Matt's Combat Commando overhaul by GrandPaul

grandpaul · Jun 10, 2011

New client project started today with Matt's engine arriving in several parts (he removed the primary & transmission to be able to get the engine out of the frame)

Matt's Combat Commando overhaul by GrandPaul

Head came off first, not too bad-

Oh, yes, it's a Combat...

grandpaul · Jun 10, 2011

Pistons look pretty typical for an old Commando-

Right bore has some etching-

Left bore looks good-

grandpaul · Jun 10, 2011

NOT good; the intake rockerbox drain at the cylinder was plugged solid, lots of fine metal shavings-

Pistons were pretty scuffed up, oil sure is dirty-

I hate to see case halves bodged together with excessive silicone sealant-

grandpaul · Jun 10, 2011

Connecting rods are scratched up, but thankfully not gouged-

Pretty dirty inside the timing chest-

Hobot · Jun 10, 2011

Besides being glad it ain't me that deep in it and you finding no ruined items, the chamber are the best example I've seen of the swirl blast on surfaces and where its stagnating and Singh grooves might apply, in engines pressing their luck with detonation. Very interesting to me,thanx.

pete.v · Jun 10, 2011

That's exciting A new project to watch. Cam looks fair. Is it real(2s)? Scrolless?
Hurry up and get those cases split. I want to see more of the PO's work.

batrider · Jun 10, 2011

Combustion chamber looks pretty darn clean and hone marks are still visible on the cylinder walls. It looks like it has been worked on recently.

grandpaul · Jun 10, 2011

Cam followers are worn and flat spotted, inner right floower is grooved badly (note lip at the left, just next to the center of the two pairs)

This shows it a little better. Cam followers get beaten up when valve adjustment is left slack, the cam beats against them instead of just riding on them.

Photo of the badly worn cam lobe is out of focus, I'll do better close-ups later-

grandpaul · Jun 10, 2011

Sloppy mess, but cases are split-

Scrolled 2S (SS stamped) cam-

grandpaul · Jun 10, 2011

Pitiful excessive use of silicone sealer. I'll bet that's what's plugging up the rocker drain hole through the cylinders. Note these are original unmodified Combat cases with the infamous oil weir-

The dastardly partner to the oil weir, plain drive side ball type main bearing-

These two items contributes to massive failures in many Combat Commandos, some at very low mileage. I'm suprised this one survived as long as it did. I'm guessing it didn't get a lot of extended high speed running, and also rarely had it's oil changed & air filter serviced. No telling WHAT they went inside those cases for, it's not readily evident.

grandpaul · Jun 10, 2011

Crank journals are in decent shape, will polish out without a re-grind-

I miss my old camera; this new Sony, while good, doesn't let me select macro, and doesn't always engage it automatically. Cr@p photo of sludge trap that was not all that bad-

grandpaul · Jun 10, 2011

What was in the sludge trap was VERY grainy, lots of shavings-

...and here's where all the shavings came from: rod bearing shells worn through to the copper cores-

MelloYellow · Jun 10, 2011

Fantastic blow-by-blow account, GP! Please keep the pics and reports coming!
Thanks for sharing, this is great!
MelloYellow

grandpaul · Jun 10, 2011

Hard to make out, but the pistons are standard bore-

Ruh-Roh! Infamous weak "slotted" pistons-

These basically have the crown connected to the body of the pistons by less than 50% of the circumference...

grandpaul · Jun 29, 2011

New parts arriving!

Pazon ignition, dual 6V coils, new plug wires & caps-

Gaskets & seals, valves, guides, rod bearings, roller main bearings, primary chain, camchain, drive sprocket, crank bolts & nuts, barnett clutch plates, tranny layshaft bearing-

Cam & tranny bushings, primary locktabs, camchain tensioner foot-

grandpaul · Jun 29, 2011

Took the cases to my knifemaker friend Enrique's machine shop to mill away the oil wier. He got it all set up and started on it-

Next thing you know, he backed off and said "you've seen how to do, now YOU do it"-

Not quite a mirror-finish job, but perfectly acceptable for the intended purpose-

hudson29 · Jun 29, 2011

When I bought my '72 the previous owner said something about it having been a Combat at one time. I overhauled it completely down to replacing the ball bearings with Superblends and even replacing the crankshaft which turned out to be cracked. What are the telltale marks of a combat? Were they serialized?

Vintage Paul

grandpaul · Jun 29, 2011

As far as I know, Combats are 1972 serial numbers only, and fall within a certain range.

The lipped oil wier at the back of the crankcase sump is something that should be removed. I believe that was the only year for that lip, and not sure what it's intended purpose was.

swooshdave · Jun 29, 2011

grandpaul said:
As far as I know, Combats are 1972 serial numbers only, and fall within a certain range.

The lipped oil wier at the back of the crankcase sump is something that should be removed. I believe that was the only year for that lip, and not sure what it's intended purpose was.

Wasn't it to prevent oil from flying up the breather?

grandpaul · Jun 29, 2011

Yeah, no oil flew out the breather, it just drained out of the blown-open cases and all over the bike and road!