The Hodaka Club Forum

Hello, I have a 93 super rat without the piston. I'm trying to find out the standard size in mm of the piston so I can figure out what piston I need. Everywhere I look it is only listed as standard, .10, .20 over etc I have bought a used cylinder that is 51.25mm approx.

Also is there a difference between the super rat and ace 100 pistons. Most places I found say there is, some say not, but nobody says what the difference is if any. I do not have a reed valve mod.
Thanks

Std. is 50.0 mm. Sorry, I missed the 2nd part of your question. The pistons are different (crown heights). Ace pistons have taller crown heights.

The different crown heights are explained in the Technical Tips section here on the Strictly Hodaka web site. Here is a link:
http://www.strictlyhodaka.com/Articles.asp?ID=252

Assuming you have measured the bore with reasonable accuracy, it sounds as if your cylinder is already bored out as far as it will go. More than forty thousandths anyway. Converted inches to millimeters, 0.040" is 1.016mm, which would be around 51.2. Add a few thousandths for clearance on the piston, and you are looking at 51.25 give or take. If your bore will still take a forty over with correct clearance, it might work out. Otherwise you are looking at having the bore electroplated.

Another difference between the Ace 100 and the Super Rat piston, the Super Rat had a single Dykes ring, the Ace used two standard rings, one an oil scraper and one for compression. I don't know if the wrist pin to crown height is the same. Someone who has swapped pistons back and forth might know.

Arizona Shorty wrote:Assuming you have measured the bore with reasonable accuracy, it sounds as if your cylinder is already bored out as far as it will go. More than forty thousandths anyway. Converted inches to millimeters, 0.040" is 1.016mm, which would be around 51.2. Add a few thousandths for clearance on the piston, and you are looking at 51.25 give or take. If your bore will still take a forty over with correct clearance, it might work out. Otherwise you are looking at having the bore electroplated.

Another difference between the Ace 100 and the Super Rat piston, the Super Rat had a single Dykes ring, the Ace used two standard rings, one an oil scraper and one for compression. I don't know if the wrist pin to crown height is the same. Someone who has swapped pistons back and forth might know.

Mine is bored to 0.060 thousand over and I think it can even go 0.080 over. Paul has these pistons.

I am on my way out the door to catch a plane. Be back Thursday. I only have type 1 ( Ace 100) pistons to 51.75mm ( +.70) over as the largest size we can offer
Thank you
Paul