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Head temp goes way up at high rev'sThis is a discussion on Head temp goes way up at high rev's within the 2-Stroke Motorcycles - Exotic forum, part of the 2-Stroke Motorcycle Forums category; Hey. I have a 1985 Husky 125 xc. I had it honed up to the next size for a new ... |
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#1
05-04-2005, 06:27 AM
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 Head temp goes way up at high rev's Hey. I have a 1985 Husky 125 xc. I had it honed up to the next size for a new piston. I wanted to make sure I didn't repeat the mistake that led to that mishap so I added a My-Chron MRT Lite mini tach/temp guage, and a speedometer/trail guage (i can't think of the name,will check the bike.. lost the manual)... anyway... that's the history part.... here's the question part: Is 240-270 Degrees F (head temp) too hot for short periods of time on a liquid cooled engine? My head temp (at the plug) is running about 187-212 degrees F (maybe higher since I don't look while aproaching jumps) when I'm not running a high rev for extended periods. As I bring the bike up to 50-56MPH I just started to notice the temp goes way up, and I got worried a little but I don't notice any performance hit or any odd smells or anything that would indicate this isn't normal. Any expert advice on head temp is appreciated.. enigne 125cc 15:1 compression Running high octane + motul 800 2t @ 30:1 or close (extra drops stay in cylinder) O/D               |
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#2
05-04-2005, 09:51 AM
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| Re: Head temp goes way up at high rev's Unfortunately, I don't think anyone is going to be able to help you with your question specifically. The temps you are reading are relative to 2 different things, your method of measuring the temp and your specific bike. You can't really talk quanitiative (sp?) numbers on something like head temp when everyone is going to measure it a little differently. In a general sense, it makes perfect sense that your temp is going to raise signifigantly when your rpms go up. I guess all I can say is, if it isn't blowing up yet, then it sounds like 270F is perfectly acceptable. |
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#3
05-04-2005, 11:11 AM
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| Re: Head temp goes way up at high rev's I`m no expert(far from it) You`ve just had you`re cylinder rebored(honed) yeah. Well I`d say it`s going to run hotter because you`ve increased the size on your cylinder,therefore it`s sucking more air+fuel in so its gonna run hotter, so thats a normal thing. what I would do because of the heat is have more, and longer cooling periods!! As you said your performance is not affected so I would`nt worry about it!! HAPPY RIDIN`  |
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#4
05-04-2005, 11:22 AM
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| Re: Head temp goes way up at high rev's Don't take this the wrong way, since I don't go out of my way to provoke anyone. I'm only looking for an educated guess from someone with this experience, which would suit me fine. I only need to know something like, "run more oil if your doing that." or "wait till water comes out of the radiator then shut it down"(kidding) If you're the man here I'll shut up, but don't end the thread before it gets started. This cylinder shouldn't be bored over again and I guess I didn't think of a better way to lure answers out of people. But the day is young yet. I'd like to see numbers from other riders who have guages set up. I'd be curious to see how the numbers stacked up after a while of comparing similar set ups. How accurate could we get? If not close, we would still have collected factual data that could prove useful. I'm just wondering how long I could keep the revs pegged before the pressure in the cooling system would probably blow the coolant and seize. I'll assume that my radiator cap blows at 12psi(I'll check that). I can get the info with one exact test. BUt I may need a few miles of straight road and a trailer to get the bike back. Seriously though, anyone who has done any testing here, chime in... Or perhapse they won't read this.. O/D |
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#5
05-04-2005, 11:29 AM
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| Re: Head temp goes way up at high rev's Quote:
As for the bore size, maybe a little diff. but couldn't be much, like the diff between 27:1 premix and 30:1 premix, I dunno... but i like experimenting. O/D |
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#7
05-04-2005, 06:50 PM
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| Re: Head temp goes way up at high rev's I apologize for the tone in my earlier posts, I've been a little maxed out at work today. I worked it off, wheelbarrowing dirt to my latest ramp project once I got home....  O/D |
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#8
05-04-2005, 07:55 PM
