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Workshop => Engine and Bottom End => Topic started by: hub97119 on September 02, 2015, 10:39:19 PM
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Going to be heading down to Winchester tomorrow. Had my sons 86 out a while back and we were running into some over heating problems. This is a new rebuild. I put a Wossner piston in it which the spec call for a real tight fit -.002". I was running non-ethanol premium. Would running race at 50/50 help with the overheating ? Radiator and Pump checks out fine. Radiator wasn't plugged up or anything else I could find. Just coolant coming out the over flow. Iv'e also switched to Engine Ice. I guess we'll see...thanks
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seems alot of people buy snake oil like engine ice to fix cooling problems. how did you determine the rad was fine ? old rads often have corrosion down inside the cores. simply pouring water in and seeing it go out the other end isnt a good test imo. the cores could very well still be partially clogged. even with 25% blockage ill bet thats plenty enough to cause alot of problems. might pickup a new rad cap as theyre cheap. might want to accuratly determine the water temp also as a bad cap may give false indication of over heating. pressure test on the cooling system aint a bad idea either
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Let me try to clarify the question a little better without the assumptions of what I have or haven't done " DOES RACE GAS REDUCE THE OVERALL OPERATING TEMPERATURE OF A CYLINDER ? " Thanks Ron
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Yes it does burn cooler
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" DOES RACE GAS REDUCE THE OVERALL OPERATING TEMPERATURE OF A CYLINDER ? " Thanks Ron
dont you meen: my engine may or may not be over heating because i havent even diagnosed the problem but in the event it is over heating will race gas make it not over heat ? it certainly wont fix a cooling problem if thats what you have. as for will it make the engine not over heat, ill have to say no on that. why not try to find the problem and fix it right rather than some bandaids of engine ice and race gas, neither of which will do you much good as youll find out
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like stated above need to figure out the problem and more info is needed . like what was the temp? what tools guage or temp gun to figure the temp were used? how long till overheating ? how much coolant came out of overflow ? your post was not a simple question. you got problems so good luck .
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Let me try to clarify the question a little better without the assumptions of what I have or haven't done " DOES RACE GAS REDUCE THE OVERALL OPERATING TEMPERATURE OF A CYLINDER ? " Thanks Ron
Yes it does burn cooler
Like btw250 replied, yes it does burn cooler.If that is the only question that you are asking, then the answer is yes. However, if you do actually have a cooling problem, then it probably won't be enough change to reduce the overall operating temperature. Meaning even with a cooler burn, it will still over heat. Might just take a little longer to reach the higher temp.
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i agree with some of the others that posted in that race gas will most definitely NOT solve any cooling problems you have. does it burn cooler?.......in the right situation maybe yes, but theres no way that it will burn cool enough to solve a overheating problem. if your overheating then you have a cooling system (maybe jetting if your running way lean but i kind of doubt it) problem not a fuel problem.
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is your head cut to run 100 octane? if no then dont. if it is then why are you only running premium?
is this an OEM radiator? like udontknowme stated just because u can pour fluid in your radiator in and it comes out the other end doesnt mean it isnt clogged partially with corrosion.
to answer the question you are "actually asking" no running 50/50 mix is not going to make your engine run cooler. dont search for bandaids for a problem, find the source of the problem and fix it right.
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If your engine is not having detonation problems and you are running pump gas, switching over to race gas will reduce combustion temperature as well as the power. After re-jetting the engine for race gas to get the power back up where you were with pump gas, the combustion temperature will be back to where it was with pump gas........end result, no change in engine temperature.
Pump gas does not usually have as high of a BTU/lb content as most race fuels and 100LL AV gas. This means it takes a little less race gas (smaller jet) to produce the same quantity of heat and resulting power. An engine has to produce a certain quantity of heat to produce one HP. This ratio of heat produced to power delivered to the crankshaft is a constant meaning every engine has it own unique efficiency. To produce more power requires more heat to be produced in the combustion chamber. Reduce the heat produced in the combustion chamber means less power will be delivered to the crankshaft. Combustion pressure is required to produce power. Heat is required to produce combustion pressure No magic, just basic physics.
I just had a customer a few weeks ago go through a similar situation. He had a stockish 86 lt 250R. He had us dyno tune a new carb on pump gas he had recently installed. We optimized the jetting to produce the most power possible with the engine package he had. We called him and told him it was ready to pick it up and he ask if he could run race gas in it. He had another bike that had to have race fuel and he did not want to carry two fuel cans. We told him he could run race gas but the air fuel ratio would probably be too rich.
He brought us the race fuel that he wanted to run in it and we re-tuned the carb. Power dropped about 2 hp when we ran it with the same carb jetting we had on pump gas. We ended up 3 main jets leaner to maximize the power with race gas but was still down 1/2 hp with the race fuel. I think that it needed to have the ignition timing optimized but he did not want to spend the money optimizing the ignition timing.
Like many have already advised. If you are having an overheating problem with the engine, the race fuel is not going to solve the problem. Repair the cooling system problem. If there are not any problems with the cooling system or head gaskets, you must spend less time running at low speeds. The cooling systems on the 250Rs were designed for racing not riding with the wife and small kids. The 250Rs were not made to run a round in 1st and 2nd gear for more that about 30 seconds without overheating especially if you are on the throttle hard in the lower gears.
