Post by: adzski on April 04, 2013, 10:04:49 AM
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
Post by: eprovenzano on April 04, 2013, 01:12:21 PM
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.
Post by: adzski on April 04, 2013, 03:00:15 PM
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.
Post by: SachsGS on April 05, 2013, 04:26:16 AM
Post by: adzski on April 05, 2013, 05:52:27 PM
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.
Post by: Stusmoke on April 08, 2013, 04:45:22 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.
Post by: Jeram on April 08, 2013, 09:29:55 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.
Post by: eprovenzano on April 08, 2013, 01:30:03 PM
Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.
Not really, many people have reported having issues with Wiseco cranks. The quality is not what you'd expect from Wiseco.
Post by: adzski on April 08, 2013, 01:58:10 PM
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
Post by: SachsGS on April 08, 2013, 03:08:39 PM
Post by: Stusmoke on April 08, 2013, 10:15:46 PM
Post by: evo550 on April 09, 2013, 01:12:38 AM
.You may be soon using words in your vocabulary you never knew you had
Post by: eprovenzano on April 09, 2013, 01:40:13 PM
Post by: Stusmoke on April 09, 2013, 10:59:10 PM
Post by: Jeram on April 10, 2013, 08:58:19 AM
Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.
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 ?
Post by: Stusmoke on April 10, 2013, 09:46:38 AM
Also, I've heard of people having siezure issues with the Wiseco crank. Use caution.
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 ?
Not sure what the problems with them were just heard of peoples wiseco bottom ends seizing.
Post by: eprovenzano on April 10, 2013, 01:00:26 PM
Post by: adzski on April 10, 2013, 01:19:32 PM
ok today i pulled the motor out.
reason why the swing arm and motor bolt wouldnt come out was, silly me forgot to loosen the suspension once i did that she came right out well with some persuasion hhaha.
im gonna make a build thread or whatever, but just rename this so if a moderator wants to move it to the selected category would be appreciated but anyway. ill puts some pics below
Post by: adzski on April 10, 2013, 01:27:27 PM
quick pic of the piston
with the motor pulled out
Post by: _X_ on April 10, 2013, 11:18:28 PM
Post by: adzski on April 11, 2013, 08:06:08 AM
http://twostrokemotocross.com/forum/project-yz/2002-yz250-top-and-bottom-rebuild-project/
Post by: TMKIWI on April 11, 2013, 08:08:05 AM
Make sure you find the reason for the damage before you ride again.
Post by: adzski on April 11, 2013, 08:12:36 AM
and yeh she defiantly needs some love
Post by: Stusmoke on April 11, 2013, 12:24:51 PM
As far as pistons are concerned? Wiseco or wossner, accept no substitute.
Post by: 2T Institute on April 11, 2013, 02:06:14 PM
Post by: moto867 on April 12, 2013, 07:32:08 AM
Post by: adzski on April 26, 2013, 02:02:12 PM
Post by: vetman on April 26, 2013, 11:08:45 PM
Post by: adzski on April 28, 2013, 05:43:06 AM
picked up the new barrel today still waiting on rebuild kit and flywheel puller from US
Post by: eprovenzano on April 28, 2013, 01:23:29 PM
Eric