WT-990 carb upgrade plus more

Messages
20
Likes
3
Location
Cincinnati
Thread starter #1
Hello everyone! New member here. I've searched through many sources and excuse me if I missed one but I'm having some problems with my new rampage MT. Bought it used, started in 3 pulls.. drove great. Rained for like 30 days so i started to upgrade Lol redcat air filter, ddm pipe, 8k spring, turtle racing pull start, kill bee switch, walbro 990 carb.. now it wont start. Ive tried agjusting the low speed, the idle, and the bag over the air filter trick.. still nothing. Wont turn over at all. Please help!!
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#2
Hello everyone! New member here. I've searched through many sources and excuse me if I missed one but I'm having some problems with my new rampage MT. Bought it used, started in 3 pulls.. drove great. Rained for like 30 days so i started to upgrade Lol redcat air filter, ddm pipe, 8k spring, turtle racing pull start, kill bee switch, walbro 990 carb.. now it wont start. Ive tried agjusting the low speed, the idle, and the bag over the air filter trick.. still nothing. Wont turn over at all. Please help!!
Chuck the 990 and get a 668
It's the same carb but has a choke
I had a 990 and it was just a PITA
Had to use starter fluid to get it going
With the choke it starts every time
 
Messages
20
Likes
3
Location
Cincinnati
Thread starter #3
Isn't that the original carb tho? There's just so many mixed reviews on the 990 (after the fact) It was just on a thread of a path to upgrade so I bought in..
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#4
Isn't that the original carb tho? There's just so many mixed reviews on the 990 (after the fact) It was just on a thread of a path to upgrade so I bought in..
Check the specs of both carbs at DDM and you'll see they'r the same.
I got conned too.
Mine is sitting in my toolbox for spares.
 

TPSF

Well-Known Member
Messages
57
Likes
4
#5
Oneal brothers said that 80 degrees outside is still cool for a 990 to crank easy, with that said in alli never got mine to run right, two 990's on two different engines so I went to a 1107 and it's a beast two pulls cranks and runs like crazy. It has a choke, but to me when the 990 was running and tuned and this 1107 running and tuned the 1107 is much more powerful and certainly easier to use and crank. All I hear about is the 990 bieng the best but for me and my two engines it was a nightmare and stayed sitting more than riding.
 

sunoco

Well-Known Member
Messages
151
Likes
27
#6
any carb with no choke has to be primed with fuel before cranking on it. get yourself a cheap nazel spray bottle- not the pump type- the type you squeeze the bottle itself. put gas-oil mix in it.-- i use the dt-1 filters- remove it- open the throttle wide open.- with all the electronics shut off- roll the motor with starter so the piston is at tdc.- squirt a small amount of fuel into the carb.- replace the filter.- light the car off as usual- just because a carb is new does not mean its internals are correct- i do loads of things to carbs- mods. i can make a wt-990 kick ass big time-- type of fuel pump diaphram, bunch of other things also.-- its the fun of the hobby- trial & error.

any carb with no choke has to be primed with fuel before cranking on it. get yourself a cheap nazel spray bottle- not the pump type- the type you squeeze the bottle itself. put gas-oil mix in it.-- i use the dt-1 filters- remove it- open the throttle wide open.- with all the electronics shut off- roll the motor with starter so the piston is at tdc.- squirt a small amount of fuel into the carb.- replace the filter.- light the car off as usual- just because a carb is new does not mean its internals are correct- i do loads of things to carbs- mods. i can make a wt-990 kick ass big time-- type of fuel pump diaphram, bunch of other things also.-- its the fun of the hobby- trial & error.
myself, when i have a new, or am reworking walbro carbs- r-c car- chain saws- ect. i pull them apart- eye ball them- check for restricted fuel flow- the newest wt-990 has no notch on the butterfly valve- replace with the older style valve- wet test the carb- off the motor. set fuel volume- record pop off pressure, reset pressure- leaking needle- bunch of other things also.- each motor-pipe-car weight-gearing type of fuel used- type of running i do - its all connected, has to be tuned tru trial and error to get it right- closer to correct-- thats the fun of the hobby- !!!!
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#7
Oneal brothers said that 80 degrees outside is still cool for a 990 to crank easy, with that said in alli never got mine to run right, two 990's on two different engines so I went to a 1107 and it's a beast two pulls cranks and runs like crazy. It has a choke, but to me when the 990 was running and tuned and this 1107 running and tuned the 1107 is much more powerful and certainly easier to use and crank. All I hear about is the 990 bieng the best but for me and my two engines it was a nightmare and stayed sitting more than riding.
I tried an 1107 on my Zen 290 but it bogged no matter how lean I set it.
Heard it's great on the 320 though
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#8
any carb with no choke has to be primed with fuel before cranking on it. get yourself a cheap nazel spray bottle- not the pump type- the type you squeeze the bottle itself. put gas-oil mix in it.-- i use the dt-1 filters- remove it- open the throttle wide open.- with all the electronics shut off- roll the motor with starter so the piston is at tdc.- squirt a small amount of fuel into the carb.- replace the filter.- light the car off as usual- just because a carb is new does not mean its internals are correct- i do loads of things to carbs- mods. i can make a wt-990 kick ass big time-- type of fuel pump diaphram, bunch of other things also.-- its the fun of the hobby- trial & error.
All that hassle when a simple choke fixes the problem?
 

