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08 800R Top End

800r ptek

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#1 Flemingo

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    2008 Summit 800r Ptek 146"
    146"x16"x2.5" Flex Edge Track
    19/45 Gearing
    Grip-n-Rip S Mod Brace and Upper A-arm Braces
    Bronze Oillite A-Arm Bushings
    Ceramic Coated Exhaust from FireBall Performance Coatings
    PDP Snowflap
    Team-KOS Front Bumper
    Stator Kev Rewound OEM Stator
    MCB Performance Cast Dual Ring Pistons
  • Sled:2008 Summit 800r Ptek 146"

Posted 14 October 2018 - 09:24 PM

Bought this sled in July been going over it since. Before I bought the sled I did a compression test. I bought my compression tester at Crapy Tire so I don't exactly trust it.
 

The test read about 120psi each side (throttle closed), I don't remember the exact readings, but it was in that ball park(115-120). The sled has 6k km on it so I was expecting low compression anyways. The guy I bought it from said he had done a top end before the previous season, but I figured he was lying, he couldn't even give me an answer on what pistons he put in it. I named all the popular manufacturers off the top of my head, but he couldn't decide lol.

 

So I got the sled and I've been going over it, so far I've cleaned the carbs(people recommended I shim the needles 0.20 to solve the midrange lean issue, so i did), cleaned the R.A.V.E. valves, replaced and repacked the PTO crank seal and some other little things. I haven't gotten around to diagnosing the top end more thoroughly So I figured I would, even though I was sure it needed a rebuild anyway.

 

I have done some research on compression tests, some people say to compare hot to cold psi and I've also read people saying about to have the throttle open and some say to leave it closed. A quick word about "hot" compression, I let the sled run for about 3min. I would have liked to let it run longer, but I only have time to work on my sleds after 9ish so didn't want to "edit for bad language" off my neighbors.

 

*I attached a picture of the results*

 

 

So I think its pretty clear I need a top end rebuild. I think I'm going to go with the MCB Dual ring pistons, I have read a bunch of people recommend them.

 

Should I hone my cylinders? Is there any issues to look out for on these engines?

 

Any input is appreciated :)

 



#2 Flemingo

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  • Interests:Previous Sled: 1997 Formula 500

    2008 Summit 800r Ptek 146"
    146"x16"x2.5" Flex Edge Track
    19/45 Gearing
    Grip-n-Rip S Mod Brace and Upper A-arm Braces
    Bronze Oillite A-Arm Bushings
    Ceramic Coated Exhaust from FireBall Performance Coatings
    PDP Snowflap
    Team-KOS Front Bumper
    Stator Kev Rewound OEM Stator
    MCB Performance Cast Dual Ring Pistons
  • Sled:2008 Summit 800r Ptek 146"

Posted 14 October 2018 - 09:27 PM

effd7811c28e7f99cef1b22395d17670.png


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#3 Flemingo

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  • Interests:Previous Sled: 1997 Formula 500

    2008 Summit 800r Ptek 146"
    146"x16"x2.5" Flex Edge Track
    19/45 Gearing
    Grip-n-Rip S Mod Brace and Upper A-arm Braces
    Bronze Oillite A-Arm Bushings
    Ceramic Coated Exhaust from FireBall Performance Coatings
    PDP Snowflap
    Team-KOS Front Bumper
    Stator Kev Rewound OEM Stator
    MCB Performance Cast Dual Ring Pistons
  • Sled:2008 Summit 800r Ptek 146"

Posted 15 October 2018 - 01:06 PM

Anyone?


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#4 stealth bomber

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Posted 15 October 2018 - 01:32 PM

Even if your gauge isn't accurate, 25 psi difference between sides says something is going on there and it's time to come apart.

I think the MCB stuff is a viable alternative to pricey oem parts.  I used SPI in my buddies 800R a couple years ago, it's still going strong.

As for the cylinders, I have honed them, not honed them, replaced one side with rebuilt next to an original cylinder and the compression numbers always even out after break in.  So IMO it's not mandatory to hone them if they are in good shape without scuffing.  I clean them well with Scotchbrite and Varsol, then wash with hot soapy water and dry with compressed air.

Things to look out for... separated motor mounts, frayed oil pump cable, delaminated reed boots, cracked y-pipe or missing bolts.  Worn crankshaft bearings would be my biggest fear.

