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Making HP ain’t free. . .
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If it’s pushing coolant it’s more than likely a HG. I don’t think it’s a compression issue. I know I’ve mentioned this numerous times, but I’m at 13.4:1, and I run 91 octane. And I’ve been to some very tight, technical, rocky trails in Missouri and northern Minnesota, and I’ve been to the dunes on the west coast on hot summer days many times and I’ve never had a problem, granted, sometimes I sneak some race gas in the 501 just because I had it on hand for my 542.

I remember one of my 501s I built I was pushing coolant on one of the first rides after the build. I finished the ride, pulled the head, and I could see where it was leaking. I cleaned it up, threw a new gasket on it and ran it for a few years without another single HG issue.

I would say stick with the setup you have, make sure you clean up the surfaces really well, use a new gasket, and torque it in several steps to 40 or just a touch over.

I personally have never seen the need for a different rad. I’ve ran my 542 with 14.2:1 in the dunes on some crazy hot days, riding for hours straight and I’ve never seen my light come on, and that’s with a stock rad, hoses, and impeller, and I’m just running Honda HP coolant.
 

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Truck Yea
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5,625 Posts
Discussion Starter #42 (Edited)
Im going to go down to 12:1, its only a little bit and then I wont have to worry. we are going to check the head and replace the head gasket and of course check the head for warping

Theres an old school trick I used to use as a tech, take the rad cap off and take a plastic bag and put it on the neck where the cap goes. then rubberband it tightly on there. if it pushes out you know you have exhaust gasses being vented out. did that and a leak down test same way and nothing.

I truly think its a very minor leak if anything, but it tends to get very hot. The 04-05 I had ran much cooler, maybe the oil cooler helps. Ill slap on the water pump and rad and see where it all takes me to with the new piston. Friend of mine had the same setup and same issue awhile back-we swapped to a cut down piston no more problems. Its not a huge deal, i expect things like this to happen sometimes. I will say, there are days I miss the old 400EX..tractor like power down low and unkillable. 450R can be fickle.
 

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Truck Yea
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5,625 Posts
Discussion Starter #43 (Edited)
Small update for those interested (hoser and duke) lol.

I am waiting on doing the HG with my friend as we want to look it over carefully and he has way more experience. Too bad it got stolen and then thankfully recovered or we would have it done already. still waiting on the scumbag to have his trial too.

Went with a 12:1 piston from az quad parts this time around. considering how hard it is to get even 91 octane in some areas Im going to play it safe. The quad had plenty of balls anyways and likely will have plenty more. if anything I think the heat is getting to it a bit, as when its colder and thus slightly more lean and less heat soak it of course runs better

I wish I had done the frame, but meh I just keep spraying up the left frame by the shifter since that seems to the only spot that really was bad. Maybe one day ill take it down and do it all up. but after doing 3 of them over the years it really isnt worth it to me.

Also Glamis in Feb for prez day weekend if Biden dont shut down the country
 

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Making HP ain’t free. . .
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4,440 Posts
Lol! I think you got other guys following along but just not saying anything lol.

Just rip that head off and have a look. It’s usually pretty easy to tell where the gasket failed if that indeed is what happened. Like I have said before, I’ve had one go not long after break-in, replaced it and never had another problem for years and that was running 13.4:1.

Glad you got a plan figured out. But because it’s me and I blab about it all the time, I just have to say. . . . .MORE COMPRESSION!! Lol! Jk. I hear ya, it can suck to not have good gas on trail rides and constantly worry about it. I bought some good octane booster that I keep in my parts tote that goes with me whenever I hit the trails, and if there is no good gas I can dump that in and still ride, but usually I just take a couple race cans full of good 91 non-ethanol when I head out.

I hear ya on doing the frame, it does look nice when all done, but yeah, a lot of work and extra money. . . . .
 

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Truck Yea
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5,625 Posts
Discussion Starter #45
yea next 2 weeks we will get to it. truth be told i have little motivation right now as im still sorta PO about the whole left. its mostly back to what it was. still waiting on the quad tech seat.

As for compression, hell if I could reliably get 100 octane id run 14:1 lol but trust me been there done that and it sucks when your out on a ride miles from home and need gas...only to find out they have freaking 89 or 91 as the only real high octane options. Octane boost helps but it isnt the best idea. I was in NH a few years back..had like 1/4 tank left.. 87 was all they had. I literally filled it up about halfway to make it back then drained it all out when I was able to get back to my stash of good gas

right now im working on beadlocks and possible new paddles if i can get them. due to covid seems EVERYTHING is out of stock. sick of the paddles leaking. i did find a GPS set (remember the vendor stopped by to say high) Im gonna try to order today

as for the frame..yea i still wanna do it but man hate taking it fully apart again. takes a good day to put it back together taking your time
 

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Truck Yea
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5,625 Posts
Discussion Starter #46
Dropped it off to my buddy today. Putting a 12:1 piston in place of the 13:1 just to play it safe as depending on where I go gas can sometimes be an issue. New headgasket and going stage 3 hotcam.

At this point were at: Athena 490 kit 43mm FCR carb, full race port with +1 valves and kibblewhite springs, stock intake with open air box and a dasa. I want to see how the stage 3 cam does the stage 2 is nice all around but the top end seems lacking imho. Im hoping Ill like the cam and I didnt waste 250 bucks..

Already put a nice mishimoto rad on it and a boyesen water pump. I had wanted to do a fludyne rad but cant sem to locate one that doesnt cost 2 arms and a leg.

Also doing all the tires as the b-tards who stole it wore them down to nubs riding on the road. Amazing what 3 hours of road riding will do.
 

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Truck Yea
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5,625 Posts
Discussion Starter #47
And we broke it in tonight. HOLY crap. All we did was a 12:1 piston and the cam, its a monster now.

Figured out the head gasket did indeed fail, the headgasket broke apart upon disassembly. Found out something VERY important too...

the athena headgasket is [email protected]. Thing was cheap junk compared to the cometic one I replaced it with. We found the failure point as well.
 
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