Ideas

[undertulsa]

Trust me the Honda guys are scared of these bikes, Im not sure your non-experts, I think people who ride them know the most from hard knocks and experience.

[knothead]

Has anyone ever overheated one of these Chinese built engines? They make such little power for their size I just don't see one overheating just from idling for 15 min (assuming it's not way lean). Usually you'll see white smoke puffing from the crank vent tube when they overheat.

It sounds to me like it is carb related... pilot circuit off or float misadjusted. Let it idle/die again and pull the plug, if it's wet then lean the pilot, if it's dry screw the pilot out an eighth of a turn.. rinse and repeat until it's fixed. Make sure the float is right before adjusting anything! And don't adjust anything with the filter off, it has to be adjusted with the filter on in order for you to get it right.

Sniff the pipe when the engine dies, if you don't smell raw gasoline it's lean.

BTW, pull the air filter off and let it idle, if it won't run or dies sooner then you're lean, if it runs without dieing without the filter then you're running rich. Won't always work, but when it does it's an easy way to diagnose rich/lean conditions.

If it runs fine when you're riding you can rule out anything but the float and idle (pilot). It's not the CDI, coil, plug or anything else, those things would show up under load.

[undertulsa]

when it dies heavy gas smell and if i try to make it start immediately im getting black smoke from tail pipe.

"It sounds to me like it is carb related... pilot circuit off or float misadjusted. Let it idle/die again and pull the plug, if it's wet then lean the pilot, if it's dry screw the pilot out an eighth of a turn.. rinse and repeat until it's fixed. Make sure the float is right before adjusting anything! And don't adjust anything with the filter off, it has to be adjusted with the filter on in order for you to get it right.

Sniff the pipe when the engine dies, if you don't smell raw gasoline it's lean."

wee is the pilot screw, is that the screw on the carb?

[undertulsa]

Im not a carb guy so help me out, where is the float, and the where is the pilot screw?

[katoranger]

Sounds like the float may be sticking or not adjusted. Do you notice any gas in the air filter?

The float is in the bottom of the carb. You remove the bowl and it is right there. The float controls the flow of fuel from the tank via the needle valve. Works like a toilet.

If this is sticking it can cause your symptoms. Too much gas is getting in at an idle. Since it sat all winter this is a likely problem.

[TurboT]

Originally Posted by katoranger

Sounds like the float may be sticking or not adjusted. Do you notice any gas in the air filter?

The float is in the bottom of the carb. You remove the bowl and it is right there. The float controls the flow of fuel from the tank via the needle valve. Works like a toilet.

If this is sticking it can cause your symptoms. Too much gas is getting in at an idle. Since it sat all winter this is a likely problem.

I really don't mean to argue here.. but really? You think?

I think you're looking for problems that aren't there. Sometimes I find in our eagerness to help in this forum, we miss simple things and go right to the carb dissassembly.

The bike starts and runs fine for 20 minutes, sitting there, at low speed, cooking itself. He drove it for 15 miles without any trouble.

I *think* if it had shit in the carb, or adjustment problems it'd run like a pile of crap right at the start, not 20 minutes later.

This is a small displacement air cooled motor. They are not designed to idle for 20 minutes. Hell, even my water cooled YZ 250 F overheats if you let it sit there and idle for 10 minutes.

I think it's a darn miracle this chinese bike has enough sense in it to shut itself off when it starts getting too hot.

knothead: I don't believe it has anything to do with 'power', or a lack of, and everything to do with metal mass. Smaller motors have less metal mass to dissapate heat. It is sitting there creating an internal explosion and has no air rushing through the fins to wick the heat away. It probably has a stock, restrictive exhaust which is holding the heat in more. Especially at low speed less airflow pushing it out.

Bikes and ATV are designed to cool when moving. If it's not moving, it has no chance to work properly. Even in a water cooled design, it requires revs and motion, one to flush the coolant through the motor, into the rad and back again, and air to rush around the rad cooling the water. Without these two things; over heat show. I've seen it on my bike when I bought it, we let it idle too long when I was kicking tires and the rad started boiling. It's even worse with aircooling.

I'm by no means an expert, and keep an open mind, but it's just my gut feeling on this one.

[katoranger]

So true to internet diagnosing.

