GL1200 overheating

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Nice work!

I looked at "upgrading" my gl1100 to a gl1200 radiator at one time, thanks for settling that issue!

BTW if yours doesn't work out for some reason, here's another option I looked at back then, a mid 90's Honda Civic "racing" radiator, pretty cheap on ebay, fairly close in size...
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If you do need a new radiator I recommend checking radiator shops first.
If your up to it they can usually build one for a couple hundred bucks.
There would be some customizing to mount it of course but that sure beats $600 new from Honda.
I don't like used for things like this. New is always the best way to go.
The only reason I'm going used on this 1200 is because we're not certain the radiator is the problem but if it turns out true then we'll build a new one.
 
dan filipi":2tlxriuo said:
mcgovern61":2tlxriuo said:
Question is, does it still make bubbles with the changed radiator?
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That's whats strange. The bubbles into the reservoir stop with this radiator and the coolant level doesnt drop when reving the engine cold with the cap off like the 1200 radiator did. :headscratch:
It acts as if a slight more flow is stopping cavitation or something. The thermo fan switch even started to work at the right temp for a few fan cycles, don't know if that's related or not but it sure seems like there's better flow with this radiator.
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Actually, that makes perfect sense! There is a blockage in the radiator that interrupts the correct flow of water causing the pump to starve and cavitate. The pump is ok, tha radiator is not. Just because water comes out the bottom does not mean it is flowing correctly. Flow rate is imperative, particularly with less cooling surface to work with! The radiator heating up from the bottom up first is consistent with pump cavitation and the heat is more than likely from the pump. Air bubbles in a positive displacement pump will create heat and will actually boil. (You should see what cavitation boils do to a ship's propeller, can actually cut a hole in the bronze!)
 
joedrum":2ktur7v0 said:
hard to beleave the radiator were downsized on the 1200. hoping the upgrade to 1100 radiator cures everything
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I don't really think it's "downsized" even though it would appear so since the 1200 rad has 13 less tubes.
It could be the "high efficiency" design having closer and more fins makes up for this.
What I do know is the earlier radiator for whatever reason makes it run cooler.
I'm still thinkin there's something else causing it to run warm.

A new development today.
I took it for a 30 mile mixed highway and street run yesterday and pulled the plugs this morning.
3 look white and one has reddish brown coloring on the insulator.
I have Prestone flush in it, could this be showing up on the plug?

I'll try to get a good picture.
 
i would rotate the plugs and see how long it takes to turn that plug red brown.

dose it run well now or down on perfomance that waisted spark ignition on 1000 can mimic all kinds of problems. its makes having everything snyc together a must carbs compression plugs

it might be if you change the plugs it might straiten everything out one bad plug can cause the cylinder on the other side to stumble and fart around enough to drive you crazy chaising your tale

id just keep rotating the plugs to truly identify what cylinder is causing the problem or hopfuly no problem
 
I agree with Joedrum, rotate the plugs, ride and see if you can mimmick the condition on a second plug in the same cylinder. It does appear to be anticorrosive, but I am not an expert. None of the spark plug reading sites include water or antifreeze fouling. IMHO, the only steel in there that can cause oxidation is in the plug if it were sprayed on.
 
Well, I fired up my bike in the garage to answer some nagging questions I needed to know. How hot is the radiator at what point in the heating cycle and where?

I got out my trusty infra-red temp scanner and went to work. As the engine is heating up, the top of the radiator was running 120 degrees at the inlet and across the top. The bottom stayed around 75 degrees except at the outlet by the water pump which reached 139 degrees at the pipe.

Just before the stat opened, the engine reached 206 degrees at the tsat housing, the top of the radiator reached 140 degrees and the bottom only reached 80 degrees.

As the tstat opened, the top reached 196 degrees initially, but cooled down to 140 within 5 seconds of the fan coming on. The bottom of the radiator reached 189 in about 3 seconds after the tstat opened and cooled to 160 within 5 seconds after the fan came on. (I thought that cooling was incredibly fast for a 29 year old radiator!)

Moral of the story Dan, unlike the 1200 radiator which was hot at the bottom and cool at the top while heating up, mine followed the normal laws of thermodynamics. Still points to a blockage in the 1200 radiator.
 
Thanks for doing those tests, that helps alot!

