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rebuilding a Johnson 1985 20 hp J20CRCOS what is a Canada Derated Motor What is WOT RPM

AGosik

New member
Hello,
I am rebuilding a 1985 Johnson 20 hp motor it is a J20CRCOS rope start.
What is the WOT RPM range ? What is a Canada Derated motor and how is it derated?
How can I hook up a Tach to tune the motor. Why would some motors use a RPM restricted Power Pack? Thank you all in advance for your help!!!!!
 
that engine can be taken straight upto 30hp.
the difference is carbs and jets.
the carb throat size is what restricts the engine revs and also maybe behind the carb is a plate to stop it getting the
fuel it needs to climb upto 5500rpm's.
these engine run good anywhere between 4800 and 5600, i had a 20hp once and changed the carbs and noticed a small restricter plate behind carbs.once i changed carb and chucked away the restricter plate it flew like a rocket and was then a 30hp.

once you do get it upto full power you might have to get a bigger pitch prop as well, or you might keep
hitting the rev limiter if it has one at all.
Most of those engines were just carb and plate restricted, like a lot of small motorcycles.

and being derated dont always mean it will last longer !!!!!!!!!!! by not letting the engine breathe it can cause
even more carbon build up on the rings.

2 strokes like to rev


phill
 
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