sounds exactly like it does when you hit the choke. In swedish it's called "bluddra", in english...choking, misfiring?
When I hit the choke it sounds the same, just even more.

Thanks! :)
Click to expand...
Blurbling?
 
I measured plug caps, seem to be ok.
The clutches are good, bushings etc new, however I have problems with overrevving from start.
I will try changing preload and see what happens
 
clutch

I would look at the secondary. Check the pressure, replace the spring, check your buttons. Make sure the sheaves move freely when you remove the spring. I had a problem with my machine blubbering away at about 3/4 throttle. Messed with the carbs for a whole season. I had a thunder shift secondary with an Artic cat spring in it. Went back to a stock secondary with the proper tension. It went away. My 2 cents :2strokes:
 
Last edited:
And the answer is:

Tadaaaaa!

The outer bushing in the primary!

I replace the aftermarket cr*p with Yamaha original and voilá: I got myself a ned sled! :D
 
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