Hi guys, I have a set of 62t cylinders that I'm going to run flat-top pistons in. The pistons I'm using have a 4mm higher wrist pin height, lowering the top of the piston 4mm. I'm thinking I need to deck the bottom of the cylinders 4mm to get my port timing back to stock. I don't want to get into cutting domes to lower port timing any more. Do u guys think I'm on the right track with this, any help will be appreciated.
Freestyle 62t flat-top exhaust port timing
- Thread starter pope91rs
- Start date
- Location
- Charlotte NC
i know nothing about motors.....but +4 mill stroker????
No you take it off the top - Those are Kawasaki pistons. You have to use different sleeves to do it correctly. NW Sleeve, R&D Sleeve, Weberpower may still sell them, just about every shop had them in the day.
You can take it off the bottom but thats defeating the purpose...what is your purpose? You can take off the bottom to retain the OEM timing. But then what is the purpose? You wont notice the difference between piston design by just converting. You also need to cut the profile in your dome. Yams are bigger dome than Kawaski - domes are totally different.
Race SJ's all ran Kawaski sized pistons (99% of all superstock or mod racers) both OEM / Wiseco / Custom R&D cut like SJ's / Riva's
You can take it off the bottom but thats defeating the purpose...what is your purpose? You can take off the bottom to retain the OEM timing. But then what is the purpose? You wont notice the difference between piston design by just converting. You also need to cut the profile in your dome. Yams are bigger dome than Kawaski - domes are totally different.
Race SJ's all ran Kawaski sized pistons (99% of all superstock or mod racers) both OEM / Wiseco / Custom R&D cut like SJ's / Riva's
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I purchased a R&D head with flat top domes for what at the time seemed like a deal. I didn't know at the time that the flat top pistons that I bought ( another "deal") had a 4mm shorter compression height, now I'm trying to build a engine with what I have.
What CC? probably 23cc or 26cc. If you take material off the bottom and cut the sleeves back so they will fit in the cases you are still going to need domes in the 30's not 20's. Nobody ever made flat top domes bigger than about 26cc for the Yamaha in the flat top configuration because nobody did what you thinking of doing.
What was normally done, remove sleeves, machine off deck, bore for bigger sleeve, and pocket for sleeve head. Then port to new sleeve. The flat top sleeves have much much bigger ports that the cylinder needs to be ported to. Lots of people preport with a slave sleeve to mark. THe advantage is you go from super low port timing to race timing without have to weld.
Advice - Get rid of you flat domes and flat pistons. Do you know if your pistons are Kawasaki or R&D Dominator Yamaha's (Kawasaki forgings modified) what size are they? In mid 90's they made 80-81 then in the superstock era 84-86.5mm (This stuff is still on R&D's website) Are they big pin or Yamaha pin? I've owned BOTH...
IF you dont understand everything I would recommend SELLING......
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