how to remove motor mount and swing arm bolt??? 94 yz 250 - Yamaha Forum : Your Yamaha Motor Products Community & Resource
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post #1 of 8 (permalink) Old 08-02-2011, 03:06 PM Thread Starter
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how to remove motor mount and swing arm bolt??? 94 yz 250

wats up i just got a 1994 yz 250 from a friend that ran good but he blew the piston and connecting rod got real hot it isnt seized but got real hot and is jammed.. i need to remove the motor to take it to a shop because splitting the case is just too far out of my league with out all the right tools... BUT i cant get the motor mount/swing arm bolt out to remove the motor from the frame.... i cant find any related forums threads or vids... someone said i gota heat it up with a torch but im sceptical to that... PLEASE HELP ME!!! thanx so much...
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post #2 of 8 (permalink) Old 08-03-2011, 12:11 PM
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Make sure all the engine mounting bolts are loosened, but no removed (it'll put the swinger in a bind if they're totally removed). I don't like using heat, mainly because the surfaces you need heated (frame bosses, swinger through-bores, and engine case bushings), really can't be accessed completely and properly.

Chances are your bearings have let loose, and/or have scored into the swinger bolt. Any rust, broken bits of needles or bearing races do a really good job of preventing the bolts from moving. Slobber this http://www.pbblaster.com/ liberally on all spots you can get to, let it soak for 4-6 hours, spin the nut back on until all the threads are engaged in the nut (to protect the threads and keep the end from mushrooming). Then smack the bolt/nut with a 4 lb. sledge hammer. If you have a brass or aluminum drift punch, that'll ease the pain to the end of the bolt.

Still won't move? Remove rear shock from swinger linkage, so you can move swinger up and down freely. Have a friend move the arm up and down while you smack it with the hammer. If it starts to move, back the nut off as needed to drive the bolt through the bosses in the frame. You'll eventually need a drift punch (long socket extensions work good also) to get it persuaded all the way through.

Still won't budge and you're building up a nasty sweat and lots of frustration? Take it to your freindly neighborhood full-service tire shop, and ask them to give it a little persuation from their air hammer. 10 seconds...... done . You might want to source a new swinger bolt.... just in case. It could get hurt from the process, or it could already be worn from dry/seized bearings.

New bearings/seals, lots of good quality waterproof grease before and during re-assembly, then you're golden.

Good luck with the engine rebuild.

Last edited by rooster; 08-03-2011 at 12:22 PM.
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post #3 of 8 (permalink) Old 08-03-2011, 12:54 PM Thread Starter
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sweet dude.. ur the man!! i appriceate the detailed post.. i got the yz as a basket case actually from my friend/local dirtbike mecanic down the road, he couldnt even get the thing out but wen i got it he already had the head off and broken piston off so its down to the crankcase and connecting rod wich gets jammed at the bottom.. but the other motor mount brackets are all off should it put em back on like u said?? i also took the shock off to get more play, like u mentoned,but the big shock linkage bolt (not the one actually holding the shock but the one closest to the motor) the hardest one to get to of coarse.... that one wont get out either!! i got that nut off but that bolt dosent want to slide thu either??.... ill get THAT penetrating oil u said.. i was using the liquid wrench one but i think THAT one is a little more heavy duty
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post #4 of 8 (permalink) Old 08-03-2011, 01:42 PM
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If the other mounts are all off, I wouldn't worry too much about putting them all back on. Maybe just the front cradle mount. You just need to get it back to proper position so the swinger isn't in that much more of a bind.

If it's the forward link bolt, a little heat on the swinger link (dog bone) will work, simply because you can get the host part (the casting) to swell up without getting the bolt hot. The front swinger is different, since you can't actually heat up the parts directly that need to expand. spray it with the same PB Blaster stuff, and dig into your bag of patience... give it time to do its' work. Sounds like you'd better get a linkage bearing kit on order. when you get the link bolt to break loose (and you'll probably destroy bearings getting it loose), you may have to grind just a touch off the hex corner of the bolt head to get it positioned right for removal. I've had several YZ's that seemed like they welded the link brackets on after the bolt was installed into the swinger

My son rides a '94 among others, and I have one complete '94 (awesome bike BTW), and one '94 basket case. I bought mine both from a somewhat local semi-pro A-rider that had them stored for several years after he got newer/later/greater bikes. The basket case is in the same predicament as yours, but because the previous owner pulled the top end, didn't store it properly, and the crank & rod bearing got moisture in and are seized. It'll be a beautiful bike when I get it fixed and completed... it's got a bunch of fairly recent sponsorship goodies on it (Applied triples, upgraded forks/shock, etc.).

