My 2005 Dyna started out as an 88" TC and is now a 95"er with cams and headwork. I want to strengthen the bottom end but instead of sending it out for balance/pin/weld/Timken/etc., I decided to just have an S&S 3 Piece Crank installed. Researching the S&S got me thinking that while I'm having the new crank put in, why not increase stroke?
S&S sells its crank with a 4 1/2" stroke to mate with S&S short skirted 3 7/8" pistons. Since I already have the 95", I already have the 3 7/8" bore.
I've done some Google searches re the S&S 106" setup and there have been some bad reviews on some forums (not this one that I've found).
I'd like to know from those that have this set up, or are familiar with working on bikes that have it, whether the problems have been overcome or whether they still exist. Do the problems result from the short skirted pistons, or from another source(s)? Any input is appreciated. Thanks.

 

As you Stated your 95" is 4.00" stoke by 3.875" bore

If you up your stoke to 4.375" you would have a 103 with different compresion height pistons.

And if you ran a 4.375 stroke and upped the bore to 3.938" you would have 107. A very proven package.

Does a 4.5" stroke clear the cases without modifications?

S&S sells a 4.375 crank assembly with connecting rods that would be perfect for the the job.

 

I too was debating which size stroked crank to go with on my 88". I decided on the 4-3/8" over the 4-1/2" after many recommendations here and elsewhere, primarily due to piston speed and premature wear. I am mating it to a set of 4-1/8" bore cylinders for a total of 117"....The motor is currently going together so ?I don't have an feedback yet.

 

Yes, the 4.5" stroked crank is "drop in" in the sense that no modifications to the case are required. I will have a Timken conversion done regardless of what I go with. My thought was that if I don't increase bore, I won't have to get new cylinders, or re-machine my current ones.
Can my stock cylinders handle 3.938" bore? I know the 98" kit S&S sells is advertised as having a 3.937" bore, and 98" is the largest you can go with the stock cylinders.

 

I believe the cylinder are the same on a 88' or 96'/103'. Boring them to 3.938 makes a 88" into a 98" and makes a 96"/103' into a 107".

Once again this is a very common and very proven reliable setup.

 

Understood. It's probably worth the cost of the machine work to bore out the cylinders to have the smoother running 107". I'll have a chat with the indie who'll be doing the work.

Thanks.

 

You are correct and 3.938" is the max on stock HD cyls.

 

Are there any issues with machining cylinders a second time? In other words, my cylinders were machined once when I went from 88" to 95", now they would be machined again to go to 107" (plus the cranks of course), does the second machining cause problems? weakness? more prone to... (I don't even know what)?
Note, I have no reason to believe the second machining does cause problems, I'm just brainstorming.

 

No issues.

 

Great. Thanks again.