Hi Guys

I need some advice on how to resolve an overheating problem with my 93 300cc King Quad.

This unit is air cooled, no rads, no fans, all it has is the oil cooler.
This unit will start missing and eventually stall as soon as it warms up while idling, if you're moving, and hence forcing air through the cooling fins, it'll go on forever.

I have a few ideas on what to do, but I might need more since this problem is bothering me for a while now.

It's definatly not related to ignition, it could be the fuel mixture. At first I couldn't even determine if it was overheating until I started pulling the spark plug and it finally came out all blueish with carbon deposits, which indicates overheating from what I know.

I'm going to try a colder spark plug, the manual calls for a DP7EA, I'll try an 8 or a 9, or both, but this does not mean the engine will be fine.

The fins are all clean, I had the engine out not too long ago for a reseal so everything was cleaned. I was told however that carbon deposits on the exhaust valve can cause overheating as well. The reason the engine came out was because of this problem as well.

If it's the fuel mixture, it's probably running lean, but I don't even know where to get started on testing this out.

Would anyone else have any other suggestions?

Thank you

xp190

 

Is your oil light coming on? Could it possibly be something as easy as the idle screw? I know that I have to mess with mine a little to get it just right after it warms up.

 

The oil light never comes on, I don't think the oil even has a chance to warm up before it starts missing unless I take it around the block a few times and then let it idle. I did mess around with the idle screw, tried to get the rpms into the range outlined in the manual, but it didn't help at all.

I'm really stumped with this. I'm gonna try a colder plug in it and see if that makes any difference, if not I might have to take it to a dealer, but I don't think they will be much help.

If I still can't figure it out, I'll have to do a leakdown test and see if maybe it needs an overhaul, I'm hoping this won't be the case.

 

Could the fuel line be close to the warm engine or other parts causing a vapor lock while sitting still and ok when moving because the fuel is flowing through and does not have a chance to get warm?

 

I'll check the fuel line, but to my recollection the fuel lines are not near the engine, they go above in the safety cover of the fuel tank.

 

I have a similar problem with my KQ300 but can control it with my idle screw. My choke nut (plastic nut connecting cable to carb) has broken and really messes with the quad while idling. My idle screw doesn't seem to do much unless you rev up your rpms and let it go back to idle. I have found that once you have turned your idle clockwise to where when you gas it, it takes a while to go back to idle rpms is where mine will idle best. But, it's weird, it will idle high in neutral until I put it into gear, then it settles down and I can then go into neutral and it will stay there. I later (after it is completely warm, which takes about a mile of riding) have to move the idle back almost a whole turn counter-clockwise, or it will continually rise in rpms in neutral.

Have you made sure that your piston has no scuffs on it which would cause it to struggle during idle, but not while throttling. Or your cylinder head? Just some brainstorming things to check.

 

I did have the piston out and did notice 2 tiny scuff marks on the cylinder walls, but idling is not the problem, once the engine starts missing, even when I throttle up it will continue doing so. The best I can describe the situation is that when the engien warms up, the spark dissapears, but I have no idea where it goes. At first it will be every now and then, and as the temp goes up it will dissapear more and more until it dies.

I don't know all theory behind spark plugs, but if one overheats, does it start conducting where it should not be? That would explain why the spark dissapears, but now how to fix this is another story.

As far as yoru idle problem OldSchoolQuad, mine does the same thing when the choke is on, the revs will go up and up as it warms up, you need to get that cable replaced.

 

check you ignition coil, classic sign of it overheating. It will cause it not to have as hot as a spark.