Stihl 029 etc. Who is the freaking moron engineer....engine pan bolts

[Jedthro]

Who on this earth thought it a good idea to spec "self tapping" screws? Got everything ready, sealant, oiled bearings, and wanting to bolt it together and snap.

I stupidly didn't look and did not realize the holes were not tapped. So I've got another project on hold until I get some replacement bolts.

After extracting the broken bolt, it looks like the holes are drilled an oddball diameter, A #6 drill slides in but 1/4x20 is .201, so I'm thinking maybe going to 1/4x28. Just for grins, after cleaning everything up, I tried carefully running one of the other bolts in and the threads look horrible.

Don't like it...not even a little bit

What do you pro's do on these engines?

 

[Mad Professor]

I avoid clamshells.

 

[Bob Hedgecutter]

Yeah, okay- the system failed you- but remember these things were never designed for Joe or Jethro Bloggs to tear apart to the bones in their garage, they were designed that any major repairs are carried out by trained Stihl technicians- just have a look at any owners manual, they show you how to change filters, spark plugs, air filters. clutches if you are lucky- after that- take them back to the shop.
When you go deep into the saw yourself, you take on all the hidden joys and risks of failure yourself.

 

[grizz55chev]

Who on this earth thought it a good idea to spec "self tapping" screws? Got everything ready, sealant, oiled bearings, and wanting to bolt it together and snap.

I stupidly didn't look and did not realize the holes were not tapped. So I've got another project on hold until I get some replacement bolts.

After extracting the broken bolt, it looks like the holes are drilled an oddball diameter, A #6 drill slides in but 1/4x20 is .201, so I'm thinking maybe going to 1/4x28. Just for grins, after cleaning everything up, I tried carefully running one of the other bolts in and the threads look horrible.

Don't like it...not even a little bit

What do you pro's do on these engines?

Not trying to be a jerk, but the 029 was also never meant for pro use, strictly a homeowner saw.

 

[cookies]

I take my time turning them in so when it gets tight I go 1/4 of a turn then back it out and when it feels too tight I take the bolt back out and blow it out to remove the aluminum chips. I use the T handle wrench with tiny shank, It takes a good half hour to cut the new threads. The fasteners/holes are metric so I would guess M8 or M10 bolt could be used after running a tap through it.

 

[frank_]

i always dip the bolt in engine oil and wind them straight in, i,m guessing the factory do the same
its all down to ease of manufacture/cost savings, and well proven on plastics for decades

 

[67L36Driver]

I never use the self tapping screws with the aftermarket cylinders.

Just go with 6mm machine threads and buy suitable socket head cap screws if necessary. [emoji106]

 

[Jedthro]

I never use the self tapping screws with the aftermarket cylinders.

Just go with 6mm machine threads and buy suitable socket head cap screws if necessary. [emoji106]

Not trying to be a jerk, but the 029 was also never meant for pro use, strictly a homeowner saw.

I know, but it's what I've used for the last 10 years strictly for firewood. Almost all are uprooted trees or trees taken down by pros that I would cut up.

I've been getting into some larger stuff, over 30" diameter the last couple years and the 029 works fine if I take my time, I just want a little more power so I bought a 49mm p/c for it. I then realized all I needed beyond that was a crank, pan and bolts to have a complete engine that I could just swap out.

According to my tap chart, it looks like I can tap an m6x0.75 still get 75% engagement. I guess that's the way I'll go with it.

I'm also going to assume it's bad practice to reuse these bolts on a new cylinder? I ran one in slowly, using cookies method and the treads on the bolt looked halfway stripped. Really seems to be a piss poor way of doing things.

 

[Jedthro]

Yeah, okay- the system failed you- but remember these things were never designed for Joe or Jethro Bloggs to tear apart to the bones in their garage, they were designed that any major repairs are carried out by trained Stihl technicians- just have a look at any owners manual, they show you how to change filters, spark plugs, air filters. clutches if you are lucky- after that- take them back to the shop.
When you go deep into the saw yourself, you take on all the hidden joys and risks of failure yourself.

I don't mean to be a ****, you don't know me and I don't know you. But I have done some stuff and a silly little chainsaw engine don't much scare me.

I didn't do the design work, but I did build the panels and wire this machine.

