motor rebuild tools

[Mick Milakovic]

Hi all,
I just began a rebuild of '75 250 motor, and was wondering what special tools I would need for a total teardown.  The bike has been sitting for 25 years, so I plan on inspecting and/or replacing everything.  Also, I don't plan on ever selling the machine.  I've got two motors for it and figure the tools will be a good investment.  In advance, thanks for all your help.

[Kip Kern]

Mick  The main tool is the tool that pushes the crank out of the left case half (bolts to the left case).  I also use this to split the cases once all of the case screws are out.  I am not a fan of the old screwdriver pry trick as it ruins the sealing surfaces on the cases.  A strap wrench and 1/2" impact can remove the CS sprocket, pinion gear, and I made a clutch holding wrench (from an old clutch plate)for the clutch basket.  The rest can be done with common tools.  Upon reassembly, it is nice to have a crank bearing pusher to seat the bearing.  This can be done with a small press.

[Big Mac]

Kips the man, so follow his advice for sure. Having just tackled this task recently on 2 KTM motors, I can tell you that, with the manual from Al B., it's really not hard at all to tear all the way down, with the following exceptions:
1) The tool to push out and later reinstall the crank in the left case side that Kip mentions would be great, but as far as I can tell, is non-existent in the market. Al B. said he knew of no one who had one for sale/borrow either. Probably could be made by somebody creative, beyond my workshop capacity.
2) In lieu of the right tool, I found that by turning things on their side, crank/rod down, supporting the case and applying some gentle persuasion, like some gentle blows with a rubber dead-blow hammer ($5 @ //www.harborfreight.com) to the left end of the crankshaft, it will push out without damage. Leaving the pinion gear nut on the crankshaft to take the hits ensure no damage to threads.
3) Once you get the crank out, the inner main bearing races are pressed on to the crank tight up to the webs. I've never figured out any way, or any tool, to remove these. Good news is I've never seen inner races that were worn or damaged to warrant replacement either. Not even sure if new replacements exist--Al B would know.
4) A good crank rebuild shop is best bet to pull the crank apart to replace the big end rod bearing, press all back into place and balance the crank to specs. If you make damn sure they press it back together to end up with the exact same width as when you started, it all should go back together with the 3-piece crank bearings having acceptable tolerance... manual talks about shimming and milli-thousandths of end play-- not sure the average Joe can tackle such fine tuning, dissassembly & reassembly, and measuring-- easier to "feel" for any noticeable end play (should be essentially none) before taking the crank out, and putting same-width crank assembly right back in when you're done.
5) Now the hard part...the same tool Kip mentions is needed to pull the crank back into the let side case on reassembly. Without said tool, you'd guess a little heat and some gentle pushing on the right end of the crank would be in order...DON'T DO IT. The webs of the crank will all get out of whack and balance and you'll have a mess of a basketcase later. Best solution I found was to take it to someone who knows their biz (in Portland OR, it's Charlie Brown of Superior Sleeve)...he used shims between the crank webs to stiffen the whole assembly up enough, threw it in the freezer, then delicately pressed it in from the right. Then pulled out the shims, and voila, all still in balance and good shape. you could do this at home with a small press and some steel V-shaped shims if you had to.

Other than that, an electric impact wrench ($45, //www.harborfreight.com) works wonders, surprisingly enough. Remember to warm the cases to pop out the various bearings... a driver is probably best, but I bought a half dozen cheap iron pipe fittings of various sizes and used them for bearing drivers both in and out, being careful to only push on the outside race of the bearings. The 3 rods that the shift forks ride on are easier to align into the right case holes if you have the official "alignment dowels"... I whittled up 3 of them from some 3/8" wood dowel and that worked pretty good. With that covered, you should be HOME FREE!

