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Overheating ???

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Hauula Pan
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Bikes: 1952 FL
Location: California

Overheating ???

#1

Post by Hauula Pan » Thu May 13, 2010 10:10 pm

Can anyone tell me the normal or at least acceptable temp. range for cylinders & heads?? I'm concerned that I'm not getting enough flow volume out of my oil pump. I ran the bike across town and checked the cylinder & head temp. with a laser/infrared thermometer and got readings of 325 - 350 degrees farenheit. The cases were cooler down around 215 degrees. I could not get a reading from the oil tank because it is chrome and reflects the beam. My cylinders are .060 over so I know they are probably going to run on the hot side but I'm concerned they may be getting too hot.



NightShift
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Re: Overheating ???

#2

Post by NightShift » Thu May 13, 2010 11:06 pm

Dear Haaula Pan,
Yes that sounds awful hot. Sixty over is when they just start to get strong unless they were botched so how long has this been broken in?Checked to see if it is sucking air? Might want to check your points and timeing too of course!
Oil is important but Pans are an aircooled motor. And Ive never seen a pump fail without shearing a key.

R'spectfully,

james
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1952 FL
Location: Wrightsville Pennsylvania

Re: Overheating ???

#3

Post by james » Fri May 14, 2010 12:00 am

I agree with Mr Nightshift. If the intake is leaking (lean) or the timing is retarded it will run hot. Frankly I would not run it until you find the cause. You may end up frying some pistons.

Jim

Cotten
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Location: Central Illinois

Re: Overheating ???

#4

Post by Cotten » Fri May 14, 2010 12:46 am

Along with Jim's observation about retarded timing,
cam-follower wear upon the points will advance the timing, and overheat in a heartbeat.

All possibilities should be investigated!

Let us know what you find,

....Cotten

Hauula Pan
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Re: Overheating ???

#5

Post by Hauula Pan » Fri May 14, 2010 3:20 am

So you're saying 325 - 350 degrees is too hot ?? Timing checked & re-checked and is dead on. Plugs look just right, no sign of being too lean. Oil is returning to the tank, although not in any huge amount, but it is circulating. Pressure on cold start up is 30psi and falls off when it heats up, as pans usually do. (But instead of just falling to around 3 psi. the gauge actually falls to 0 psi. but oil is returning to the tank.) The motor is fresh. It was bored .060 a few years ago and never run, it just sat. I pulled the heads & jugs to make sure everything was ok & put them back on. So far it seems to run ok but I'm just concerned that its running too hot and it may be because the pump is worn and not circulating enough oil fast enough. I'm going to look at a buddy's pan & see how much oil is returning to his tank & compare. My 1st thought was timing, 2nd thought was lean mix. and since those appear ok my last thoughts were poor oil circulation or just rings still seating. So next I'll compare oil return. So does anyone know what temp. the cylinders should be running at ???????

Bosheff
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Re: Overheating ???

#6

Post by Bosheff » Fri May 14, 2010 9:28 am

If timing is to far retarded or the fuel mixture is exceptionally lean, or both at the same time, there is a good possibility that yer exhaust pipes will turn red hot and discolor the chome. This condition is especially easy to identify at night. The pipes will actually glow red. Back in the early shovel days, H-D offered a cylinder head temp. guage as an option. It had a sender that was mounted to a fin on the top of the cylinder head. If you have access to one of those guages, it will show the peramiter of the cylinder head heat range....bosheff

partshunt
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Re: Overheating ???

#7

Post by partshunt » Fri May 14, 2010 11:03 am

I had an 82 shovel FLT with the temp sender on the rear head. Generally it ran around 300 degrees and cooled down to 200 when at a stop lite idling. With 94 octane, it went to 375 degrees climbing a ten mile uphill mountain highway in the mountains around here. And we have lots of em in my area, good for tests like this. Anyway, ten minutes later at a stop lite, it dropped to 200 degrees. It ran that way for ten years and I still see it around town today, the owner loves it...I noticed also, higher temps with higher octane fuels, but that makes sense. Higher energy and higher BTU's arent free of hi temps. You also mentioned riding thru town, so possibly a cooler run would have been on the highway at mid throttle, try that and your temps may not be all that hi...Joe

Cotten
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Re: Overheating ???

#8

Post by Cotten » Fri May 14, 2010 1:09 pm

Joe and All!

The higher the octane rating for the fuel, the cooler it runs.
That's why hotter running low-compression flattys use lower octane fuel, and high-compression OHV motors need higher octane fuel. Compression and heat are synonymous; OHVs run cooler because they make up for it with compression.

I, too, found with my infra-red temp gun that temperature readings change rapidly after a machine rolls to a stop at my door, and there is quite a range of temperatures as well.
It may be the best baseline for our comparisons to settle on just a few spots, and the order in which we check them as quickly as possible. I suggest the VIN boss, as it may represent the best average, and somewhat independent of immediate flux of heat from finnage.

And at risk of repeating myself, over-advanced timing will overheat a motor dramatically.
The sooner the combustion, the longer it remains within the combustion chamber.
Late timing allows combustion to continue as it goes out the pipe, discoloring it of course, but transferring less heat to the motor (and less power as well!)

