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Author Topic: '81 yz250 build  (Read 6894 times)

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Offline xs850triple

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'81 yz250 build
« on: May 18, 2013, 01:00:00 AM »
hey guys, new here and excited! so today i finally got me a little two stroke dirt bike for a sweet deal, traded my xbox stuff for it :D but it needs to be rebuilt which im looking forward to.. well im having a problem right from the get go, i cant get the rear engine mounting bolt off and its pissin me off! its the bolt that goes through the swingarm, got the nut off on the other side easy but when i went to pull the bolt out it wouldnt budge, stuck my breaker bar on there with a two inch extension to try and twist it out and ended up twisting my 2 inch extension into two peices! i plan on replacing it as i hammered on the other side to try and force it out and kinda dinged up the threads at the top but how in the heck do i get this off? ill cut it if i can, maybe im being igornant with this being my first dirt bike. also if someone knows anywhere where i can access a manual for this bike, or just a good place for resources that would be greatly appreciated as i havent found any yet

ill try and post some pics later so you can see what im starting with.. gulp and then see what i can do to it  :D
thanks in advance!
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline TMKIWI

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''81 yz250 build
« Reply #1 on: May 18, 2013, 01:13:10 AM »
As I posted in your other thread, you will need to soak it with some wd40 or similar.
Worst case senerio is you will have to cut the bolt into 3 by cutting with a sabre saw inbetween the cases and swingarm.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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If you don't fall off you are not going hard enough

Offline xs850triple

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''''81 yz250 build
« Reply #2 on: May 18, 2013, 01:57:35 AM »
ya its been soaking in some pb blaster.. sorry for the double post, didnt really mean to do that i guess my main concern was that the bolt wasnt threaded in there and i wasnt screwin stuff up bangin on it, so i guess after soaking im gonna pull the rear shock and have someone move the swing arm up and down while i smash the crap outta of it is what ive read, and then get a new bolt along with all new bearings
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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''''''''81 yz250 build
« Reply #3 on: May 18, 2013, 03:41:49 PM »
In the past I've drilled out mushroomed/seized swingarm bolts. Drill out in increments and leave about 13mm/1/2 inch in the centre undrilled so that you have a "ridge" to drive against. When the bolt gets drilled thin enough it will collapse in on itself and you can hammer it out.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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''''''''''''''''81 yz250 build
« Reply #4 on: May 19, 2013, 03:52:43 PM »
Sorry I don't quite understand, are you saying to drill out the bolt from both end and leave half an inch in the  middle of the bolt.. I'm gonna try it with a torch tonight if that doesn't work then ill either try drilling or cutting.. so here's the bike, the kid says its an 81 but he has no title, it looks to have the 81 frame but the seat and gas tank don't look like an 81 at all so I'm not sure really what it is.. all I can say is I got a lot of work to do
http://s1343.photobucket.com/user/baby_shaker/media/IMAG0356_zpsf2877bf7.jpg.html" target="_blank">http://i1343.photobucket.com/albums/o782/baby_shaker/IMAG0356_zpsf2877bf7.jpg" border="0" alt=" photo IMAG0356_zpsf2877bf7.jpg"/>" alt="" class="bbc_img">
http://s1343.photobucket.com/user/baby_shaker/media/IMAG0355_zps775c8673.jpg.html" target="_blank">http://i1343.photobucket.com/albums/o782/baby_shaker/IMAG0355_zps775c8673.jpg" border="0" alt=" photo IMAG0355_zps775c8673.jpg"/>" alt="" class="bbc_img">
http://s1343.photobucket.com/user/baby_shaker/media/IMAG0351_zpse229584e.jpg.html" target="_blank">http://i1343.photobucket.com/albums/o782/baby_shaker/IMAG0351_zpse229584e.jpg" border="0" alt=" photo IMAG0351_zpse229584e.jpg"/>" alt="" class="bbc_img">
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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''''''''''''''''''''''''''''''''81 yz250 build
« Reply #5 on: May 22, 2013, 01:40:29 AM »
I don't know why the pics aren't showing up, photobucket is acting weird.. so I was able to cut the bolt off that goes t. The rear suspension, but when I went to cut the swing arm bolt it didn't even scratch it, I was cutting between the swing arm and the engine, it looks like theres a sleeve on there, got it red hot with the torch also, that helped break it loose, I can now turn the bolt a quarter turn, but the head is to stripped and the other end of the bolt is to mushroomed to come out.. ill work on it more when I get home, hopefully ill get somewhere.. I can get a rebuild kit for the swing arm on eBay for like 50 bucks, should I get that or is there a better way to go
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''81 yz250 build
« Reply #6 on: May 22, 2013, 02:59:26 AM »
Drill the bolt out from either end and leave a little undrilled in the centre so you have something to hit against when you hammer what is left out.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''81 yz250 build
« Reply #7 on: May 22, 2013, 04:49:44 AM »
Oh that makes sense.. but I don't have a drill or drill bits, but I do have a saws all with some good blades, I already cut half of it off on one side of the engine, but the other side I can't even get a cut in, I cut through the side with the nut, and I clearly cut through what looked to be the bolt, but the other side I can't even scratch, I'm afraid I'm cuttin into a bearing as it doesn't look the same as the other side
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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'81 yz250 build
« Reply #8 on: May 24, 2013, 07:59:14 AM »
The cylinder wall
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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''81 yz250 build
« Reply #9 on: May 24, 2013, 08:02:07 AM »
And the ring that snagged it
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline evo550

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''''81 yz250 build
« Reply #10 on: May 24, 2013, 08:19:55 AM »
Quote from: xs850triple on May 24, 2013, 02:58:26 PM
kind of interesting when I pulled the head, what it looks like happened was the piston ring snagged on the intake, is this common?

It can happen if the cylinder has been rebored to a big oversize, which is usually done on these old abused bikes. What oversize is it?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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''''''''81 yz250 build
« Reply #11 on: June 09, 2013, 01:15:28 AM »
How could I tell if it was oversized? Measure it? Crap, I just ordered a wiseco piston, 71.2mm bore which I was assuming was the first or second oversize.. so I finally got back to the bike this weekend and got the stupid swing arm bolt out, had to hit with the angle grinder on both sides then drill it before it finally came out, what else needs to be replaced in there.. I need to find a manual, so it looks like there were some sort of bearings or sleeves that are still seized to the bolt, along with a bunch of pellet things I'm assuming to be the bearings.. so what all do I ha e to replace assuming everything is broken
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline adzski

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''''''''''''''''81 yz250 build
« Reply #12 on: June 09, 2013, 03:15:25 AM »
swing arms use needle bearings, when the seize and break up and the rollers come out the look like the pellets you mentioned.

just buy a new swing arm bearing set ( bearings, sleeve, seal)  and a new swing arm bolt.
i recently just did my own and got my baring from my local bearing store, but i still need to find seals.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline xs850triple

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''''''''''''''''''''''''''''''''81 yz250 build
« Reply #13 on: June 09, 2013, 09:44:46 PM »
Ya that's what i wanted to do but all I can find for the it is the 1983 stuff, nothin for 81-82, unless I could use an 81 yz250 kit, I can find those, would that work?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline adzski

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''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''81 yz250 build
« Reply #14 on: June 10, 2013, 01:49:24 AM »
82-83 would probably work, but don't hold me to that.
You could also take one of the bearings to your local bearing store and try will match it, but you stil won't have seals, sleeve.

Go to your local mx shop and see if they can order it from Japan for you
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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