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i had a bike one time that would shoot some coolant out the over flow but the engine was never very hot and this was confirmed with a inline gauge and no the rads was never overfilled. you may want to find a way to measure the temp first and fore most and then procede accordingly in a process of elimination. could be as simple as not riding fast enough like jerry said
also if you care to read about it theres plenty of info out there about the ill affects on the radiators ability to exchange heat with corrosion in the cores
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Hell, might not even be a radiator problem. You might have a slight leak in the head gasket and getting a small amount of combustion gasses into the cooling system, which would DEFINITELY cause your radiator to overflow, and subsequently overheat once you lost a bunch of coolant. Race gas ain't fixing that problem.
But who knows, it might actually work. Switching to race gas (as Jerry pointed out above) will often effectively richen your jetting. If your overheating problem is caused by a lean condition, you might actually stumble upon an effective solution by accident. Of course, if that IS the case, re-jetting would be just as effective and a whole lot cheaper.
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Just got back from four days of riding. I used the engine ice, 50/50 race gas mix and went to a colder plug. Bike ran fine with very little over heating but my son likes to plow the side hills and run the hole shots a lot. That is when we noticed the over heating, so essentially slower, lower gear riding. Never did heat up when we were on a longer run. One of my concerns was if the wossner piston and the tighter set-up would be creating more friction, thus more heat. Thanks for all replies - Ron
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colder plugs wont fix a overheating engine. why not just take it to a shop and get it sorted out
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To be clear, a "colder" plug doesn't really do anything for overheating. The plug itself will run "colder" because it has a shorter path for heat to escape, but it doesn't remove an appreciable amount from your combustion chamber. It's like pulling 1/2 cup vs 1/3 cup of water from a bathtub. It makes a difference to the cup, but you're not going to see the difference in the bathtub. And if your bathtub is overflowing, 1/2 cup won't prevent it.
The plug heat range is a fine line between keeping the plug hot enough to burn off deposits (and prevent fouling), but not so hot that it creates a hot spot in the engine and creates detonation issues. It has nothing to do with your engine temperatures and overheating.
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colder plug on a engine that doesnt need it, usually just results in a fouled plug in short order. ive found this out myself
if your in arlens neck of the woods just take it to him and get it fixed right
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Just got back from four days of riding. I used the engine ice, 50/50 race gas mix and went to a colder plug. Bike ran fine with very little over heating but my son likes to plow the side hills and run the hole shots a lot. That is when we noticed the over heating, so essentially slower, lower gear riding. Never did heat up when we were on a longer run. One of my concerns was if the wossner piston and the tighter set-up would be creating more friction, thus more heat. Thanks for all replies - Ron
The amount of heat the cooling system has to get rid of is a function of the power the engine produces. If the engine produces 10% more power, the cooling system will have to get rid of 10% more heat that it did when it was producing 10 % less power. Increase the power 50 %, the cooling system has 50 % more heat to get rid of than it did when it was producing 50 % less power.
Running the engine's air fuel ratio rich, will decrease the heat the cooling system has to get rid of in proportion to the reduction in power, plus the additional heat that is absorbed in the rich unburned fuel and carried out the exhaust port.
When or if the piston clearance becomes too tight, the friction between the piston and cylinder wall will generate enough heat on the surface of the piston skirt to burn up the oil film and seize the piston. The escalation in piston skirt surface temperature that causes a piston seizure happens over a very short time span of usually 10 seconds or less. If you are not having piston seizure problems, the clearances are not tight enough to raise the coolant temperature measurably in a two stroke.
Contrary to common folklore, running an engine leaner than the mixture that produces max power does not increase the coolant temperature significantly but can increase the exhaust temperature to the point that it may burn the edge of the piston next to the exhaust port. If the mixture is too lean, it will usually burn the piston before the coolant temps are raised high enough to raise a red flag.
About 70 % of my customers that are having an overheating problem are due to riding too slow and or have radiators that have the tiny fins peened over from gravel and debris striking these delicate little fins. If 20% of the fins are peened over, there will be approximately a 20 % reduction in heat dissipated by the radiator. If you have fins peened over, the fins can easily be straightened by pushing a zip tie of the appropriate width through the radiator from the back. It will usually take less that 30 minutes to straighten a radiator that has all of the fins peened closed.
In all of my years of developing and testing two strokes, I have not found a coolant that improves the heat transfer from the engine to the coolant or improves the heat transfer from the coolant to the radiator enough to justify the cost of these coolants with magical properties. If you have to use these magical coolants to keep your engine temperature off of the red line, you have other problems that need to be addressed.
A colder spark plug will not reduce the engine temperature one degree unless the previous heat range was causing detonation. Too cold of a heat range will decrease spark plug life and increase the probability of fouling.
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Very very very nicely said!
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I was having heat issues with engine ice and a larger aluminum radiator. I also had my carb jetting Rich. After trying bandaid fixes I took my motor to hybrid engineering (Pete). It turns out my pump dome wasn't a pump dome, but instead a alcohol dome. My compression was way high at 215psi and my ratio was 17.5-1. My cases were also .010" off so he decked them. My porting was also crappy. So long story short.... Get your engine checked out by a reputable builder. You will save yourself some headache.
Loren