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2009 YZ250F with Athena 290 Kit, Need to move on


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I'll keep this brief because I love the bike I just need to know from some mechanics... is this a sell or keep bike?

 

I bought a well maintained 2009 YZ250F with the Athena 290 kit (2013). It had about 20 hours on the new kit. I have put about 40 hours on it. I saw the maintenance records, so everything was in spec until I bought it. I knew about Yahama's figure out how to start it thing... but that came to crashing halt. I don't race bikes, don't want to, but I prefer the race bike to the trail bike... go figure. All these hours are soft, and suddenly it's like a demon I can't ride unless I force it down a hill. 

 

Now I get that someone is going to scream about hours but I'm not forcing it. I rarely ride above 8000 rpm. Either way, whatever, I'd rather take the bike to a shop but I want a guy's opinion before I pay. Because shops like to take money or do inferior jobs and take more money. Mechanically, I've worked on two stroke and four stoke engines since I was 12. This problem baffles me and I don't feel like finding tools to figure it out, I just want to ride. 

 

When I got the bike a it was hard to start unless you knew how. Now, it just won't start below 90 degrees. It has a weird hanging idle sometimes. Prior to that I know it was never professionally tuned for the 290 because it rides like a two stroke... lug lug lug... POWER. If I was a racer and rode in the rev range needed this would work, as is it was good. The lug thing has gotten stupid... and the transition to power kind of more like LUUUUUUUUUUUUUUG.. POWER. Another rider noted a weird vibration, and I wouldn't mention it except I might not notice it because I also ride quads and just don't care. I've learned on a bike (after 15 years of being off one) that every little thing means something. It doesn't make weird noises, aside from hanging idle, it doesn't sound bad, but it just won't start cold. 

 

I'm planning on going to 300 two stroke, but I'm not selling this bike to someone if it isn't fixed. My guess is valves are bad (hard starting cold, normal hot) and I will get a report on the internals when I get them shimmed or a call saying "you need a new top end". I've worked on a lot of engines, but they were all simple. Based on what you that have been doing this longer than me... is this bike worth keeping and paying for? Or should I get it in spec and sell it? I don't race, don't really want to, I just want to ride. I could fix a two stroke with my eyes closed, this whole four stroke thing... valves, shims, hours, cam chains, piston life, varnish in the carb, and everything being measured in less than a DAY? Screw that, I ride for fun not for work. I love my bike but it's become a monster... and yes that comes with buying used. 

 

So all said, I have a YZ290F that won't start cold period. It has a hanging idle now, and it's transition from lug to power is weak and doesn't usually work. It's my first bike back into the two wheeled dominion, I'd keep it if worked. Once alive it will carry me faithfully as far as I'm willing to push it. It will start after life and not a hard lay down on the first kick. The power is still there, if it is in the rev range. It's like riding some sort of weird beast that demands I force it to work, then it is happy to work as long as long as I don't make a mistake. I won't sell it broken, but thoughts on repair because I love it and would keep riding it? And because I think someone that knows the 4t engine could get a great bike. 

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Listen man, you are getting all freaked out over a clogged pilot jet. Your symtoms are 100% this.

 

Best bet, since you can't say how well it was jetted before you got it with the Athena jug, call up James at J.D. Jetting and have him put together a kit for you.

You have a great bike. Tune it so it runs properly and keep it for awhile. They aren't nearly as fragile as you seem to think they are. Or as complicated.

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I think the big bore 250's are some of the best bikes you can buy/build. Light, nimble, good power, no flame outs in the woods, no need for a rekluse, e/t/c...

 

That being said, you need to make a decision how you want to spend your time...If you have $ in the bank and don't feel like spending time on the bike dump it and move on.

 

Otherwise get your hands dirty and start with the 3 basics. Fuel Air & Spark

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jetting and check the vavles.  you could also call Travis at Thumper Racing, he has the jetting down for these big bore kits and will tell you which jets will work so you can cross reference what you have.

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the lug lug power profile has me sort of baffled. That sounds like rich jetting to me but that would contradict the "only starts over 90 degF symptom."

While i'm leaning toward jetting or a clogged PJ as stated previously, you need to do the basics as previously mentioned...fire,fuel, compression.

Clean the PJ circuit and get a NEW PJ. Take out the fuel screw and make sure all the parts are accounted for...screw, spring washer and oring.

During the checking of your valve clearance, check and make sure the cam timing is correct because if you jumped time, it will affect both starting and power delivery.

Like the others stated, don't get freaked out about the cams etc. If you can rebuild a 2T, you can do this.

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