Jump to content
Sign in to follow this  

New owner, help don't know what to do...

Recommended Posts

Hey guys, i just got a 2002 yz250 from single owner, he gave a bunch of stuff like seals, yamaha decals and stuff, he bought the bike and used it on a farm.. When i picked up the bike, it started after 3 or 4 kicks from cold, but it felt kind of easy to kick, i mean i dont have any point of reference im just going from what i've read here, that it's really hard to kick and  what not, when i got home i even kicked it with flip flops( I KNOW ITS NOT A GOOD IDEAD) i just wanted to make sure it was easy... Im about 5'8" 180 pounds..

 

I ride street, couple of crotch rockets. When younger about (20 years) had cr 125 and did the whole track thing. I have no idea what to look for on a smoker....

I rode the bike, off the line it wanted to lift the front, but that was it, 2nd 3rd and 4th felt pretty mild, no kicks or anything, as i got higher in the range it felt like gargling...pretty sure it's been stiing with the same fuel for at list a month...

 

 

So after introductions here she is.....please tell what to do, what to look for how to bring it back , i can hold my own with a wrench so dont be afraid to get technical..... THANKSSS

 

https://www.dropbox.com/s/jjvulboyxs3m6kf/2013-09-01%2019.55.41.jpg

https://www.dropbox.com/s/9fhqkgwn8vxhtip/2013-09-01%2019.53.09.jpg

https://www.dropbox.com/s/onx2d3yezbdgu6t/2013-09-01%2020.02.35.jpg

https://www.dropbox.com/s/ftlgsvzul0nvh7a/2013-09-01%2019.52.07.jpg

Share this post


Link to post
Share on other sites

If it were me I would at least do a fresh top end in it but more than likely I would replace bottom end bearings & seals too,

I've always found when I accrue used bikes there not as fresh or in as good shape as the sellers let on

I'm a firm believer that preventative maintenance is cheaper than waiting to do repairs

Eg: cheaper to do a top end before it lets go and needs a rod & cylinder and maybe more depending on the 2 stroke gods that day lol

Share this post


Link to post
Share on other sites

Hey thieaux. Nice looking bike. My bike started as a '02. I would start by getting your dial indicator out and checking the condition of the big and little rod end bearings. This will give you starting point as to how far your going to get into the motor. Use the timing thread in this forum, very helpful. While you have the stator cover off give the crank a quick shake to check for any play. If all is good I'd pull the cylinder, check/ measure and replace as needed. While apart clean power valve and carb. These are good bikes and are very dependable with just a little PM. Use this forum to your advantage, its loaded with good info.

Share this post


Link to post
Share on other sites

Sorry to say is sounds to me like the all too familiar "you bought a YZ250 with a blown top end" .  The first step needs to be a compression test with a gage. Those YZ250's are up around 175 psi. You say the bike does run but the power is poor ? I'm betting the psi is down around 125 psi which suggest a worn out top end. Hopefully the cyl bore is still good. The top end will need to get torn down.

Share this post


Link to post
Share on other sites

Hey thieaux. Nice looking bike. My bike started as a '02. I would start by getting your dial indicator out and checking the condition of the big and little rod end bearings. This will give you starting point as to how far your going to get into the motor. Use the timing thread in this forum, very helpful. While you have the stator cover off give the crank a quick shake to check for any play. If all is good I'd pull the cylinder, check/ measure and replace as needed. While apart clean power valve and carb. These are good bikes and are very dependable with just a little PM. Use this forum to your advantage, its loaded with good info.

Thanks trailman very helpful. Ill start it off and update....

Share this post


Link to post
Share on other sites

Sorry to say is sounds to me like the all too familiar "you bought a YZ250 with a blown top end" .  The first step needs to be a compression test with a gage. Those YZ250's are up around 175 psi. You say the bike does run but the power is poor ? I'm betting the psi is down around 125 psi which suggest a worn out top end. Hopefully the cyl bore is still good. The top end will need to get torn down.

I cant say anything about it, after i get a compression reading ill let you know...Im startimg with new plug, filter and fresh gas and go from there.

Share this post


Link to post
Share on other sites

like suggested above i'd start with a fresh piston. The yz250 should have a tough kick. Much tougher then a yz125 and even harder to kick then a 450. You should not be able to kick a fresh yz250 with sandals on. Tear that cylinder off and inspect everything.  By building it right now, you will have hours of worry free riding later.

  • Like 1

Share this post


Link to post
Share on other sites

like suggested above i'd start with a fresh piston. The yz250 should have a tough kick. Much tougher then a yz125 and even harder to kick then a 450. You should not be able to kick a fresh yz250 with sandals on. Tear that cylinder off and inspect everything.  By building it right now, you will have hours of worry free riding later.

