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madman
01-14-2009, 12:29 AM
Has anyone ever pressed apart snowmobile crankshafts and rebuilt them? I have a 1979 Yamaha exiter that needs some attention. Rebuilt crankshaft required. How hard is this really? Thanx Guys madman

rode2rouen
01-14-2009, 12:50 AM
With the correct tools, it's not a bad job.
I have done 1, 2, and 3 cylinder bike cranks.


Rex

dave727
01-14-2009, 01:11 AM
I have done single cyl bike and atv cranks- Need a hydr press, big brass hammer for adjustments, dial indicator and you can use a lathe with live centers on both sides to hold the crank while you rotate it by hand and check it with your dial indicator to check it for true- then take it out and adjust with BFH then recheck and repeat as needed.

Shop manual for your engine would be a great idea- you need the clearances and total thickness specs.

rdfeil
01-14-2009, 01:11 AM
Madman,

Getting them apart is easy :D , Its putting them back together that is the problem. Ok, now that I got the smart a$$ out of my system on to the problem... I have been involved in rebuilding cranks for Artic Cat machines, I think they are basically the same. The way we did it was to carefully press the journal out of the outer counter weight. The next part is the tricky part. You will need to heat the outer counterweight to expand the journal pin hole. We did it in a crock-pot of oil set on high temp for several hours to expand the hole. Chilling the journal pin to shrink it will help also. Get everything ready to reassemble, new bearings and con rod if needed. We never had a jig but if you have the materials to make one it would be much better for the reassembly. To reassemble you just slip the heated counterweight on the journal pin and try your best to keep it in alignment, if you are off a large brass hammer will move it while it is hot. Now for the bad part... after this type of repair the journal / counterweight press fit is weakened and will likely twist eventually binding the crank and possibly damaging the crankcase. We finally gave up on these repairs as the failure rate was nearly 100% in less than 3 seasons. A new crank assembly is actually a better investment after you get over the sticker shock :eek: . This was many years ago so I don't know how the new locktite formulas would work or if they would improve the reliability. I really think I would abandon the repair due to the unpredictability of the accuracy of the alignment and the investment in time and the potential for more damage if the repair fails.

Robin

sdeering
01-14-2009, 01:16 AM
I have done 2. Parts are quite cheep to do the whole thing. The rod kits are the most at around 150 per. Bearings you can get at you normal brg. place.

I use a cheep 20t. press. You will need to make or somehow get a hold of a C bracket that will support the counter weight, as you press the big end rod pin out. I made mine out of a 1/2 plate. I hang the crank in a piece of large pipe, my press is too small to hang it through the press bed.

Pressing things back together is a little easier press wise. But you have to have the 2 counter waits lined up as you press it back together. Press a little check, press more check ect.

I put the crank between centers in the lathe to check run out, V blocks could be used. Check it before and check each individual piece for run out when it is apart.

A large lead or brass hammer works well for tweaking as you press and align as it is going back together. Scribe lines can help as well (before pressing apart).
This is my self thought teck. I would like to hear others as well.
Good luck
Stephen

torker
01-14-2009, 01:52 AM
Sled cranks are unreal expensive... AC580...$1500 plus tax. 600 triple..$2300 plus tax. The triples are like hand grenades at the best of times. Buy a new crank for a triple for the $2300 and you now have a sled that's worth at LEAST $1500 :D
Peter (Brockely 1) does quite a bit of work on sled motors...not real sure about cranks tho..

chief
01-14-2009, 06:31 AM
I have done a lot of M/C crankshaft work, my first suggestion is to do some research, some Japanese crankshafts a not repairable. Other crankshafts require different presses. A crankshaft for a 250 OSSA requires 40T press,
anything less aint' gonna work. I would also suggest manufacturing a fixture
that fits between the crank webs and con rod to support it and avoid trashing the crank with pressing.

Circlip
01-14-2009, 06:53 AM
I can never understand the stupidity exhibited by manufacturers when it comes to spare part charges. We all know how much you would expect to pay to have a "One off" manufactured, but this isn't the case as once the go button is pressed, there are dozens on the floor. I know it costs to store and the guy that has to pick it off a shelf has to have a wage but shelves have more on them than the bit I want and the picker doesn't sit waiting for my order. It's difficult when you manufacture components in small quantities to a contract specific design, but the major manufacturers don't. Our throw away society is driven purely by greed.

