Walbro WT carb and Extended Intake

Akutey

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Joined
Dec 10, 2018
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30
I agree it's probably the alcohol, had a experince once with a cheap magneto seal that melted because of it. I guess I will start getting alcohol free gasoline again. Nearly all fuel pumps around here are labeled saying they have up to 10% Ethanol.
 


Akutey

Member
Joined
Dec 10, 2018
Messages
30
That map is pretty good, not much up here, mostly independent stations. Chevron should be labelled on there, found out their premium is alcohol free. Whenever I'm in doubt I check the pump sticker.
 

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Akutey

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Joined
Dec 10, 2018
Messages
30
Update. 7.95mm venturi carb will limit you RPM under load on a moderately modified 66cc china girl. Without load it will still overrev but wont safely produce power past 5500RPM. It can produce power past 5.5K but it requires leaning out the high end mixture to dangerous levels and being on flat road. Other then that the throttle response and control is very precise and I have a nice little cruiser. I put the stock 44T back on replacing my 36T so now on 20inch rims I went from the engine slightly struggling in a pedal-less start and having to use a bit of throttle to slip the bike forward. Now I can have it idling high, engage the clutch and immediately start doing 5-6km/h. Future reference would want to use any HDA/HD/WJ series (provided the particular model has no governor) or you could use 2 WT carbs. :giggle:
 

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Sep 26, 2018
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130
Update. 7.95mm venturi carb will limit you RPM under load on a moderately modified 66cc china girl. Without load it will still overrev but wont safely produce power past 5500RPM. It can produce power past 5.5K but it requires leaning out the high end mixture to dangerous levels and being on flat road. Other then that the throttle response and control is very precise and I have a nice little cruiser. I put the stock 44T back on replacing my 36T so now on 20inch rims I went from the engine slightly struggling in a pedal-less start and having to use a bit of throttle to slip the bike forward. Now I can have it idling high, engage the clutch and immediately start doing 5-6km/h. Future reference would want to use any HDA/HD/WJ series (provided the particular model has no governor) or you could use 2 WT carbs. :giggle:
5500rpm is low for a 2 stroke... The stock carb is a 11mm if I'm not mistaken with the intake id being smaller... Anyway, I'm running a 21mm at 7000rpm and it gives it fuel for days. With the YZ85 pipe, it chokes the engine with a 3 inch header to 7500rpm (extra rich and polluted charge as a safety) which is a blessing to my old engine because stock length, the pipe cuts at 12,500 and the old thing blew it's connecting rod wrist bearing at 8000 going downhill one day.

Maybe someone with a pumper carb can tell us more because most people run normal carbs
 

Akutey

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Joined
Dec 10, 2018
Messages
30
Well the walbro broke, carb metering plate took a hit, bent and broke the screws. Have a zama 7.94mm on it and now at 7000rpm (36km/h) then it stops and I haven't really adjusted the high end yet. It's supposed be adjusted under load as its high end circuit is separate and different to a walbro.
 

Akutey

Member
Joined
Dec 10, 2018
Messages
30
Think fixed the issue. Lever 2mm below flush of the carburator body and a shorter spring. Got 41km/h on speed radar so I'm hitting 7800RPM (4.4/20inch) It's pulsing now at top speed instead of going flat in power.
 
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