 

I think you need to decide if it's worth just doing the top end in the sled or if it would be a better idea to pull it and go through the whole thing.  How many miles?  Crankshaft runout check and a leakdown test may help you decide. 



#5 Flemingo

Flemingo

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  • Interests:Previous Sled: 1997 Formula 500

    2008 Summit 800r Ptek 146"
    146"x16"x2.5" Flex Edge Track
    19/45 Gearing
    Grip-n-Rip S Mod Brace and Upper A-arm Braces
    Bronze Oillite A-Arm Bushings
    Ceramic Coated Exhaust from FireBall Performance Coatings
    PDP Snowflap
    Team-KOS Front Bumper
    Stator Kev Rewound OEM Stator
    MCB Performance Cast Dual Ring Pistons
  • Sled:2008 Summit 800r Ptek 146"

Posted 15 October 2018 - 02:22 PM

Even if your gauge isn't accurate, 25 psi difference between sides says something is going on there and it's time to come apart.
I think the MCB stuff is a viable alternative to pricey oem parts. I used SPI in my buddies 800R a couple years ago, it's still going strong.
As for the cylinders, I have honed them, not honed them, replaced one side with rebuilt next to an original cylinder and the compression numbers always even out after break in. So IMO it's not mandatory to hone them if they are in good shape without scuffing. I clean them well with Scotchbrite and Varsol, then wash with hot soapy water and dry with compressed air.
Things to look out for... separated motor mounts, frayed oil pump cable, delaminated reed boots, cracked y-pipe or missing bolts. Worn crankshaft bearings would be my biggest fear.

I think you need to decide if it's worth just doing the top end in the sled or if it would be a better idea to pull it and go through the whole thing. How many miles? Crankshaft runout check and a leakdown test may help you decide.

I have checked the motor mounts they’re good, I’ll check that oil pump cable, reeds are good and just got the whole exhaust ceramic coated so I know the y pipe is in good shape lol.

As for the crank bearings, the sled has about 6000km on it so I’m not sure. Do you have a link to a thread on how to do a leak down test and how to test crank runout? And when when you say “go through the whole thing” you mean a crank rebuild, right?


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#6 stealth bomber

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Posted 15 October 2018 - 03:00 PM

I'm not having any luck pasting a link into my reply but if you go into the rev chassis trail forum, at the top of the pace there is the FAQ subforum, click on that and then engine subforum, you will find a good thread on how to do a leakdown test.  First I would check runout of the PTO crankshaft stub with a dial indicator.  Crank bearing condition... that's anyones guess unless it comes apart for inspection.  The inner main bearings seem to go first.  At 6000km you might be ok for a while yet, but it's hard to say without checking them.   



#7 Kbar

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Posted 15 October 2018 - 04:38 PM

To the OP.  I will send you a PM


Past Sleds - 1976 Olympic, 1979 Citation 300, 1986 Tundra, 1990 Safari L, 1993 Bravo, 1991 Formula Plus, 2008 MXZ 800


#8 Thumb2bar

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Posted 15 October 2018 - 06:22 PM

Compression readings are weird. There are a lot of factors that make a piston and ring ride correctly in a jug, and seal correctly. Low rpm dynamics vary greatly from what is happening at 7,000+ rpms with heat .  I had a strong reading on my 09 800r around 135 per, after six years, 6,400 miles. Good gauge, swapped to other motors, verified close. I would scratch the jugs a bit , with a wire hone or rough scotch brite. New rings ask for some love. To me, I would not throw a ton of ching into an 08 motor. Go about your plan, redo top, and then hope you can get some good miles with smiles. Stock 08 motor was improved upon with 09 and then 10 800r cranks and bearings. If you really love the sled, think about dropping around 2k into a complete, new tight motor with new crank,  bearings, seals, pistons, blah blah.



#9 MCB Performance

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Posted 18 October 2018 - 08:47 AM

"Low rpm dynamics vary greatly from what is happening at 7,000+ rpms with heat" 

 

The importance of this comment cannot be understated. This is exactly why you hear stories of 80 psi engines that continue to run with only a slight loss in power. They are still a ticking bomb, but still running.

 

- Scott @ MCB  


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