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RE: Mcculloch Torque values and seal interchange chart
hi guys,

heres the torque values for a mc motor as set forth by Mike Savin in his booklet "Speed Secrets and Tuning Tips"

torque values
Coil/lamination Screws ------------55-60 inch pounds
Condenser screws ----------------30-35 inch pounds
Con rod - mc49 mc 91 -------------105-110 inch pounds *
Con rod - mc101 ---------------90-95 inch pounds *
*torquing to 110 possibly could result in a cracked caps.i myself do 85-90 inch pounds
Crankcase End Cover Screws --------60-65 inch pounds
Crankcase Bottom screws -------- --95-100 inch pounds
Cylinder Head Screws -------- --55-60 inch pounds
Exhaust Header Screws -------- ----55-60 inch pounds
Fan Housing Screws ----------------55-60 inch pounds
Flywheel nut ----------------------300-360 inch pounds
Spark plug -----------------------216-264 inch pounds
Clutch Nut ------------------------ 260-300 inch pounds

Bonus info:
the following piston to cylinder clearances are recommended
mc49 series .0045 to .0055 inches
mc91 series .0065 to .0075 inches
mc101 series .0070 to .0100 inches


  second  bonus
Levi Shepherd

  coil gap .018" and points .018" to start with before timing is set. Make sure your timing light is firing when the timing mark on your flywheel hits the front side of the magnet going from left to right. This will give you a good spark and ensure your timing is not advanced to far.

To test your condensor you can take a multimeter set on ohm's to charge your condensor (capacitor) by placing the negative lead on the mounting screw and the positive lead of the multimeter on your condensor lead while it is not hooked up. You should be seeing your meter take incremental readings until it over loads.  Quickly switch back to voltage DC and watch your voltage drop back to zero.  This will give you an indication if your condensor is still good.
hers the seal chart for modern seal interchange
heres two sites that have them cheap

for this site just plug in the seal number and look for what's written below
this is another source though generally they cost more.


Steve Welte

MC91/49/250 PTO NAPA 7414 seal


MC 91/92 Flyweel side NAPA 6763

I think thats right

Vince Hughes
If you have the 3/4 crank, the pto seal is the same as 91mc and 101mc. (numbers are down in the shop) These are different from all other Macs. If you have the tapered crank, 92/101 pto seal is the same.


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Not sure if Vince is responding to the question about the Mc 70 seal but just to be sure, a 101/92 PTO seal will not fit the 70 PTO side. The PTO side journal on the 70 is the same as all of the other pre 101 Super Series motors with an OD of around .785"... much bigger than the 101/92 cranks.

Attached Files
.html   mcculloch seal chart.html (Size: 8.56 KB / Downloads: 41)
Flywheel key specs on a MC92.
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3/8 by 1/8. #213 key at Fastenal or other places.
Ted Johnson,
on cranks seals:
10 hours on crank seals is a real low estimate.
They'll usually run a lot longer than that.
I have to say that I've never had any difficulty in making a Mac run a long time.
They're easy to build, though the super series ignitions are still a P.I.T.A.
Just don't forget to seal those six case cover screws with blue Loctite or RTV.
Use a good torque wrench: #10 fasteners don't give a lot of leeway!

On assembly, I just make sure to tease the crank seal lips with a chisel-tipped Popsicle stick so they don't invert, seal the gaskets, use lots of oil on crank seal areas and pistons and go.
Lots of guys use WD-40 instead of gasket sealer.
Your choice.
I use a bent coat hanger to hold gaskets while spraying.
 Double check that carb pulse hole for clearance.
If you run alky Mikunis, an external pulse is a good idea.

on another note
 I'd never built a Bend (610/820) until about six years ago, and they're the easiest engines of all to do.
They have no vices, and the larger fasteners are a joy to work with.
Love those 5/16" side mount bolts!
A good 610/820 Bend with the exhaust timing corrected will run very well indeed, though they need thinner rings than the stock .062 units!
I expect to have my new Dave Bonbright 610 ready for Fremont.
It'll have .024 rings.


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