0 compression

Well, I finally got my '70 back in to one piece after picking up a "it ran great when I put it away 30 years ago" bike for cheap.

I ran a compression test yesterday and the left cylinder read a hefty 0. From my understanding, this could be a holed piston or tight/stuck valve...or ? I adjusted the valve clearances, which all needed to be backed off but had to fiddle with the left inlet valve several times. Turns out that after turning the engine through, the gap closes up again. This rocker also has some slight sideway shift, and the valve has about half the range of motion (up/down) as the right inlet.

I poked a screwdriver down the plug hole to check piston movement, and the motion felt smooth/correct fwiw. I also swore quite a bit , but that is hardly useful for troubleshooting purposes.

The previous owner told me that he had replaced the pistons and rings shortly before storing it. I was so excited at the time that I didn't ask the obvious question of "why?".

So, Pardon my novice question and thanks in advance for any advice.

Bugger .

A Compressor would be handy, connect to spark plug hole and listen for escapee's .
Sounds like your right about Cam / Valve. But otherwise , after 30 years , the
rings could be gummed up - stuck .
Dumping A.T.F. or Redex in cylindr could clear it. BUT TH RSPONSIBLE thing to do
is lift the Barrel , inspect the Camshaft , and the ' wobble ' in the rods for Big End
Clearance.

A full strip and CLEAN would see minimal investment pracicable . If theres 30 Yrs of
Monsters and boogymen in there , they could wreak havok, and tear everything to bits .

However , Cleanliness is next to Godliness , to eradicate , dismantle , inspect and clean .

Thos silly spring washers let the Rocker push sideways ( cheap skates) snobs use spacers .

Good advice Matt. Sorry House. Get some spanners.
30 Years of condensation.... pistons are alloy but rings are steel,... stuck pushrod,...stuck valve,.... the list goes on.
AC.

And if you did get it going the voice of doubt in your head would be deafening. Good luck. Graeme

Thanks for the responses!

GRM 450 said:

And if you did get it going the voice of doubt in your head would be deafening. Good luck. Graeme

Click to expand...

I was thinking about this exact thing, and you are absolutely right. I have no idea what could be botched up or half busted, and finding out at 60mph might be a tad irresponsible :|

Matt Spencer said:

A full strip and CLEAN would see minimal investment pracicable . If theres 30 Yrs of
Monsters and boogymen in there , they could wreak havok, and tear everything to bits .

However , Cleanliness is next to Godliness , to eradicate , dismantle , inspect and clean .

Click to expand...

I'll start tearing down this week and update with what I find. Perhaps i'll go ahead and strip her all the way down for powdercoating while i'm at it.

I've got a engine sitting in a frame now and will start the rebuild soon. I picked up the club rebuild DVD, along with a few missing tools.

I need to order up gaskets and seals and was wondering is anyone has a recommendation - or are they all created equal?

Thanks!

Old Britts is in your neck of the woods and are a good source for parts and information.

Russ

Got the bike torn down to the frame and motor, with the head off. Here's what I found inside so far:



and



Going to get the cylinder out for rebuild while I move forward.

Oh my, if that ain't a vote to listen to the deafening sound of doubt on a new arrival. You can but other motorcycle but by golly a Commando must learned to the core and made your own. Don't risk old rod bolts get all new and check their seat clearance. You do know the ancient accepted British Iron motto...
"Clean the Sludge Trap".