sunoco

Well-Known Member
Messages
151
Likes
27
#10
thing is-- the choke plate & the shaft doubles the restriction tru the carbs bore. less flow. Gitzmotors -n Florida sells a new type of throttle shaft- stainless steel that is cut in a more logical fashon.- it allows more air flow than the factory shaft.- its optional when ya purchase a carby from him. I install them myself - nothing to it really. DDM just shows the size of the carbs bore- most all are the same i-d. I need to get into Walbro web site and study part #-s on the 1107.-- high speed check valve #, pop off spring numbers- ect.-ect.-- It sounds as if the 1107 on the zen 290 could be dumping too much fuel into the engine.- Its a 28mm stroke after all- not as strong a fuel signal that a longer stroke-30mm motor has. - When you turn the fuel screws in- clockwise on the 290 zen and its still rich- Its a tell tale sign that fuel enrichment- is occuring at too low a pressure.-- assuming the fuel bulb is 75% full.- there is more to this actually-- Just for hecks & giggles- remove the pressure spring out of the wt-990, just the spring, and put it into the 1107 carby- this is just a wild guess because i have not seen part numbers for the 1107-s spring yet.-- Walbro carby rebuild kits come with 3 fuel pump diaphrams.-for the wt series carbs. the -usually factory stock one is the lighter colored one- this one flows less fuel than the black rubber one. the blue colored one can be used with methanol. - it could? be a choice for american pump gas- it does have ethanol in it after all- pretty certan au- and europe gas does not have ethanol in it-- pardon the spelling- dave.
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#11
thing is-- the choke plate & the shaft doubles the restriction tru the carbs bore. less flow. Gitzmotors -n Florida sells a new type of throttle shaft- stainless steel that is cut in a more logical fashon.- it allows more air flow than the factory shaft.- its optional when ya purchase a carby from him. I install them myself - nothing to it really. DDM just shows the size of the carbs bore- most all are the same i-d. I need to get into Walbro web site and study part #-s on the 1107.-- high speed check valve #, pop off spring numbers- ect.-ect.-- It sounds as if the 1107 on the zen 290 could be dumping too much fuel into the engine.- Its a 28mm stroke after all- not as strong a fuel signal that a longer stroke-30mm motor has. - When you turn the fuel screws in- clockwise on the 290 zen and its still rich- Its a tell tale sign that fuel enrichment- is occuring at too low a pressure.-- assuming the fuel bulb is 75% full.- there is more to this actually-- Just for hecks & giggles- remove the pressure spring out of the wt-990, just the spring, and put it into the 1107 carby- this is just a wild guess because i have not seen part numbers for the 1107-s spring yet.-- Walbro carby rebuild kits come with 3 fuel pump diaphrams.-for the wt series carbs. the -usually factory stock one is the lighter colored one- this one flows less fuel than the black rubber one. the blue colored one can be used with methanol. - it could? be a choice for american pump gas- it does have ethanol in it after all- pretty certan au- and europe gas does not have ethanol in it-- pardon the spelling- dave.
In other words it's too rich for a 290 as I already said.
Why would I bother mucking around with carbs when I have one that works perfectly?
You could look at the shaft from another perspective and by interrupting the air flow it is helping with atomisation of the fuel.
We have the option of fuel with or without ethanol.
 

sunoco

Well-Known Member
Messages
151
Likes
27
#12
In other words it's too rich for a 290 as I already said.
Why would I bother mucking around with carbs when I have one that works perfectly?
You could look at the shaft from another perspective and by interrupting the air flow it is helping with atomisation of the fuel.
We have the option of fuel with or without ethanol.
 

