Tunnel Heat Exchanger on the MH

[Ausm7499]

If you use the waterless coolant it doesn't boil until 375f and can be run at 0-psi so less stress on your hoses as well. but the bottle is nice so you can see your coolant level and makes filling easy. this is also a great solution to adding a stat to a KX500 since the head outlet is only 1/2 inch from the radiator inlet.

I thought about running Evan's this year but with this new coolant system I can't see it ever getting hot enough to boil. One thing worth mentioning is that with this type of setup it's tough to get all of the air out of the system so the first ride out I carried a 1.5l bottle of coolant with me and topped the coolant bottle off twice throughout the day before I finally got all the air out.

 

[teal_210]

The heat exchanger and coolant bottle are off of a 07-08 Arctic Cat M-Series I think it cost me like $50 for both of them. The heat exchanger requires flattening which is easy to do with a press and some fab work to make it fit in the MH tunnel. I used some aluminum strap and had it welded to the heat exchanger and then aluminum angle was welded to the strap (see pic above) the heat exchanger mounts in the stock MH holes and will be easy to swap from kit to kit. The hose is all 3/4" ID heater hose except for the little bit of hose that comes off of the head which is 5/8" ID. It may be hard to see in the pictures but I have a KTM thermostat and trail tech coolant temp sensor plumed in.

A single 3/4" port coming out of the head would certainly simplify the pluming and probably improve efficiency, do you know anybody that makes a head like that?

Got my second ride in yesterday and the system worked flawlessly. I made an effort to pay more attention to temps throughout the day and have revised coolant temps and a couple questions. With this system the thermostat is getting a workout I can watch the temps climb to 155-170 depending on how hard I am working the bike and then when the T-stat opens the temp suddenly drops to 130-140 and it just plays that game all day long.

Here is my question does that instant 30-40 degree drop in temp cause any expansion contraction issues with the cylinder? I don't want to be in the middle of a hard pull with a hot piston and then have it get squeezed when that cold water hits the cylinder.

Another added benefit that I don't think I mentioned is the added coolant capacity that this system has I think it takes about 3/4 of a gallon to fill it which is probably about three times as much as the stock setup. This added capacity equals better cooling and my coolant temps stay pretty warm even after sitting and eating lunch.

In your case, I would plumb in a bypass before the t-stat.

 

[Ausm7499]

In your case, I would plumb in a bypass before the t-stat.

My T-stat has a bypass but it's plugged right now. My concern is that the temps will never get up with a bypass.

 

[summitboy]

My engine machinist Adam from Millar Racing has converted piles of them to a single outlet. I asked him about it when i saw your thread. He also does the head decompressor which makes a big difference in kicking. Excellent CR500 big brain !

 

[PalousePoo]

Last season I had two 1/8" holes in my KTM stat, and that seemed to let too much coolant pass by, and temps wouldn't get very hot. To stop the radiator breaking off problem, quit riding with crazy Teal and Kerr!!!

 

[wwillf01]

My T-stat has a bypass but it's plugged right now. My concern is that the temps will never get up with a bypass.

So I am finishing the tunnel cooler up any other recommendations on your set up that you learned running this set up?

 

[Ausm7499]

So I am finishing the tunnel cooler up any other recommendations on your set up that you learned running this set up?

I only ran my setup for one season before I gave up on the CR500 dream but it worked much better than the radiators did. I never did hook up the bypass on the thermostat.

 

[jethro450]

I only ran my setup for one season before I gave up on the CR500 dream but it worked much better than the radiators did. I never did hook up the bypass on the thermostat.

Why did you give up on the 500 dream?

 

[Ausm7499]

Why did you give up on the 500 dream?

Several issues made me swap over to a MX 450. For one the 500 vibrates a lot which means you are going to have bolts break, loosen, and fall out, I had all of the above frequently happen. Carb icing was an issue which I think can be solved now with the avid carb heater assuming you can keep your coolant temps warm enough which can be a problem in cold deep powder. Keeping the motor on the pipe was difficult as well, I tried several different gearing variations and settled on a good ratio but still found myself frequently out of rpm needing to shift but not having enough power to pull the next gear and keep it on the pipe.

Bottom line the 500 takes a lot of setup and maintenance and still won't hold it's own against a 450 mx bike, I know a lot of you 500 guys claim that they will walk all over a 450 but I owned and rode both for a couple season and can tell you that was not the case for me and believe me I really wanted to make the 500 work. A couple other down falls of a 500 is the outdated frame geometry, not a big deal but something to be noted. The stock 500 forks flat out suck and need to be upgraded to crf forks. Lots of people don't like a kick start period especially on a 500 but I don't mind kicking and my bike was usually a one kick bike once warm. Another thing to note is fuel consumption is quite a bit higher than the 450.

 

[dhdey]

Several issues made me swap over to a MX 450. For one the 500 vibrates a lot which means you are going to have bolts break, loosen, and fall out, I had all of the above frequently happen. Carb icing was an issue which I think can be solved now with the avid carb heater assuming you can keep your coolant temps warm enough which can be a problem in cold deep powder. Keeping the motor on the pipe was difficult as well, I tried several different gearing variations and settled on a good ratio but still found myself frequently out of rpm needing to shift but not having enough power to pull the next gear and keep it on the pipe.

Bottom line the 500 takes a lot of setup and maintenance and still won't hold it's own against a 450 mx bike, I know a lot of you 500 guys claim that they will walk all over a 450 but I owned and rode both for a couple season and can tell you that was not the case for me and believe me I really wanted to make the 500 work. A couple other down falls of a 500 is the outdated frame geometry, not a big deal but something to be noted. The stock 500 forks flat out suck and need to be upgraded to crf forks. Lots of people don't like a kick start period especially on a 500 but I don't mind kicking and my bike was usually a one kick bike once warm. Another thing to note is fuel consumption is quite a bit higher than the 450.

you must have been way off on getting it running right. me and my buddy are both on 500's and they destroy any of the mx450's. kicking takes a bit to get used to but once your dialed its no big deal and fuel consumption is only slightly more then a 450. i think you have too much temp and carb ice issues to have a real feel for what the 500 is capable of.
..ya the vibrations suck...

