PTO Piston Skirt Clearance Issue

[Sean Wills]

HI All,

I m having a clearance issue as stated above. With the standard PTO on my CMB .21TT the piston skirt hits the flat cut as it comes toward BDC. You can actually see where it touches in the photo( shiny half moon mark). The stock back plate has a half moon cut in it I'm assuming for piston skirt clearance. Would machining some material off the flat to get the proper clearance be my best bet for fixing the issue? I'm new to Outboards so not sure which way to go with this and I dont want to do something that could damage the engine. This engine will be mounted on a Lawless lower. Using the O.S. PTO thats mounted on it in the photo is an option but that requires an additional adapter which Im trying to avoid buying. Thanks in advance for your suggestions.

Sean

 

[moparbarn]

to use the os pto, you will need to clearance it, sean. the cut in the cmb pto is for piston clearance, as you thought. i've got a cmb ls greenhead on an os pto that bob kensill set up. i've never taken it apart to look at what he did to make it work. i'll take a look today & let ya know what i find. maybe you can find someone to trade the os adapter for a k&b adapter for the lawless, & use the cmb pto.

 

[Sean Wills]

Thanks Robin for replying. I decided to clearance the PTO my self. Took some measurements of the PTO and the case to piston skirt measurement at BDC and put the PTO in a Mill and removed some material. It came out great!

 

[Kevin Krogness]

Nicely done!!

 

[Sean Wills]

Thanks Kevin. It took me 30 minutes to read up on how to set things up for a Mill to make sure you get a true cut and 30 seconds or so to make the cut. Time well spent I think. I was going to farm it out to someone cause I was nervous about doing it myself. Glad I didn't. Lesson learned, confidence built.

 

[moparbarn]

good job, sean!! + something learned, always a good thing

. i pulled mine apart, bob had cut the "eye brow" in the os pto he used.