I think that the needle is leaking just enough to dump too much gas at idle and then when running at more than idle is using that gas where you don't noticed the problem. But on the other side if it was leaking there I was thinking that it would be running out the carb too.

Now I am usually wrong, but that is my theory with the gassy smell. Espically since it was fine before being put in storage. Maybe something was not put back together right also. Too rich at idle.

The coil prospect also makes sense too, with the bike being fine with the air moving. I never had any problems with mine. Even on 102 degree days while stuck in traffic.

[katoranger]

Originally Posted by undertulsa

Not sure how to see if float needle is sticking, but the carb was just cleaned and jetted for the altitude in NM by a bike shop. Rode it for several months here with no probs something gunked up the carb.

You say jetted for NM. Are you still at this elevation? Maybe the low speed circuit is jetted wrong?

Agreed on the extended idle not too good either.

[undertulsa]

Well I appreciate all the advice, believe it or not it really helps. Im exploring everyones possibilities. Elevation 5700ft, carb just cleaned they mentioned that jetting was a possibility but i dont think they did it.

Gonna continue testing, thanks for all the ideas to run down. Thank you! Ill let you know what i find next. Its like a moving puzzle.

[2LZ]

That long idling.....then black smoke upon restart....sounds like it's loading up and dying to me.
Not sure why you let it idle so long. It's not like yer stuck in the snowey highway and need a heater...but I digress. 8)
The plug has to be AWFUL by the time it dies. I'd start with the simplist of the fixes..... Clean and gap the plug, then screw your idle mixture screw in all the way and back it out 2-2.5 turns. then....go find a snowey highway and run the heater for a while. :wink:
Keep us posted!

[2LZ]

One other thing I thought about....I know the standard fix on these lean units is to drop the c-clip on the needle to the bottom slot, but I can only drop it one here because of where we ride. I may ride at 300 above sea level a lot but then we head up to Truckee and hit over 7000 feet.
I know that doesn't have a lot to do with the idle circuit unless the idle screw is screwed way in lifting the slide more than it should be.
I set my c-clip one below the middle slot and it works fine for me with stock jetting....and again....just 2 or 2.5 turns on the idle mixture screw. Maybe even less where you're at.

[knothead]

Originally Posted by TurboT

I really don't mean to argue here.. but really? You think?

I think you're looking for problems that aren't there. Sometimes I find in our eagerness to help in this forum, we miss simple things and go right to the carb dissassembly.

The bike starts and runs fine for 20 minutes, sitting there, at low speed, cooking itself. He drove it for 15 miles without any trouble.

I *think* if it had sh-- in the carb, or adjustment problems it'd run like a pile of crap right at the start, not 20 minutes later.

Hmmm... ya think? I think you're very wrong. If the pilot is too rich it will load up on idle. When the bike is in operation the main circuit takes over and the effect of the pilot lessens. Take a look at what he said the bike is doing, it's loading up and has a strong gas smell. It's either the pilot or float, nothing else! I tend to agree with Kato, the float is hung (which acts like a rich pilot).

Originally Posted by TurboT

This is a small displacement air cooled motor. They are not designed to idle for 20 minutes. Hell, even my water cooled YZ 250 F overheats if you let it sit there and idle for 10 minutes.

I think it's a darn miracle this chinese bike has enough sense in it to shut itself off when it starts getting too hot.

Sorry, but that is a daft statement. Bikes are machines without intelligence. It dosen't know to shut itself off if there's a problem. If it's fuel related then it's too lean to support ignition or so rich that it cools the chamber to the point it won't support a flame. If it's excessive heat the piston will deform and force the rings or skirt into the cylinder... most of the time you'll hear it scape or squeal (if you let it get that far), an air cooled engine will smoke from the breather tube as the oil in the head starts vaporizing from the heat.

I have ran my Lifan in very tough conditions. Very low speed, fins clogged with mud and running like that for hours. It has NEVER overheated. And yes, I have left it idling for extended periods with zero issues.

Heat is always a byproduct of power. A 200cc engine that puts out 50hp is going to generate much more heat than one that only puts out 16hp. That's simple physics.