Regards Ian.

motorworks
01-14-2009, 07:30 AM
Yamaha single throw:
If the crank has not been damaged too much;

1) then carfully measure around the two throws and record (just in case you do not have the factory specs)
2) blue crank and put scribe marks using a machinist square across each throw.
3) remove all bearings*. make sure you record what side each was on (PTO or Flywheel) Note any pins,dowel hole etc and what side they are facing.
Record any numbers on the connecting rod and what direction they face
ie Towards the PTO side or the Flywheel side.
(A drawing aways helps)
4) Set up the crank in your Press (You will need 30 to 50t)
You will need plates, etc to hold. BE CAREFULL
5)With your crank supported via plates/jig press out the pin from one side
of the throw.
6) turn over and press pin out of other throw.
7) Clean up crank parts that are to be reused.
DO NOT REUSE any rod bearings,pins or thrust washers
8)Set one side of the throw on the press, lube the new pin and press in.
9)With the new bearings, washers and rod in place, put other side on top of the throw with the pin already in it.
and using a machinist square line up the scribed marks.
10) press on about 1/3 the way down.
11) take the crank out of the press and using the square and a large brass hammer line up the scribed marks.
12) put back in press and press together , stopping from time to time to check the distances between throws. Match the measurement you recorded or the shop manual specs.
13) Using your square against the side of your crank check to see that the throws are concentric. use your brass hammer to adjust.
14) Put your bearings back on the crank. (bath of hot oil works best)
15)Set up crank on Vee blocks and using a dial recheck to see if the throws are concentric and parallel. Adjust with brass hammer. TIR of 0.001" or better.
DO NOT put the crank between centers to check.Most center holes get damaged during removal of flywheels and clutches.Always do the final check on vee blocks with the new crank bearings installed.

* Be supper careful removing crank bearings.If you press them off, wrap then
in rags just in case then break. I prefer to split them with a reinforced Dremel cut off wheel.

eddie

Circlip
01-14-2009, 07:45 AM
And to re-emphasize, hardened bearing outers and inners break like shrapnel, and a cut from one seems to bleed forever.

Regards Ian.

GKman
01-14-2009, 08:51 AM
Motorworks, as fine of "How To" I've ever seen. Thanks for the fine write-up.

That's the way I learned it from a HD trained mechanic in the '60's without your improvements re scribe mark and v blocks. Took a 200 twin Suzuki to an excellent machine shop, Luther-Shelton, in Kansas City. Instead of the support plates and press he simply placed 6 bolts with long nuts (rod couplers)screwed on them between the disks and started unscrewing the nuts off the bolts to press the disks apart. No special tools and done in no time. If anyone doesn't understand my narrative I'll post a drawing. It's a wonderful trick to know.

Oldbrock
01-15-2009, 11:48 PM
Reading Motorworks description seemed to follow what I used to do with twins and tripples. It's fussy and time consuming but considering the cost of a new bottom end it's worth it. Have never had one come back. Peter

GKman
02-10-2011, 11:35 PM
Here's a sketch of using miniature "jacks" made of bolts and long nuts to push crank wheels apart. Space several between the crank disks and start wrenching the nuts off a 1/6 turn at a time.

http://img.photobucket.com/albums/v494/gkman/P2100013.jpg

doctor demo
02-11-2011, 04:00 AM
There must be a fold in the Time-Space fabric:) at least this one isn't seven years old like the ''pin'' thread earlier.

Steve

BigMike782
02-11-2011, 08:56 AM
Sounds cheaper and easier to drive your pick up truck to the bar.....what?, you mean not everyone that rides snowmobiles does it just to get to the bar:confused: ;)

Good luck with your rebuild......post some pics it sounds interesting.
Obviously I never look at the original post date,DOH!

John Stevenson
02-11-2011, 09:29 AM
Once tried to get one of those twin cylinder works DOHC Honda 50cc racer cranks apart [ not mine ! ] The ones that used to rev to 25,000.
my press at 20 ton wouldn't move it, works one at 45 wouldn't either.

So took the crank down to ZF gears workshop and the foreman let me use their 125 ton press.

At 90 ton I bailed out, too much was creaking and groaning including my sphincter :D.