Custom design for electrolux to machine weedeater cylinders. Built in 2003, I've slept since then and a lot of the details are hazy, but I kept some the project files, mostly the PLC program stuff.

This is the setup file for 25cc cylinders:

(25cc)
Drill 1 Retract Point= 5.0000
Drill 1 Clearance Point= 4.0000
Drill 1 Drill Start Point= 3.9000
Drill 1 Drill End Point= 0.5000
Drill 1 Dwell (sec)= 0.00
Drill 1 Approach IPM= 50.0
Drill 1 Drill IPR= 0.008
Drill 1 Retract IPM= 50
Drill 1 Drill RPM= 2640
Drill 1 Offset (inch)= 0.0000
Drill 2 Retract Point= 5.0000
Drill 2 Clearance Point= 4.0000
Drill 2 Drill Start Point= 3.9000
Drill 2 Drill End Point= 0.5000
Drill 2 Dwell (sec)= 0.00
Drill 2 Approach IPM= 50.0
Drill 2 Drill IPR= 0.008
Drill 2 Retract IPM= 50.0
Drill 2 Drill RPM= 2640
Drill 2 Offset (inch)= 0.0000
Tap 1 Retract Point= 5.0000
Tap 1 Clearance Point= 4.5000
Tap 1 Tap Start Point= 2.0000
Tap 1 Tap End Point= 1.0000
Tap 1 Dwell (sec)= 0.50
Tap 1 Approach IPM= 50.0
Tap 1 Tap In RPM= 500
Tap 1 Tap Out RPM= 500
Tap 1 Retract IPM= 50.0
Tap 1 Pitch (mm/rev)= 1.25
Tap 1 Offset (inch)= 0.0000
Tap 2 Retract Point= 5.0000
Tap 2 Clearance Point= 4.5000
Tap 2 Tap Start Point= 2.0000
Tap 2 Tap End Point= 1.0000
Tap 2 Dwell (sec)= 0.50
Tap 2 Approach IPM= 50.0
Tap 2 Tap In RPM= 500
Tap 2 Tap Out RPM= 500
Tap 2 Retract IPM= 50.0
Tap 2 Pitch (mm/rev)= 1.25
Tap 2 Offset (inch)= 0.0000
Bore 1 Retract Point= -5.0000
Bore 1 Clearance Point= -4.0000
Bore 1 Bore Start Point= 0.0000
Bore 1 Bore End Point= 2.0000
Bore 1 Dwell (sec)= 0.250
Bore 1 Approach IPM= 50.0
Bore 1 Rough IPR= 0.010
Bore 1 Finish IPR= 0.004
Bore 1 Retract IPM= 50.0
Bore 1 Rough RPM= 6500
Bore 1 Finish RPM= 6500
Bore 1 Offset (inch)= 0.0000
Bore 2 Retract Point= -5.0000
Bore 2 Clearance Point= -4.0000
Bore 2 Bore Start Point= 0.0000
Bore 2 Bore End Point= 2.0000
Bore 2 Dwell (sec)= 0.250
Bore 2 Approach IPM= 50.0
Bore 2 Rough IPR= 0.010
Bore 2 Finish IPR=0.004
Bore 2 Retract IPM= 50.0
Bore 2 Rough RPM= 6500
Bore 2 Finish RPM= 6500
Bore 2 Offset (inch)= 0.0000
Bore 3 Retract Point= -5.0000
Bore 3 Clearance Point= -4.0000
Bore 3 Bore Start Point= 0.0000
Bore 3 Bore End Point= 2.0000
Bore 3 Dwell (sec)= 0.250
Bore 3 Approach IPM= 50.0
Bore 3 Rough IPR= 0.010
Bore 3 Finish IPR= .004
Bore 3 Retract IPM= 50.0
Bore 3 Rough RPM= 6500
Bore 3 Finish RPM= 6500
Bore 3 Offset (inch)= 0.0000
Bore 4 Retract Point= -5.0000
Bore 4 Clearance Point= -4.0000
Bore 4 Bore Start Point= 0.0000
Bore 4 Bore End Point= 2.0000
Bore 4 Dwell (sec)= 0.250
Bore 4 Approach IPM= 50.0
Bore 4 Rough IPR= 0.010
Bore 4 Finish IPR= .004
Bore 4 Retract IPM= 50.0
Bore 4 Rough RPM= 6500
Bore 4 Finish RPM= 6500
Bore 4 Offset (inch)= 0.0000

 

[Jedthro]

I don't mean to be a ****, you don't know me and I don't know you. But I have done some stuff and a silly little chainsaw engine don't much scare me.