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| Re: Head temp goes way up at high rev's a higher temp at high revs sounds normal...if ya want to do a little testing, you can try using a good quality coolant mixed 50/50 with distilled water, and do a few runs on it to see if the temps are the same...at higher speeds, the airflow over the radiators should compensate for the higher temps...i dont have any experience with husky, but on my cr,i took off the rad. louvers and drilled about 75 holes in each to let a little more air through.  let us know how it goes...this sounds like an interesting topic...the faster you can disipate(sp?) the heat,the more power can be produced...also if freezing is not a problem in your area, i have known people that used straight distilled water or a 25/75 mix...the coolant will help lubricate the water pump area...the only problem with using the straight water is, you will have to change it often...i run a 50/50 mix,and change it every top end replacment.about two or three times a season...good luck. keep us posted. |
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#9
05-05-2005, 07:48 PM
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| Re: Head temp goes way up at high rev's I will give the distilled water Idea a go, right now it's straight antifreeze. It gets cold in the winter here (wash dc area) but for the summer I'll do the 25/75. Great idea thanks! Next ride tomorrow, I'll hit it then! O/D |
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#10
05-05-2005, 10:20 PM
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| Re: Head temp goes way up at high rev's Quote:
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#11
05-05-2005, 11:42 PM
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| Re: Head temp goes way up at high rev's most straight antifreezes will go solid at a higher temperature than a 60/40 mix of antifreeze and water will. the manufacturer can supply you with the exact temp that their product will "freeze". So running straight has no positive affect that i can see, unless you dont have distilled or deionized water available. Havent used the temp gauges on heads in years. Never did do it on a liquid cooled bike. EGT is more useful, so I no longer use the head temp gauges. My 125's will sizzle water after being run hard though. |
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#12
05-06-2005, 01:21 PM
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| Re: Head temp goes way up at high rev's Quote:
Would the exhaust gas temp show much higher on an engine that is overheated? It seems that the exhaust gasses would remain at a constant, regardless of melting motor parts? I can see using it to fine tune your carb though to make sure your burn is good. I suppose I'll have to get one of those next since the only carb I can tune is a holley 650. I'll hit the supermarket on the way home and get a couple gallons of distilled H2O... O/D |
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#13
05-06-2005, 01:44 PM
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| Re: Head temp goes way up at high rev's The EGT will definitely give you more notice on when you are going to meltdown than a heat temp gauge in my experience. I have seen lots of seized engines and lots of pistons that had half the crown missing and never boiled over in the process. What you get at the head with the old under the plug sensors that i used was directly related to how efficient your cooling system was working, but told me little about what was going on inside. It worked better on the air cooled heads in my opinion than with the liquid coolers. As long as you are using it on the same bike, though, I think the head temp can be useful to see what changes affect it. On liquid cooled engines, I saw no affect in a 2 step main jet change though, and you know there has to be one. On the EGT that will give you a 125 degree swing in lots of cases. You are certainly on track with using it for jetting. I have a snow machine with three cylinders and all jet differently. We tune it via a digitron with a memory. |
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#14
05-07-2005, 08:41 PM
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| Re: Head temp goes way up at high rev's I bought distilled water, but spent much of the day cleaning the house and watching my 2 year old(wife worked)since relatives were invading. I did ride but didn't even turn the head temp sensor on since I was farting around my small track, and since i wasnt able to repeat any runs i had..... didnt do any testing.... just warmed it up for my little cousin so he could ride. hes 23.. if i learned anything it is to not ride when drinking... tomorrow i drain the fluid an get the percentage right for the mix of distilled water to anti frigid...more mothers day stuff, hope i can ride on the main road and check the numbers! I want an egt now but dont know how wacky a 3rd guage is gonna lookk.,.... maybee tastfully done.. yep i will do it I can weld most anything.....will the bung interfere with the flow of exhaust gas?.. . good thing im not drinvin now...nice to have parties at my house...... love.... O/D |
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#15
05-07-2005, 09:44 PM
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Re: Head temp goes way up at high rev's 
