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+4mm stroke 68mm bore cub motor gets hot fast


Ducman

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Just wondering if others with cheetah cubs are getting away with running them using the stock radiator or did you need to get a bigger aftermarket radiator. I can keep it in a normal operating temperature range as long as I dont "hot lap" it to much and I drive it around nicely for a bit after every banging up through the gears into a 6th gear WOT blast. But, If I turn around and run back to back WOT runs say 3 or 4 times it overheats. Just wondering if most people running cubs needed to go with a bigger radiator or did you just ride it smarter and make sure you give it a chance to cool down very often?

 

I put a billet water pump impeller in it, run engine ice, and put my stock grill back on which I think flows more air than the blingy flame one I was using at first. I also jetted it a bit fatter on the mains than it needs to be to see if that would help it run cooler, it did, but only slightly. I used to be able to run the piss out of it with the dune ported stock cylinders +4mm stroker on a stock water pump and not wory about overheating. It is also near 100 degrees in NorCal every day now so its hard to get a realistic "typical conditions" run which I normally run it in air temps 80 degrees F or less. The high temp surely makes it overheat easier, but I had some issues in cold weather the first time out at the OR dunes too. The radiator doesn't seem to suck fluid back out of the overflow. It seams like it wants to push fluid out when it gets hot untill the level in the radiator is at the top of the fins/bottom of the radiator tank. This is enough fluid to fill the overflow about 1/2way up from empty and then it seems to stabilize and not push any more water out. I've had somwhat similar experiences with my banshee doing this before the cubs but it seems a little worse now. If I start out wiht the coolant overflow more than 1/2 full it will fill it up 100% and piss out a bunch of fluid. These cubs seem to put out a lot of heat along with the gobs of HP. Just curious what every one elses experiences were with keeping these bad boys cool.

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I never had any issues with mine getting hot, I think you may have another problem somewhere in the cooling system, the cylinders will hold alot more water than the stockers will also. So when you put the cubs on it just magnified your existing problem. Is your radiator in good shape? is it old? anything that might be restricting coolant flow?

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Take your radiator down to any good radiator shop and have them clean it. They will pop the tanks off, dip it in a solvent tank, then run a rod through all of the passages to dislogde any crap that might be in it. Than they put back int the solvent tank, and put back together. Be sure to tell them u don't want it repainted cuz the paint will effect heat transfer. If that don't work get a PWR, Fluidyne, etc etc...... Have fun with ur cub! :beer:

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It's an 04 and the radiator is still in very good condition. The fluid is circulating correctly. So everybody is saying that they can do at least 4 back to back WOT blasts from a stop to the top of 6th gear and hold it a couple seconds each time in 6th (say 1/8 mile+) 100 deg F and it wont overheat at all on the stock radiator? I'm not trying to sound sarcastic. I used to be able to do this with my old 4mil motor. It was like as long as the R's were high (therefore lots of circulation) and my speed was fast (losts of air moving throught the rad) it would almost never over heat. It seams like I'm not going to be able to do this on the cub. But then again I'm almost never going to run it back and forth WOT like I describe at the dunes in 100 deg heat, just on my test/drag strip which is the creek bed, made of loose gravel, near my house.

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Sorry...Duc...

I'm jealous, I wish I could find a wide open space like that.

I pulled a ton of passes at the 300ft sand drags, no problems.

I guess the first time I get to Silver Lake I'll have to tell you!!!

 

Have you tried straight water, by any chance??

I'm pretty luckey but only in the late summer and fall when the water in the creek is low.

 

Yes, I tried straight water is way worse than running engine ice. I used straight water at the dunes (first trip anywhere with the cub) because I lost too much engine ice out of the system and didn't have anymore to put in. I've been thinking that part of my problem is that when I do the WOT 6th gear tests that I have to slam on the breaks when I run out of room and that it isn't giving it enough time to flow some air through the radiator at speed to cool it off. The more I think about it the more I think the problem may just be self induced. I'll have to go out and ride it like a 1/2 way sane person would and see how it does.

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I also forgot to mention that I weigh 270 so shee has to work prety hard just to get my ass moving.

 

I ran it around again yesterday, 101 degrees F out side, and I tried to cool it down inbetween runs and it did OK, still pushed about 1+ cups of fluid into the overflow and was pretty hot, but far from the point where I would be worried about cooking the motor. No temp guage, whish I had one now. I'm thinking cooler air temps, say 80 deg or less would probably make the stock cooling system work OK and keep the coolant temp under controll, but I think I should start shopping for a larger radiator anyway just to be safe.

 

I geared it to 13/40 with 21" rear tires and went the fastest is ever been in 6th gear, I swear it felt like 80mph in the creek bottom. I might have to put the 14T front back on just to taste 90mph. This thing is a lot of fun. Its hard to believe how much different it is now compared to just a few years ago when it was bone stock.

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Yep...fun indeed!!

I had mine setup yesterday at the strip with 15/41 gearing...leaving in 1st. Just didn't feel right, so I went back to 14/41...much better.

Yeah, 101 temps is hot, no matter how you cut it...

Just put alky on it, that'll solve all issues...Ducman...:)

 

You might be a candidate for a larger radiator I'd say...when it gets 90 plus here, with all that humidity...it stays in the garage...

 

Something about sweating your arse off while you're putting on pants, boots and a helmet before you even kick start it...just say no way for me...

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I also forgot to mention that I weigh 270 so shee has to work prety hard just to get my ass moving.

 

I ran it around again yesterday, 101 degrees F out side, and I tried to cool it down inbetween runs and it did OK, still pushed about 1+ cups of fluid into the overflow and was pretty hot, but far from the point where I would be worried about cooking the motor. No temp guage, whish I had one now. I'm thinking cooler air temps, say 80 deg or less would probably make the stock cooling system work OK and keep the coolant temp under controll, but I think I should start shopping for a larger radiator anyway just to be safe.

 

I geared it to 13/40 with 21" rear tires and went the fastest is ever been in 6th gear, I swear it felt like 80mph in the creek bottom. I might have to put the 14T front back on just to taste 90mph. This thing is a lot of fun. Its hard to believe how much different it is now compared to just a few years ago when it was bone stock.

Are you sure your not overfilling the radiator? cool, it should be at the top of the fins, no higher. Do you have a temp. guage, so you actually know what temp. your runing?

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