Building a SP125C / 101B Kart Saw

[ozflea]

The Go Power reed cage I just bought has no stops at all. The manifold basically acts as a stop as close as the cage fits in there.

Whats the reeds made of are they metal ? if so a broken reed is disarster fibre ones will do less damage if they fail.

McBob

 

[Eccentric]

Don't worry Aaron, you'll know when they start to fray...

Mark

Well yeah Mark. I was trying to get a gauge of how long these 'homebrew' reeds cut from hobby shop fiberglass or CF would go before that happened.......

Supposedly the Boyson reeds are "two stage" I think, which gives a better response at idle and better top end. Have no idea how much difference it makes, but I have been told that it makes a huge difference. I am guessing that there are two thicknesses involved....... I wonder if they sell "uncut" versions of those reeds that you can cut yourself....? Or is it just two thin reeds that are partially overlapped?

The 2-stage reeds have stiffer bottom reeds with windows cut in them, and more flexible top reeds that cover said windows. Look at Turtle's RC2 reed system pics. The top reeds open at lower flow rates (and the intake charge flows through the ports in the bottom reeds........supposedly increasing charge velocity), while the stiffer bottom reeds only open up at higher flow rates for more flow. I used to run the fiberglass Boysens on my dirt bikes in the 1980's. They did seem to add more "snap" to the bottom end. Top end seemed about the same. Maybe a scosh stronger. The big thing was the piece of mind gained by ditching the SS reeds for ones that the engine could 'eat' with less damage....

 

[blsnelling]

Whats the reeds made of are they metal ? if so a broken reed is disarster fibre ones will do less damage if they fail.

McBob

They're fiber reeds.

 

[24d]

Who saw is this?
View attachment 212208

 

[cpr]

Looks like the one apse sold a couple years ago. I have a bunch of pictures of it. Beautiful saw.

 

[24d]

Beautiful saw.

Yes, it sure is that.

 

[54stude]

I'm sure what most of you are missing is the total reed area thats why the V4 reed gives the 101 and the SP125 such a lift in performance and why i chose to modifiy the airbox to let one use the sloper manifold and V4 reed block and keep stock appearance .

And heres what a stock bog 125c goes like with this conversion.

McBob.

For argument sake, how close to a true "kart saw" would a 123cc mac stock saw (797, sp125, cp125) be with a v4 reed setup, sloper intake, and big carb?

For example, unported 101b saw = 100%
then unported sp125 v4 sloper saw = ??%
and stock sp125 = ??%

I understand 797 and cp125 porting might be a little better than some other saws, but how much of the "kart saw" is in the kart block and porting, and how much is carburation, intake, and reeds?

Thanks in advance to all of the knowledgeable guys on here for sharing info!

 

[cpr]

Far from an expert and I'm not sure it is totally quantifiable, but I'd say it has to work as a system. 1:1 changes, the intake is worth more than porting, but to maximize either, you need both since that's how they were designed to run. Bob's SP-125 block with sloper and big carb works so well because he's ported it to maximize the whole shootin' match.

 

[ozflea]

For argument sake, how close to a true "kart saw" would a 123cc mac stock saw (797, sp125, cp125) be with a v4 reed setup, sloper intake, and big carb?

For example, unported 101b saw = 100%
then unported sp125 v4 sloper saw = ??%
and stock sp125 = ??%

I understand 797 and cp125 porting might be a little better than some other saws, but how much of the "kart saw" is in the kart block and porting, and how much is carburation, intake, and reeds?

Thanks in advance to all of the knowledgeable guys on here for sharing info!

Well the major difference is the removable head on the 101 and boost ports the 125 has neither unless your like me and do the boost port mod on the 125 ports are standard and the same in both cases.

The saw in the video has not had the ports altered it is stock.

McBob.

 

[blsnelling]

I had some time this afternoon to make some good progress on this 1st 101 engine.

New bearings installed on the crank.

Crank installed and PTO side seal installed.

The first of the two flywheel side seals.

Second seal.

 

[blsnelling]

Goo grease to hold the new rod bearing needles.

New 190,000 rod bolts.

Torqued to 90 in pounds.

This one his the block a little.

Beveled just a little for clearance.

 

[blsnelling]

Block sanded smooth and flat on the sealing surface.

The oil tank will be coming back off. I need a gasket for it. I wanted to get the engine closed up.

 

[RTK]

Looking Good

 

[Tzed250]

That interference between the rod bolt and case is one of the reasons for the use of the spline drive bolts.

BTW, what bearings and seals did you use? I need a set!

 

[blsnelling]

That interference between the rod bolt and case is one of the reasons for the use of the spline drive bolts.

BTW, what bearings and seals did you use? I need a set!

Both were provided by Terry Ives. I can get you PNs for the seals if you'd like.

 

[leeha]

That interference between the rod bolt and case is one of the reasons for the use of the spline drive bolts.

BTW, what bearings and seals did you use? I need a set!

The factory allen head rod bolts have a rounded head so
they clear the block.

Brad, Did these rod bolts come from Terry as well?
They look like standard hardware.


Lee

 

[blsnelling]

Brad, Did these rod bolts come from Terry as well?
They look like standard hardware.


Lee

Yes. They are 190,000 psi bolts.

 

[leeha]

Good to know. I will be placing an order with Terry soon.
Waiting for pistons to arrive.




Lee

 

[Tzed250]

Both were provided by Terry Ives. I can get you PNs for the seals if you'd like.

That would be great!

 

[blsnelling]

The seals are SKF 6763 and 6816, available from NAPA.