 

[wwillf01]

you must have been way off on getting it running right. me and my buddy are both on 500's and they destroy any of the mx450's. kicking takes a bit to get used to but once your dialed its no big deal and fuel consumption is only slightly more then a 450. i think you have too much temp and carb ice issues to have a real feel for what the 500 is capable of.
..ya the vibrations suck...

I was surprise what gears I can pull on climbs.... I find I had to lower my revs a bit because it was not needed... But mine loves fuel.... I did swap to newer forks and I just got my tunnel cooler back from Mylers so they could reduce the line size and 90 them towards the bike... I will post pics tomorrow.. Interesting point about the carb freeze and using more fuel.....


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[Uncle si]

I think you had an issue with your 500. My bone stock kx5 is a whole lot more powerful than a KX450f -if- you keep it on the pipe. With 13-17-17-20 gearing and a 2.5x146" track she wheelies in gears 1-3 on flat snow. On wheels I have never hit the throttle stop.

 

[summitboy]

I have to agree. I have put my bike against 450s, 520BB, 610 BB and it does make them look slow. My friends (he is 20lbs lighter lol) 610BB would be getting stuck on a deep pow climb and my 500 would sail right past him and keep going. Its all in the porting and setup ! If your burning too much fuel and its most likely way to rich and full of ice gets u down on power imo.

Carb heat is a must. I made my own flange and i have been ice free ever since. The cooler is the best setup in my opinion, the 500 likes to get hot going up the trail. Once its in the deep snow you don't really need either the cooler or the stat. Some guys thought the motor would run too cold. Portgrinder kinda first tested that out and the 500 likes 90F all day long which some still believe too cold. I also found on the 500 the intake is crucial especially on my Pulse setup. Just hacking the bottom of the box off wasn't enough. I cut out the back as well which gave it all the air it needed for my big Pulse mains.

That 2 stroke pipe sure sounds nice in the backcountry compared to a wet fart paper bag 4 stroke LOL

 

[Ausm7499]

I knew you guys would be chiming in. Not going to argue with you but my bike was setup pretty good (pwk 39.5, gore porting, ran the gnarly and fatty pipe) and would flat out run hard but not hard enough. I would like to ride with one of you guys that has a 450 crushing 500 it might change my mind as I like the 2 stroke (run a 300 in the dirt) but I am going to have to see it to believe it.

As for fuel consumption I don't care how well you have it setup it's going to burn more than a 450.

 

[teal_210]

I knew you guys would be chiming in. Not going to argue with you but my bike was setup pretty good (pwk 39.5, gore porting, ran the gnarly and fatty pipe) and would flat out run hard but not hard enough. I would like to ride with one of you guys that has a 450 crushing 500 it might change my mind as I like the 2 stroke (run a 300 in the dirt) but I am going to have to see it to believe it.

As for fuel consumption I don't care how well you have it setup it's going to burn more than a 450.

Let that be a lesson - never ever say anything even remotely bad about a 500.

 

[jethro450]

Several issues made me swap over to a MX 450. For one the 500 vibrates a lot which means you are going to have bolts break, loosen, and fall out, I had all of the above frequently happen. Carb icing was an issue which I think can be sol.....

I hear your concerns on the carb icing and vibrations, but the one day I had the 500 out last spring for the first time ever, the first thing I noticed was it pulled a gear higher everywhere over my 450. And that was a stock motor. I had it ported and milled over summer and it's even better now. I'm pretty stoked to give it an honest go this winter, but I do worry about the carb icing issue. Running my 450 bone stock, no mods like thermobob or anything, I've only froze the carb twice in 7 seasons of abuse.

 

[SEOINAGE]

I hear your concerns on the carb icing and vibrations, but the one day I had the 500 out last spring for the first time ever, the first thing I noticed was it pulled a gear higher everywhere over my 450. And that was a stock motor. I had it ported and milled over summer and it's even better now. I'm pretty stoked to give it an honest go this winter, but I do worry about the carb icing issue. Running my 450 bone stock, no mods like thermobob or anything, I've only froze the carb twice in 7 seasons of abuse.

Debating a carb heat solution myself for the 500. But I really don't want to if I don't have to. Curious if the right intake, and maybe a carb boot that also wraps the motor? Or I have seen people use basic copper tubing to route around their carb, plus a boot.

My plan is to run it till it is a problem, then scramble to get a solution going so I don't miss riding. The stuff on the market looks decent, but stopping one of the outlets, and all the extra you have to put on the bike keeps me from wanting to do it outright.

 

[M5-]

Don't waste your time without carb heat it WILL freeze up fast they just move too much air not to freeze. What carb are you going with?

M5

Ps My 500 stomps my 520 BB KTM.

 

[Ausm7499]

My 500 would stomp my 525 but the modern day 450's are a whole different animal that rev's fast and high with a very broad power curve. I have ran a 06' 525, 09' 300xc, 01' CR500, and 12 KX450; The Kawi is by far the fastest most powerful and most versatile with the least amount of setup and tinkering. I know that no amount of words will sway you 500 lovers but these are my findings. I do believe that a big 2 stroke would make the ultimate snobike but not without a cvt.

 

[SEOINAGE]

Don't waste your time without carb heat it WILL freeze up fast they just move too much air not to freeze. What carb are you going with?

M5

Ps My 500 stomps my 520 BB KTM.

For now I am running the stock PJ carb.