sunoco

Well-Known Member
Messages
151
Likes
27
#13
i suppose i just like to tinker with things-- lol. there are quite a few places on you-tube that show people pressure testing pop off springs.- they say go for 10- 15 psi release-ect. this could work on bigger displacement engines. fact is though, when you pressure test these carbs -it should be done wet. why? because air compresses. liquids do not. also, the fuel pump produces 5 to 7 psi.- this is too close to 10 psi the fuel pump pressure could over ride the lighter pop off spring-- resulting in a far too rich mixture. - yea, i do tinker on things here. --- as for a stock wt-990- pop off happens @ approx 34 psi. some folks with big long stroke ported engines will install the spring that is factory stock on the wt-257.- part # 98-304-7.- just saying---
 
Messages
20
Likes
3
Location
Cincinnati
Thread starter #14
Thanks for the replies everyone. Everything I looked into b4 all pointed to the 990.. guess I Should have done a little more homework. Maybe I'll look into the 1107 if it's not too much over kill. Anyone kno a part number to the "pop on and off" style air filter. I have the crappy aluminum Redcat filter now and it's a pain to take off and on.
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#15
Thanks for the replies everyone. Everything I looked into b4 all pointed to the 990.. guess I Should have done a little more homework. Maybe I'll look into the 1107 if it's not too much over kill. Anyone kno a part number to the "pop on and off" style air filter. I have the crappy aluminum Redcat filter now and it's a pain to take off and on.
DDM sells a Baja double element filter that fits.
 

sunoco

Well-Known Member
Messages
151
Likes
27
#17
there are many options for these cars- at ddm, here are a few-- af-372. af317. av-540. there should be no clearance issues with the choke plate with af-317. as for air filter oil-cleaner, i go to a dirt bike shop and buy No-Toil brand. you can wash it-oil it in the kitchen sink with no issues- the kitchen sink spray nozzle helps too- just make shure your wife is not home when you clean it. You will also have to buy 2 bolts to bolt the velocity stack to the manifold. ddm can suggest correct bolts if you call them.--
 
Messages
20
Likes
3
Location
Cincinnati
Thread starter #18
Thanks Sunoco for those part numbers. Well I took the advice and ditched the 990 carb and replaced it with the 1107 from large scale rc (terrible response but i got it in a day so pick yr battles) got the truck all back together and still nothing. Changed the plug, tried everything. doesn't even try to start. The killer bee switch mini circuit board has no green LED. I'm running a FS-GT3C radio. Any suggestions? Also is there a correct bolt down pattern for the gearbox, engine mounts, etc? I've had this thing apart like 6x and sometimes I get squeal from the clutch housing on pull start sometimes I don't?
 

sunoco

Well-Known Member
Messages
151
Likes
27
#19
Thanks Sunoco for those part numbers. Well I took the advice and ditched the 990 carb and replaced it with the 1107 from large scale rc (terrible response but i got it in a day so pick yr battles) got the truck all back together and still nothing. Changed the plug, tried everything. doesn't even try to start. The killer bee switch mini circuit board has no green LED. I'm running a FS-GT3C radio. Any suggestions? Also is there a correct bolt down pattern for the gearbox, engine mounts, etc? I've had this thing apart like 6x and sometimes I get squeal from the clutch housing on pull start sometimes I don't?
trace the 2 gas lines back to the gas tank. the fuel line with the filter in the gas tank goes to the bottom- lower inlet of the carb. pull the spark plug. put the cap on it- ground out the plug in the area it threads into. in a shaded area, turn on the radio- pull the starter cord- look for spark on the plug. even if you have to hold the plug- its a weak spark- not like some g.m hei ignition- its not gonna knock you across the room-- as for the bolts- just tighten in a X pattern, little bit here- go to next bolt- little bit at a time on each one. once the gearbox is seated- just approx 1/8 turn more on each bolt.-- on the new carb-- if the gas lines are correct, and the carb is in correct working order- you can push the bulb forever and it will not add a drop of gas into the engine. The bulb simply purges the air out of the carb body. It should actually be called a purge bulb, not a primer bulb-- but thats just my way of thinking i suppose. best of luck to you.
 

Phill

Well-Known Member
Messages
1,961
Likes
58
Location
Yeppoon QLD Au
#20
Thanks Sunoco for those part numbers. Well I took the advice and ditched the 990 carb and replaced it with the 1107 from large scale rc (terrible response but i got it in a day so pick yr battles) got the truck all back together and still nothing. Changed the plug, tried everything. doesn't even try to start. The killer bee switch mini circuit board has no green LED. I'm running a FS-GT3C radio. Any suggestions? Also is there a correct bolt down pattern for the gearbox, engine mounts, etc? I've had this thing apart like 6x and sometimes I get squeal from the clutch housing on pull start sometimes I don't?
Have you tried taking the kill switch off and starting it?
 

Members online

Latest posts

Top