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Just bought 2 07's: What Maintenance Should I Do?

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From what I recall, both bikes had similar power. Neither bike has had any major engine work (from what I was told, no tear down or rebuild). Any suggested tests I should run to look for problems?

Bike A:

One of the bikes is in excellent condition, runs great and starts in ~4 kicks w/o throttle, but it does backfire a lot (mostly under engine brake condition but also on throttle blips). Is this a carb issue? Should I do maintenance there?

Bike B:

I don't want to comment on how the bike starts just yet, i need to test it out a few more times. But once started it noticeably vibrates a lot more than bike A. It feels like: if there were rubber engine mounts, the rubber would be worn out. Also, the choke plunger is worn out and doesn't stick in the out position very strongly. Unfortunately that's all i can say about it right now. I'll ride it a little today and see if I can take more notes.

I'm concerned about Bike B and think I should start doing some engine maintenance on it right away. I was thinking, Piston, Ring, wrist pin and timing chain and check the valves while its apart, but i'm really not sure what is best here.

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On Bike A it sounds like a carb issue and is the most painless to address through the carb. Sounds like you need to go up one size on the pilot jet. Because you are in Texas you may be able to get away with a 42 pilot even if its winter. You can gain access to the pilot through the float bowl drain plug on the bottom of the carb, no need to remove the carb.

On Bike B, I am not sure. Check to make sure that all motor mounts are torqued to specification, especially the head stay under the tank. Another possibility is the crank bearings going out. After some searching on TT most seem to say to look for bronze,copper-colored shavings in your oil and/or excessive vibration at the footpegs when the crank bearings are going...

I have an '07 and love the thing. It is my first bike in about 8 years after racing quads in my youth and I have not had any mechanical issues with the thing, granted I stay up on all of the maintenance. Just had to adjust the valves at 78.2 hours and am loving this bike! You picked a good year!

Good luck and keep us posted.

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I have put about 45 hours on my '07 in less than a year, I love that bike, I did a rebuilt head with KW SS valves, JE 13.8:1 and new timing chain, the bike runs like a top! Bike A you just need to do the team green jetting...all of it including the needle, it really wakes the bike up! Im not sure about bike B but I would probably look closer for sure.

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I would check the connecting rod for any play as well in bike b. When I replaced my topend it was borderline within specs and I decided to let it slide and I ended up paying for it in the long run. With the new crank in it runs so much smoother.

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Thank you so much guys for your suggestions.

Does someone sell a carb rebuild kit with all the things I need? Including springs for the choke and everything?

Chily: if I just replace the piston rod wrist pin and ring, will that fix this concern? Or are you suggesting the crank be replaced also?

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When you have the piston off just check the rod for play, if it has play you might want to go ahead and replace the crank or you risk grenading your motor. I am sure there are a couple guys on here that could chime in with more info though.

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Ok, I swapped the stock #40 pilot jet on bike A for a #42... it fixed the backfiring all together. Thanks race250r.

I love how the internet community is smarter and nicer than the guy at the parts counter of my local off road store.

I'm going to rebuild the top end soon and see if i find anything interesting in there.

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Hey m8 congrats with the new bikes ..To fix the Choke not sticking Use a zip tie on the choke.

Search How to Fix YZ250f Choke

That should work

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