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Author Topic: yz 250 engine seized, i think  (Read 7932 times)

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Offline adzski

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yz 250 engine seized, i think
« on: April 04, 2013, 10:04:49 AM »
hey im new here,

anyway strait to the point my 2002 yz 250 i believe is seized.

was riding it and heard a weird noise then worried i turned aorund to ride back then it bogged out, tried to kick it over n it kinda fired up but bogged out, now the kick start wont go down.

so im thinking of doing a complete over haul, im a refrigeration mechanic by trade so i do this stuff on a larger scale often.

besides what is listed below what else would i need?

http://www.ebay.com.au/itm/Yamaha-YZ-250-Wiseco-Complete-rebuild-kit-Crankshaft-Piston-Gaskets-2002-/271024997432?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D14%26meid%3D6744111324731573999%26pid%3D100015%26prg%3D1006%26rk%3D1%26sd%3D271024997432%26

 
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline eprovenzano

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yz 250 engine seized, i think
« Reply #1 on: April 04, 2013, 01:12:21 PM »
1st Welcome to the forum....  2nd sorry to hear the bike seized. 

The kit you are looking at contains all the required pieces.  I do have a few questions.  You will need to pull your cylinder and head to see if there are any problems, (scratches, or scoring).  I'm not sure but I'm assuming the kit is made of all Wiseco components.   I'm not a fan of their cranks, but that is just me...  One other tool you will need is a flywheel puller.  If you don't have one, a local shop usually will pull the flywheel for you for a small fee.

Its not too difficult to split the cases and replace the crank, it just takes time and a little perseverance.  Take pics along the way for reference, and maybe put together a build thread.

Good luck, we are here to support you and hopefully answer any questions you have along the way.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Eric Provenzano
2019 KTM 300 XCW TPI
2000 KTM 300 EXC (Son's)
2001 KTM 380 EXC
Sold 1991 KDX 200... fun play bike
Sold 1999 KX250
Sold 1999 YZ125 (son's)
Sold 2001 Yamaha TTL 125 (son's 1st bike)
Sold but never forgotten 1974 Honda Elsinore CR250M
Sold 1974 Honda Elsinore CR125

Offline adzski

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yz 250 engine seized, i think
« Reply #2 on: April 04, 2013, 03:00:15 PM »
thanks for the warm welcome!

ill be pulling it apart soon to see exactly what is wrong. im thinking perhaps it may not be completely seized as i was moving it about in gear and got the kick start to push all the way down, after this i stopped as i dont want to do anymore damage.

plan of attack

1. have a look at the kick start mechanism see if a kog is jammed and see if fly wheel will turn, if not
2. pull of the head and cylinder.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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yz 250 engine seized, i think
« Reply #3 on: April 05, 2013, 04:26:16 AM »
Pull the head off and look for pitting. When a crank fails the bigend needle bearings usually fracture and wreak havoc in the combustion chamber area.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline adzski

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yz 250 engine seized, i think
« Reply #4 on: April 05, 2013, 05:52:27 PM »
pulled the head off and found the problem, seized piston.

i believe the piston over heated expanded and got stuck in the bore, pulled most of it apart last night.

im hoping the conrod isnt damaged, i havent pulled the bore off yet (only 2 bolts remaining)

will pull the bore off in a tomorrow and look for other potential problems.

plan is to have it back up and running by next week.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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yz 250 engine seized, i think
« Reply #5 on: April 08, 2013, 04:45:22 AM »
Quote from: adzski on April 06, 2013, 12:52:27 AM
pulled the head off and found the problem, seized piston.

i believe the piston over heated expanded and got stuck in the bore, pulled most of it apart last night.

im hoping the conrod isnt damaged, i havent pulled the bore off yet (only 2 bolts remaining)

will pull the bore off in a tomorrow and look for other potential problems.

plan is to have it back up and running by next week.

Buy a cylinder bore gauge and check your cylinder for warpage too. Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Jeram

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yz 250 engine seized, i think
« Reply #6 on: April 08, 2013, 09:29:55 AM »
Quote from: Stusmoke on April 08, 2013, 11:45:22 AM
Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.

??? That defies logic doesn't it ???


