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Pro circuit head

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Long ago in a land far away people rode two strokes. A local racer, who has recently turned pro, rode a clapped out KX 125 faster than anyone I have ever seen. It had a beautiful golden pro circuit head. I would kill for a similar piece of hardware. Does anyone know where I can find one and try to bring back some of my childhood

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Have your stock head gold anodized. The rider was faster than anybody you had ever seen not because of his PC head but because he was able to hold the throttle to the pin longer than anybody you had ever seen. He still would have smoked everybody on a stock bike.

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look at vhm heads i have one its gold made in holland and is bad ass. it will cost you around 500

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Long ago in a land far away people rode two strokes. A local racer, who has recently turned pro, rode a clapped out KX 125 faster than anyone I have ever seen. It had a beautiful golden pro circuit head. I would kill for a similar piece of hardware. Does anyone know where I can find one and try to bring back some of my childhood

Get a can of gold spray paint, spray the stock head gold, then shave 0.25mm off the gasket surface and you have something equal to any of the aftermarket heads and a spare $200 in your pocket.:) Measure your squish first and you'll be fine.

I am being a bit sarcastic but it will work fine. Most aftermarket heads are just lower chamber volume = higher compression. Some have differnt squish band widths and this can affect power but i honestly dont think that the guys at the track will care... they'll be so blinded by the gold paint that they will think you're riding faster than you actually are anyway.

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I got one of these . I like 'em!!!! You can change domes for different compression too. I have the close to stock one because I wanted it primarily for the improved cooling but I can always switch it out for the high compression one whenever I want to get a bit more oomph. Gotta run race gas all the time if you do that though.:thumbsup: You can pick different colors if you want too. I thought it was a very reasonable price for what you got.

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Your head gasket on your Honda regulates how the head cools, not the head. The intake side of the head gasket is restricted and the exhaust side open to promote an even head and cylinder temperature.

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Your head gasket on your Honda regulates how the head cools, not the head. The intake side of the head gasket is restricted and the exhaust side open to promote an even head and cylinder temperature.

1987CR250R . Do you know what kind of gasket a phathead has? ..an O ring. There is no "gasket". So that regulates how the head cools ? I don't think so...at least not by very much. Of course the phathead having around 3 to 4 times the volume of coolant that a stock head has nothing to do with letting my bike run cooler right?! Let me guess ..You don't have a phathead on your bike do you?...just like the other threads.

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That's what I'm saying, their idea of better cooling is to remove the restrictions in the head gasket the Honda engineers so thoroughly thought out. They are there for a reason. Adding volume doesn't improve the cooling rate, either. Increasing flow does.

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That's what I'm saying, their idea of better cooling is to remove the restrictions in the head gasket the Honda engineers so thoroughly thought out. They are there for a reason. Adding volume doesn't improve the cooling rate, either. Increasing flow does.

Adding volume doesn't improve the cooling rate? Where do you get that? So if there is a fire it isn't more important to shoot a larger amount of water on it but to make sure the flow rate is faster? Racers from all types of motorsports regularly run larger radiators for larger volume of coolant to absorb more heat. For mx racers fluidyne is the company that comes to mind that makes larger radiators for mx and offroad bikes . People run longer radiator hose as a cheap way to gain more coolant volume along with the companies that make larger volume heads like phathead and eddie sanders. The honda engineers are like engineers of any company. Their product , in this case the cr 250 head can and has been improved by other engineers that have since put out after market products that improve on the original design. I agree with the increased flow improving cooling. The flow is also increased with the phathead. Boyesen also makes a better flow water pump system to help with that. There have a bunch of times where I have seen or experienced boiling radiators in the trails. I gotta say that sucks. The engineers may have made a decent initial design but an evolution of design has been added because of demand.

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Increasing the flow crossectional area of the head (increasing the volume) without changing the flow rate slows the flow down. With the slower flow rate, the coolant will have more time to absorb heat. This means the coolant in the head will be hotter and the temperature difference which drives heat transfer will be reduced. Also, the boundary layer thickness is greater with the slower flow which increases the resistance to heat transfer.

Well, the interchangeable domes are cool but how often do you do that? Everthing else they say is unfounded advertising drivel.

Sorry if I'm so critical of every part you have on your bike, I'm just an engineer over here. That and I just don't care for bling which might affect my attitude towards certain things.

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Increasing the flow crossectional area of the head (increasing the volume) without changing the flow rate slows the flow down. With the slower flow rate, the coolant will have more time to absorb heat. This means the coolant in the head will be hotter and the temperature difference which drives heat transfer will be reduced. Also, the boundary layer thickness is greater with the slower flow which increases the resistance to heat transfer.

Well, the interchangeable domes are cool but how often do you do that? Everthing else they say is unfounded advertising drivel.

Sorry if I'm so critical of every part you have on your bike, I'm just an engineer over here. That and I just don't care for bling which might affect my attitude towards certain things.

Here's the bottom line engineer...My bike runs way cooler with the phathead than the stock head. Am I going to change back to the stock head? Nope. Are you familiar with the phathead? Again I don't think so because you would see by the design that it has a larger volume and increased flow. You seem to be talking about something you do not know about because you do not have this kind of head running on your bike. As far as having interchangeable domes : How hard is it to change domes? It is easy and fast. If I wanted to go race a motocross I could put on the high compression head and get more power. If I wanted to go race the MaunaKea 200(check MK200 ) I could run a lower compression head. If I ran my stock head what choices do I have? just one ... and that is ok but for around $200 I know it is a great buy for what you get. As far as unfounded drivel , I would be calling it that if it didn't work. You are critical of some things that are on my bike. I don't understand how you can criticize a part or a mod that you don't run and I do. It doesn't make sense.

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with my vhm head i can run my bike all day long and the head and water temp is luke warm i am not sure why but they say that head cools better i know it is much larger than stock.

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with my vhm head i can run my bike all day long and the head and water temp is luke warm i am not sure why but they say that head cools better i know it is much larger than stock.

The stock head holds very little coolant . I didn't realize how little till I compared to my current one. There is a big difference. I never heard of vhm till now. I googled it . It looks similar to the eddie sanders heads. Nice.:thumbsup:

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The engineers at Honda provided the riders with what they asked for, a stiffer frame. The riders got what they asked for.

Careful with putting all of that additional cooling capacity on your bike, these bikes don't have thermostats to regulate their temperature and if you subcool the engine you can cause increased wear rates and even the dreaded cold-seize. Hey, some of the engines I work on actualy insulate most of the cylinder liner and only cool about the top 25-30% of the liner to reduce wear rates.

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the head has been on for somewhere between 120 and 150 hard riding hrs and no not all the same top end...lol. i think that the cooling is just fine for the motor or maybe i have been lucky. i dont know much about it but i like it and i think they did their homework with them.

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