298 husky

[Timberwolf]

Had a time getting this one running, just a bit of gunk in the governer circuit. Pulled the carb apart 3 times before I found the trouble.

PITA to start so put a D handle on it, still was bad so put a decomp in the head, much better after that.

Getting rid of the limiter is as easy as blocking the little passage from the limiter seat to the carb bore. A little disk of aluminium in there jumped the RPM up a couple thousand.

 

[Timberwolf]

New inside calipers coming in handy for measuring port widths. With the width of the piston skirt there was lots of room to go wider.

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[SkwerI]

I wish I understood exactly how a carburetor works. I understand the concept, but I have no idea what all the little ports and passageways are for.

 

[rskybiz]

Looks and sounds good :tumbup:
what did you give and where did you get that digital caliper and by the looks it does o.d. as well?

 

[Timberwolf]

Just in case anyone wants to add a decomp to one of these drill pilot in right at the edge of the flat surface on the top of the cylinder at 35 degrees, cut a seat 19mm in diamiter to fit the 13mm socket, then drill out to 8mm and tap 10mm x 1mm. Reach on the hole should be just under 10mm in length leaving the tip of the decompressor flush with the inside of the head. Decomp will also need the vent hole on the side drilled out to about 1/16 in.

 

[Timberwolf]

The calipers came in a set (inside and outside) from Lee Valley which is a specilized tool and wood working store up here.

The idea behind these governers is they are a passage that floods the saw rich at the limit speed. It works by using a ball bearing on a spring, that is tuned to resonate at ~190 hz. Soon as it hits the resonant frequency it unseats and passes fuel directly into the carb bore driving the mixture rich and keeping the RPM down.

One note on the intake is the pulse passage cylinder base to the carb is very close to the intake wall, I ended up blocking the original off with an aluminium slug sealed with JB and drilled another so I could get another couple mm of intake port width.

 

[Al Smith]

The carb on my 2100 is about the same .I thought I had it bypassed but evidently not so .

Now for Skwerl .Get on Tillotsons web site and download something like a model HS carb manual .They tell in detail how the things work .Good drawings ,good discription .

 

[Cut4fun]

I wish I understood exactly how a carburetor works. I understand the concept, but I have no idea what all the little ports and passageways are for.

Maybe this will help some.

If something is amiss with this. Please speak up.

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[jred630bb]

Brian, thanks for the help and tips you are so willing to pass along to others. Im always learning so much from you and others like you. Great work you did with the 298 Husqvarna. Rick!