March 25, 2017 at 7:00 pm #79723
Looking for some advice. We have a 2013 Top Kart Speedy Chassis with a 08 Leopard engine. Today we took it out for the second time and continued to have cooling issues. First time out last week was partly sunny and around 60F ambient. We were seeing temps as high as 160 before we would come off track. I flushed the system at the track, added fresh water with water wetter and no change. The braided belts were covered in blow by of oil and grease or possibly chain lube mix.
This past week I took the pump off, disassembled, no crap or build up, flushed radiator out again and checked all of the hoses, The water pump is an aluminum aftermarket with no play or notch in the bearings and spins freely, the radiator appears to be a standard leopard size radiator which was leaned over pretty far so I raised it slightly more vertical to about a 20 degree angle. I cleaned the belts, reassembled everything and filled again with fresh water/water wetter mix.
We ran again today and were seeing temps in the same range again with higher ambient temps in the 75 degree F range in full sun. We are using a Mychron 4 with the sensor in the head, we were questioning the sensor since a quick scan of the inlet and outlet ports of head, sensor bung area and general surface showed a 25-30 degree temp difference with a non contact laser temp gun.
When we got home I swapped the sensor out with one from our Rotax engine and both read the same at 74 degrees F. We are running a 50mm axle with the split pulley so we are spinning the water pump pretty fast. Could it be causing cavitation because the flow rate is too high not allowing enough saturation time in radiator?
What else would you suggest trying? New water pump? Run belt directly on shaft? Replace sensor? Larger radiator?
ThanksMarch 26, 2017 at 8:39 am #79734
As a reference, our pre-09 ran a 124F water temp on a 75 degree day during a road race. But, we did not have a sensor in the head. We had it in the hose from the head. Would expect a sensor in the head to read higher. How much higher I don’t know.
Try putting the sensor in boiling water to test the gauge’s accuracy. Check the radiator cap to see if it’s holding pressure. I an not fan of the type of pump belts you’re using and would try a conventional belt. If you do go that route, put on extra belts and tie wrap the spares to the center bearing support. And I’m assuming you are purging the air out of the system before you hit the track.
Another cause could be your chassis set up. If the chassis is too bound up, that will cause the engine to work harder, causing more heat. Look at the gear alignment.
Let us know what kind of RPM’s you’re turning. There should be someone on the Forum that’s run with a head temp. And it might be time to call your local kart shop.
LAD Specialties / tony kart / rotax / kt100March 26, 2017 at 12:44 pm #79735
We are total Kart newbies, new to karting but I have road raced for over 10 years, so what would we do to loosen chassis up? Feedback from both of my sons was that they were not experiencing any hoping or strange handling characteristics.
We are turning in the 15K-15.4K range and on well worn Bridgestones and only the second outing we are only 4 seconds off the pole at the last race at same track with all the racers on brand new MG yellows so I assume there is at least 1-2 seconds just in tires.
We have been purging the air at the head so I do not think that is it. Water level is filled to just below the neck to allow for some expansion. The cap I noticed is holding pressure so that may be a cause, I can blow air out the inside of the cap thru the relief hose but not thru the hose end out the inside of the cap.
Before next weekend my plan was to install a brand new pump and belt setup, new sprockets and new chain and align everything fresh.March 26, 2017 at 7:17 pm #79742
Why do you believe that 160 is too high? There maybe nothing wrong with your engine. If there are other Leopards at your track, ask them. We didn’t run a probe in the head of a Leopard but did have one on a Rotax. 150 to the high 160’s were acceptable water temps. Do not throwing parts at your engine until you’re sure there’s a problem. A spare pump, belts and gears are good to have as spares. Unless the gears are severely worn on their sides or the teeth are misshaped, there’s no reason to replace them. If they are worn, replace them and the chain. Another good spare for a Leopard would be clutch.
How are you purging the air from the cooling system? Are you removing the temp sensor and spinning the rear wheels until water comes out? We used to run the engine on the stand until it started to warm up. Then would tip the left side of the kart up so the radiator was higher than the engine. Make sure the pump was turning, set it back down and fill the rad up to the top. No need to leave room for expansion. The radiator cap is suppose to hold pressure and allow some water to escape if the pressure builds to high. Have a catch can attached to cap.
If the rear width is not at the max allowable, move the hubs out a quarter inch to free the kart up.
See you PM.
LAD Specialties / tony kart / rotax / kt100March 26, 2017 at 9:36 pm #79744
Do you have a thermostat installed? 160 is really warm for that kind of ambient temp on a Leopard. Also, have you made sure there is no obstruction in the radiator or cylinder head?March 27, 2017 at 6:26 am #79760
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