Author Topic: Sachs Dolmar 122 rebuild  (Read 63 times)

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Offline Yozhek

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Sachs Dolmar 122 rebuild
« on: June 21, 2021, 03:49:25 am »
Hi,
My name is Ade, i am now of an age that folks here in the UK call 'second childhood'.  OK so i still have control over my bowls and i don't dribble (except for when i see a KMS-4), but i do have some fond memories of my first job working for a small garden machinery company and some of the saws and generators we sold and repaired.  Back then Dutch Elm diesease struck the UK and we sold lots of Sachs Dolmar, 118, 122, 144, 152 and i think 2 KMS-4, plus Pioneer and some Homelite.

122's were the most popular, good tough farm saw with magnesium castings, ball bearing mains, Tillotson Carburettor and Antivibe. So when an early 122 came up for sale on EBay i bought it just because i like them :-)

The saw wasn't i too bad shape externally but the cylinder was scored quite badly, looked like it had seized at one time.  Time to strip, clean and check what parts were OK and which were bad.

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The chain/clutch cover was broken but thanks to those great folks at Chainsawr i have a new one, decals are of course wrong.  Also someone drilled holes in the cylinder cover to fit a horrible hand guard so i kind of covered it up with a 122s hand guard until i can find better.

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Antivibration mounts are a comon failure on 122's and four of the five has split apart, lucky they are available as pattern parts.  Fuel tank vent rubber sleeve had long since split and gone.  The oil tank was filled with old engine oil and needed a good clean out, lucky the clunk pipe was in good shape.  Fuel tank gasket failure is not uncommon on these saws but the early ones vented the oil tank through the gasket, later models had a jiggle pin vent.

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Once i get the engine parts i will post some more, thanks for reading :-)

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Offline Yozhek

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Re: Sachs Dolmar 122 rebuild
« Reply #1 on: June 23, 2021, 12:55:20 pm »
Crankshaft and crankcase.

The original crank looked good but was a little bent on the chain side
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Chainsawr to the rescue again, they had a NOS crank and proper 122 crankcase gasket. The crank was quite rusted but the big end was waxed and good, 15 minutes with some Jenolite got rid of the lumps of rust on the shaft and it was good to go  ;D
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The 122 crank is a tight fit in the main bearing on the chain side and a sliding fit on the flywheel side, i find it easiest to warm the main bearing and oil pump worm gear and drop them onto the chain side of the crank first
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Then warm the crankcase and drop the crank assy in
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Next warm the flywheel crankcase and add that main bearing, followed by the oil seal. The old stock gasket was hardened with age but a little grease softened it and helped it fit.
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Once the seal lip was greased it was time to assemble the crankcase. The crankcase halves can get slightly rotated in relation to each other resulting in a bit of misalignment on the cylinder base gasket face, this can be prevented by temporarily bolting down the cylinder to align everything before final tightening of the crankcase screws.
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Bottom end nearly done, thanks for reading.
Ade
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Offline Yozhek

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Re: Sachs Dolmar 122 rebuild
« Reply #2 on: June 23, 2021, 05:33:03 pm »
Oil pump

The Dolmer 122 achillies heel, the oil pump is driven off the crank by a worm gear and pumps using a piston with a cam and spring mechanism, the flat on the end of the piston working as a rotary valve. The pump never wears out but the worm gear pair wear rapidly if engine lubrication is less than perfect and eventually the teeth strip resulting in a loss of bar oiling.

Dolmar modified the pump twice during the 122's lifetime, first the drive end of the pump was extended to form a support bearing (122S) and secondly the whole pump was moved from part of the crankcase to a seperate casting as in the later 123 saws (later 122S & 122SL).

As this saw is an early 122 model it has the early type pump, for which parts are no longer available. Lucky for me the pump was not in bad condition, the worm gear has some life left and fitting it on the crank in the opposite orientation presents unworn gear teeth to the pump pinion. The pump was showing wear but as only the later 122s type pump piston is available as a spare part i had to modify a 122s pump by removing the support bearing with a lathe and increasing the depth and diameter of the spring recess with a carbide drill.
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Thanks for reading :-)

Ade
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Offline Cut4fun .

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Re: Sachs Dolmar 122 rebuild
« Reply #3 on: June 24, 2021, 06:54:23 am »
Very nice work. 
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Offline Yozhek

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Re: Sachs Dolmar 122 rebuild
« Reply #4 on: June 24, 2021, 06:08:15 pm »
Thanks Cut4Fun :-)

Offline Yozhek

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Re: Sachs Dolmar 122 rebuild
« Reply #5 on: June 24, 2021, 06:21:17 pm »
Clutch and Magneto

With the oil pump back in the crankcase, the oil flow adjuster fitted and everything checked the pump side oil seal can be pressed in.
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There were two types of clutch used in the lifetime of the 122 series, both are interchangable, the early ones had bonded clutch shoes, they didn't wear the clutch drum out like the later all metal clutch but if they got overheated or oil soaked the clutch lining would come unbonded and could wear through the side of the crankcase. The clutch on this saw was dry and in good shape so it was refitted.
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The 122 and 122s used a Bosch points magneto, these things are indestructable, in all the years i worked with these saws not one replacement part was ever needed for one of these magnetos. All i had to do here was clean the points, add some grease to the points pivot and cam wick and check the gap was 15 thou, perfect spark...
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By the way, the points cam fits with the key piece toward the flywheel and the wavey washer under the cam not on top.
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On with the flywheel, fan and starter dogs
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And we have something looking like a saw again, just got to be patient while i wait for the barrel and piston to come from Chainsawr.
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Thanks for reading
Ade
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Offline Yozhek

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Re: Sachs Dolmar 122 rebuild
« Reply #6 on: June 25, 2021, 08:46:36 am »
Final assembly.

I got a present in the post this morning from Chainsawr
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Nice NOS barrel and piston
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Piston, barrel and exhaust all fitted
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This saw has a Walbro SDC carb instead of the later Tillotson HS-148A, this makes me sad  :(
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Chainsawr managed to find me 2 new O rings for the oil pump, good job the pump can be removed without taking the clutch off again  ;D
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Finally all done, runs very nicely, smooth and quiet like it should. The carb is leaning out after prolonged idle so need to get some new diaphragms and check it.
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Many thanks for reading this far :-)
Ade

 

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