990

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andyken

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I have a 990 carb on my Xb, with a jet pro rear pipe.


I like the performance, but miss the choke.


I can usually get it to start, after alot of pulling, and covering the air filter... most times I need starting fluid.


What is another carb [good performance] I can use with a choke?


I hear you can add a choke to the 990, but not recomend due to possible air leaks..?


I replaced my stock carb , because I had to turn the needles way in to get it to run.


It was like 3/4 turn out or less.


The tune on this 990 is pretty good, when it finally starts.
 
I think the 813 is the same size carb and has the choke but the downfall is it has a fuel pump and tends to leak . There is somebody on here using a different style of carb and hopefully see this post and give their input
 
Those were designed for the gopeds. They let air in behind the filter, so not recomended for off road use.
 
try this starting method with your 990

prime the bulb until full/hard... usually 3 or 4 pushes if the car has been sitting awhile, then push it 2 more times.

grab pull start rope and slowly pull it about 1/3 of a full pull to turn the motor over, repeat this one more time and then yank the rope to start it on the 3rd pull as you normally would.

it should start on the 2nd or 3rd pull.
 
Last edited by a moderator:
Inertia Racing Products said:
try this starting method with your 990prime the bulb until full/hard... usually 3 or 4 pushes if the car has been sitting awhile, then push it 2 more times.

grab pull start rope and slowly pull it about 1/3 of a full pull to turn the motor over, repeat this one more time and then yank the rope to start it on the 3rd pull as you normally would.

it should start on the 2nd or 3rd pull.
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I'll give that a try...thanks!
 
Inertia Racing Products said:
try this starting method with your 990prime the bulb until full/hard... usually 3 or 4 pushes if the car has been sitting awhile, then push it 2 more times.

grab pull start rope and slowly pull it about 1/3 of a full pull to turn the motor over, repeat this one more time and then yank the rope to start it on the 3rd pull as you normally would.

it should start on the 2nd or 3rd pull.
Click to expand...
Tried it, no luck
 
813 has no Choke but easy to start. Prime bulb open throttle full 3 or 4 times and pull. IMO it's the pick of them I've had no problems with them.
 
andyken said:
Tried it, no luck
Click to expand...
Hmmm thats odd..

you said in th OP that it runs decent once it starts, with a 990 it should scream like a banshee with very snappy response...

what motor is this on and how many tanks do you have through it ?

what do you have the L needle set at ?

you also mentioned using starter fluid, man that cant be good for the diaphram inside the carb, lmk the answers to the above and i'll try to advise from there...

as a worst case , switch over to the 668 carb, it has the choke and i have run them on some pretty nasty motors, reed and piston port before the 990 came out, and they wroked just fine with very good performance.
 
Inertia Racing Products said:
Hmmm thats odd..you said in th OP that it runs decent once it starts, with a 990 it should scream like a banshee with very snappy response...

what motor is this on and how many tanks do you have through it ?

what do you have the L needle set at ?

you also mentioned using starter fluid, man that cant be good for the diaphram inside the carb, lmk the answers to the above and i'll try to advise from there...

as a worst case , switch over to the 668 carb, it has the choke and i have run them on some pretty nasty motors, reed and piston port before the 990 came out, and they wroked just fine with very good performance.
Click to expand...
I bought it used, stock motor said to have 1 1/2 gallon thru when I got it.

Had stock carb and jet pro rear pipe.I've done almost 2 gal... about a 1/2 gallon of it with stock carb.

It was ok [esp with a choke] but had to screw the needles way in...like less than 3/4 out.

I am at 1 1/4 turns on the 990...last I knew.

If I put a drop of gas down the plug hole it starts right up.

Or if I squirt like a 1/2 sec of starting fuil on the air filter it will start.

Once warm it will restart easy.
 
andyken said:
I bought it used, stock motor said to have 1 1/2 gallon thru when I got it.Had stock carb and jet pro rear pipe.I've done almost 2 gal... about a 1/2 gallon of it with stock carb.

It was ok [esp with a choke] but had to screw the needles way in...like less than 3/4 out.

I am at 1 1/4 turns on the 990...last I knew.

If I put a drop of gas down the plug hole it starts right up.

Or if I squirt like a 1/2 sec of starting fuil on the air filter it will start.

Once warm it will restart easy.
Click to expand...
ok thanks for the info, i will be able to give you a better idea once i swap out the stock carb on the stock motor to the 990 i have sitting on the bench as far where i end up up needle settings.

right now as part of my build thread i am going to run the stock carb a few tanks after i finish the break in of the motor so i have real data on the difference the 990 makes on the stock motor.

now what i can tell you for now is what my settings are on my other motors with the 990 carb versus a 668 carb.

on my gizmomotors GZ-30.5 with a 990 the L needle is set at 7/8 of turn out and the H is at 1 1/2 turns out. if i go over 1 turn out on the L needle its a female dog to start , loads up quick at idle and a slug on the bottom end

on that same motor with the 668 carb the settings were closer to what so called " standerd " settings are 1-1/4 L ,and 1-1/2 H...

on my Flowsystem 27.2, 3mm LR motor with the 990 the L is @ just a tick under 7/8 and the H is just a tick over 1 1/2 on most days...

now this motor is a finicky beotch, a 10% change in humidity meens a change in the tune.

keep in mind this is a full tilt boogie, 1 off custom ,with super tight tolerances. the carb metering spring " pop off " is set so light that if i leave gas in the tank i have to loosen the gas cap to keep pressure build up from blowing by and filling up the cylinder.

so i would guage this more off the gizmomotors for your settings

both motors run pump gas with 927 oil @ 25.1 on those settings.

one last note on L needle, keep in mind its job is just basically for idle up to approx 1/3 throttle to transition into the H side.

i hope this helps.
 
I'm running 25-1 927 as well, I wish pushing the primer with throttle open would squirt some fuel into the engine.

When it's cold, I can try all day to start and not get the plug wet.

But runs well once started...
 
I was wondering if low compression would be the problem? I had a similar issue with my daughters quad . I had to pull the plug and squirt 10cc of IPA to get it to fire and once warm it was fine and started no problem till it cooled down. Repeat step one.
 
BertR said:
I was wondering if low compression would be the problem? I had a similar issue with my daughters quad . I had to pull the plug and squirt 10cc of IPA to get it to fire and once warm it was fine and started no problem till it cooled down. Repeat step one.
Click to expand...
Could be...anyone know what psi it should be?

If it turns out to be low....new head and ring, or new motor?
 
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