That said. If your YZ overheats after 10 minuets, you definately have issues. I think the Yamaha engineers are good enough to design the bike not to overheat in that short time. My liquid cooled Yamaha TDM 850 could sit and idle all day and never offer to overheat, same goes for my air/oil cooled DR 650. Sounds to me that you're not even properly maintaining your own rides.

Originally Posted by TurboT

knothead: I don't believe it has anything to do with 'power', or a lack of, and everything to do with metal mass. Smaller motors have less metal mass to dissapate heat. It is sitting there creating an internal explosion and has no air rushing through the fins to wick the heat away. It probably has a stock, restrictive exhaust which is holding the heat in more. Especially at low speed less airflow pushing it out.

Less mass means they give up their heat faster. More mass means more heat retained and slower to cool. Again it's simple physics.

No explosion, it's a rapid, controlled burn. An explosion is called pinging and detonation, which eats pistons and spits out slag.

Originally Posted by TurboT

Bikes and ATV are designed to cool when moving. If it's not moving, it has no chance to work properly. Even in a water cooled design, it requires revs and motion, one to flush the coolant through the motor, into the rad and back again, and air to rush around the rad cooling the water. Without these two things; over heat show. I've seen it on my bike when I bought it, we let it idle too long when I was kicking tires and the rad started boiling. It's even worse with aircooling.

I'm by no means an expert, and keep an open mind, but it's just my gut feeling on this one.

At idle the bike is under no load and simply should not generate enough heat to hurt anything. If any engine (air, oil or water cooled) overheats at idle (the only state with less stress on the engine is when it's not running) then something is wrong.

[katoranger]

Had a similar issue on a XR80 that was loading up. Found a pin hole in the brass float. Replaced float and bike was fine. Of course it wouldn't run well at idle or while riding.

I believe the lifans use a float type or plastic float. Not likely to leak, but very possible to stick.

As knothead suggested the jetting may be wrong too.

Allen

[TurboT]

Hi knothead,

Thanks for taking the time to write out such a detailed account of your opinions. I enjoyed reading it.

I think perhaps my initial response was worded a bit wrongly. I sometimes forget the reader can't hear my voice or see the smile on my face.

I appreciate everyone in this forum is here to help those in need have a better experience with their toys. My point was that sometimes, in our wish to help, we overcomplicate things in a make work for someone fashion.

I also was using terminology in a hyperbole fashion, trying to ad a little 'colour' to what could be construed a boring rant.

Yes, I'm aware of detenation and it's result. I've seen more destroyed pistons in my life than I can count, but thanks for reminding me.

I didn't mean to imply I literally believed undertulsa's bike had a brain, and was deciding since nobody was riding me, it would turn itself off. My point was that something is reaching a point of non functioning and shutting itself off before it melted itself into oblivion, which I think is a good thing.

As for my YZ, this is not a road bike, or even a light trail bike. It was designed to be raced, jumped, and revved like an mf'er. It was NOT designed to troll at low speed or idle in a driveway. It needs and wants rev's and speed. The rad is small and doesn't hold much water volume, so it needs to be in constant movement with air flow over the rad to cool it. It is not maintained badly, and it got warm idling in the bike lot when I was BUYING it, before I owned it. I expect your big bike you mentioned, has a much larger rad, more space in the water jackets of the motor and holds more water volume in the rad; therefore probably is sufficient to keep itself cool idling for longer.

Back to undertulsa's bike now. I think what was lost in all this is he seems to have no problem if he rides his bike. With the motor revving and the wheels spinning, it is probably just fine. The bottom line is he probably might have a minor rich condition, which is showing up more when it idles for that long a time, as the motor isn't scavenging the unspent gas as well as it would revving at speed. If he lets it warm for 5 minutes, rides it, he probably never has this issue and doesn't need to rip his carb apart, unless he wants to.

I think you're correct that it's rich, and that when it runs for 20 minutes it fouls the plug. Is it too rich? I think if it was it'd die faster and run like a POS immediately when he tried to go ride it.

I stand by my feelings don't idle your bike for more time that is needed to get heat into it, then RIDE it.

[TheRealWorld]

I should not comment but I cant help myself. First, does it have spark when it quits?

Next, The float not only can stick open but it can stick closed also.

I read everything here but I am a poor reader and don't know if those points were made.