I have two Coolster 125cc atv's that I purchased a few months ago, just before Christmas. One was for my daughter (trade up from bmx 70cc) and one for my nephews. So after a few weekends of riding I decided to do a tune up/ oil change on both quads. Ever since they both are still running great with no problem starting but both seem to be getting quite a bit hotter than they were initially. All that I did was check the gap on the plug and change the oil. I did both per spec, 15w40 oil.

Does anyone know why they would be overheating?

 

Welcome to the forum cdrobin!

Only thing I can think of is maybe the 15wt is too thick for the winter? But so many others are using it its more than likely not it..

Do you have a temp gauge (one of these remote laser things?) Or does it just feel hotter?

 

I am also wondering if the engines are really too hot.

Sometimes when changing the oil a little gets splashed somewhere outside the engine where it gets hot. Then later the oil starts to burn which causes the engine to smell really hot.

 

No temp gauge, however the atv got hot enough to make the paint on the engine smoke.

 

They definitely get hot if the kids are putt-putting around with them where there's not a lot of air circulation around the engine. Same thing with idling. They'd get hotter than heck if running lean, but you'd have performance issues prior I'd think.

Joel

 

how hot are they supposed to run? I have a laser temperature gauge and I can check and see what it is running.

 

I don't know the answer to your "how hot" question. I hoping someone else does. Even without that input, it would be great if you could measure your quads temps in various locations and post them. It may spur others to do the same. I'm thinking cylinder head fins, base of cylinder fins on the block, and exhaust manifold temps.

As Joel (OneTenCC) said, lean fuel can cause overheating. So can ignition timing issues. But ignition timing is fixed (not adjustable), and you have *two* quads doing the same thing. I think that points away from timing issues. Lean conditions (and overheating for that matter) will be evident by looking at the spark plug.

I'm still leaning towards the idea that your quads are not overheating. New quads, new paint, now you've changed the oil and gapped the plugs... and suddenly the quads overheat. Changing the oil does not affect the operating temperature. Maybe now that you've changed the oil and gapped the plugs you are allowing the quads to drive harder? I don't know, I'm just throwing out ideas...

The temp measurements would really be helpful.

Lynn

 

when I let it idle and warm up it was getting about to 300 +- degrees. I know that when we are out running that they get a lot hotter than that. Due to snow I am unable to get them out and test how hot.

If I were running a lean fuel scenerio wouldn't I have trouble starting, idling and low power? Also what would I look for on the plug?

 

Where on your quad did you measure the 300 degrees fahrenheit?

If you've read many of my previous posts you would see I'm fairly comfortable with electronics issues. I don't have a lot of experience with quad engines per se, so I'm a bit out of my league here. But I did take a break from work today to do some reading on typical cylinder head temperatures on air cooled engines. There isn't anything readilly available on quads, but there is a lot of info on VW bugs and aircraft engines. 300 degrees F doesn't seem all that unusual. I don't know how well that translates over to air cooled quads. Here are a couple links to give you an idea of the kind of info out there:

eBay Guides - CHT Gauges for Air Cooled Engines

German Supply - Parts for VolkswagenŽ Cars - Home

Some more data points to consider: How hot is your engine oil (in degrees F)? Does your engine ping at all when it running too hot?

As far as running lean, the air/fuel mixture is set by different carburetor circuits at different speeds. You could be fine at idle and low speeds but way lean at wide open throttle. But it still seems strange to me that you have two quads doing the same thing.

To read your spark plug check out the following link:

Google Image Result for http://www.aa1car.com/library/reading_spark_plugs.jpg

I think there are better spark plug reading links than this. But in a pinch this was all I could find. You'll have to click on the link, then click on the thumbnail picture in the link...

 

I joined these threads just to try to help you all. I bought one of these coolsters for my daughter and it suddenly started to overheat. I was pulling my freaking hair out trying to figure out what was causing this. Your rear disk brake pads are sticking producing drag on the motor=overheat! Wiggle the rear brake lever and it will pop the pads loose. Hope this helps...