Modified Homelite Trimmer Engine

This is a Homelite trimmer motor that has been water cooled, giving major port

and cyclinder modifications, larger carburator, and advanced timing to increase

horsepower and RPM's.

This is a picture of a degree wheel mounted to the crankshaft. This is the setup you use to measure port

timing and is a very simple unit to make costing only a few dollars.

Here are the Spec I built my 25cc homelite too which more than doubled its original power.

Homelite Specs

Piston to squish clearance: .015" to .022"

Exhaust port timing duration: 168 to 172 degrees

Intake port duration: 148 to 155 degrees

Blowdown: 30 to 33 degrees (Exhaust Port Opening to Transfer Port Opening)

Piston ring clearance: .002" to.004"

Crankpin to backplate clearance: .020" to .025" (stock is around .150")

Ignition to flywheel gap: .008"

Use Champion plugs gapped at .018" .022"

Transfer ports are slightly widened and raised to achieve correct blowdown

Ignition timing is advanced 12 degrees

Engine is fitted with a machined from billet water jacket and separator ring

First Engine

0.050 Off the bottom of the jug yielded 0.018 Piston to Squish Clearance

0.090 Off the bottom of the intake port yielded 150 degrees duration

0.080 Off the top of the Exhaust Port yielded 172 degrees duration

0.005 Off the Top of the Transfer ports Yielded 28 degrees Blowdown

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