The 100 KTM is running!

[Mike Lenz]

My KTM/Sachs 100 is finally running, but not quite right I feel.  It wont run out real clean on top. I went from a 135 main to a 130 with not much difference. It hits the powerband and starts pulling hard and then it feels like its hitting a rev limiter. In neutral it wont clean out all the way if pegged either. I took out the filter just to see what would happen and that helped some but did not fully cure the problem either. I set the deck hieght as for a 125 ktm and timed it as for a Sachs at between 2.75 and 3.25 mm btdc. These are 125 specs, is the 100 different? I noticed the timing for the Sachs 1251/6BGS is between 2.5 to 2.7. I guess I could try that. I havent tested the compression yet. Do any of you know how many PSI The Sachs are supposed to have to run right? Im kind of lost here.

[Rocket]

Mike
I would think that anywhere from 150-175 lbs of compression would be great.  Are you sure the exhaust pipe not plugged or maybe it needs to be repacked.  What carb are you running, one with the cable operated enriching plunger?  If you are, maybe the rubber on the plunger is bad.  I think the timing anywhere around 3mm should be okay.  Sounds like a neat project and I sure you can get it running great.
Rod

[firstturn]

Mike,
  I would check the pipe as Rocket suggested and also try it without the pipe and see what the results are.  Give us a reading on the compression and the plug.....man this is a neat project.[]  Sounds like the Old Mike Lenz days...making things happen.

Ron Carbaugh

[Mike Lenz]

I uncrusted the pipe with a torch. Its clean inside and has new packing. I will take the spark arrester off and see if that makes a differance, and check the compression.
THANKS

[Mike Lenz]

Well I may have found the problem. I have 122 psi warm and 132 psi cool, compression. I know I checked out the cylinder/piston clearance and put in a new set of rings, but this project has gone so slow I cant rememberr if I had the clyinder bored or just honed it. So, My problem could be: A bad bore, I set too much deck hieght on the cylinder, there is too much room in the cases and Im not getting a good enough charge into the cylinder from the cases (since the 72/73 175 lower end has a full circle crank with large holes that I stuffed I thought I would be ok here), or could it be the piston is just not seated in yet all the way?? Anybody ever paid attention on how much compression raises from new to fully seated? It sounds a little loose to me when at rpms, but Im not fimiliar with the "Sachs sounds" enough to be sure. I know its not the carb choke because I couldnt get the parts and filled all the choke passesages with silicone. By the way, were the 100 and 125 pipes different? Also were there different thickness head gaskets for the Sachs? Thanks for your time and knowledge.

[Paul Danik]

Mike,
  There was only one thickness of head gasket for the Sachs and both the 100 and 125 used the same pipe.
Good luck.  
Paul

[Lew Mayer]

Does removing the spark arrestor help or hurt the powerband or is there no noticeable difference?

Lew Mayer

[Rocket]

Mike
I would think that anywhere from 150-175 lbs of compression would be great.  Are you sure the exhaust pipe not plugged or maybe it needs to be repacked.  What carb are you running, one with the cable operated enriching plunger?  If you are, maybe the rubber on the plunger is bad.  I think the timing anywhere around 3mm should be okay.  Sounds like a neat project and I sure you can get it running great.
Rod

[firstturn]

Mike,
  I would check the pipe as Rocket suggested and also try it without the pipe and see what the results are.  Give us a reading on the compression and the plug.....man this is a neat project.[]  Sounds like the Old Mike Lenz days...making things happen.

Ron Carbaugh

[Mike Lenz]

I uncrusted the pipe with a torch. Its clean inside and has new packing. I will take the spark arrester off and see if that makes a differance, and check the compression.
THANKS

[Mike Lenz]

Well I may have found the problem. I have 122 psi warm and 132 psi cool, compression. I know I checked out the cylinder/piston clearance and put in a new set of rings, but this project has gone so slow I cant rememberr if I had the clyinder bored or just honed it. So, My problem could be: A bad bore, I set too much deck hieght on the cylinder, there is too much room in the cases and Im not getting a good enough charge into the cylinder from the cases (since the 72/73 175 lower end has a full circle crank with large holes that I stuffed I thought I would be ok here), or could it be the piston is just not seated in yet all the way?? Anybody ever paid attention on how much compression raises from new to fully seated? It sounds a little loose to me when at rpms, but Im not fimiliar with the "Sachs sounds" enough to be sure. I know its not the carb choke because I couldnt get the parts and filled all the choke passesages with silicone. By the way, were the 100 and 125 pipes different? Also were there different thickness head gaskets for the Sachs? Thanks for your time and knowledge.

[Paul Danik]

Mike,
  There was only one thickness of head gasket for the Sachs and both the 100 and 125 used the same pipe.
Good luck.  
Paul

[Lew Mayer]

Does removing the spark arrestor help or hurt the powerband or is there no noticeable difference?

Lew Mayer

[john durrill]

Mike,
I missed some info on your project some where chuckle chuckle,
 Your using a 175 KTM lower end and a 100 cc Sachs top end?
What size carb are you using and which pipe?
 The pipe for a 100/ 125 CMF Penton were the same Part #. I went the other way in 72 with my 100 and the 125 top end worked fine with the 27 mm Bing and the stock 100 pipe. I think I went up to a 135 main jet with 40 to 1 oil to fuel mix for the 125 cylinder and head.
 How close did the transfer port area match between the cylinder and the cases? You can use some .063 ( its a common size) electronic's solider ( rosin core) through the spark pug hole to check your deck height. Stock is about .045+ or minus.005 on the ones i have checked. Sachs base gaskets were about .020 thick and the head gaskets about .045 compressed , only one thickness for each. 145 to 160 on compression with the throttle wide open and 5 good kicks on the rebuilds i have checked.
 It could be a spark problem. A timing light and some chalk on the flywheel should show you if the spark is droping off at high RPMs. Swipe a battery from somewhere to power the light.
  Man this is a neat project can you post some pictures for us ?
John D.

[tlanders]

Mike,

Congratulations!!!! After I rebuilt my 125 D engine, I had over 180 psi compression. Then I put a Monark head on it and got 220 psi. The engine didn't last long!!!!

Teddy