Simply wash the bore with muriatic acid and a cotton wool bud to remove any alluminium from the Nikasil bore.
Then inspeact the nikasil for any damage (chips and deep scores etc)

Then inspect the piston to identify the type of seizure you encountered.
http://www.off-road.com/dirtbike/tech/dirt-bike-tech-twostroke-seizure-52428.html

If the seizure type simple indicates that the bike lean seized, as long as the bore is OK you can put the motor back together with a new piston.
Make sure you clean the carb and put bigger jets in it before you ride it again.

If the seizure is another type then fix the issue and put it back together.
eg: will most likely require a replate and a piston if the piston to bore tollerances are too small.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline eprovenzano

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yz 250 engine seized, i think
« Reply #7 on: April 08, 2013, 01:30:03 PM »
Quote from: Jeram on April 08, 2013, 04:29:55 PM
Quote from: Stusmoke on April 08, 2013, 11:45:22 AM
Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.

??? That defies logic doesn't it ???



Not really, many people have reported having issues with Wiseco cranks.  The quality is not what you'd expect from Wiseco.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Eric Provenzano
2019 KTM 300 XCW TPI
2000 KTM 300 EXC (Son's)
2001 KTM 380 EXC
Sold 1991 KDX 200... fun play bike
Sold 1999 KX250
Sold 1999 YZ125 (son's)
Sold 2001 Yamaha TTL 125 (son's 1st bike)
Sold but never forgotten 1974 Honda Elsinore CR250M
Sold 1974 Honda Elsinore CR125

Offline adzski

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yz 250 engine seized, i think
« Reply #8 on: April 08, 2013, 01:58:10 PM »
hey guys


pulled the bore of today, i know lazy hahaha


anyway back to the point alot worse than i originally thought, piston exploded and a really really good potion was missing and appears most went down into the crank, also the whole crank and conrod assembly was looking in poor condition so a complete rebuild is going to happen.

i really go stuck into it today. the bottom end is about ready to come out, but i just couldnt get the bolt that goes through the motor and the swing arm to come out so will have a another crack in a day or so. then illl order the rebuild kit from wiseco and the rebuild will begin
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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yz 250 engine seized, i think
« Reply #9 on: April 08, 2013, 03:08:39 PM »
Soak everything in penetrating oil and let it sit overnight.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Stusmoke

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yz 250 engine seized, i think
« Reply #10 on: April 08, 2013, 10:15:46 PM »
What Sachs said. drench it in Degreaser, WD-40, whatever you can find. Don't mix the chemicals together though lol.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline evo550

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yz 250 engine seized, i think
« Reply #11 on: April 09, 2013, 01:12:38 AM »
While you've got the credit card out, I'd order a new set of swingarm bearings as well.. sounds like they have rusted themselves to the swingarm bolt ><img src=" title="Angry" class="smiley">.
You may be soon using words in your vocabulary you never knew you had :D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline eprovenzano

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yz 250 engine seized, i think
« Reply #12 on: April 09, 2013, 01:40:13 PM »
When I rebuild my son's Honda 400EX, due to lack of, or no maintenance by the PO, I has to cut the bolt, as it was seized to the engine case.  I then had to have it pressed out...  Needless to say, now on all of my equipment the swingarm bolt get pulled and the swingarm bearing and bolt regreased and replaced.  That was a total nightmare I don't want to relive.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Eric Provenzano
2019 KTM 300 XCW TPI
2000 KTM 300 EXC (Son's)
2001 KTM 380 EXC
Sold 1991 KDX 200... fun play bike
Sold 1999 KX250
Sold 1999 YZ125 (son's)
Sold 2001 Yamaha TTL 125 (son's 1st bike)
Sold but never forgotten 1974 Honda Elsinore CR250M
Sold 1974 Honda Elsinore CR125

Offline Stusmoke

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yz 250 engine seized, i think
« Reply #13 on: April 09, 2013, 10:59:10 PM »
Yup. When they decide to get stuck, they get stuck. I've heard of people having no luck with 800 kgs of pressure on it.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Jeram

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yz 250 engine seized, i think
« Reply #14 on: April 10, 2013, 08:58:19 AM »
Quote from: eprovenzano on April 08, 2013, 08:30:03 PM
Quote from: Jeram on April 08, 2013, 04:29:55 PM
Quote from: Stusmoke on April 08, 2013, 11:45:22 AM
Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.

??? That defies logic doesn't it ???




Not really, many people have reported having issues with Wiseco cranks.  The quality is not what you'd expect from Wiseco.


But how does a crank cause a seizure?

It would take alot of tiny smashed crank fragments to seize the motor ?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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