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Just Bought A YZ250F With Engine Problems-Where To Start?

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Like the title says I bought a "parts bike" for a really good price. The guy told me that it had been getting harder, and harder, to start and that occasionally it would backfire. He seemed to think that the intake valves were gone. Bike will not start at all at this time. Have not tried to bump start it yet, but will not start with the kickstarter-does not even pop, or sound like it's trying to fire.

 

I figured I could part the bike out for less than I paid for it and make a little money if it comes to that so I bought it.

 

The good; The engine turns over. The bad: The engine turns over very easily like it has no compression. Seriously I can just rest my foot on the kick starter and it will fall all the way down. If I put my hand over the exhaust I can feel air coming out while kicking so I know the crank is good, and the kickstarter is turning the engine internals.

 

I guess I'm wondering where you guys would start. Compression test? Or, jump straight to checking valve clearance?

 

 

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Theres no need for a compression test if you feel none while kicking it. I would start off with valve check and depending get all that to spec and i'm almost positive that it will fire right up. IT sounds like its your intake valves.

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Chase thanks for the info. I was able to get it to start using starting fluid. I squirted it with just a tad into the air filter/box and then choked it, and kicked it and it fired right up. It is backfiring through the air filter and will not idle so I believe you are correct, the intake valves are probably zeroed out and no longer sealing.

 

So, who has the best deal on doing head work if I pull it and ship it off? Do you need to swap over to stainless valves like we do with the Honda's? 

 

I've heard that it is mandatory to change the timing chains on these bikes when doing a top end. Any place to pick up a timing chain, valve set, springs, valve guides, etc;????

 

I was very relieved to hear the engine run. It verifies that the crank & bottom end is good and that is very good news. I don't mind splitting cases, but if I can avoid it, and the costly crank rebuild/replacement, I'm better off. I think I'll fix this bike and sell it off. The exterior of the bike is flawless with lots of new parts on it to include chain & sprockets, grips, both tires, graphics, new set of bars, new bar pad, all new plastics, new seat cover, looks like the forks have been serviced.. I can't believe I picked it up so cheaply. I guess when faced with internal engine work on a 4 stroke it just scares the crap out of some people. The guy I bought the bike from said that he already bought a new bike and did not want to work on this one anymore. Lucky for me (I hope!). I seem to find these cheap deals, that turn out being not so cheap wihen it is all said & done.  I better start a sheet tracking my expenses.

 

First Yamaha motorcycle for me. I am all Honda's at the house so far, and now a blue bike to mingle in with the rest of them.

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Im with Chase, pop the valve cover off and check that out. And no on the switch to SS....complete oem replacement with a 5 angle seat cut is typically recommended and will last a lot of hours with proper bike maintenance. I dont know if you have ever tried to seat them by "lapping" in the past, but this is a big no-no with the OEM Ti valves. The timing chains are a preventative maintenance item, I just go with the OEM ones again and with a top end sounds about right. Far as where to get it all. Well...you can find some deals on ebay sometimes. Otherwise just keeping an eye out for people selling stuff. In fact, I thought I seen someone in the classifieds selling some OEM stuff. I dunno if its ALL you need, but may be some of it.  I guess I would make sure its the valves first though, lol.

 

 

If you're in a hurry, anywhere (ie motosport or TT) sells oem parts. I would agree on tracking the expenses before you even do it. Depending on what you paid for it and what year it is (because i didnt catch it if you said what year)....it may not be worth it. I would check values of running bikes of similar condition to see if there is any profit to be made. You can assume if you have to do valves and you do go OEM...you're going to need to send the head or take it, to a qualified machinist to cut the seats for you. Basically plan on it being around $600 for all the components (valves, gaskets, timing chain, etc) and head work (roughly). I mean you may be able to find someone else parting out a bike with a complete head thats still ok for much less but has "some" hours on it. Put that on, and sell your head as parts.

Edited by J_YZ2fittyF

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If I end up fixing it, I will fix it right. My last flip project turned into a nightmare and I ended up putting too much money into that bike. I still have it as I could not get my money back out of it. Not complaining as it has been a great bike once I pumped some life, and love, back into it. ($1500 +/-).

 

I'm hoping I can fix this bike for a reasonable price and then sell it. If I keep it I will have to re-spring it for my weight, re-valve the suspension, and all the other things that people do to make a bike their own. Better that I fix it and sell it instead of getting into all of that.

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Well, a flip is a nightmare the minute you start losing money...kind of defeats the purpose because at very least you should of made a LITTLE off it to be worth your time and effort. So all I was saying was try to price it out as best as you can and compare your total costs + bike price with what values are. Obviously you dont know for sure what it will cost to fix yet or what itd sell for, but its better then blindly spending $ on it if you're sole purpose is a flip. I mean they are good bikes if you do the work right.

Edited by J_YZ2fittyF

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Is it common for the cam to get damaged if the valves zero out? That's what happened on a Honda I had. Valve zeroed out and then took out the bucket & the cam.

 

I'll pull it all apart tomorrow and post back after I check valve lash, and get a visual on the cam.

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Is it common for the cam to get damaged if the valves zero out? That's what happened on a Honda I had. Valve zeroed out and then took out the bucket & the cam.

Not with a Yamaha, or at least not in my experience.

I can get get the seats cut for $100 around here.  I just did one of these and went back with stock valves.  If you go stainless, you gotta do springs too.  Some guys replace springs, keepers, etc every time, so consider and inspect... good luck.

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