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Old 03-23-2015, 11:39 PM
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Davezilla Davezilla is offline
Motorized Bicycle Elite Member
Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: Who's Running the Super Rat?

Same thing happened to me when I built up mine, I made the mistake of thinking all these kits were the same when I bought my first kit and my bottom end lasted a whopping 90 minutes of run time before I noticed a critical problem that would have destroyed it in short order but I already spent a lot of time porting my jug and getting it just right so instead of starting over I got a Dax f80 bottomnend and my piston stuck out past the deck a little over a milimeter. This was after I milled the deck and base to get everything just right on the old bottom end.
Got a new jug from BGF on ebay and the ports were tiny and slanted... not wanting to deal with a LOT of cutting to make that jug perform I opted to raise the original one by making a .040" thick spacer and sandwiching it between a set of. 025" thick copper base gaskets to set the piston back where it needed to be in the cylinder.
I learned my lesson there and it took a little extra work but I ended up with a great engine and also gained quite a bit more rpm on top since the Dax lower was balanced so well. Found out later on that there are different rod lengths both for the 38 and 40 mm stroke bottom ends and this is why I ran into these problems, but I learned from it and still ended up with a really nice screamer of an engine.
I am planning another engine build really soon and gathering parts so I can get it all put together in the next week or so. I hadn't been paying a lot of attention to some of the latest engine geometries but I'll definitely check up on all this before I buy the top end parts...
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