03 yz 250

J

John92YJ

Member

Mar 5, 2008

42

0

• Jun 11, 2012

• #1

was riding and hit a little water crossing only a foot deep and when i got back up to 3rd gear motor bogged out. went to feel for compression with my hand and it went down ease and then locked up. its a friends bike so I'm hoping i can get away with just putting some new rings in or am I looking a new top end? bike was pulling hard and running great before. thanks for any info you can pass my way.

 

A

arnego2

Member

Mar 8, 2008

271

1

• Jun 11, 2012

• #2

That depends what you see in the cylinder. How old is the piston?
O burned a hole into my piston once and was still able to ride home. Needless to say that only the piston was not what I had to do. Full bottom and top end rebuild, cylinder replate plus all material came to about US$ 400.

 

J

John92YJ

Member

Mar 5, 2008

42

0

• Jul 23, 2012

• Thread starter
• #3

ok finally took the head off and found a nice hole in the piston :bang: guessing that the peaces are in my bottom end and thats what is making it lock up? here is a pic. looks like a oem piston?

dont think it was the water that caused this. what do you think. was running 40.1 was that to lean? Thanks

 

A

arnego2

Member

Mar 8, 2008

271

1

• Jul 23, 2012

• #4

That depends on how you ride and how you jet.
I run now the JD red needle @ 4rth with a 45 pilot and a 178 main.
I mix @ 28:1 sometimes 25:1 even.

In my case a broken oil seal did the trick.

You are looking at:
minimum, rod kit or if cheap just the lower needle bearing with spacers plus the crank bearings and seals.

To split the engine you need a flywheel puller and a generic 3 finger extractor or engine splitter.Quite easy to do actually. You'll be surprised.

 

J

John92YJ

Member

Mar 5, 2008

42

0

• Jul 23, 2012

• Thread starter
• #5

took the cylinder off and the crank is moving freely :nod: think i can just do a topend and be good?

 

J

John92YJ

Member

Mar 5, 2008

42

0

• Jul 23, 2012

• Thread starter
• #6

 

A

arnego2

Member

Mar 8, 2008

271

1

• Jul 23, 2012

• #7

Nope I would not do that as that parts end into the needle bearing and in the crank roller bearings. You could have luck and get away with only the top end but why taking the risk?

Engine is open and to do the bottom end cost you about 3 hours of work. Maybe 5 if the first time.

Could be a wiseco piston OEM as no number on the crown.

 

J

John92YJ

Member

Mar 5, 2008

42

0

• Jul 23, 2012

• Thread starter
• #8

ive never split a case before and dont really want to make a mistake on a bike thats not mine. but dont want to haft to take it all apart again ether.

 

A

arnego2

Member

Mar 8, 2008

271

1

• Jul 23, 2012

• #9

Not doing it could cost you a friend. Why not doing it with him?
Case of cold beer and you have it done in 3 hours.

 

J

John92YJ

Member

Mar 5, 2008

42

0

• Jul 23, 2012

• Thread starter
• #10

your right, thanks for the help

 

A

arnego2

Member

Mar 8, 2008

271

1

• Jul 23, 2012

• #11

No problem at all, as a thanks have one in my behalf :) :laugh:

 

2

2strokerfun

Member

May 19, 2006

1,500

1

• Jul 24, 2012

• #12

It does look to me like it was running on the lean side of perfect. Not lean as in too little oil mix--although I would never run less than 32:1 and prefer 28:1--but lean as in too much air to fuel/oil mixture. Lean may be great for short races where you replace engine parts regularly. But it's hell on the engine and pocketbook if you want a daily rider.
Good pictures for your post, by the way. Good luck.