I rode my Quadracer last Monday and it started boiling over out the vent tube after an hour ride time. The coolant then dripped on the frame and burned the paint right off. After I got back home trailering it and it cooled down, I checked the coolant level and it was only down slightly. I'd say a half an inch down. That shouldn't be enough to over heat it, should it? What else could cause this problem? I've changed the coolant about 200 miles ago, and it was 60 degrees last Monday in Florida.

Thanks.

 

Sounds like ya got a leak. Sometimes you get the leak that leaks into your cylinder, causing the engine to not run properly, or could get real bad and "hydraulic" your engine (remember physics class? You can't compress a liquid) causing something internally ie. con rod to snap. Then you have your leaks where, the compressed fuel/air mixture is forcing its way into the cooling system, heating things up, and basically just over pressurizing your radiator cap, causing coolant to spill out the vent tube. Everything is doing it's job, like it is supposed to, except either a gasket or a EEEEGGGAAAAAADDDDDDDD.....a crack in your jug, head, or lower end! Anyways, you need to do a pressure check on your coolant system, they make coolant pressure testers, they run about $60 for cars, but alas it is not that easy, you need to find one with the proper size adapter to fit the neck on your radiator where the radiator cap goes. This will let you pump in a certain pressure, say 10lbs, then see if the motor holds it. If it does not you have a leak in your coolant system. Another way is really intended to test your motor for no leaks, not exactly coolant leaks, but it will do, ever heard of leak-down test? What you need to do with that is plug off your exhaust port (remove the pipe) with a rubber freeze plug, you can get them from NAPA or any automotive store, do the same for your carb end, where your reed cage fits around your carb. Also, plug off the vent line, the small rubber line on top of the engine cases, under your carb. Remove your spark plug, get a suitable fitting to screw in in place of it and connect a small pump via a rubber line with an inline gauge. Basically, your pressurizing the whole engine this way, crankcase, trans, cylinder, and if you have a coolant leak somewhere, it should leak into the coolant system as well. This may force some coolant out your vent hose on your radiator. Do a search on the net for leak-down testing 2 stroke engines, you'll find pics showing what I am describing. You can buy those also, but you can also make them with a little bit of thought. you can even use a bicycle tire pump to do it with, just use what you have available. An even better way would be to attach a gauge in the vent line also, to see if it builds pressure when you pump up the engine. If it does, you got yourself a leak. Either way, if ya wanna do it, you'll find a leak. Might be a bad radiator pressure cap as well, check the obvious first. Then dig in deeper.

 

Thanks for the adivce. I'll have to trouble shoot it and hope for the best.

 

I had a problem with my 91 with it spitting coolant out the hose. My problem was I was using a 87 head gasket instead of the 91. The 87 had more openings in it, this caused the coolant system to pressurize and release the radiator cap system in turn shooting out the hose at the cap. A new correct gasket and 10 minutes of time and it was back to running normal. If you recently reuilt or replaced the head gasket I'd check this.

 

I drained the cooling system today. Jammed a hose in the top of the radiator and flush the system. Then refilled it with 50/50 anitfreeze, add the Bar's Leak that my Clymer manual says to use, and blead the system according to the manual. It seems to have fixed it. I also fixed a bunch of bent fins in the radiator, and reinstalled the air deflector that I removed when adding a Amardillo front bumper. I had to modify it to fit.

It was also 15 degrees warmer today (75) so the engine was also running richer. I don't know if a lean engine situation led to the overheating. It did start when the temp dropped below 65.

I hope the repair holds up!