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Discussion Starter · #1 ·
I have few sets of Wiseco bigbore kits for the Arctic Cat 650/700 case reed twin
engines. I have been playing with them for about 5 or 6 years now on three different
Wildcats. One set is an original prototype sleeved cylinder kit, another is an original prototype
bored and plated kit, another is a pair of my own cylinders bored and ported with extra exhaust
booster ports added. I bought the prototypes from US Chrome after they did the testing
with Wiseco and Eric Gore of Forward Motion. Eric did all the porting.

I have had mixed results. The 790cc overbore did not work well on my 650 cases, but
have worked well on other customers 650 cases. I have had good results on my
700 cases. I had knocking and overheating issues on the 650 crankcases, but no such
problems on 2 700 crankcases. They are supposed to be the same cases, so I don't know
where I went wrong.

As far as power, I do not have access to a dyno, and have made so many other changes
to exhaust and clutching, that I don't know how much more power the kits make.

Eric warned me of loss of low end with the big exhaust ports I had him do. The engines
are pretty boggy at low rpms. Notice it most when starting off on a slope- like at the
bottom of a trailer ramp. These engines have no exhaust valves, and are a good example
of what happens when you do huge exhaust ports without them. Stiff primary springs help
some, getting engagement rpms up.

Anyone else out there use any Wiseco bigbore kits? Anyone else do big exhaust ports
on engines without exhaust valves?
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