Gave the crank back and said sorry, no can do

aboard_epsilon
02-11-2011, 09:40 AM
Once tried to get one of those twin cylinder works DOHC Honda 50cc racer cranks apart [ not mine ! ] The ones that used to rev to 25,000.
my press at 20 ton wouldn't move it, works one at 45 wouldn't either.

So took the crank down to ZF gears workshop and the foreman let me use their 125 ton press.

At 90 ton I bailed out, too much was creaking and groaning including my sphincter :D.

Gave the crank back and said sorry, no can do

http://www.khulsey.com/motorcycles/zoom_honda_cr110_racer.html

didn't know it existed until you said

even more confusing is this one ..looks modern

http://www.youtube.com/watch?v=bVEC8z0QYnA&feature=related

all the best.markj

John Stevenson
02-11-2011, 10:00 AM
That's the production single cylinder racer.

The RC116 was the works twin.

http://www.vf750fd.com/Joep_Kortekaas/1966.html

Quite rare as most of Honda's old machines were broken up for scrap so one one got their hand on them.

masheenest
02-11-2011, 10:49 AM
Back in the (1979) day, serious Yamaha snowmobile shops had acess to special tools to split the inner crank halves. This was necessary when replacing seals and bearings. Re-assembly was helped along by the 13 tooth spline joint which mated the two parts. You couldn't put them together wrong. Find a Yamaha dealer from that era and he may still have the tools.

Highpower
02-11-2011, 11:00 AM
Deleted. Didn't notice that I was responding to a 2 year old post... :o

aboard_epsilon
02-11-2011, 11:35 AM
That's the production single cylinder racer.

The RC116 was the works twin.

http://www.vf750fd.com/Joep_Kortekaas/1966.html

Quite rare as most of Honda's old machines were broken up for scrap so one one got their hand on them.

right ..found a site with many pics ..

including scematics the lot

http://www.elsberg-tuning.dk/honda.html#rc116

all the best.markj

bborr01
02-11-2011, 01:06 PM
Motorworks, as fine of "How To" I've ever seen. Thanks for the fine write-up.

That's the way I learned it from a HD trained mechanic in the '60's without your improvements re scribe mark and v blocks. Took a 200 twin Suzuki to an excellent machine shop, Luther-Shelton, in Kansas City. Instead of the support plates and press he simply placed 6 bolts with long nuts (rod couplers)screwed on them between the disks and started unscrewing the nuts off the bolts to press the disks apart. No special tools and done in no time. If anyone doesn't understand my narrative I'll post a drawing. It's a wonderful trick to know.

The old Suzuki twins must have had a problem with crank seals.

I remember in about 1970 my dad, an excellent toolmaker, taking the crank for a 150cc twin apart and re-assembling it on the kitchen table.

He used a couple of flat bars maybe 3/8 X 1 X 4 or 5 inches long with tapped holes and clearance holes. Also some bolts or threaded rod, can't remember for sure.

I asked him if the table was flat enough for that kind of work and he told me that by rotating the crank in v-blocks he could guarantee it would be straight.

As usual, dad was right. I ran that bike into the ground and the engine still ran.

Watching dad work miracles like that was largely responsible for me going into the same trade. Worked alongside him for a while too. We should all be so lucky.

Dad is 80 now and can't do much with tools and such. It is a tremendous frustration for him to have a willing mind and an unwilling body.:(

I don't look forward to that day coming for me.

Brian

Racebrewer
02-11-2011, 11:56 PM
Great info in this thread even if its two years old.

The only thing I can add is that the new crank pins and the holes for them in the crank halves often have sharp edges. When I assemble a crank I deburr the ends of the pins with an abrasive nylon wheel Beartex. I also deburr the crank half holes with a 3M pad or fine sandpaper.

When pressing the pins I use either Sunnen Press Lube or automotive gear lube.

When I start pushing two halves together, I start the process using my mill vise. While I can't press them all the way home, it makes it easier to get them started andto recheck the alignment. It makes for less correcting after pushing them home.

I was also told by a guy in sunny California, who has done this all of his life, to let the cranks sit overnight before the final straightening. It lets all of the stresses created by shoving them together relax and the final straightening is easier. That definately seems to be true.;)

Many of the cranks I have done have damage to the threaded ends which causes straightening using solid ends in a lathe to be a problem. I use V-blocks on a granite surface plate for straightening.

