i went to advance auto and bought a cap with a relief valve for my 250. it was like 8 bucks. same as a mazda b2000 i think. but if you take your cap in its easy to match.

 

"Any ligiud cooled ATV without a fan working proprerly will over heat in a instant,let alone not have one period."

"Thats a bad design, on oil coolers a fan just asist,but on a rad the fan is a MUST. I seen them over heat just because the fan is wearing out and does not turn fast enough"......"Fan stops, the coolant boils out of the over flow bottle,thats how it goes."

"Never knew they could even make a liquid cool system even work without a fan, it should be on all ATVs it would eliminate the need for a temp sensor and simplify things greatly."


Wow! No offense TLC, but if you didn't know "they" could make a liquid cooled system without a fan, I wouldn't be taking any advice from you for my quad, especially not on cooling! Ever heard of a Quadzilla, LT250R, Honda 250R, Kawasaki Tecate, Yamaha Banshee, or ANY liquid cooled 2 stroke MX dirtbike for that matter (Suzuki RM, Honda CR, Yamaha YZ, Kawasaki KX)? I could go on... By and large, the vast majority of liquid cooled ATV's and dirtbike have never had fans. It's only been with models designed in the last decade or so that you're starting to see more and more with fans. And that's mostly because they're either larger bore 4 stroke utility ATV's that have undersized radiators and get ran hard at slow speeds, or they are 4 stroke sport machines that are very high strung from the factory (in order to match the performance of the old two strokes) and require a lot more cooling. The old racing two stroke ATV's were not very high strung from the factory, and weren't too hard to keep cool in stock motor configurations.

As for your issues pathxbox, as others have suggested, I would check your water pump first. This is very important and your's is very old! Next you can test your radiator cap. If you have to get a new one, do not get one with a relief valve. Since the zilla's have overflow bottles, you want to try and recollect any overflowing antifreze by letting it flow through the factory relief hole in the radiator neck. (Not a bad idea on a 250 though as Newport suggested since those don't have overflow resevoirs.) If necessary, I'd just get a new Suzuki one if I were you.

If your zilla is all original like you claim, it should definitely not be overheating if things are functioning correctly. (If it's been ported... that's another story depending on how well it's been ported and what type of riding it's been ported for.)

Here's a couple other overheating possibilities:

Pilot Jet: It's not impossible that your overheating issue is related to your carb. If you're pilot jet is partially blocked (causing a lean condition), this could definitely cause the motor to overheat while it's idling. (it would want to rev high also when trying to idle.) When you take your carb apart to inspect it, i would suggest blowing out the pilot jet and running a torch tip cleaner through it. Also look for any varnish anywhere in the carb. Any signs of that and the carb will need to be professionally cleaned and possibly have the jets replaced.

Air leak: Any air leak between the carb and jug will cause a lean condition just like a blocked up pilot jet, which again will cause it to over heat. While running, spray a little starter fluid around the reed cage (stay away from the intake side of the carb and the air filter.) If the motor revs, you've got an air leak! Be cautious when doing this. Too much reving if there is an air leak is not good on the motor!

Predetonation: If the overheating happens while it's being ran hard (not just while idling), you may have a problem with predetonation. While the zilla's don't have overly high compression, they do have a very large diameter piston and a poor squish design from the factory which is a recipe for predetonation. You might want to try running race fuel once, or at least mixing some race fuel with some 93 pump gas and see if that helps. The ultimate solution is to have a machinist who is knowledgeable on these bikes work on the head. If the squish angle is fixed, you can actually raise the compression and still be less likely to predetonate.

As far as the motor starving for fuel when running hard, again, inspect the jets when you take the carb apart. Look for any debris (a grain of sand is common) in the jet. What elevation are you running? Even though you claim your zilla is original, If you are closer to sea level you may need a larger main jet than the stock Suzuki calls for.

Also think about checking the filter screens on the top of the petcock valve. These have tiny screens that can get clogged up if it's had debris or old gas in the tank for a long time.

(There's also a very trick mod you can do to a zilla petcock to allow more fuel to flow to the carb on very high HP zilla motors. Essentially it allows fuel to flow from both the "On" and the "Reserve" inlet tubes at the same time. For more info on this, go to quadracerhq.com)

Hope this helps.

 

thanks yeager good advice never have had cooling problems on my zilla or 250r have inline temp gauge and they both run about 150-170 degrees all the time have heard of first yr zilla having w/p issues but never had a problem with mine

 

No problem 2strokezilla. '87 zillas don't have any problem with their water pumps... other than being 23 years old. The water pump is no different that the later year zilla's to my knowledge.

The main problem with the '87 zilla was it's small 8mm (relative to the size of the cylinder) head studs, and the fact that there were only 6 of them. In '88, they added an additional stud, plus they are stepped (8mm on top for the head, 10mm in the cylinder).

A common fix for the '87 cylinders is simply to have the stepped cylinder studs installed, or even a straight 10mm stud installed. This requires boring the holes on the head obviously. Easy fix, and you can torque your heads down more when done.

The flywheels come apart also on earlier zilla's (87-89) if you really flog them long and hard all the time. I've never seen it happen, but I also don't abuse my zilla's. In 90, they added a larger hub flywheel with stronger design on the rivets. Easy fix on the earlier ones is to simply have them welded.

The carb on the '87 also had a slightly different fuel metering system that is less desireable than the later years.

The 4 and 5th gears are also slightly higher in the '87 model. Some people like it, some don't. Not quite as good for most drag racing (sand), but a possible benefit for long track asphalt racing where top speed can be reached if you have a strong motor that can take advantage of it.

Don't think for a minute that your '87 is an inferior machine. Stock, there are a few problems that need to be addressed, but an '87 jug, in good shape, is a rare and valuable thing! They have a much larger intake track, and in the hands of the right people they can be made into very very high hp zilla's. To see pics or read about some of these bikes, check out quadracerhq.com

 

Who cares, good luck with that slow speed air flow with no fan.

 

Dude, these things have been running for 25+ years in some cases w/o a fan. The 2 stroke dirt bikes STILL don't have fans, and probably never will.