Trailmaster xrs 150 doesn't stary

[rcrico]

I'm trying to repair the kart for my son. Fuel is going to carburetor and it will turn but won't start unless a spray cleaner or fuel into the carburetor filter intake. I completely disassembled and cleaned carburetor, added new fuel, changed plug which has spark. But won't stay on. I ran the fuel hose straight to filter intake and it starts up but won't stay on. Could it be bad fuel filter or fuel pump? I am going to try setting the ratio screws(little gold screws). How would one set the valves? Any help would be appreciated.

[liduno]

If it only runs when you spray fuel in the carb, then it sounds like you aren't actually getting fuel to the carb.

Does it have a vacuum operated petcock? IIRC I don't believe there is a fuel pump.

[rcrico]

Yes, it is a petcock. I took carburetor apart and fuel was in the bottom area at floaters. So I figured it was getting fuel, maybe not enough of a stream. Should it be a strong flow of fuel. It seems kind of weak and thought to change filter and oetcock.

[liduno]

If the petcock is vacuum operated, make sure it's getting good vacuum. They are only supposed to let fuel flow when they are getting vacuum, so a vacuum leak can be an issue.

You can take it out of the tank to see if it's clogged, they are usually cleanable.

[rcrico]

Since it does want to start when I add fuel to carb filter intake side, does that mean fuel is getting to spark plug? I'm worried that it might not be getting enough vacuum to reach plug.
I'm going to try new fuel filter and clean out petcock and adjust the carb. fuel/air ratio screws and hope that works.

[liduno]

Well if it runs then gas is getting to the sparkplug. I recommend you don't start adjusting the carb. It's not likely the issue here.

More than likely you have a fuel delivery issue. Make sure the petcock is clean and flowing fuel. If there is crap in the tank you may need to clean the carb again. 1 tiny piece of crud in a jet can keep it from running.

[rcrico]

Thanks for the advice. I'm going try cleaning the fuel system/hoses and carb again.

[liduno]

Have you checked to see if the choke is working? If the tank and petcock are clean and working properly, I would probably check that next.

You still haven't said if it had a vacuum operated petcock or not. If it does, you want to make sure it's only opening when vacuum is supplied. If it's letting fuel out with no vacuum that can mean it's bad.

If it's just a normal gravity fed petcock, then makes sure it's clean and flowing.

[neo71665]

If it's got a vacuum petcock save yourself headaches now and just order a normal one that has the on/off lever. The vacuum petcocks rarely work right for more than a month or 2. The normal ones don't cost any more.

[rcrico]

Yes it's a vacuum petcock.

[liduno]

A vacuum petcock should only let fuel flow when there is a vacuum supply, if it's letting fuel flow when the engine isn't running, then it's possibly leaking fuel into the vacuum line.

[wildbob]

If you end up replacing the vacuum petcock with a gravity feed, don't forget to get a rubber vacuum cap to block off the port on the intake (or wherever you were getting vacuum from). I found the vacuum petcocks to be problematic from the get go, and and the carbs not much better. I bit the bullet and got as mikuni carb with a manual choke.

[Gippeto]

Originally Posted by liduno

Have you checked to see if the choke is working?

X2...would block off most of the inlet to the air box and see if it fires or starts before digging further.

Even a minimal supply through the petcock should be enough to keep the carb fed enough to start and idle...choke is where I'd be placing my $$...even more so since you say you've cleaned the carb.

Al

Edit: Note to self...check dates before posting lol