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Athena 290 big bore

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I was just wondering what some peoples opinions are on the Athena 290 big bore on a wr or yz250f. Will I notice a difference in power? Is it worth the money? Is it hard on the engine?

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I used 290's  for ever.  I race and ride primarily off road.  Loved them.  Never had to change my maintenance habits going from 250 290.  It's the most noticable thing you can do to the yz250f.

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Do it! Best bang for the buck, great for woods riding and I love reeling those new bikes in on my old 01 when we get in the open fields, and for what it's worth , I stayed with stock compression ratio and have had absolutely no issues for 4 months now with weekly beatings

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290 makes you lazy😄. With good clutch control 3rd gear pretty much does it all. I love mine. Beautiful power for off-road riding. I run stock cams, standard compression and a ported head. Put 120 hours or so on first piston and have just over 100 on this one with no issues. Plan on going to 150 on this piston. Athena cylinder and pistons. I might have to replate cylinder at that point, just have to see. Clay

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I ran the 290 kit on my 07 WR for 3 top ends, I ran 100-120 hours per kit. The only thing that ever measured out of spec was the wrist pin. The chrome was pretty worn, if you can get a DLC coated wrist pin you could probably get 150-200 hours pretty easy. 

The power was like a 250 with more torque across the board. I never felt a loss of high rpm pull, and my tachometer confirmed the bike would still rev over 13,000 rpm's with ease. I ran a 14 tooth countershaft sprocket to spread the power out, ended up riding that thing for 10 years it ran so well. 

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Do it! Best bang for the buck, great for woods riding and I love reeling those new bikes in on my old 01 when we get in the open fields, and for what it's worth , I stayed with stock compression ratio and have had absolutely no issues for 4 months now with weekly beatings


Hey I’ve recently upgraded my yz250f with the Athena 290 big bore kit. But I can’t get it to run.
I have fuel, spark and air but still won’t run
Any ideas guys?

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, I had a shop do the rebuild with big bore,so I personally never had to experience the start up issues,  i do know they had the change cams for some reason and rejet the carb but dont know if both where done to maximise performance or to make the whole set up work correctly . Sorry for not being much help but I'm sure someonewill jump in.

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, I had a shop do the rebuild with big bore,so I personally never had to experience the start up issues,  i do know they had the change cams for some reason and rejet the carb but dont know if both where done to maximise performance or to make the whole set up work correctly . Sorry for not being much help but I'm sure someonewill jump in.

Ok thanks mate
Do you know the labor price for all that?

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I'm sure shop rates are differnt around the globe , but my rebuilds parts, porting and labor generally run around 3500 , but that is all new everything except cases and trans gears and stator as long as they check out.

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I'm sure shop rates are differnt around the globe , but my rebuilds parts, porting and labor generally run around 3500 , but that is all new everything except cases and trans gears and stator as long as they check out.

Ahhh ok thanks man

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18 hours ago, James2015 said:

 


Hey I’ve recently upgraded my yz250f with the Athena 290 big bore kit. But I can’t get it to run.
I have fuel, spark and air but still won’t run
Any ideas guys?

 

If you have all of those and the engine is timed halfway close, it would have to run. Check all three of those again and check the cam timing. 

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If you have all of those and the engine is timed halfway close, it would have to run. Check all three of those again and check the cam timing. 

Ok thanks man

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I have had mine for 300 hours of racing off road, changed piston and rings a few times and its still sweet, a very good upgrade for more power and torque!

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