McCulloch Chain Saws

[minosi]

Thank you!

I will definately be looking into this.

Will the same setup be on my 1-70?

View attachment 257235

Answered my own Q, this has been removed from the 1-70, leaving just a "stub"...I was wondering what that was for!

 

[cpr]

Mark

Quit some time ago I thought about the De-tuning of McCullochs by the reduction of ports in
certain blocks.

I may be wrong, but I think that those small boost ports are not used as boost ports but
only to blow some gas and oil (mostly oil) into the wrist pin.

If their are any other thoughts on this please jump in guys.

ODW

Happy reading.
Karting Magazine - The Archive

AN EXPLANATION OF THE RELATIONSHIP BETWEEN 3RD PORT DESIGN AND 9 PORT

McCulloch 3rd port ..................... UPDATED 28-8-08 ....

 

[minosi]

Minosi - I really like my 1-72, starts and runs well and I really like the peculiar roller nose bar on mine. I have used it in place of my 066 and prefer the 1-72 for bucking,

And Aaron, it's LOUD and LOUDER.

Mark

View attachment 257236

I'm in that club too Mark, who makes this bar?

Mine only has an engraved part number...came on my 1-70

Andy

 

[minosi]

Alright, have a question...

Does this look normal to you guys?

View attachment 257237

Note that there is no scoring, just discoloration...in case it's not a clear enough picture.

Compression is a little low, at 130.

I do have a thinner head gasket I could throw on there but don't want to do more "damage" if that whats going on.

Seems like blow-by is happening...I'm surprised at how thin the rings are, given the thickness of the 1-70 rings...the cylinder still has clear machine marks.

So, is this normal? What would be the right ring set, if not?

-Andy

 

[cpr]

Rings look fine, but 130 ia getting down there. I need to re-ring mine, too.

 

[Eccentric]

I agree. Everything looks fine, but the rings are probably just worn/tired. That's how my 790 is. Still runs fine, but doesn't have the compression of Randy's 790 or my 740.

 

[OldDeadWood]

Ports

Happy reading.
Karting Magazine - The Archive

AN EXPLANATION OF THE RELATIONSHIP BETWEEN 3RD PORT DESIGN AND 9 PORT

McCulloch 3rd port ..................... UPDATED 28-8-08 ....

Thanks for the links to port info, I am still reading all I can on this subject, however I think I was
missunderstood, when I entered my thoughts about Mark's comment.

Note: I was not countering Mark's comment, I was just trying to add some information.

I have found meny de-tuned cylinders, the kind with two exhaust and two transfer ports, to have
a single small boost port. This boost port is only about 3/8" in diameter and to low to be affective as a boost port.

The only reason I can think of for its being their is to supply fuel mix and therefor oil into the
wristpin, which is the most effeciant way to oil the wristpin bearings.

If any one has any thoughts on this theory please jump in.

ODW

 

[cpr]

Oh yeah. I just pulled out a 200 jug and looked. I remember seeing that little port drilled off the corner of the back channel. I have no idea what it does, but you may well be correct.

 

[cpr]

Like the one at 1 o'clock on this 200 block?

View attachment 257288

 

[joeymt33]

Hey fellers, can one of you McGurus tell me about this handle bar brace? Is it an original Mcpiece or a redneck homemade brace?

 

[Mr. Bow Saw]

Yeah they come with the brace.

 

[joeymt33]

Yeah they come with the brace.

Thanks, is that just for the 70cc motors? Or full wrap handle? Or bow saw? I haven't seen that on the 54cc models.

 

[homelitejim]

Thanks, is that just for the 70cc motors? Or full wrap handle? Or bow saw? I haven't seen that on the 54cc models.

I will check later today to see if there are mounting holes on my gear case but off the top of my head I am going to say not on the 54cc models.

 

[heimannm]

It looks to me like the holes are there, I believe this to be a 2-10G.

I picked up the handle bar some while ago off e-bay not knowing for sure what saw it would fit. When I brought this saw home and took the wrong handle bar off (too short on top) I realized what I had in the attic.

Joey, let me know if you are serious about the G-70; I have it in my watch list but won't pursue it if you are going to bid.

Mark

 

[watsonr]

Thanks, is that just for the 70cc motors? Or full wrap handle? Or bow saw? I haven't seen that on the 54cc models.

On the gear drives only.

 

[OldDeadWood]

Like the one at 1 o'clock on this 200 block?

View attachment 257288

Thanks for taking the time and interest to check this out.

ODW

 

[Eccentric]

Here's a McCulloch block you don't see every day...

This engine is in the McCulloch 740 sent to me by an AS member a while ago. Block # is 58486A. I've only found that # in one McCulloch publication (one of the earlier Pistons/Rings/Cylinders lists). Listed as W1 Welder engine. 103cc, and shares one piston # with one of the bevel drive 'two man' saws. Notice that it has an oval, unbridged exhaust port, thin rings, an unmachined DSP valve boss, and much larger cylinder head fins than a 'normal' super series one man saw engine. The fins aren't rounded either. Whoever put this engine in the 740 bent some of the fins over so they'd fit under the cylinder shroud. There is a blind hole where the third muffler bolt would go. Bolt spacing for the muffler matches 'standard' McCulloch saw mufflers. I haven't put the saw in wood yet, but it has tons of compression and 'feels' very snappy when revved.

Here's my very dirty 790 engine for reference. This block is marked "1-76/1-76" with strikes through those numbers, and "790" on the unmachined 'lubrimac' boss. I measured the bore through the exhaust port and it matches the 103cc saws (rather than the 99c saws such as the 1-76 and 1-86). Notice the smaller, more rounded head fins, the threaded boss for the third muffler bolt, the lack of a DSP valve boss, and the 'normal' three port exhaust.

 

[heimannm]

I have a "790" at home with a 940 welder block installed. Guess I need to have a closer look at it one of these days...

Mark

 

[Eccentric]

I have a "790" at home with a 940 welder block installed. Guess I need to have a closer look at it one of these days...

Mark

This W1 is really an odd one. I don't access to my pistons/rings/cylinders catalogs right now (computer crash), but the W1 was only listed in one of them (1962 IIRC). The later catalogs don't have it (although some have the W170 engine....which shares much with the 940).

The W1 has different ring #'s, and most of the piston #'s are unique as well. Bore measurement 'ranges' are slightly different than what's listed for the other 103cc Mac engines IIRC. I haven't been able to locate an IPL or any other literature for the W1. I do have an IPL for the W170..........on the hard drive of my crashed computer.:bang:

Have you seen any other large frame Mac engines with an exhaust port like what's on my W1 engine? IIRC the SP105 and SP125 saws have ports like that. I don't recall any others. I don't know much at all about the kart engines...

 

[Overtrained]

Got a vid of that saw running eccentric?