Mikuni 34mm flatslide dumping fuel

mhornfeck72205

mhornfeck72205

New Member
#1
#1
So my 34mm mikuni flat-slide keeps dumping fuel out of the bottom drain tube. I use it along with a fuel pump on my 390 and it doesn't start dumping until i give it some throttle. It'll idle fine, no dumping, until i give it throttle, and then all it does is dump like crazy..

I'm not sure how to remove the float needle because it is clipped in, and under the float lever which seems irremovable. i'd like to try cleaning it out because it would seem to me that its just a dirty seat. only three possible causes of bowl overflow.. bad needle valve, bad float adjustment(not sure how to adjust) or broken floats, but they are fine..

anyone have a manual for this carb?
 
minidragbike

minidragbike

Supporting Speed Nut!
#2
#2
You should be able to change the height of the float. Normally by slightly bending the lever under the bottom in the center of the carb. You will see a little piece of metal connected to the float pushing a needle up and down. The needle need to go up, which closes the fuel from entering. Bend it up a little and it will close a little early.
 
mhornfeck72205

mhornfeck72205

New Member
#3
#3
adjusted it to the point of it barely opening and it sits and fills with fuel just fine, but then the minute i turn it on, the pump over fills it and it starts dumping.

I can pinch the pump pulse line, stopping the pump, and it stops overflowing. I think the needle seat is dirty.. gonna try and open it up and clean it out. :p
 
minidragbike

minidragbike

Supporting Speed Nut!
#4
#4
Carb sounds like it's made to run with out a fuel pump. I had a Lectron carb made that way. Once you idle, the pulses pump to much fuel. So you need to run it by gravity only.
 
mhornfeck72205

mhornfeck72205

New Member
#5
#5
odd since NRracing included a pulse fitting in the kit..

Saves me a fuel pump then because I need one on my gx200 for the drag bike.

heres an off topic pic. another 7" longer and a new motor mount. :)
 
mhornfeck72205

mhornfeck72205

New Member
#7
#7
took the pump out today, ran beautifully. :) this motor has some power once it warms up..

mdb, you know where to get some 390 stamped ratio rockers? Not looking to go roller just yet. maybe in a few weeks.
 
minidragbike

minidragbike

Supporting Speed Nut!
#9
#9
mhornfeck72205 said:
took the pump out today, ran beautifully. :) this motor has some power once it warms up..

mdb, you know where to get some 390 stamped ratio rockers? Not looking to go roller just yet. maybe in a few weeks.
Click to expand...
Parsons use to sell them. But has been out of stock for a good long time. Try NR-Racing
 
mhornfeck72205

mhornfeck72205

New Member
#11
#11
tried tuning it today. got a pretty good top end tune but when I punch the throttle it bogs until about 20mph to where it just rips and engages hard! I adjusted the slide needle for more top end fuel. I dont know how I should go about getting more or less fuel to the mid/low range portion of the rpm band.

kart topped out at 47 today as well. I'd like to hit 50-55ish for the flat 1/8mi. road by my house so I'll probably be re-gearing when my rockers and new valve springs come in.
 
mhornfeck72205

mhornfeck72205

New Member
#12
#12
I'm still having this issue with my 22mm mikuni on my gx200.. Is there any way to lower the pumping force? I have no idea whats causing these to dump so much fuel.. :-(
 
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