Walbro WT-990

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No probs here once I found out you only move the screws one hair at a time.

Before that I was too heavy handed.

What's wrong at your end?
 
Phill said:
No probs here once I found out you only move the screws one hair at a time.Before that I was too heavy handed.

What's wrong at your end?
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Sounds like my problem, got to give that a try.
 
Im having a lot of trouble starting the engine. Usually 20 pulls or so. Engine floods. Pull the plug. Engine fuel drain. Reinstall plug. Another 5 pulls to start.

I guess its the carb. I dunno.
 
Silent_chaos said:
Im having a lot of trouble starting the engine. Usually 20 pulls or so. Engine floods. Pull the plug. Engine fuel drain. Reinstall plug. Another 5 pulls to start.I guess its the carb. I dunno.
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Sounds about right, thats why I pulled it off. Let me know if you find one easier to tune.
 
claude bigelow said:
Does that have a choke on it?
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No choke. its the same as the 990, but it has a pump inside.

And according to my calculations, i guess with a pump(998) you can squeeze out more power. Same concept of your casual every day car. More pressure from Fuel pump means more bhp.

I know this from my brother's turbo car, he has a 160bar fuel pump and he wants to put another one.
 
Silent_chaos said:
Im having a lot of trouble starting the engine. Usually 20 pulls or so. Engine floods. Pull the plug. Engine fuel drain. Reinstall plug. Another 5 pulls to start.I guess its the carb. I dunno.
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Mine is 2 slow pulls after priming the bulb and it starts on the next hard pull.

I find giving it a little throttle on that 3rd pull helps
 
Silent_chaos said:
No choke. its the same as the 990, but it has a pump inside.And according to my calculations, i guess with a pump(998) you can squeeze out more power. Same concept of your casual every day car. More pressure from Fuel pump means more bhp.

I know this from my brother's turbo car, he has a 160bar fuel pump and he wants to put another one.
Click to expand...
It's an exciter pump

Just gives a squirt when you open the throttle
 
990 vrs stock 30.0 cc engine

for me, the wt 990 is a great carby. in my humble opinion, this 990 and the stock hy 30.5 cc engine operates best without a velocity stack. tried them all. when i do usethe stock engines, i prefer the DDM torquer stack. not an accurate name. sorry ddm!! it is not a velocity stack at all. just a way to mount a clamp on air filter. The stock hy 30.5 engine does not have the porting to fully use the increased flow that the 990 & a velocity stack flows. just my opinion, your opinion & results may vary. a example on varables-- the venrable CY 29 two bolt & wt 990 & 3/4" velocity stack is a great set up. great basher engine-- has more bottom end power than it should-- its the way its ported & the way the jugs base was machined. agan- my opinion.
 
here is another enigma. A over carburated engine will tend to run lean. Why? because the engine will not have enough displacement and - or porting to pull enough vacumme tru the carby-- less than zero vacumme at wide open throttle at the intake manafold is proof-- and a way to fine tune carby sizes. this applies to any engine with a carby. full sized or a r-c.
 
MY MT has the OBR 30.5 with the race porting. Brand new rebuild. Installed the 1/2 inch stack. Runs a JetPro rear pipe.

Closed both needles. Open low side 1.5 turns and high side 1.25 Primed the bulb. Slow pull twice. Third time it fired up. And has done over the last three tanks.

Two slow pulls. Then yank it!
 
yup no 2 engines start the same! cedar city? rode dirt bikes all over that state, salt flats up north, wendover-to the north, little sahara, pony express trail with the truck& camper, months in a touring kayak based out of bull frog marina, drove dirt roads from bullfrog to page in january--i9ts cool and good how your state shows the BLM who is boss there, keep up the good work utah!!!!!
 
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