....Cotten

hogboy52
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Re: Overheating ???

#9

Post by hogboy52 » Fri May 14, 2010 4:32 pm

It's running too hot because it's not broken in. New bore, rings, pistons make lots of friction. It can take several cycles of running up to temperature then cool down before the bike becomes normally ridable. Running too hot can make the rings lose tension or scuff piston skirts.

Hauula Pan
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Re: Overheating ???

#10

Post by Hauula Pan » Fri May 14, 2010 4:36 pm

Thanks to all for the replies and info. The terrain here around town has a lot of hills so I'm often having to choose between some higher rpm in 2nd or almost lugging 3rd. and with a lot of stop signs I'm constantly going from idling back up to speed. So not a lot of nice cooling air flow like I'd get on a long run. The motor was also last built with the .060 over LOW COMPRESSION pistons and an Andrews #1 cam in order to accommodate the non-lead lousy modern gas. The pipes look OK no discoloration at all on the front and just a bit of gold at the top S bend on the rear and it is still nice chrome above & below that area. It is only the cylinders & heads that are reading 325 - 350 degrees and the engine cases are reading around 150 - 200 degrees, so from the info. about the shovel temp. gauge reading 375 I'm thinking I'm running a bit hot but not enough to do damage. I'm going to see if I can get my buddy to ride his 1949 with me & we'll compare. Also it seemed to run a bit hotter the 1st 2 times I rode it (didn't have the temp. gun then) and may be just the fresh motor seating the rings in. So a few more miles may improve things. I'll know soon enough as I'm planning a longer ride down to the valley next week. She'll either be fine or worse case she'll burn up and I'll have a lot of work to do. I'll let you know how it goes.

NightShift
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Re: Overheating ???

#11

Post by NightShift » Fri May 14, 2010 6:13 pm

Dear Everybody,
Hogboy52 speaks the truth if you found a really anal motor man. And thats a good thing. But thats all about the lower end not the cylinders. Rings are not supposed to break in any more. Bores are supposed to start out already perfect.
Just ask Hastings.

Dear Haaula Pan,
Please be gentle and dont lug her and dont rev her at stoplights either.

She will love you a long time,

duoglide58
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Joined: Mon Apr 09, 2007 7:08 pm
Location: Oklahoma City

Re: Overheating ???

#12

Post by duoglide58 » Sat May 15, 2010 3:58 am

While you are checking your buddy's pan, why not take some temp readings of his bike. While I have not taken the temps of my bike, I have taken engine head temps on my car around the exhaust much hotter than 375 deg. Exhaust temps are about 1200 to 1300 deg in an engine. So 350 does not sound hot to me especially if the lower part of the engin is 200 deg.
Late timing allows combustion to continue as it goes out the pipe, discoloring it of course, but transferring less heat to the motor (and less power as well!)
Late timing will actually raise temps higher than advanced timing. Retarded timing sharply raises cylinder head temps. Years ago I visited with an automotive engineer that did his masters work on internal combustion engines. I asked him if advanced timing caused high temps. He said you will hear it pinging before it gets really hot. He said if you want to see the effect of retarded timing, disconnect the vacuum advance on the distibutor and watch the temp climb. If you have an old car with a distributor equipped with vacuum advance that runs off of manifold vac, pull the hose and plug th line and watch the engine temp start climbing. I see this whenever I map out the advance on the distributor.

In the late 60's and 70's ignition systems on cars were equipped with dual vacuum advance cannisters and some had thermostatic coolant/vacuum source switches. At idle, manifold vac was directed to the vacuum can to retard the timing. This had the effect of raising the temps and helping warm up the engine quicker. The goal was to reduce emissions during cold starts. Once the engine was warmed up a thermostatic switch changed the vacuum source.

I agree that the retarded timing results in less power. Retarded timing has less complete combustion and combustion can continue in the exhaust ports making pipes glow. The engine with advanced timing reaches more complete combustion and generates more power. When an engine makes and uses more power, it is more efficient and converts more heat/energy to work. Work extracts more of the heat out of the gases.
Doug

partshunt
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Re: Overheating ???

#13

Post by partshunt » Sat May 15, 2010 5:52 am

Well done Doug: I just cant seem to find the time or think of everything when posting but you covered it well....Joe :wink:

Cotten
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Location: Central Illinois

Re: Overheating ???

#14

Post by Cotten » Sat May 15, 2010 12:49 pm

Let us all at least agree that proper timing is best.

It is puzzling how many manuals for American v-twins prescribed manually retarding the spark for heavy loads, such as climbing hills and the like, circumstances where the most heat is generated.

Perhaps I was right after all for advising against it.

....Cotten

john HD
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Re: Overheating ???

#15

Post by john HD » Sat May 15, 2010 2:22 pm

It is puzzling how many manuals for American v-twins prescribed manually retarding the spark for heavy loads, such as climbing hills and the like, circumstances where the most heat is generated.
perhaps that was because the best gas you could get back then was 66 octane at a phillip's station. that and flatheads were the norm in bikes and autos not the exception.

john

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