I didn't do the design work, but I did build the panels and wire this machine.

Custom design for electrolux to machine weedeater cylinders. Built in 2003, I've slept since then and a lot of the details are hazy, but I kept some the project files, mostly the PLC program stuff.

This is the setup file for 25cc cylinders:

(25cc)
Drill 1 Retract Point= 5.0000
Drill 1 Clearance Point= 4.0000
Drill 1 Drill Start Point= 3.9000
Drill 1 Drill End Point= 0.5000
Drill 1 Dwell (sec)= 0.00
Drill 1 Approach IPM= 50.0
Drill 1 Drill IPR= 0.008
Drill 1 Retract IPM= 50
Drill 1 Drill RPM= 2640
Drill 1 Offset (inch)= 0.0000
Drill 2 Retract Point= 5.0000
Drill 2 Clearance Point= 4.0000
Drill 2 Drill Start Point= 3.9000
Drill 2 Drill End Point= 0.5000
Drill 2 Dwell (sec)= 0.00
Drill 2 Approach IPM= 50.0
Drill 2 Drill IPR= 0.008
Drill 2 Retract IPM= 50.0
Drill 2 Drill RPM= 2640
Drill 2 Offset (inch)= 0.0000
Tap 1 Retract Point= 5.0000
Tap 1 Clearance Point= 4.5000
Tap 1 Tap Start Point= 2.0000
Tap 1 Tap End Point= 1.0000
Tap 1 Dwell (sec)= 0.50
Tap 1 Approach IPM= 50.0
Tap 1 Tap In RPM= 500
Tap 1 Tap Out RPM= 500
Tap 1 Retract IPM= 50.0
Tap 1 Pitch (mm/rev)= 1.25
Tap 1 Offset (inch)= 0.0000
Tap 2 Retract Point= 5.0000
Tap 2 Clearance Point= 4.5000
Tap 2 Tap Start Point= 2.0000
Tap 2 Tap End Point= 1.0000
Tap 2 Dwell (sec)= 0.50
Tap 2 Approach IPM= 50.0
Tap 2 Tap In RPM= 500
Tap 2 Tap Out RPM= 500
Tap 2 Retract IPM= 50.0
Tap 2 Pitch (mm/rev)= 1.25
Tap 2 Offset (inch)= 0.0000
Bore 1 Retract Point= -5.0000
Bore 1 Clearance Point= -4.0000
Bore 1 Bore Start Point= 0.0000
Bore 1 Bore End Point= 2.0000
Bore 1 Dwell (sec)= 0.250
Bore 1 Approach IPM= 50.0
Bore 1 Rough IPR= 0.010
Bore 1 Finish IPR= 0.004
Bore 1 Retract IPM= 50.0
Bore 1 Rough RPM= 6500
Bore 1 Finish RPM= 6500
Bore 1 Offset (inch)= 0.0000
Bore 2 Retract Point= -5.0000
Bore 2 Clearance Point= -4.0000
Bore 2 Bore Start Point= 0.0000
Bore 2 Bore End Point= 2.0000
Bore 2 Dwell (sec)= 0.250
Bore 2 Approach IPM= 50.0
Bore 2 Rough IPR= 0.010
Bore 2 Finish IPR=0.004
Bore 2 Retract IPM= 50.0
Bore 2 Rough RPM= 6500
Bore 2 Finish RPM= 6500
Bore 2 Offset (inch)= 0.0000
Bore 3 Retract Point= -5.0000
Bore 3 Clearance Point= -4.0000
Bore 3 Bore Start Point= 0.0000
Bore 3 Bore End Point= 2.0000
Bore 3 Dwell (sec)= 0.250
Bore 3 Approach IPM= 50.0
Bore 3 Rough IPR= 0.010
Bore 3 Finish IPR= .004
Bore 3 Retract IPM= 50.0
Bore 3 Rough RPM= 6500
Bore 3 Finish RPM= 6500
Bore 3 Offset (inch)= 0.0000
Bore 4 Retract Point= -5.0000
Bore 4 Clearance Point= -4.0000
Bore 4 Bore Start Point= 0.0000
Bore 4 Bore End Point= 2.0000
Bore 4 Dwell (sec)= 0.250
Bore 4 Approach IPM= 50.0
Bore 4 Rough IPR= 0.010
Bore 4 Finish IPR= .004
Bore 4 Retract IPM= 50.0
Bore 4 Rough RPM= 6500
Bore 4 Finish RPM= 6500
Bore 4 Offset (inch)= 0.0000

