Does anyone have experience with Athena Yz 300f big bore kit?

vanillaice782
Edited Date/Time 4/26/2015 12:29pm
Hey I just picked up a 2011 Yz 250f and I planned on racing it in an age class so displacement doesn't matter. I was always suspicious of big bore kits because they can have thinner cylinder walls. I just wanted to know of anybody had any experience with one and what they thought as far as reliability and how much faster it made the bike. Thanks! I won't do it for now but will probably bite the bullet if I have put in a new top end.
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racer369
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racer369 4/23/2015 12:12pm
4/23/2015 12:12pm
be sure and use engine ice if you do. that shit works
chillrich
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chillrich 4/24/2015 9:11am
4/24/2015 9:11am
I have about 80 hrs(?) on a Athena 290cc kit in a 2009 YZ250F. Here is what I've learned and experienced;

Get the Cometic or Athena head gasket for better head seal, they're expensive but good piece of mind.

There is also better water flow through the Athena gasket because the are cut for the passages in the cylinder.

I had a piston oil seal ring fail at ~25hrs on a JE piston that scored the bore and had to have it replated, not sure what the cause was though. Went with Athena to replace, everyone says JE is a great product too.

I started burning through clutches and ended up going with stiffer springs, EBC CSK137 are 15% stiffer and work fine with Rotella T 15-40 and Tusk plates.

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vanillaice782 4/25/2015 9:19am
4/25/2015 9:19am
chillrich wrote:
I have about 80 hrs(?) on a Athena 290cc kit in a 2009 YZ250F. Here is what I've learned and experienced; Get the Cometic or Athena...
I have about 80 hrs(?) on a Athena 290cc kit in a 2009 YZ250F. Here is what I've learned and experienced;

Get the Cometic or Athena head gasket for better head seal, they're expensive but good piece of mind.

There is also better water flow through the Athena gasket because the are cut for the passages in the cylinder.

I had a piston oil seal ring fail at ~25hrs on a JE piston that scored the bore and had to have it replated, not sure what the cause was though. Went with Athena to replace, everyone says JE is a great product too.

I started burning through clutches and ended up going with stiffer springs, EBC CSK137 are 15% stiffer and work fine with Rotella T 15-40 and Tusk plates.

How did the power feel? I loved the ktm 350 that I rode and was hoping for a little bit more power like it had.
chillrich
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chillrich 4/25/2015 9:26pm
4/25/2015 9:26pm
Power is more torquey and broader bottom mid, higher revs slightly flatter but I short shift and lug more so works for me.
vanillaice782 4/26/2015 12:29pm
4/26/2015 12:29pm
Good deal that sounds perfect for me. I would rather lug it a little than rev it higher.

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