Both the 1200 with an 1100 radiator and my 1100 run around the temps your getting except for the wide top to bottom difference
"Just before the stat opened, the engine reached 206 degrees at the tsat housing, the top of the radiator reached 140 degrees and the bottom only reached 80 degrees.."

Could this be because we're 60-70 degrees outside and yours are much lower meaning the coolant is alot colder?

"(I thought that cooling was incredibly fast for a 29 year old radiator!"

The 1100 radiator and cooling system is very well designed. It impresses me how well a early 80's design can maintain temps under control even when we were at Yosemite in stop and go traffic at 108 degrees!
 
dan filipi":2t1gvv3z said:
"Just before the stat opened, the engine reached 206 degrees at the tsat housing, the top of the radiator reached 140 degrees and the bottom only reached 80 degrees.."

Could this be because we're 60-70 degrees outside and yours are much lower meaning the coolant is alot colder?
Click to expand...

Yep, my coolant was about 41 degrees when I started this test. (It was actually a warm 41 degrees today!)
 
wow the plugs look or pretty good to me they must be pretty new. thats some good info gerry sounds like a neat tool to have. i think on a waisted spark system a bad connection or resistance causes problems all the way back to the coils even though they checked out good they did not work right. i went ahead and changed to dyna coils that didnt need a balist resistor to work and dyna ignition. i know the 1100 is different but im just trying to say that the coils get weak over time from not up to par wires,plug caps and plugs. just something to think about. on my bike it was the coils that cause the poor running the most
 
I pulled the right head and here's what I found in the #1 exhaust port :
IMG_0932.JPG

IMG_0933.JPG

IMG_0941.JPG


What looks like a hole to the left of the valve stem is the exhaust gas port on the 1200 heads.

I think I've found a crack!
Judging by the cleanest spot right below that hole I'm thinkin there's a crack inside that exhaust gas passage.
The other side's exhaust ports are evenly dark like #3.
 
Man, you are one relentless mothertrucker! Good work.

I don't know what that white coloration means, but just that it's different means something isn't right. So does that show that water is getting into the exhaust? Why would that make it overheat? Pardon the dumb questions.

And what is the small hole for? It vents the exhaust to somehwere?
 
great finaly some sign of what to do to get it fixed. probablygot hot enough along the way to crack the head from the restricted flow from the radiator. im sure you will find a head. its nice to know what to do.id like to know what you think about how the front forks compare to stock for handling.
 
The white is corrosion from steam. The crack is an expanding crack that only expands when hot and only a tiny amount of water can pass. The droplets are turned to steam and clean out the carbon only in the direction the steam expands (which is only about a drop at a time, other wise the whole chamber would be clean.) Exhaust gasses mixed with coolant additives and water are corrosive to aluminum.

I agree with Joe, this is from a previous overheating condition most likely caused by the restricted flow in the radiator. As you mentioned before, the rt head was off for some reason. The crack on the exhaust side is consistent with what we discussed about exhaust gasses getting into the system when hot.
 
Coolant leaking on that side of the valve would cause it to have steam out the tailpipe...I don't remember you ever mentioning that. The entire back-side of the valve is clean, so it's definitely getting water sprayed on it from somewhere. Does the piston for that cylinder look clean/white like the valve?
A crack in the head on the back-side of a valve shouldn't create an overheat condition in itself, but the loss of coolant would. It also wouldn't cause the bubbles in the radiator.
Whatever, you definitely have found a problem!
 
AApple":dzouz0b3 said:
Coolant leaking on that side of the valve would cause it to have steam out the tailpipe...I don't remember you ever mentioning that. The entire back-side of the valve is clean, so it's definitely getting water sprayed on it from somewhere. Does the piston for that cylinder look clean/white like the valve?
A crack in the head on the back-side of a valve shouldn't create an overheat condition in itself, but the loss of coolant would. It also wouldn't cause the bubbles in the radiator.
Whatever, you definitely have found a problem!
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Joel, if it is a heat expansion crack that only opens when hot, it may not produce enough water to create steam out of the tailpipe, only a drip.
 
Yer prolly right, Gerry. :eek:k: I don't know enough about the design of the heads in this case, so I'm not understanding how/where the coolant if flowing around the chambers.
What the heck is the exhaust gas port, anyway? Is it similar to an EGR set-up on automotive engines?
 

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