WT-990 Carb Needle settings

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h20guy

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Hi, I need to know a good starting point with the High and Low Needles for a WT-990 Carb on a stock 30cc Fuelie engine that has a moderate tuned pipe on it. Thanks in advance for your responses.
 
Ive got a question along the lines of tuning a 990 also...i've got a GP290 and a 990 carb. Its not running bad or anything but my question is, how lean can i go with my settings without damaging my engine? I mean, how do i know if i'm running to lean? right now, when my truck is idling, it's got good smoke coming from the pipe, i'll rev it a bit and a nice puff of smoke comes out and also good smoke when i pin the throttle. I'm assuming i'm on the rich side. should i see smoke at all? i would say right now i'm at 1 turn out on the low and probably 1 1/4 out on the high. still got good smoke all around, but no bogging really. kinda slow on the takeoff. would leaning the low out more help that? also, how high should my idle be set at? low idle or on the higher side? also, my gas mileage...(is it called gas mileage lol?) sucks!! i get prolly 10 mins from a tank... is this normal?? :confused:

thanks guys in advance!!
 
I run my carb on the ragged side thats little smoke on rev and almost none at idle you can gage it off of looking at the plug also . It should be a brown paper sack color when needles are set optimal . You can mess with the idle screw say when you lean it out some you can tame the rev by backing idle out .I hope this helps dude and remember to wear your gloves lol. we are in for a cool weekend
 
BertR said:
I run my carb on the ragged side thats little smoke on rev and almost none at idle you can gage it off of looking at the plug also . It should be a brown paper sack color when needles are set optimal . You can mess with the idle screw say when you lean it out some you can tame the rev by backing idle out .I hope this helps dude and remember to wear your gloves lol. we are in for a cool weekend
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i run the 990 and can not get it to run at all i have just put it on it wont idle when i do get it starteed it sounds like it always running out of gas and dies... please help
 
Does the prime bulb stay almost full of fuel? It should have fuel in it. Normal is about 3/4 full.
 
take off the fuel delivery line to the carb and loosen the tank cap and blow in the line . If it has twice the restriction of a drinking straw your clunk filter is plugged up.Your primer bulb should reform immediate with fuel after pressing it down If its slow you have a restriction to the carb.
 
+1 Bert... where were u when i needed you lol?? yes. def check to make sure your lines arent plugged or pinched. I had the intake line getting pinched in my grommet... took me 3 days of troubleshooting to finally try blowing into it.... damn...
 
my low end is set at 7/8. will flood very easy if not set like that. Runs and starts and idles very well at that setting.
 
dansmg said:
my low end is set at 7/8. will flood very easy if not set like that. Runs and starts and idles very well at that setting.
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that L needle setting is ok..

there are so many factors that go into needle settings.

ambient temp

humidity

Actual fuel/oil ratio ( sometimes when mixixng you can get an oz. or 2 off and that will change the tune )

brand/make up of oil

engine itself ( how mild or wild the engine is )

these are just the more common variables, there really is no set it and forget it tune.

i run the 990 on all of my motors and everyone of them is set differently... my wildest , nastiest motor , settings are the oddest of them all.

carb tuning is an art form, and for the guys that came up through the nitro ranks always have a better handle on settings.

nitro's are very finicky, but man they teach you alot.

in closing the absoulte best ways to set the tune for your area and application is reading the plug and learning to tune by ear.

tell tale sign of af lean condition is bogging, it will literally seem like 1/2 throttle application on take off for the low side and it will act like its cutting out on the top end if it is lean.

i hope this helps !
 
these are just the more common variables, there really is no set it and forget it tune.i run the 990 on all of my motors and everyone of them is set differently... my wildest , nastiest motor , settings are the oddest of them all.
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No two carbs are exactly alike either.
 
RCDAD said:
No two carbs are exactly alike either.
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Hey RCDAD, Did you ever rebuild any of your 990's? I just received my rebuld kit from ddm and all the parts in the bag are not the same as the ones in the carb....like the reed gasket especially. You know why that might be?
 
Those carb kits cover several different models of carb there will be disposable parts you don't use for your application.

I have noticed that 990 carbs seem like a leaner setting than my other carbs my Mt 32cc lsn is at 7/8 and HSN at around 1&3/8 but that's where the motor likes to be I've learned not to fret over it if it's a king some smoke and the plug is on the darker side of brown let it eat.
 
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