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Discussion Starter #1
I just placed a RTK head on my mxz800 01.I failed to check the compression prior to the change.I now have 135 and 132 lbs .Am I in the ball park?This is a sea level head.I believe that the new head doesn`t change the compression.AmI correct.THANKS
 

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I can't speak to the 800, but my '02 700 Summit had 140 psi stock.
 

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cooldude, I just replaced my head with the rkt and had porting done with a shim kit and carbon tech reeds and my compression was 120. Stock should be around 140, dealer claim. I know my compression should be lower because of the shim kit but I didn't think that low. You didn't say you had a shim kit so based on your numbers I feel a little better about my low 120. My rings didn't have any flaking but the moly does show signs of wear. What are some other compressions fellas? I hooked up my belt and raised the rear and after warm up ran it up to 7000 and it never got above 700 degrees. When warmed up it idles at around 4-500 degrees. Anybody else see these similar numbers?
 

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check you gauges fellas, just used a different gauge and got 135 a side... whew.. i feel alot better about that...
 

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:) Stock compression test on my 01 MXZ 800 was 150lbs. and 152lbs. cold. Check your rings, by putting a little bit of oil down the spark plug hole and recheck it. If it raises the compression, it is probably time for rings. Seems to be an ongoing thing with the 800's.
 

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Discussion Starter #9
I guess I am o.k. with my readings.I wonder what the maxium compression
that we can run on pump gas?I didn`t check the squish,but I think that we could safely run 145-150 lbs.Would have to cut the domes to achive it.I would think that it would be a must with porting.Any thoughts.. SWRules
 

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Cool Dude - I am guess ing your gage is a little de-funct. I have 2 gages, one reads 130 lbs and one reads 148 lbs in the same cylinder.

Also, there is allot more to consider than just PSI when it comes to fuel. Squich band, squish angle, volume and compression ratio all have to be thought about.
 

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Discussion Starter #11
I guess I`m from the old school and time when the easiest mod was to plane the head and increase the engagement.You are hitting on the techinical side of things which don`t get me wrong ,I try to understand but tend to overlook the many variables.I will try a different compression guage
to get a true reading.Any help greatly appricated.
 

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well i decided there was enough snow on the ground to run down the street to check everything out and it seems fine up to 7000 as that is all I had room for. Temps never got above 800 degree and they were right around 700 at 6000rpm. I'm at 430 mains right now with the stock pilot and needle. Looks like I still have some room to come down and will probably have to shim the needle down. This is with 130-5 lbs in both cylinders. These compression gauges are amazing, not! My pyro is pretty consistent with both cylinder temps. whew.... Should I even waste my time with a shim for the needle or should I just get the 942 needles?
 

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Discussion Starter #13
MXZ800!!You the man.I had #1 son bring his snap-on compression tester home from the shop
and Voila 165lbs on each cylinder.Quite a difference.I feel much better now.I guess my 55 yr old arms vs his 28 yrs didn`t hurt any either.I guess I will just have to spend more time at the gym.Now to install my goodwin.I`m a firm believer in lots of weight.any suggestions?Thanks all... SWRules
 

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On my 02' 800 I got 135 per side. Havn't checked my 03' yet 9gives me something to do tonight)
 

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cool dude i have the same sled as you with a rkt head,i moved the shim on top of my needle,so far so good,im also running 450"s(for now)if you move the shim let me know your temps in midrange and wide open..thnx
 

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Discussion Starter #16
Bare ground here still.May have to travel to c.b. highlands to get the bugs out.I don`t have exhaust temp gauges,but I moved my shim and jetted down to 480`s last winter with the stock head.I had no trouble at temps of 0 degrees f .I ran a Dalton 50/44 with the gold belt and was very pleased with both the performance and the milage.I am expecting better this year.I have had the 6`s 7`s and the 800.All have been great sleds.I was a little disappoint with the 800 at first ,but it came around with a little coaxing.Enough of this chatter........ SWRules
 

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oopss sorry i meant skidude..lol :)
 

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I'll try moving the shim tonight when I go out. Last night I went back out and put about 5 miles on it checking the temps and clutching. My temps at 6000 and 7000 never got above 1050 so I'll try moving the shim tonight and I'll post my temps. Clutch felt great but I think I can put a little more weight in the end. LET IT SNOW!!!
 

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ok sounds great can you also note the ambient temperature...thnx
 
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