"Warm Saw" Stihl 024/034 mess of parts!

[weeks auto]

I was looking through my parts saw boxes and after some pondering and a few non-educated measurements. I decided to try and build a 024/034 hybrid. After looking at the pile of parts I decided to jump in and cut the chamber/head off and try to put something together that atleast runs. The piston will need a little taken off the bottom then it will fit down in the case. The cyl mounting holes need to be slotted and the holes through the fins need to be opened up a bit. After cutting the head off and doing some grinding I got the cylinder to fit pretty nicely. No rubbing on the flywheel. The stock 024 muffler will fit with some modification and the upper plastics might fit. I am going to try and fit an 046 carb with a velocity stack.

As for port timing I have no idea what to shoot for or even what I can get but by Taking 2mm or so off the base and dropping the new head 2-3mm down into the cyl I should have decent comp.

This is all new territory for me since I have never built a raw like this, heck other than one 036 port job I have not done anything like this to a saw. But after rereading chainsaw jims 064/394 thread I thought why not give it a try. The only thing I can lose is time since all the parts were in the junk boxes. Maybe if it runs I will be able to build a pipe for. Or maybe it will be a huge pos and my 33cc homelite plastic saw will cut circles around it. We will see.

 

[Fruecrue]

Looks like you’re having fun!

 

[Michael Rupley]

Tough build. The 034 is 46mm bore and 34mm stroke. The 024 is 42mm bore and 30mm stroke. You will have to do careful measuring and port timing and then the completed machine may be rather out of balance and shake a bit. Anyway nobody hit a home run without a few strikes. Go for it. Mike

 

[weeks auto]

Tough build. The 034 is 46mm bore and 34mm stroke. The 024 is 42mm bore and 30mm stroke. You will have to do careful measuring and port timing and then the completed machine may be rather out of balance and shake a bit. Anyway nobody hit a home run without a few strikes. Go for it. Mike

I was going to try and lighten the piston and pin as much as I fell comfortable doing to try and get the piston weights closer. The port is the area that I have not much experience with. Hoping to find some general number to start with and see if I can get it anywhere close. We will see. I ordered the material for the head, long m5 hardware and some mandrels delrin. I also order some other pistons to give myself a few tries. Thanks for the comments I have some other ideas for this build like a small reed box and perhaps a pipe if it runs.

 

[drf256]

Cool build. Thanks for sharing.

 

[drf256]

Anything near 100/120/80 will run. It's hard to get good numbers on these frankenbuilds.

I have one in the works that got put on hold using the same slug you are. But I used a 46mm 028 Super jug and an 024 standard crank. My hopes were to still keep the CC less than a 346NE for competition.

The 028 has the same base pattern as an 024/026

It was tough to get any near normal numbers, at least on my build, even for a pipesaw.

 

[weeks auto]

Thanks for the info about the timing numbers 028 pattern. I am excited to get the aluminum so I can start on the head. I think this one worked out to 3.042 cubic inches.

 

[drf256]

If you swap in a standard 024 crank, you'll gain case volume and you may be sub 3 ci

Edit:is this a super or standard 024?

 

[weeks auto]

it is a standard 024 30mm

 

[weeks auto]

I thought I saw somewhere that the classes were 3.0 cu in and under and 3.1 cu in and over. I read that as 3.0 to 3.1 is still in the lower class, but I have no idea. I have never raced a saw before. But I am starting to really enjoy figuring it out so maybe it will turn into something. I am hoping I can shed some weight off the piston and pin to try and keep it balanced, but not sure how much material I can remove safely from the id of the pin and from the bottom of the piston.

 

[Fruecrue]

Taking material off the top of the piston is the quickest way to drop weight, be sure to keep enough material above the ring for support.
I would get as far as I could into assembly and fitting before I made that decision.
Timing numbers will probably weigh heavily on what you can / can’t do.
A pop up, while frowned upon by some, can sometimes be very convenient to hit your timing and compression goals.

 

[drf256]

Often, you can't get the compression height you need in these builds.

I had that issue, went through the entire meteor site, and found that the 034 has the highest comp height of any non-strato piston in 46mm.

Any lower crown height, I couldn't get timing right.

 

[weeks auto]

I was thinking of boring the pin out a little or tapering it from thick in the middle to thinner on the outside then taking a little off the bottom of the piston for clearance issues then seeing where I’m at. The pistons weigh around 45grams on the 024 and 61 grams on the 034. Hoping to get timing numbers this weekend after I clearance the piston.

 

[Michael Rupley]

Those wrist pins are really hard. It is not a home workshop job to bore them. Ceramic tools may be needed. I found the 044 and 066 (and maybe others) have a pin that is already tapered inside like you want. If it is the same outside diameter you can grind the length to fit. Mike

 

[drf256]

Those wrist pins are really hard. It is not a home workshop job to bore them. Ceramic tools may be needed. I found the 044 and 066 (and maybe others) have a pin that is already tapered inside like you want. If it is the same outside diameter you can grind the length to fit. Mike

They are tapered. Thicker towards the center.

But they are 12, not 10mm pins.

 

[weeks auto]

I measured timing and if I take 2mm off the base I will end up with 98. 118. 76. Not sure how those number will run as I don’t know much about port timing. I took .015” off the piston skirt to clear the counter weights. I was thinking about taking more off the intake side of piston to uncover the port all the way. I also got the mounting holes opened up so my mounting studs can make it all the through to the top of the Cyl. I reweighed the new 034 piston against the oem 024 and its only a 12gram difference and that’s before machining and polishing. Should be pretty close. Now I’m just waiting on cyl head material and studs.
Any suggestions on porting the lower part of the transfers and should I leave that point that hangs down from the roof of the intake port. Thanks for the comments

 

[Fruecrue]

I’d run it as described. Learn what you can.
It’s easy to go back in to take material out, putting it back in is the problem.

 

[drf256]

Those are great numbers. Pretty much spot on.

Are you freeporting at TDC on the ex floor?

If you aren't, go with more off the skirts. But be careful, it's super easy to get too much intake timing, and I think you're spot on now.

Widen the intake and Exhaust and leave the transfers alone. Don't go beyond the skirt, keep a comfy margin there. Mark where the lower ring gap is, and make sure you leave that corner of the intake port rounded. Leave the tit in the port. Most modern saws don't have one, but it doesn't hurt anything.

That's my $.02. YMMV

 

[weeks auto]

Thanks for the advice! It’s very encouraging.

 

[weeks auto]

I spent some time on lightening the piston tonight. I got it down to 57 grams and the oem 024 piston was 51 grams. If I only ran the top ring that would drop it another 2 but I am not sure if that is wise. I may be splitting hairs here.