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ATV Racing Top end??
http://www.pilotodyssey.com/PO/viewtopic.php?f=25&t=14596		 Page 1 of 1
Author:  rarerat [ Wed Aug 06, 2014 6:12 pm ]
Post subject:  ATV Racing Top end??
Hey guys,
What direction would you all go with this top end? The head has been milled and what else I don't know, it has ATV scribed to the side of the cylinder. It had 146 lbs of compression here @ 5500' cold. When I shined a light up the exhaust port I could see some marks so I pulled the cylinder off for a better look. I pulled the top ring off & slid it in the cylinder in it looks like it has 22 thousandths gap. The piston is 80.5 and clearly wasn't real happy in the cylinder. There is a grove in the piston and a mark in the cylinder to match. It also looks like there is a mark above the top ring grove right at the ring pin. The cylinder doesn't feel to bad but the piston you can feel the groove with a finger nail pretty good. Previous owner claimed the Engine work was done aprox 7 years ago but the owner passed away right after & it just sat. The daughter said their teenage son had been riding it a bit with premix gas bought from a auto parts store, basically weed wacker mix @ 50-1. :shock:

What would you guys do with this? Can this piston be cleaned up and reused or do I just need to go to 81mm? I was really hoping to swap this into my Pilot.
Thank you in advance,
Nick

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Author:  rarerat [ Wed Aug 06, 2014 7:34 pm ]
Post subject:  Re: ATV Racing Top end??
A few more pics..

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Author:  Pilot bird [ Wed Aug 06, 2014 9:47 pm ]
Post subject:  Re: ATV Racing Top end??
Hone the cylinder then see if boring will be required, if not maybe you can get away with just replacing the piston. I was very lucky in my 500 and only need to hone the cylinder and get a new piston:)

How does the bottom end look?
Any pics?
Does it look to have a lot of hours, will the bottom end need to be serviced?
Author:  rarerat [ Wed Aug 06, 2014 10:03 pm ]
Post subject:  Re: ATV Racing Top end??
Thanks, I think the bottom end is good to go although I didnt do a leak down before pulling the cylinder. I don't think there are any 80.5 pistons available is the reason I was asking if this one might still be salvageable. I guess I should grab an 81 while they are still out there for down the road. :-)
Author:  Pilot bird [ Wed Aug 06, 2014 10:16 pm ]
Post subject:  Re: ATV Racing Top end??
rarerat wrote:
Thanks, I think the bottom end is good to go although I didnt do a leak down before pulling the cylinder. I don't think there are any 80.5 pistons available is the reason I was asking if this one might still be salvageable. I guess I should grab an 81 while they are still out there for down the road. :-)


Sorry, brain fart! Thanks for enlightening me:)

I thought Steve was looking for the same size piston? Maybe a group buy is in order;)
Author:  rarerat [ Wed Aug 06, 2014 10:39 pm ]
Post subject:  Re: ATV Racing Top end??
I think he is, but last I heard he hadnt found one. :-(

If it has to go 81 because I cant find a piston, I wonder if I could clean up any ruff edges of the one groove in the piston and just run it for a while as long as the compression is up?? I ASSume I cant hurt any worse where it wouldn't clean up @ 81??
Author:  rarerat [ Tue Oct 21, 2014 7:58 pm ]
Post subject:  Re: ATV Racing Top end??
Thought I would do a follow up on this Engine. I took a piece of sand paper on a paint stick and cleaned up deep grooves in the 80.5 piston a bit, this was before adnoh was so kind to have some made. I did a real light hone on the cylinder but I didnt really have the right hone so it didn't turn out that great. :-( I bolted it all back together with a Speedchaser base gasket, leak tested it and installed in my Pilot. I've run 8 gallons of fuel thru it so far and knock on wood runs really well. Just did another compression test on it today and to my surprise with the pull cord I got 155, here @ 5800'. :-)

Ahh... The Pilot gods were smiling on me.. lol... :-)

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Author:  adnoh [ Mon Oct 27, 2014 6:06 pm ]
Post subject:  Re: ATV Racing Top end??
I see the c- clip is not installed correctly. The open end should face either up or down. probably be ok. If you installed it up or down and the c-clip has rotated than it should be replaced. The rings show a lot of blow by. You put new ones in it ?

Adnoh
Author:  rarerat [ Mon Oct 27, 2014 8:00 pm ]
Post subject:  Re: ATV Racing Top end??
adnoh wrote:
I see the c- clip is not installed correctly. The open end should face either up or down. probably be ok. If you installed it up or down and the c-clip has rotated than it should be replaced. The rings show a lot of blow by. You put new ones in it ?

Adnoh



Thank you sir, I did not realize the clip was installed incorrectly, that was the way it was installed when I took it apart. No new rings, just bolted it back together with a new base gasket. Honestly I wasn't really sure what to expect as I have almost zero experience with Pilot engines. It ran well before I pulled it apart so i had hoped it would be ok to get me thru a couple of rides before the season was over. Over this winter I will pull it back off and swap in the new 80.5 i got from you or if it needs bored an 81.0.

Thank you again sir for the info and of course for your work getting us all a new 80.5 pistons made. :-)
Author:  mudbogger [ Sat Nov 01, 2014 7:45 pm ]
Post subject:  Re: ATV Racing Top end??
Adnoh both rings look like they are allowing blow by or IMO the bottom only. Please if you could illustrate the section/s where you see a possible leak if you could, I love the science of it.
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