I bought one of those cheap 6"x6" granite plates with a steel column mounted dial indicator. The 6"x6" was way too small so I took a larger surface plate, drilled a hole in it and mounted the steel column using a 2" spacer to raise it up.

BTW, a 5 lb brass hammer is the minimum. I know, I have several smaller ones.:cool:

John

S_J_H
02-12-2011, 12:55 AM
Was reading the info on those 50cc 4stroke race engines in 1966.

16hp at 22,500 rpm 45 years ago. That is just incredible that they made 16hp from just 50cc. And a 9 speed gearbox.. :eek:
Awesome!
Steve

John Stevenson
02-12-2011, 05:59 AM
When I used to put cranks together I had two old thick vee blocks and a drilled a hole thru the base of each in the centre of the vee.

To press the crank together one side would be assembled then with the pin lubed the top half would be started as square as possible for a short distance.

then the vee blocks would be laid on their sides and a long length of studding / all thread pulled them together so the flywheel halves were cradled by the block, then pressed home.

Most time they didn't need any further lining up.

madman
02-12-2011, 10:25 AM
Just got a tall old die set perfect for realigning crank sections square. Old post is still interesting. I made a pipe machined slot milled down side, now have to try to figure out my new ??? $150 buck 30 ton hydraulic press and ancient power pack. It needs conversion to a two way switch. Currently i use air to raise the cylinder back up., Late rmike

motorworks
02-12-2011, 11:23 AM
Hi
I don't do many now....hated dealing with the general public...
But
Thanks John
That vee block idea is great!!
e2die

John Stevenson
02-12-2011, 12:43 PM
Eddy,
I stole the idea from a jig that was sold to the motor cycle industy for putting cranks together. It was a big screw press with an upstanding angled corner and a loose curved block bolted to it with a long screw to hold it in line.

I just 'adopted' the idea and used two vee blocks and a press, the jig may have been made by Alpha for Villiers, not sure, probably from between the wars.

Just done a search and this is available in the US

www.roweusa.com/PDF/09-1179%20%20Truing%20Instructions.pdf

Alpha's words and music is here.

homepage.ntlworld.com/david.../v.../Alphacrankreconditioning.pdf

The latter is very good reading but never seen one of these jigs.

RobbieKnobbie
02-12-2011, 12:43 PM
I can never understand the stupidity exhibited by manufacturers when it comes to spare part charges. We all know how much you would expect to pay to have a "One off" manufactured, but this isn't the case as once the go button is pressed, there are dozens on the floor. I know it costs to store and the guy that has to pick it off a shelf has to have a wage but shelves have more on them than the bit I want and the picker doesn't sit waiting for my order. It's difficult when you manufacture components in small quantities to a contract specific design, but the major manufacturers don't. Our throw away society is driven purely by greed.

Regards Ian.

I know this thread is old, but I have some pennies to throw in on this one...

a lot of parts orders ARE one offs. In these days of Just In Time and Kaizen, any parts that are on the shelf for more than a certain period of time (I've seen companies that use as little as 6 months!) they are discarded as the cost of keeping them on the shelf is greater than the profit in selling them.

So when Joe Shmoe comes along looking for a crank, someone has to go dig up the print, spend time making sure it's still manufacturable as drawn. That's money right there and no one's made a single chip yet.

Then someone in purchasing has to get bids on the newly revised print (I haven't seen many one-offs made in house, they seem to always get farmed out). Then some shop has to make it. Since it's a one off, they have to build the cost of mistakes and/or learning curve into the bid price. Still more money and still no chips yet.

Then some guy makes the part, it has to be inspected individually, since there's no in-process or batch inspection.

Finally the parts come back, they have to be packaged and shipped to the store you ordered them from via ten or twenty levels of distribution.

Of course, the company has to ensure a profit on the part, so they mark it up 100 to 200% before they will sell it to you at all.

I've seen parts MUCH simpler than a crank being sold for saveral thousand dollars. I fealt bad sending out the quote sometimes, but everyone along the line has to get their share.

motorworks
02-12-2011, 04:39 PM
Thanks John
That Alpha book is excellent
Funny, although I never saw it before, I build many of the same type jigs in the shop when I rebuilt cranks....
Trouble now days is the dealers have made the bearings,rods, washers, and pins cost almost as much as the crank. That along with some aftermarket ATV cranks coming from China...
e2die

Don Young
02-12-2011, 10:42 PM
Just done a search and this is available in the US

www.roweusa.com/PDF/09-1179%20%20Truing%20Instructions.pdf


That looks almost exactly like the ones used by Harley and Indian dealers back in the 40's and 50's.

