MCCULLOCH The official McCulloch thread

[Vinnywv]

Ive got a saw story to share. Win in the end....last week i got a mcculloch g70 off ebay. Been wanting one for a spell. It was buy it now for 150+ shipping. Looked a bit rough. However, i was not afraid of a bit of dirt. The seller stated good compression but no spark, non running. I figured it would be a junk cylinder and piston. I have 3, 7-10 saws that all run very good. So i bought it planning on an engine swap. Didnt realize it would not be as simple as id expected. So i started taking apart the g70. Nearly a complete saw. Missing bar plates was it. I got into it a bit and found gritty sap all over under in and out of this poor southern saw. Cleaned off fairly easily. But it was thick. The recoil was a bit weak. Opened it up to wind it a turn and found a broken ear on the pulley. Alas, i had a new one!! Win. The oil pump was missing the little disc. Had a spare there. Win. The fuel tank was absolutely disgusting. Thick corrosion top to bottom. Plus a few pin holes. No problem, the 7-10 is good ill use it. The cylinder had a massive gouge in it, "great compression".. yea right. The piston was toast. Air leak on fw seal. No problem ive got one. After comokete dissassembly i had a box of dirty parts, but a 7-10 for help.....So i began taking the 7-10 apart at 430pm yesterday, stopped at 10pm with a nearly complete new saw. The cylinder from the 7-10 donor was slightly different and needed some material removed from the pto bearing side. Belt sander and 45 minutes later it fit very well. I was very happy with that. Took my time there. Next came piston swap due to g70 crankshaft being very different. No big deal, one pin out one in and viola. Gooped up the surfaces and stuck it together. It turned nicely now. Then all the little bits followed. Now, the fit from a 7-10 that had a dsp on the stop button to the matching cylinder was a must. But it fit just fine, heck it just came off that saw. Then the big gear box...no issues really. It attaches to the oil tank not the cylinder so it was just figuring out what went where and in what order. Today i cut a new oil tank gasket and had to test run it!!! It fired up on a few pulls and everything rotated as expected. Spent a bit getting a chain on it but boy it runs good. Borrowed bar pkates from a 250, and a bar off a sp105 to test run it. The spur gear came off a 55 and it took a bit of cleanup to fit properly. Ill replace it with a new one. Already got it in the works. I cut out a crude oil pump gasket but ive got a good one also on its way. Plus a good handle bar from mark h. Ill post pictures in the next slide. But after 2 full days a taking apart, fitting, and putting back together....i now have a great running and functioning and clean mcculloch g70. Pictures to follow.....

 

[Vinnywv]

This is the saw before taking it aprt

 

[Vinnywv]

The cilinder faired ok other than this deep trench. Its much worse than the picture looks. The other side was also scored up as well.

 

[Vinnywv]

This is the fuel tank. Very thick stuff there.

 

[Vinnywv]

And the saw back together. The bar looks too new for it but again it was for a test run only. Thanks for reading along. It was a fun project.

 

[Steve]

That is super awesome Vinny! That's how I bought all my saws. Loved making them new again! Can't wait to see a video of that beast cutting.

 

[Maintenance Chief]

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The cilinder faired ok other than this deep trench. Its much worse than the picture looks. The other side was also scored up as well.

Very Cool, I lust for one!
I noticed that the old cylinder had a partially divided transfer port, did your replacement have that as well?

 

[Maintenance Chief]

That thing has some......

 

[Vinnywv]

Lmao, yes it has extra nuts. The new bar from mark will be correct.

The cylinder used did not have divided transfers. But runs great nonetheless.

Ill try to make a video soon. I did get a correct length chain for the 24 inch bar. Its a hardnose pro mac. With yellow and black painted tip. Has some war scars. It matches much better now.

 

[Vinnywv]

 

[heimannm]

Does the G70 have a longer crankshaft? I have a few 10 Series "extra long" crankshafts on hand and I am not sure where they are used. One of them came with/in a 70 cc block that was supposed to be a 7-10 but I never really looked it over that closely.

Mark

 

[Vinnywv]

Yes mark. It was much longer. On the pto side.