[tomale]

Jon,
It does not sound all that easy to me, but then the engine is not sitting in front of me either. I thought I could not rebuild the top end of my son's XR 200 either but I did it and it runs really good. And no extra parts either.
I have a bottom end of a Bultaco to do as soon as my shop is built, My 10x12 shop now is just not big enough unless I clear all of my tools out and remove the bikes. Time for a bigger shop. good new is that It is all layed out and I am ready to start. Lumber is already here I just have to find some time to get started, hopfully on thurday.
I have been thinking about some of those tools that seem to be unavailable. some of that stuff should not be too hard to make. I got a couple of ideas on how I can make them. I will let everyone know if it works and either you can make one or I will make one for ya. but that is still aways off. don't wait on me. Maybe that guy in sweden has a line of some of the stuff. Could not hurt to ask.
To get the magneto off I went down to harbor freight and bought a tool that looks like a set of lock pliers only it has a chain on it that hooks into it. It is used to hold pieces of pipe. but works just fine on the mag. I was worried that it would scratch it up but it has not. I used it on the XR200 as well and it worked really good. All you need is enough pressure to keep it from turning in the "jaw" as it turns out it is not that much because it is holding on so much surface. If you have to squezze really hard to lock it... that is too much pressure and I am sure that you could crack it or just as bad warp it. I pull the mag off every couple of months just to make sure that everything is in good shape. If it has be especially muddy... I check it. The race in december was really muddy. It was like racing in a mud pit. Everything was under water....Really just ask BigMac he was there. I felt like moses parting the red sea! Were did I put that staff anyway.

Thom Green,I own and ride a 76 250 MC5 MX which I bought new.

[Mike Lenz]

Kip, your right. However thats the only motor tool I DONT have. I believe I have pressed them out if they wont tap out. I use spacers and washers, using the crank nut to pull the crank back in,increasing the thickness of the washers or spacers every time I run down the nut.

[Big Mac]

Mike-- You're a genius, don't know why I didn't think of the pinion gear nut and spacer idea for sucking the crank back thru the left side case and bearing during re-install. I believe it's a left hand thread, and since the nut doesn't have a whole lot of thread -- maybe a quick cheap tool to be made up for this purpose would be a very wide nut cut with left hand thread and hardened. That and a bunch of spacers could be made up pretty cheaply, and a batch handed off to Al B for sale when needed.

I haven't had a problem getting the crank out w/o damaging, and that tool would be a bit more complex and expensive to make up...Hmmmm.

For anyone who's fought the battle of removing or installing the big high torque nuts (mag nut, pinion gear nut, sprocket nut) without an impact wrench like Thom, I gotta tell you...once you've used an impact wrench you'll never go back. A high-zoot air impact is probably great, but the cheapo Chinese built electric impact for $45 has worked like a champ for 3 years on a half dozen engine teardowns..never met a nut it couldn't beat.

[Kip Kern]

Actually, the crank pushing tool would be real easy to make.  It is a flat plate, roughly 1/4" thick that bolts into 3 clutch cover screw holes ,on the left case, via 3each 6mm x 15mm allen heads.  there is a hole drilled to allow this plate to slip over the crank end.  Welded to/around this hole and surrounding the crank end is a pipe with a nut welded on the very end.  You then introduce a 12mm hardened bolt into the nut, thread it down to the end of the crank and tighten.  Viola, the crank is being pushed out of the left case and the cases are splitting (after you have removed the 12 6mm's on the other side)!  Very easy tool to make only if I had spare time I would make them!;)

[Mick Milakovic]

Kip, et al, this is great!  I have a welder and access to metal, so I may be trying to build this and then can post specs to this site.  Then if I build Rocket's motor jig out of wood I'll have a regular cottage industry!

[Big Mac]

Mick -you're the man. Make two and I'll buy one to share with any West Coast guys willing to pay to ship it around. I've figured out how to split KTM cases and rebuild, just never learned to weld. [xx(]

[vmx1963]

quote:Originally posted by Mick Milakovic

Kip, et al, this is great!  I have a welder and access to metal, so I may be trying to build this and then can post specs to this site.  Then if I build Rocket's motor jig out of wood I'll have a regular cottage industry!

Mick - did you ever get around to drawing up the specs for the crank pushing tool?  I've put in a birthday order for a welder with my long-suffering wife and will knock up a motor jig as well.

VMX1963
Western Australia
VMX KTM

[Mick Milakovic]

VMX, that project has been back-shelved until the racing season gets going (probably mid May to June).  Hard to believe, but I'll have more time then because the other bikes in the stable will be running.  It is something I'm going to do, so when it happens I'll post back here.

For the jig, I just used some 2 x 4s and a plywood bottom to rest the cases on.  If you search "motor jig" you ought to find the dimensions.