We always used a lead hammer for alignment.

I have several Kawasaki triple crankshafts I need to rebuild when I get one of them round things (tuits).

Thomas Staubo
02-13-2011, 07:42 PM
...
Alpha's words and music is here.

homepage.ntlworld.com/david.../v.../Alphacrankreconditioning.pdf

The latter is very good reading but never seen one of these jigs. John, your linky doesn't worky.

But here (http://www.saltmine.org.uk/pdfs/alphacrankreconditioning.pdf)is another link to the same document.


.

John Stevenson
02-13-2011, 08:28 PM
Thank you Thomas it doesn't work for me either but Eddy looked at it somehow ???

Anyway fixed now thanks to your link.

motorworks
02-13-2011, 10:07 PM
John
Put your old non working link in google...and I found a link that works
Book printed off and in "shop notes" binder...thanks again!!
eddie

madman
06-07-2012, 09:08 AM
OH just wished to mention a pin shooting out of a 30 ton press WILL go tright through a Concrete Block Wall. !! (I did this when i was around 20 years old trying to take cranks apart back then, afterwards I ga=ve Up . NOW though Im a lot dumber at 54 years of age and want to try again .Thanx All Mike

justanengineer
06-07-2012, 10:17 AM
Several years ago myself and my father took an excavator bucket we had bought into the local Cat dealer bc it had both ends of one mounting pin mushroomed a bit and solidly stuck in the bucket regardless. They torched a chunk out of the middle of it (between the mounting ears) and two of their machinists used a "sledge on pick" combo to remove half of the remaining pin from one bucket ear. They then used the torch again to blast a hole through the center of the other half to hopefully allow it to flex a bit, and they put their big portable track press on it. Somewhere between 40-50 tons the remaining 2 lbs or so of steel pin let go with a big bang and took a 5 inch deep chunk out of their concrete wall. Luckily nobody was hurt, and their shop walls were something over a foot thick of poured "cratered" concrete, so it was no big deal.

Long as you stay out of the way youre good, but I highly recommend presses that have remote pendants or scatter shields over them.

MrFluffy
06-07-2012, 11:09 AM
Here's my bits, I've split 4 cylinder cranks that have been welded in the past with this. Its just two pins (one halfmoon to miss a drive gear which obscures the pin) and a large C plate which the hollow bit of the C corresponds to about 4mm wider than the big end outer. The picture quality sucks but you get the idea.
http://www.oldskoolperformance.com/forum/download/file.php?id=3839

The pins are just offcuts from a car halfshaft (range rover). You need to use them because the crank nose will foul the press frame otherwise. Ive got a hollow on my press these fit inside.
http://www.oldskoolperformance.com/forum/download/file.php?id=3840

The right hand nose has evidence of weld. A lot of people say you can't strip cranks once they've been welded, but the weld is very weak in the plane where you push it out so I've managed with only a 20t chinese press. Once apart you can clean up and reuse, if there's no marks that won't machine out. The cranks are welded as they're assembled so you build that cylinder, get it true and then weld it, and build the crank up as 4 separate units. Or 3 or 2...
I stand with the frame between me and the job, and wrap a blanket round it loose to try and take some of the energy out of things should they ping out.
Unwelded crank's are much less nerve wracking. I'd like a better press one day. I had to widen the anvil area to get the crank to fit down inside it.
http://www.oldskoolperformance.com/forum/download/file.php?id=3841
Something under the press in the event to catch the crank remains as they drop out underneath/are fired out downwards that wont hurt the crank is a good idea too. My main grief is getting replacement conrods.

You'll want a ground precision test bar the diameter of your wrist/gudgeon pins, the final check of index once its all back together is to slip the bar in and make sure it feels right. I weld them after theyre indexed for the street (the factory started to do this in the last few years...) and next time I'm adding some pins intersecting the big end pin and the crank web that I'm going to weld over the top of once its done.

flylo
06-07-2012, 02:22 PM
All I know is Rotax 2stroke aircraft cranks are very high price & they recomend 300 hour replacements & claim they're not rebuildable. Rotax was smart, when all the other 2 stroke makers left the aviation market the stayed & just trippled they're prices. The joy of toys!