BTW, my heart goes out to whoever has to work on this thing if its still in service. We had LOTS of issues as there are servos in the bottom section getting flooded with coolant and chips and i could see it being a nightmare after even a month in service. We did a runoff, I forget how many pieces we had to do, but it was several hundred. I could be wrong but I seem to recall the requirement was maybe 16 hours without a failure. We got kinda stressed meeting that.....

 

[lone wolf]

@dmb2613

 

[dmb2613]

where did you get the replacement cyl? If you bought an oem cyl you will have more in the saw than it is worth. If it was aftermarket it is tapped for straight threads

 

[Gord404]

I avoid clamshells.

Me too

 

[Jedthro]

I never use the self tapping screws with the aftermarket cylinders.

Just go with 6mm machine threads and buy suitable socket head cap screws if necessary. [emoji106]

Got 10 m6x1x55 on the way.

The holes are slightly oversize for 75% thread engagement by 0.2mm but I should get at least 60%. A little blue locktite and it should be fine. Worst case it blows up and I'm out 100 bucks. I can live with that.

 

[Jedthro]

where did you get the replacement cyl? If you bought an oem cyl you will have more in the saw than it is worth. If it was aftermarket it is tapped for straight threads

I bought a nicosil cylinder and piston from dukes salvage for $55. But the holes do not come tapped, which I didn't even look at when I tried to run them in. My fault for assuming.

Yeah, stihl sure does love their parts. While it may cost a little more to produce their stuff, it sure as hell doesn't cost them anywhere near what they charge.

 

[Jedthro]

i always dip the bolt in engine oil and wind them straight in, i,m guessing the factory do the same
its all down to ease of manufacture/cost savings, and well proven on plastics for decades

I'm thinking these aftermarket bolts are a lot softer than oem. I can't prove that because I have no oem bolts but that would be my guess.

As far as plastics, I get it but I sure can't see it on aluminum, at least the bolts I have.

You can either displace material, which works fine in plastic or the bolt will have a slot cut with a sharp edge to cut into the material. The bolts I have just look like m6x1.5 standard thread. As I said, I don't have any oem to compare to.

 

[Mad Professor]

Tech bulletin on Stihl self-tapping screws. Use new screws that are lubricated, or coat with oil, when forming threads

 

[Jedthro]

Tech bulletin on Stihl self-tapping screws. Use new screws that are lubricated, or coat with oil, when forming threads

Thanks.

I think my issue is with the aftermarket screws. I went out and tried again, just as a test and the only metal being being displaced were the screw threads themselves. I'm also wondering if the alloy of this cylinder is harder than oem. From what I can see, those screws made hardly no impact.

Lesson learned professor.

 

[Maintenance supervisor]

Ive done the 029 to 039 swap and its a very good boost in power.
Like others have said ,I used oil 3in1 to lubricate the process and to be perfectly honest my wrist was sore from the slow tapping of cutting new threads with the bolt.
That cylnder was made to "NOT" have threads so they weren't forgotten. The process of putting the new bolts in helps hold everything together.
By the way a Pro Mac 7-10 is a clam shell design and it took most other manufacturers 25yrs to make a saw that would even come close to cutting with it in the 70cc class, McCulloch may have been an exception to rule but there are no hard fast rules to most things.

 

[Bob Hedgecutter]

I don't mean to be a ****, you don't know me and I don't know you. But I have done some stuff and a silly little chainsaw engine don't much scare me.

I didn't do the design work, but I did build the panels and wire this machine.

Custom design for electrolux to machine weedeater cylinders. Built in 2003, I've slept since then and a lot of the details are hazy, but I kept some the project files, mostly the PLC program stuff.

