Motoplat Removal

[PJM]

O.K. gentlemen, what is the trick to remove the reverse threaded motoplat nut.  An air impact wrench at 100 psi has not worked.  I've laid the bike on its side and have given it a daily spray with PB Blast for 3 weeks now, but no luck.  Any suggestions on what to try next?

Pat

pjm

[firstturn]

Pat,
  It sounds like you have the patience of a spider and thats good.  The problem is what damage can be done trying to remove this nut.  I don't know what method to offer not being right there to examine the engine, but the next step for me would be heat.  I would let this post(on the Forum) set for several days and see what the experts say.  One other note if you use heat be prepared to check and/or replace the seal behind tne flywheel.  Also if you can try to put some type of heat sink to absorb some of the heat.  And I have assumed we are talking about a full flywheel as opposed to a internal flywheel.

Ron Carbaugh

[tmc3c]

Hi PJM. I just went through the same thing.Here is how I won the battle...Soaked with pb blaster,got the biggest strap wrench I could find along with a large friend to hold it while I pulled the long 1/2 drive pull handle,and after a couple of tries the battle was won.Do you have the puller you need to remove the flywheel ? If not Al has them I just had to but one myself. Good Luck!!

Thomas Carmichael

[john durrill]

Pat,
 You might want to go easy with this. you could snap off the threaded end of the crank.
 another option could be to  use something like a dremmel tool and cut a slot in the nut. I believe Al has nuts for both a Sachs and KTM engine's on hand.
 cut down till the metal of the nut is thin and then try removeing it.
you should not cause any thread damage to the crank shaft end that way and relieve some of the presure holding the nut on.
 If its a Sachs engine the shaft end is small , i have 3 that folks snapped off at the taper on the shelf.
John D.

[tmc3c]

I was working on my 250 ktm.

Thomas Carmichael

[swamp fox]

Pat,
John was right on my thoughts. I agree with the dremel tool also. Cutting the nut twice at 180 degrees and you can split it carefully with a small chisel. Good luck, and may the force be with you.[^]

You may not be able to get 180 dgs, but cut the top off.[|)]

Robert Manucy
72 Berkshire

[Gary Brinton]

I use a chain wrench which I wrap around the flywheel and "jam" the handle against the frame.  I got the chain wrench at Sears for $15. This keeps the flywheel from turning. Then a 1/2" drive xx mm socket with an 18" +/- breaker bar to remove the nut (reverse thread as you mentioned).  Then use the flywheel remover.  This has worked on both my KTM and Sachs motors.

[tomale]

I like John's idea of using the dremel to remove the nut. As long as you do not go all the way through. The only thing that I would like to add is that if you get it to turn,.... go slow. do not try to ssnap it off or use too much force. I have seen guys use big wrenchs with a piece of pipe over it to get enough leverage but this is not a good idea...you could very well snap off the treads too if it is really rusted on. you can not just weld them back and it will mean that you will have to replace the whole crank. It would be better to make several cuts into the nut than to use too much force. I have been in situations that when I cut is once it was not enough but twice made a big difference.... Good luck

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

[PJM]

I want to thank each of you for your suggestion.  Each seems like a plausible choice.  Here is the 3 step process that I tried:  
1) I took a chisel and hammer and tapped the end of the crank a few times and tapped the face of each side of the nut a few times thinking I might break the rust in the threads free.
2) I then applied the impact wrench with 100 psi :(and finally
3) I then pushed the bike 3/4 mile [V] to the service station and bingo...to my surprise []the mechanic used their impact wrench with very little thrust to take the nut off with ease.

That college level logic course I took sure comes in handy...if step 1 & 2 didn't work, then 3)pushing the bike 3/4  mile did, right?!?!  Who would have guessed that?  Sure the hell not me.  Do you think I'll get rich selling this advice?  

Well the bright side is that I educated two more people (the mechanic and the 80 some year old service station owner) about Pentons, there was no service fee, and I got some good exercise pushing the bike 1.5 miles.

Ron Carbaugh, not only was I patient as a spider, but I was as determined as a bull.

Pat Mickevicius

pjm

[john durrill]

Pat,
 we have had problem over the years with air impact tools. here is what we found.
  the air supply could not provide the volume needed to run the tool at full power.
 we have upgraded over the years to a 80 gallon tank and a compressor the will deliver enough CMF at the rated psi to drive the tool.
 the length and size of air hose plays a big part also.i can run a cutoff tool with a blade at fill rpm with our set up but if i go from a 25 ft hose to a 75 ft to work in the yard it takes a lot longer to cut and will bind and stop a lot. the difference is the long hose cant provide the needed cmf at the rated pressure  the tool needs.
 bet thats what you were running into.
 John & Peter D.

[firstturn]

Pat,
 And your a nice guy, but I would be disappointed to find out that you didn't wear full Moto-X gear during the push to the station.  Keep in touch.
John,
  Just to add to your excellent point on the long hose.  The reason for the problem is friction. The extra hose lowers the pressure dramatically the longer it is.  And another point for those that have a portable air compressor, DON"T run a long extention cord(electric)unless it is industrial grade.  It will ruin your motor (burn it up) under extended use.  Don't ask me any embarrasing questions on this -Trust Me.

Ron Carbaugh

[Dr.2Stroke]

i had this problems several times,annd the strongest air tool dont work,because the flywheel is beginning to rotate. use the original KTM special tool to hold the flywheel,use a strong 17 nut and the equal wrench,take a long bar which is fitting over the wrench,and may be you need to be two person. the one holds the tool,the other the wrench ,and pull smoothly,and suddenly the nut is coming! but its a left thread,dont forget!