Need Help Carb Tunning

[vwbulla]

Hey guys new to the forum, had my xt for a few months now but im having trouble adjusting the low speed needle.


I watched a lot of the videos that I could find on youtube about how to adjust the needle and what the factory needle setting are but here is my issue.


when I have the lsn set at the factory setting and I turn the truck on it starts to walk on me. if I have the truck up on stand and turn it on the tires will spin faster and faster. and my idle screw is completely out.


then when I back off the lsn a bit the car bogs down under light acceleration and sometimes stalls.


how do I fix this??

 

[Deluge]

Sounds like an air leak, man. Spray some carb cleaner around the gasket areas of the engine, if the idle changes at all, that's where your air leak is at. If you can't find an air leak, you might have to swap the carb if you're still running the stock one. They've been known to be complete bastards to tune.

 

[vwbulla]

Really air leak on a brand new truck? that only had 2 tank fulls through it? Yes its a stock carb also.

 

[Deluge]

Well, if you have the idle screw completely backed out, and your LSN is at the factory setting (Which is on the rich side) when your truck tries to walk, it's sucking in air from another location. Make sure the carb bolts and the intake bolts are tight.

 

[andyken]

If the idle is way out, does the rpm change when brake is applied? The throttle trim, linkage to carb/butterfly not closed?

 

[vwbulla]

I have tightened the intake bolts, where are the carb bolts located?

the rpm does not change when I hit the brakes. but that's what im thinking I think the trim linkage is not fully closed and it walk. how to I adjust that properly?

 

[Ildy666]

Check ur head gasket.their known to blow out.mine blew out before the first tank was finished and caused nothing but tuning issues and the stock carb. Is hit and miss most change out to a genuine walbro..but it sounds like and air leak...

 

[vwbulla]

do you have a link to where I can get the proper walbro carb for this truck?

 

[Deluge]

You have a few options.

Walbro WT-668 Carburetor w/Free Choke Lever

Walbro WT-990 High-Performance Carburetor for Zenoah / CY Engines

Walbro WT-813 High-Performance Carburetor for Zenoah / CY Engines

The 668 would be like the stock carb, but more reliable. The 990 and the 813 are basically the same, only the 813 has an acceleration pump to help with low end lag. I've had good results with the 668 and the 990. Note the 813 and the 990 do not have a choke installed, which means starting could be tricky. But once you get them tuned right, they'll fire up without any hassle.

 

[rcgasser]

Have you cheeked the throttle trim on your radio? Is your carb arm resting on the idle screw? If you have your trim on the radio set to high and your carb arm is not resting on the idle screw it will not matter how far you turn the idle screw the engine will not idle down.

 

[vwbulla]

im gonna mess with all the radio setting when I get home make sure its all set right..