This is the setup file for 25cc cylinders:

(25cc)
Drill 1 Retract Point= 5.0000
Drill 1 Clearance Point= 4.0000
Drill 1 Drill Start Point= 3.9000
Drill 1 Drill End Point= 0.5000
Drill 1 Dwell (sec)= 0.00
Drill 1 Approach IPM= 50.0
Drill 1 Drill IPR= 0.008
Drill 1 Retract IPM= 50
Drill 1 Drill RPM= 2640
Drill 1 Offset (inch)= 0.0000
Drill 2 Retract Point= 5.0000
Drill 2 Clearance Point= 4.0000
Drill 2 Drill Start Point= 3.9000
Drill 2 Drill End Point= 0.5000
Drill 2 Dwell (sec)= 0.00
Drill 2 Approach IPM= 50.0
Drill 2 Drill IPR= 0.008
Drill 2 Retract IPM= 50.0
Drill 2 Drill RPM= 2640
Drill 2 Offset (inch)= 0.0000
Tap 1 Retract Point= 5.0000
Tap 1 Clearance Point= 4.5000
Tap 1 Tap Start Point= 2.0000
Tap 1 Tap End Point= 1.0000
Tap 1 Dwell (sec)= 0.50
Tap 1 Approach IPM= 50.0
Tap 1 Tap In RPM= 500
Tap 1 Tap Out RPM= 500
Tap 1 Retract IPM= 50.0
Tap 1 Pitch (mm/rev)= 1.25
Tap 1 Offset (inch)= 0.0000
Tap 2 Retract Point= 5.0000
Tap 2 Clearance Point= 4.5000
Tap 2 Tap Start Point= 2.0000
Tap 2 Tap End Point= 1.0000
Tap 2 Dwell (sec)= 0.50
Tap 2 Approach IPM= 50.0
Tap 2 Tap In RPM= 500
Tap 2 Tap Out RPM= 500
Tap 2 Retract IPM= 50.0
Tap 2 Pitch (mm/rev)= 1.25
Tap 2 Offset (inch)= 0.0000
Bore 1 Retract Point= -5.0000
Bore 1 Clearance Point= -4.0000
Bore 1 Bore Start Point= 0.0000
Bore 1 Bore End Point= 2.0000
Bore 1 Dwell (sec)= 0.250
Bore 1 Approach IPM= 50.0
Bore 1 Rough IPR= 0.010
Bore 1 Finish IPR= 0.004
Bore 1 Retract IPM= 50.0
Bore 1 Rough RPM= 6500
Bore 1 Finish RPM= 6500
Bore 1 Offset (inch)= 0.0000
Bore 2 Retract Point= -5.0000
Bore 2 Clearance Point= -4.0000
Bore 2 Bore Start Point= 0.0000
Bore 2 Bore End Point= 2.0000
Bore 2 Dwell (sec)= 0.250
Bore 2 Approach IPM= 50.0
Bore 2 Rough IPR= 0.010
Bore 2 Finish IPR=0.004
Bore 2 Retract IPM= 50.0
Bore 2 Rough RPM= 6500
Bore 2 Finish RPM= 6500
Bore 2 Offset (inch)= 0.0000
Bore 3 Retract Point= -5.0000
Bore 3 Clearance Point= -4.0000
Bore 3 Bore Start Point= 0.0000
Bore 3 Bore End Point= 2.0000
Bore 3 Dwell (sec)= 0.250
Bore 3 Approach IPM= 50.0
Bore 3 Rough IPR= 0.010
Bore 3 Finish IPR= .004
Bore 3 Retract IPM= 50.0
Bore 3 Rough RPM= 6500
Bore 3 Finish RPM= 6500
Bore 3 Offset (inch)= 0.0000
Bore 4 Retract Point= -5.0000
Bore 4 Clearance Point= -4.0000
Bore 4 Bore Start Point= 0.0000
Bore 4 Bore End Point= 2.0000
Bore 4 Dwell (sec)= 0.250
Bore 4 Approach IPM= 50.0
Bore 4 Rough IPR= 0.010
Bore 4 Finish IPR= .004
Bore 4 Retract IPM= 50.0
Bore 4 Rough RPM= 6500
Bore 4 Finish RPM= 6500
Bore 4 Offset (inch)= 0.0000

That is not my point- I care little what you do, what you have done in the past, present nor future.
You implied the design was at fault- I implied the design was never intended to be torn apart and upgraded by owners of consumer grade saws and using non OEM parts from dubious manufacture..