Twister/Hammerhead 150(GY6 Engine?) won't stay running. I took it out of mothballs to get it running again. Exhaust is off of it to fix mounting bolts on the head. Filter box is off so that I could fix the starting problem. Fixed the starter and installed a new battery. Changed oil. Decided to fire it up(figured the carb would be gunked-up...I was right and proceeded to clean it up thoroughly). It would not fire. Shot some gas into it, and it fired right up, but it shut down after it ran the shot of gas out. Did this a few times to see if it just hadn't gotten the bowl full of gas, but it still wouldn't keep running. I noticed that there was just a small amount of fuel in the fuel filter. There are 2 vacuum lines coming from the carb...1 coming off the side of the carb and 1 coming off the elbow between the carb and the head. They are joined at a "T" fitting and the third line goes from the "T" to this peice that is attached to the gas tank where the gas comes out. Is the piece attached to the gas tank some kind of fuel pump operated by vacuum? What do you think the problem is?

 

I think the problem is just a clogged carb- take it apart and give it a good punch out with some carb cleaner- make sure you clean every port good. Those filters usually don't fill up with gas completly- engine just takes what it needs to run.

 

I will take it off and clean it again...not too difficult and does not take long. I took everything off the carb and proceeded to use a torch tip cleaner to clean the ports out. Made sure that I could spray carb cleaner thru every orifice. Thought that would do it, but no luck. Will try again, though. Any ideas about the vacuum lines that go to a fitting under the gas tank that the gas comes out of? Thanks.

 

if I remember correctly- those carbs has a lot of problems with the automatic choke. Try just using a remote gas tank hung above the motor and gravity feed the fuel line directly to the carb, bypass the fuel regulator if it has one- if it stays running like that- at least you know the carbs working.

You can make an easy quick gas tank by drilling out a 2qt oil bottle cap and squeezing a fuel line in the cap that you just drilled- fill the bottle with gas, screw on the cap and hook your line to the carb. Poke a small hole at the bottom (now the top) to equalize the pressure.

 

Will give that a try before I take the carb off again. thanks!

 

I'm not familiar with the twister hammerhead. This is a buggy, right?

On some machines there is a vacuum operated valve that only connects the fuel line up to the carburetor when the engine is running and producing vacuum. This shuts off the fuel at the tank everytime the engine is shut down - as compared to using a manual petcock valve which many people don't use (or forget to use).

But there is a deadly embrace here. If there is no fuel in the carburetor the engine won't start. There is no vacuum to open up the fuel valve to let more fuel in, and there you sit.

Look up where the vacuum line connects to at the tank. Is there a lever that has a "prime" position (along with off and on)?

Pull off the fuel hose at the carburetor and see if gas comes out freely.

The fact that you quad starts when adding fuel manually point to fuel delivery problems.

 

The Twister/Hammerhead is a full suspensioned go kart with a roll cage, bench seat, body harnesses, lights, reverse, and a 150 cc engine. Where the gas comes out of the tank, there is a regulator-looking thing that the fuel line comes ou of and a vacuum line goes into. I finally got fuel to ge into the bowl yesterday and managed to get it to start with some delcate operating of the accelerator(I had to crank the engine over for a few seconds with the accelerator depressed, and while still cranking the engine, I slowly let the accelerator back until the engine fired). It took several times for it to stay cranked...it was sort of cool outside. It then ran fine; however, if I have to do this every time, it is going to wear out my starter and probably kill my battery. It seems as though it is not getting enough fuel to start. The carburator has this damper-type piston in it that opens up from the vacuum created by the engine running, and on the end of this damper is a needle that goes down into a hole that goes directly into the bowl of the carb. I suspect that the needle is too far down into the hole and may be seated...not allowing the fuel to be sucked up by the vacuum from the engine cranking over. I am going to check that out a little later today. By the way...there is no manual cut-off or primer position on the regulator-looking thing on the bottom of the gas tank. In the mean time, if anyone knows the solution, please tell me. Thanks!

 

I've worked on these carb before- the main jet isn't your problem (needle in the hole as you called it), like I mentioned before, it's the choke (enrichment) circuit- it's a known issue with these engine carbs- just google it and you'll see.

 

here-

BuggyDepot.com Tech Center - 150cc GY6 Knowledgebase! Yerf Dog, Twister Hammerhead, Tomberlin Crossfire, Carter Talon...

 

So if I interpret your symptoms correctly, it was very hard to start then once started ran fine? Once it was running for 30 seconds, would it start up instantly after that?

The bystarter valve (choke / enrichener) is one possibility, but valve adjustment is another possibility. Valves require periodic adjustment. They get tighter with wear, and they get tighter still when the engine is cold. Thus the symptom of valves needing adjustment is hard starting when cold - eventually leading to no starting if ignored long enough.

Do you have a GY6 service manual? There are some out there for free download.

BTW, I found a hammerhead twister manual online (2005) at www.buggynews.com. The vacuum line going to the gas tank *is* a vacuum operated fuel enable/shutoff valve. Apparently the cranking vacuum is enough to open it up because there is no "prime" setting (as you already stated before).