TAAAAH TA TA TAAAAAAH .....NO AIR FILTER!!!! Looks like this puppy is getting torn appart

Share this post


Link to post
Share on other sites

TAAAAH TA TA TAAAAAAH .....NO AIR FILTER!!!! Looks like this puppy is getting torn appart

That suck's :thumbsdn: !!!  I had the exact same issue with a bike my wife bought for me as an anniversary gift.The bike looked almost showroom condition but when I took the seat off there was rotted crumbling fragment's of what use to be an air filter.Anyway,you have a very nice bike and if you take your time and don't be afraid to ask ANY QUESTION'S you will have a bike to be proud of and that get's the job done,,,,quickly.

Share this post


Link to post
Share on other sites

I recently had to rebuild my yz 250 and it' not that complicated if you have a flywheel puller and a bit of knowledge about 2 strokes

As mentioned above: ask everything, here are very expierienced and helpful members!

Share this post


Link to post
Share on other sites

That suck's :thumbsdn: !!!  I had the exact same issue with a bike my wife bought for me as an anniversary gift.The bike looked almost showroom condition but when I took the seat off there was rotted crumbling fragment's of what use to be an air filter.Anyway,you have a very nice bike and if you take your time and don't be afraid to ask ANY QUESTION'S you will have a bike to be proud of and that get's the job done,,,,quickly.

Yep same thing, the filter was desintegrated, my questions is, if theres no play in the con rod , can i get away with just a fresh top end, or do i need to split the case.?

Share this post


Link to post
Share on other sites

Its your call. As Dirty Harry once put it, " Do you feel lucky punk". I've seen lower ends suck in dirt and the guy flush them out with kerosene, run them with no problem others same deal and grenade the first time out. If the cylinders toast and needs replated / replaced I sure would not chance it. And did the previous owner run it with the filter trashed or did it sit so long that it just rotted?

Share this post


Link to post
Share on other sites

It sat so long the filter disintegrated itself, thats why im leaning towards a fresh top end only, he only used motul, this bike practically sad in a barn a d used to ride around the property.....I just want to know the signs that tells me I need to split the case

Edited by thieaux

Share this post


Link to post
Share on other sites

first i would check if the crankshaft bearing at the ignition side has play, if he does => i would split the cases

when you do thetop end, check if the crankshaft has play too and if it rotates freely and without any noises 

Share this post


Link to post
Share on other sites

Found my air filter.....

 

 

Also how the hell do you remove the swing arm bolt, ive smashed the shit out of it and wouldnt budge...

2013-09-04 18.41.38.jpg

Share this post


Link to post
Share on other sites

Ok, so cylinder is off...

 

1-There was some sludge on the piston, maybe from sitting all this time.

2.Fair amount of blow-by.

3.Plug was black and sooty.

4.The cylinder wasnt scratch, my nail didnt cath on anything (thank god),even thow i cant see the crosshatch, i have to clean it to get a better look.

5.THe con rod had "some" side to side. but no up and down not even a mm.

 

So what now, get a bore caliper ?

what else ?

 

 

 

 

2013-09-05 16.49.58.jpg

2013-09-05 16.49.53.jpg

2013-09-05 16.49.48.jpg

2013-09-05 16.49.44.jpg

2013-09-04 18.41.38.jpg

2013-09-05 16.54.45.jpg

Edited by thieaux

Share this post


Link to post
Share on other sites

Damn the PO ran the hell out of that piston! I'm surprised it ran with that much blow by leaking past the rings. It amazes me how cheap some people are. That explains how It was easy to kick. Bore gauges are pricey, you could just take the cyl to a machine shop and they will measure the bore and taper for free or a few bucks.

For the crank, use feeler gauges and measure the side to side clearance, then compare your measurement to the spec in the service manual, if its near the higher end of the spectrum then it should be replaced. There can't be ANY up/down play though, or it will self destruct. Also rotate the rod through its full range of motion and feel for any binding or grit from running it without a filter. Clean the hell out of the carb and you should be good to go.

Share this post


Link to post
Share on other sites

Damn the PO ran the hell out of that piston! I'm surprised it ran with that much blow by leaking past the rings. It amazes me how cheap some people are. That explains how It was easy to kick. Bore gauges are pricey, you could just take the cyl to a machine shop and they will measure the bore and taper for free or a few bucks.

For the crank, use feeler gauges and measure the side to side clearance, then compare your measurement to the spec in the service manual, if its near the higher end of the spectrum then it should be replaced. There can't be ANY up/down play though, or it will self destruct. Also rotate the rod through its full range of motion and feel for any binding or grit from running it without a filter. Clean the hell out of the carb and you should be good to go.

Awesome, thanks theres a lab at my old university that has plenty of goodies, including a hass cnc machine, and i drop by from time to time to do some machinig, maybe they have a bore gauge i can borrow, tomorrow ill check the side to side clearance...Another thing , i read that you can clean the cylinder with wd40 and scothbrite, is this true?

Share this post


Link to post
Share on other sites

Update...I got the bore gauge seems im in 65.00 limit...I went ahead and bought a prolite 66.4 wiseco....ill see how it goes..I think its time for replating, I called millenium tech and got a quote around 250 for replating.., they dont have my jug in stock to qualify for a core exchange....

Share this post


Link to post
Share on other sites

That carb looks as if it has a hole burned through it. What happened there? Or is that just grunge?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×