Hammerhead Twister 150cc GY6 won't start
 

I've got a Hammerhead Twister 150cc with the GY6 engine. It's worked sporadically in the three years we've owned it (bought it used). Last fall, it stopped working, so it sat all winter. This spring, I can't seem to get it running.

I've replaced the battery, spark plug, and starter this spring, but with no change in the situation. Changed the oil & filter. The transparent fuel filter is full of fuel. The carb was professionally rebuilt two years ago, so it should still be good.

When I turn the key, it sounds like it fires zero, one, or two times, then just buzzes or grinds. This video shows what it sounds like.

https://www.youtube.com/watch?v=leTX938PKIM

I'm a decent mechanic, but I'm not sure what the problem might be, and I don't have the time or money to just keep randomly throwing mail-ordered parts at this problem. This time of year, all of the small engine repair shops in town are booked solid with landscaping equipment.

Any idea what might be wrong?

Sounds like the starter is not engaging the flywheel.

Your starter is hitting then popping back out. Could be the solenoid but I would pull the starter and have it tested sounds like it's not fully engaging. Clean it good throw it back on and see if it's still doing the same thing.

That was my thought, too, but I just replaced the starter yesterday, and nothing changed. The old starter (just 3 yrs old) didn't look like the teeth were mangled, which I would have expected if it wasn't engaging properly. As for the solenoid, I tried shorting across the solenoid with a heavy wire, and it still made the same noise.

Can an auto parts store use their standard starter testing machine to test a tiny little starter like this? I suppose I could test it in a bench vice with some jumper cables and a car battery...

This doesn't really sound like a flywheel problem, because if I hit an empty spot with no good teeth, it wouldn't engage at all from then on, would it? I'm hearing it fire once-ish every time I turn the key.

Is it possible the flywheel is actually spinning on the crank?

The auto shop should be able to test it its just smaller than your used to but not much different than a Mazda starter lol. If it is a new starter and its doing the same thing the old one is I would say that it is probably not your starter

The teeth on the starter may not be messed up but the ones on the flywheel might be and that's all it will take.

I would say the solenoid is probably good.

These engines have a secondary gear that the starter engages into called a starter clutch and that is sounding much more like the culprit. because when it first hits it grabs but then lets go. Google gy6 150cc starter clutch and see what pops up on YouTube I am willing to bet that this is what is causing your issue.

OK, I did some looking around about the starter clutch. I agree that that's sounding like the culprit. Not a simple job to replace it. Is there any way to test it before I open everything up in order to verify that it's really faulty? Can I test it after it's open? What am I looking for?

Is it possible to remove the stator cover with a standard gear puller instead of that special tool?

Removing the starter clutch nut with a chisel is straightforward, but how do you torque it down during reassembly?

Are there any other wear items that I really ought to replace while I'm in there?

Starter clutch. I just went through that

So, if it is the starter clutch, at the very least, I'm going to need these parts:

* starter clutch
* timing cover gasket
* crank seal

Anything else? Can I get by without those two special tools mentioned above?

I did not replace the crank seal. The cover gasket is all I would say extra. I had to buy the special tools. I was causing more damage to that crank not than I was comfortable with. You can get the too for 12 bucks. I bought 2 because the first one was taking to long to show up.

Which tool did you buy? The flywheel puller or the 4-pronged socket? What did you use for the other tool?

Buy the puller they are not that expensive and you will cost yourself far more in damage trying to make something work trust me.

I'm sorry I forgot about the flywheel puller that was 9 bucks. The crank socket cost me 12 both with free shipping from Amazon Prime.

Buy both don't try to redneck it. Together they are like $20 if you damage stuff trying to make something work then you end up paying way more. If you damage the crank you will want to shoot yourself for not buying the cheap tool.
As far as the starter clutch. Never had to do one yet but I bet you will be able to tell it's bad once you can put hands on it.
I'm by no means anything close to an expert still learning about things on these buggies myself. I have read through nearly every post on every forum that deals with these things and some things I have had to do myself before i could really understand what and why people said To do it a certain way. Most of the stuff on these buggies is not as complicated as it looks but it can seam daunting when your not familiar. Pop the hood of a car and I can go to town but I have had a lot to learn on these. The people on these forums are awesome and know their stuff couldn't have done half the work I have done on mine and not tear something up without their help. Just take your time watch several vids on how to do it, lay out your parts as you take them off and go in order putting them back. You can do it.

I am a mechanic but never done one of these. It really is very easy. Go slow, stay organized and you'll be fine.just remember the are small fasteners so don't go crazy tightening them.

Well, I ordered a new starter clutch, right crankcase gasket, flywheel puller, and 4-prong socket last night. Just $42 total off eBay, and it should arrive in 3-4 days. Hopefully, I'll have this thing running again before the weekend's done.

Am I going to have to remove the CVT in order to hold the crank in place while I tighten the clutch nut back on, or can I hold it stationary by grabbing onto the new clutch?

Anybody know where I can find the torque specs for all of these nuts & bolts?

Man, I really hope this fixes the problem...

How is it coming?

The new parts arrived on Thursday. Weather constraints (both really good & then really bad) have prevented me from installing them yet. I'm hoping to get to it in the next couple days.

OK, I finally got around to replacing the starter clutch in my Hammerhead Twister last night. Took about 3 hours, working at a leisurely pace.

I just guessed at the torque settings upon reassembly. Those two nuts that tighten around the crankshaft just got "setting 3" on my impact wrench, so I hope that's OK. The two special tools (the flywheel puller and the 4-prong socket) were money well spent.

I was worried after I pulled the old starter clutch, because it felt like it was in perfect working order. No obvious wear, and everything moved & grabbed the way it should. What should I look for to identify a non-working clutch? The old clutch looked to me like it was a beefier design than the new clutch that I bought for $11 off eBay. You can compare them in the photo below.

Nevertheless, as long as I was in there, I installed the new one. Once I got it all buttoned up again, the kart started better than it has in a long time.

Thanks for all the help diagnosing this problem!

Your old one and new one looks just like mine did. I could feel issues in my old one but never the less the new one worked.