2 Simplex projects

[pd]

Another option :

IF your connecting rod is in good condition and you think you want to increase compression , deck the case cylinder mating surface by .030" , along with the bottom edge of the cylinder sleeve . Then chamfer the inside lower edge of the sleeve about the same amount .

IMHO, this is not a good idea.  If you deck the case, you take strength out of the mating flange; same thing if you deck the cylinder.  I am dealing with this on a motor now.  The guy that built the motor for my sportsman did this, with catastrophic results.  The flange on the cylinder broke, leaving it useless.  The case was cut so much that the piston head had to be cut to regain clearance!


The stock rod is the weak link, get rid of it.  This is easier and cheaper than decking the case or cylinder.

That's the reasoning I was looking for , Rick .

I'm sure at least a few have considered decking the case , myself included . We have to remember that these motors are 50+ years old and have been subjected to any type of abuse and conditions . That along with the fact that the materials used are not as 'advanced' as they are today .

I do like that 7075 rod .

Pete .

[Bruce]

Why the case and case end of cyl?  Why can't they deck the top?

[Ricks]

Why the case and case end of cyl?  Why can't they deck the top?

Top of what?

[Craig]

I was looking through old posts when I found this, Rick I am very jealous of your build. Its BEAUTIFUL, it has class and style. When I tear my engine apart for the first time what should I be on the look out for? should I put that conn rod in while I'm in there? Any heads up (since I have no experience with these engines) would be great. (I am a mechanically inclined. I worked as a tech at a dealership for 10 years and now teach auto, but I just found these sweet bikes for the first time and have no experience with their idiosyncrasies.

[Mike Sal]

Personally, I think the stock parts are ok to use, given the likelihood of these engines being abused in the future is pretty remote.  Replacing the bearings & restoring the "gap" for the fuel transfer (if needed) is as far as I'd go on them.
Mike Sal

[Ricks]

Thanks for the compliment!  This was my first simplex also, as I came over from the aircooled VW world.

I have one motor running a stock rod and 2 motors running the billet rods.  One of the old timers, who is an expert in these motors, strongly suggests replacing the rod.  He claims it is the weak part of the simplex engine, and that more engines died from a broken rod than anything else.  Cheap insurance in my book.  I have done a couple of things to increase performance, such as a longer rod and .090 oversize piston, and cleaned up the port work inside the center of the crank.  It definitely picked up speed and power.

BTW, this bike is not a trailer queen.  It is registered and insured and I ride it down to the local shops during the nice weather.