 

[Woodslasher]

Just a heads-up, @Funky sawman has what appears to be a n.o.s. 70cc Mac block in the trading post.

 

[Dream]

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And the saw back together. The bar looks too new for it but again it was for a test run only. Thanks for reading along. It was a fun project.

Just me, but I like those bars better than the grey/black it would have come with.
Thanks for sharing Vinny!

 

[Vinnywv]

Thanks, if it were 24 id likely put it there but its awfully heavy with that 28 inch bar and .404 chain. One thing i found odd was its a right hand start but the clutch is not keyed nor is the crankshaft for a keyed clutch. Just a tight fit. And it only oils when the chain is moving. Its not a pulse pump. Anxious to test cut.

 

[Al Smith]

That's another model I've never seen .As far as a keyed clutch it was mentioned with the 125 it was found a tapered fit worked better than a keyed system so I might assume they used the same thing on later 10 series .I have several 10 series crankshafts in one of the drawers with damaged ends .I found that info I think on a micro fiche write up produced by McCulloch .I don't have as large of a collection of this stuff as Mark does but I have a lot .

 

[Al Smith]

I looked it up and this model was only made about two years .Why they offered a gear drive in this small of a displacement saw I have no idea . Usually in my way of thinking a big robust reed valve engine would be a better choice in this application . Then again why McCulloch did a lot of things I've never figured out . I mean think about it they couldn't make up their mind which side to put the recoil starter and some of the carbs where not the best option available at the time . This mention of the oil pump has me interested in delving into that question .I'll have to see if I have an IPL on this model .

 

[Steve]

I looked it up and this model was only made about two years .Why they offered a gear drive in this small of a displacement saw I have no idea . Usually in my way of thinking a big robust reed valve engine would be a better choice in this application . Then again why McCulloch did a lot of things I've never figured out . I mean think about it they couldn't make up their mind which side to put the recoil starter and some of the carbs where not the best option available at the time . This mention of the oil pump has me interested in delving into that question .I'll have to see if I have an IPL on this model .

2-10g was the smallest gear drive they made. 54cc.


There where a few manufacturers that made gear drive saws even less displacement than that.

 

[Al Smith]

As luck would have I did have an IPL of this thing .From that this is what I think have figured out .It's a 3 to 1 reduction .The oil pump is indeed a gear drive perhaps similar to what design used by Stihl .Driven from a worm gear machined into the output shaft of the final reduction gear .The pump body itself appears to be on the far right hand side on the gear reduction unit .So unlike an impulse pump this would indeed need the chain engaged moving to pump oil .The chain sprocket used I only assume could be like used on other gear drives except the numbers don't exactly match .They made those thing in many pitches from .404 up to 9/16" .In my little stash of parts I only have .404 and 1/2" sprockets then again I only own one gear drive Mac saw and that's an 87 c reed valve model 650 .
Try as I might I can't figure out why a gear drive using such a small engine unless it's to run larger chain aside from the standard 3/8" used on other direct drives .They can do well with a 28 " bar using 3/8" chain but in say .404 probably not so good

 

[edju1958]

Kudos Vinny on getting that G70 & getting it back in running shape!

I've decided to put a PM650 together with all the parts I have laying around.There are only a couple of parts that I need - oil tank,skid plate,& cylinder jacket.I just bought the jacket for $10 on Feebay.randy Duncan wanted $30 for one.I've got a line on a used oil tank & skid plate & have put offers in on both.I have an oil tank here,but when I dug it out I found it had only one bar stud.After seeing it I remembered that it came off a 610 that had the stud nut overtightened & when I tried to loosen it it just turned inside the tank.I ended up cutting & drilling the stud out of the chain brake,what a job that was! I don't know of any way to make that oil tank good again.I might have to get some odds 'n ends hardware,but that's about it as far as I know.I have:engine w/flywheel,oil pump,throttle handle (in need of new triggers),muffler,ignition module,rear plate,front handle,recoil/fuel tank,clutch & drum,carb,AF cover & filter,engine & carb insulators & gaskets,& chain brake.