throttle hesitation

justin patterson · Jul 10, 2015

I got a 701 with a Coffman sizzler exhaust and brand new 44mm carb. The problem is when I pull the throttle it has a slight hesitation and then will run good. It will do it every time I let off the throttle and try to go again. Any suggestions?

yamijumpn · Jul 10, 2015

what throttle position is it happening at? off idle? between an estimated throttle %? Im fighting a similar problem were it hesitates bad around just off idle to 1/4 throttle then starts to go. if I hit it wot it hesitates for a split second then takes off like no other! its pilot/pop off related more than likely.

Vortex · Jul 10, 2015

Play with with the popoff and pilot jet first.

If the opening point of the needle is incorrect you will have it hesitate every time.

Jetting is just a matter of richening until it blubbers then back off.

If it's still hesitating after you coast for a second then you can install an extra anti siphon valve into the valvebody (the thing that covers the jets and held by 2 screws)

yamijumpn · Jul 10, 2015

whats the point of the extra antisiphon valve? ive never heard of this^

Vortex · Jul 10, 2015

Read the mikuni manual.

When coasting from high speed, there is fuel present in the diaphragm but the engine does not need it. This build up can cause a momentary rich condition when accelerating out of a turn, for example. The siphon valves relieve this build up. I have not had to do this before either. But apparently you just drill another spot in the valvebody for an additional plastic valve.

justin patterson · Jul 10, 2015

Off idle to around 1/4 throttle is we're it's happening.

Vortex · Jul 10, 2015

Pop off. You may need to change needle size to get proper pressure.

justin patterson · Jul 10, 2015

Needle size as in the bowl. Or the jets?

Vumad · Jul 10, 2015

Try turning the low speed screw out first because it is free. If that does not work, try lowering your pop off. Use the mikuni chart and a pop off gauge to determine what you have now and what components you will need. Try going down by 10psi. Use the smallest needle and seat combo that will let you get the psi you desire.

It may not be your pop off, but you probably don't need 2 anti siphon valves. I understand that to be very rare.

throttle hesitation

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