Hi!

I'm stuck trying to get one of the quads running. It's a clutchless 125cc quad.

This is where I am.....
* It will run briefly if I shoot a bit of fuel into the carb. But only briefly.
* I've already pulled the carb apart and cleaned ou all out, blew compressed air through the bits and pieces, and reassembled.
* I obviously have spark. It's also a brand new plug.
* The mixture screw appears to be the second screw moving away from the air filter. It's currently 2 turns out. I do have another near identical quad which I have running and had set the carb screws to the same as that one, which meant the mixture screw was 3/4 out, but still no joy.
* I was expecting the plug to be wet with fuel, but it isn't .With the amount of cranking the motor should be flooded, but I haven't had that problem yet lol it is a little hard to tell with the plug being brand new.
* Compression seems to be good. I stick my finger on the hole for the plug and it blows it off. I do have a compression tester but haven't gone that route yet. While turning the engine over I see air coming out of the exhaust.
* I currently have the air filter off.

I have thought about swapping carbs with the one that's currently running, but I'm worried I'll then have issues getting the running one working again; these Chinese bikes do seem to be finicky.

Keen to hear from some people here who know more than me!!!

Cheers
Dean

 

Update:

It's getting late here, almost dark, so I've decided to call it a day. Before doing so I thought I'd do a compression test: I get a little under 75PSI.

Is this a good result? Keep in mind that I reckon this quad has only been used a couple hours at most.

I tried to do the same test on the I've that's running; I can't right now because its starter has decided to die grrrrr I when tried hitting it with a hammer but still no go. Guess I'll be working on that one again tomorrow lol

 

Sorry for bumping my thread again....

I was just reading on another thread how the brake needs to be on before they start. The fact though that it starts when I pour fuel down the carb means that this doesn't apply in this instance, right?

 

75 seems low but it should still run... I would advise against running without the air filter and proper intake restriction. If and when you do get it running correctly and you dont have the air filter on, when you put on the filter and the airbox there is a good chance it wont run right and you will have to adjust it again for the new intake restriction. Have you pulled and blown out the air passages in the carb?

 

Thanks for the tip! I will reattach the air filter in the morning .

Yes I have blown out the air passages.

 

Probably worth saying that 75psi is pretty much deaths doorway for a 4 stroke. Rebuild is very close in your future. Minimum running psi for a full size bike is 100psi, if it was a lawnmower or small boat engine 75 would be ok. If I was looking to buy a bike or quad and it had under 100psi I would walk away.

 

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thanks for that info.

Could compression really go down that quickly from use? It's been taken care of and it's only had a couple hours of run time. I'll do the test again in the morning but this time I'll drop some oil into the cylinder. If it doesn't go up, maybe it's a valve sticking.

 

What brand is it? The Chinese and Taiwanese clone engines are hit or miss on longevity. They have much lower tolerance standards for their engines in general. It would suck if it really does need a rebuild and it hasn't been run long but I wouldn't doubt it if its a Chinese or Taiwanese knockoff. Good example of 'get what you pay for' unfortunately.

 

Unfortunately the brand isn't obvious. I bought it from a local place and they just have their own stickers on it.

 

Ah you may be out of luck bud. Have you tried ether to try to get it to fire up? If it isn't running off gas at all but will fire and run with ether chances are your compression is too bad to run with gas. Ether will make very damaged engines run because its ignition point pressure/mixture is so much lower than that of gasoline. Keep in mind though that running ether through the engine is an absolute last resort, it can damage your engine badly. If it runs off the ether but not the gas you may just have a big paperweight until you rebuild your top end.