I'm a big guy (6'4" / 240 lbs.), and love the YZ250's. My primary rides are my CR500's, but the 250's are a blast to flick around through the woods.

Aloha!!

Last edited by rooster; 08-03-2011 at 01:49 PM.
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post #5 of 8 (permalink) Old 08-03-2011, 04:07 PM Thread Starter
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ok sweet.. mines a 94 too.. are u going or do u split the case your self? im debating weather or not to buy the tools (tusk flywheel puller the case splitter) and give it a try or dish out the 75/hour x 4or 5 hours they said the local yami/kawi dealer here in town..i no messing with the case isnt something anyone should do unless there completly confident about it.. but i kinda jus want to conquer that mountain and do it my self because if i do it right that would be some great knowlage to stash in my archives.. im only 23 but i been riding and wrenching for bout 5 years now and have got every bike i ever owned running and flipped for good profit.. but this is the first full mx bike i got my hands on and want to hold on to this baby cuz i got it for 50 bucks..
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post #6 of 8 (permalink) Old 08-03-2011, 04:48 PM
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Yep, I'll split the cases. I'm 52 years old, and do all my own work except machining - have been wrenching/tuning/rebuilding bikes since I was 12 years old (split my first case at 14). Did it professionally for several years. I know.... fish tale..... no, seriously.

If you can foot the bill for the tools (some you can now rent from the bike shops), and are mechanically gifted/inclined, confident and want the experience, I would recommend you do it yourself. I use a puller to dis-assemble, but use the freezer and propane torch or oven for re-assembly of press-fit assemblies. Less stress (re-assembling with the tool makes me nervous - I've seen a lot of cases over-stressed and cracked), and I'm never out of spec on the crank by the time I button things up. The parts just drop into place, let the temps equalize to normal and viola.... no fuss - no muss.

If you don't have one, spend the 20-30 bucks on ebay for a good Yamaha workshop manual (CD or hardcopy), take your time, stay focused, and hit up the forums if you have any questions, concerns or problems. It's not hard at all. Either re-install nuts, bolts, etc. wherever you can, or tag and bag them in zip-locks. Keep as many sub-assemblies laid out in order and assembled as much as you can keep them. Get a couple old shoe boxes, draw the outline of your covers and case halves, poke some holes in the locations where the bolts go, and you'll never have to guess if the right bolt went in the right hole. I still do that, even after all these years. The shoe box doubles as a good place to keep your bagged small parts.

When you pull the transmission shafts out, keep them tight, in sequence and rubber band them together at each end. That'll keep them from separating or sliding off the shafts. Put them in clean box or wooden tray to keep them intact. That way you can reinstall them just as they came out. Otherwise, or if you want to inspect everything thoroughly, you'll have a learning curve on how to properly re-assemble a transmission. Watch out for the sneaky little thrust washers that stick to the ends of the gears (don't loose them or put them back in the wrong place). Keep everything in proper order, or it won't shift right when it's re-assembled.

It's exciting to us old guys to hear of a young guy bailing into their first case work. Keep us informed of your progress!! There's a huge amount of satisfaction knowing you did it, it works, and you'll now do it again (cuz it really wasn't that bad).

Good luck, learn a lot, and have fun doing it

Last edited by rooster; 08-03-2011 at 05:03 PM.
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post #7 of 8 (permalink) Old 08-05-2011, 09:59 AM Thread Starter
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you know off hand wat year newer plastics will fit i know the front fender and number plate can be switched out but not sure bout the rest... thanks again!!
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post #8 of 8 (permalink) Old 08-11-2011, 01:00 PM
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Just replied to your other post.
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