New guy, stihl 024 44mm bore jetting question

[ozarkjeep]

First of all,

GREAT website.
ive been browsing for a few days, spent ALOT of hours reading, and searching.

I recently bought an OLD stihl 240av, from a guy that works at a stihl deal/repair place.
he swapped a 026 cylinder and piston.

saw runs great, starts and idles perfect.

anyway.

After reading here, I realize that the saw must be a 024super, since it shares the stroke length with the 026.
but the cowl only say 240 av woodboss.

But I guess it could have been swapped?

next thing.

I removed the muffler to inspect the piston and bore, looks great.
while I had apart I did some reading here on muffler mods.

SO, I matched the gasket, and drilled a couple of holes in both factory baffles, muffler looks stock outside, cant tell much difference in the sound.

my question now, do I need to rejet the carb?
or adjust the High speed jet?

I richened it a BIT, about 1/8 of a turn, and tested it. stated easy, revved good, idled fine.

I shut it off ( no cutting, dark outside already)

do I need to worry about anything else?

ive got a tach, I COULD measure rpms and tune that way, but I figure there might be some experience here to someone who has tuned a 024 with a larger bore and modded muffler?

Thank you in advance, and again, this site is GREAT, good folks, and the best info out there for this type of stuff.

 

[Lakeside53]

This stuff gets switches around all the time.

Just treat it like an 026.. 14,000 prm bar and chain on. Probably around 1 1/8th turn out on the H, but start at 1.

Whether you need to re-jet ot not will depend on the carb. If you have a WT22C or a WT194, it will be fine.

Does it have the 024 air filter or the 026?


Did you mod the muffler cover as well as the internal baffle? Did you cover have 4 smal holes on the side or four vertically, or???

 

[ozarkjeep]

Hey Lake,

I was hoping you would see this.

I dont know what air filter it has?

If I post some pics, could you describe what it is?

I have a feeling its an OLD frankenstihl.

 

[Lakeside53]

Yep.. Pics are best.

 

[ozarkjeep]

muffler mod ( Ill post pics later) I simply drilled a hole in the inner baffle straight out, and 3 holes in the outter baffle plate.

I probably messed it up.

It seemed to run the same, I wont know until I cut something with it.

here are photos.
can anyone ID this cylinder as a 026 for sure?
the top cover is trimmed to fit the cooling fins.

 

[ozarkjeep]

oh yeah, my sprocket looks spent, is this what I would need to convert to the newer style drive?

http://store.baileys-online.com/cgi-bin/baileys/5051?mv_session_id=9gSi3rHq&product_sku=RD 32457

ive got 4 'pro' chains, 0.325 .063 that came with it, I assume the drive rim is pitch specific, but NOT gauge specific right?

7 teeth or 8 teeth, this is for? speeding up the chain? trade some torque for some speed?

 

[Lakeside53]

Looks in good shape. It's an 026 cylinder. The 024 airfilter kills the performance, but to change it you'll need to change the top shroud and air filter cover.. .Cheap used..

Check the compression... If it's low.. that means they put an 026 cylinder on a standard 024... The ground wire terminating on the upper left buffer is not something I've seen on an 024S before..

 

[ozarkjeep]

whats the LOW compression number?

have gauge will check.

 

[Lakeside53]

If it's not over 145, I'd be checking.. Be sure to use the right type of guage (search on AS - lot's of posts on this issue).

 

[ozarkjeep]

cheap gauge, removed the long plug adapter, used the short plug adapter, ( matched spark plug threads)

reads 125psi.

EDIT:

reasearched here like you said, schrader valve is RIGHT AT the gauge head base, probably 12" of hose between there and the plug.

Will check again with an another comp gauge to get an idea.

 

[ozarkjeep]

Other gauge shows 120, BUT same design, and its about 15 years old ( its been reading low for years)

the saw starts easily, idles great, and seems to cut well, although I can only compare to cheap saws ive used before.

Should i be worried about it?

any definative way to measure the stroke with out dissassembly?

would a squish measure suffice?

What if I removed the cylinder base gasket?
and run 93 octane fuel?

open to ideas here, and I do appreciate your help.

 

[ozarkjeep]

so, ive got a freind with a 026, Ill check his compression with MY gauge and also check my squish. for comparison purposes.

anything else I can do to increase compression if in fact ive got a long cylinder on a short stroke?

 

[Lakeside53]

It will be low on HP... and to modify - would be hard to do anything meaningful - you'd need to adjust everything by 2mm...

 

[ozarkjeep]

How thick is the base gasket?

I can easily raise the transfers and exhaust ports 2mm.

decking the cylinder base would be harder, I no longer have mill or lathe access.

should I just ditch the saw and get another?

 

[Lakeside53]

The base gasket is ony 0.5mm.

Check your squish with solder put in through the spark plug - you'll soon know if there is an excessive gap.

 

[ozarkjeep]

IM getting barely enough pinch on the solder to measure, right around 0.064

that is 1.625mm

( so its obviously a 026 jug on a 024 NON super crank)

too much squish. saw runs great, I guess im just not sure HOW powerful its supposed to be.

gasket is .5mm?

if I eliminate that base gasket that would make the squish 1.125mm
or 0.044, at the VERY loose end of the safe range right?
( ive read 0.022-0.25 is safe here)

IM looking for your serious opinon here, should I run it as is?
screw with it?
ditch it?

I also noticed, both High and low mixture screws, were at about 5/8 turns open.

is this to lean it enough to run with such loose squish?

I have porting tools, ive ported a few PWC engines ( 700 CC 2 cylinder, 2 stroke)
I COULD clean up and raise the transfers and exhaust ports, but decking the cylinder that extra 1mm will be hard for me.
unless I could emulate a surface grinder, with a sheet of glass and some 240 grit sand paper.

Your ideas, input, and help thus far are GREATLY appreciated!