Overheating

ThePsuedoMonkey

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I know that the engine should be hot to the touch, as it is air-cooled, but this is different. All last year it ran quite well and somewhere in the comfortable temperature range (under say 80C by best guess) even on the longest rides on the hottest days. On really cold days, I would be able to grab the upper cylinder to warm up my (gloved) hands, and this heat was never unbearable.

This year, it seemed to run quite a bit hotter. Measuring with my thermocouple, it seemed to be at least 90C on the cooling fins, and around 80C or so at the crankcase. This is very different from before, so I am convinced that something is wrong, as there is no reason for the crankcase to be that hot. I knew that one of my floats was sticking, probably letting fuel into the oil, so I serviced the carbs and changed the oil. This does not seem to have affected the temperature.

The only thing that I can think of that would still make it run hot is a lean condition (or maybe fuel still in the oil pathways). All last year I was using 45mm pods about 3" past where the stock airboxes would have been, under original jetting (135 main, 42.5 pilot). During the carb service, I installed a 140 main and 47.5 pilot and put on 54mm EMGO pods. The lack of power at top end tells me (I assume) that this is lean, so I have a pair of 145 and 150 mains on order, as well as a set of the "bench tested" pods from MikesXS.

My question in all of this, is if the lean condition is the culprit in the overheating engine. Should I be thinking about another rebuild to look at bearings and rings and such?
 
These bikes run from 250f to 275f ( at the head next to the plugs) depending on ride speeds and outside temp. My stock 79 temps are more the 275 than my modded 80 with 2-1 exhaust and pods witch runs 250-260f. I use a IR gun to check the temps. Even with the difference between the bikes mods both carbs use 142.5 mains x-4 needle jets 5Z1 needles set on third clip and 42.5 pilot jets. The mix screws are a little different with the 79 set at 2 turns out and the 80 set at 3.5:shrug: How do your plugs look?
 
my tracker was very hot before the jet changes. It even smelt funny.

after re jet it was fine but it did get really hot in 2 hour stop start riding on the toy run.
 
My carbs don't have the needle clips, so I'm SOL there. Idle mix adjustment is to come after I get the main jets correct; the manual didn't explain how they work very well, but I take it that screwing them in restricts the idle air flow (richer) and vice versa? As for the plugs, the attached pic shows the most recent set I've put in: BP7's after a cleaning and subsequent 30mi ride (that's copper anti-seize on the threads). Could your aim your IR gun on the crankcase the next time you get a chance? I measured mine a little bit in front of the kickstart shaft.

Unfortunately, my nose doesn't work well, so I can't say for sure that it doesn't smell funny. I did notice some vapor, but I think it's from fiddling with the fuel line. Knowing that your tracker was very hot does help to put my mind at ease though.
 

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The one on the right looks a little funny but the other don't look too bad maybe a tad rich. Th crank case on the clutch side is 160f and the alt. side is 140f. Screwing the pilot mix screws in makes it leaner.
 
I double checked the timing, it was a little advanced (2-3 degrees) so I took care of that now. Now it's spewing oil from the timing cover :doh: so I need to fix that too. Good times.
 
Yeah, I wish I had the mechanical inclination of the Drewpster...
I disassembled the pickup coil assembly, turns out the rubber seal popped out. I applied a coat of black RTV to the outside and reinstalled it. No more leaking :bike: still super hot with the 150 main :mad: plugs are starting to change from white(ish) to tan(ish) so I figure 155 aught to do it... OR I could go back to the old air intake and have the set of 140's on it. I may just try that tomorrow and see if it helps the temperature. I'm gonna be really :( if I have to open up the engine again.
 
Have you tried to raise the needle on the slide to make it richer in the mid range? The main jet only gives it more fuel from 3/4 to full throttle.
 
Heat ranges are almost always a heavily debated topic. Race bikes will have oil temps nearing 300F if not surpassing it. Then you have melting points of the metals in the engine all being above that mark as well..

blah blah blah.

Bottom line:

Are you experiencing a loss of power? Is it generating a new buzz? Bucking? Anything that feels wrong beyond you THINK its too hot?

If not: Your bike is fine.

*A dude who rides in 120+ degree temps on the freeways of phoenix.*
 
I guess it can't hurt that much if everyone else' runs that hot, but it still seems odd to me. I tried the old setup with 140/42.5 main/pilot jets and my top end was about right, but won't idle without choke. I figure the air jets are gummed up, since I wasn't able to get 'em out without risking damage to them. Now I need to come up with a better way to run carb cleaner through 'em...
 
I guess it can't hurt that much if everyone else' runs that hot, but it still seems odd to me. I tried the old setup with 140/42.5 main/pilot jets and my top end was about right, but won't idle without choke. I figure the air jets are gummed up, since I wasn't able to get 'em out without risking damage to them. Now I need to come up with a better way to run carb cleaner through 'em...

if air jets are gummed, you wouldn't need choke as it would be super rich running.
 
:doh: I'll get the hang of this eventually. I tried cleaning all of the jets anyway, but there doesn't seem to be a way to remove the idle air jet :shrug: there was some junk left in the main air one though, so I ran a lot of carb cleaner through the idle jets just for shiggles. What do you know, it's working pretty well now! :bike: I'm not sure if I want to try straight pods again or not, as I'd rather be riding than working on it. Maybe if they gave me more power, but otherwise I don't know if it's worth the effort.
 
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