For heating of the rocker shaft removal.... heat the inside end of the shaft seating area of the head, not so much the outer end area, it is the inner seat that is the interference fit. And, in this case it is not "They Say" that make this statement, it is the original engine designers, their instructions are clearly written in the Workshop manual for these engines.
Be sure to check for hairline cracks when looking down the two small stud holes in the cylinder block...use a light into the holes and check if light gets into the pushrod tunnels....quite typical on the Commandos from the stud holes being drilled too close to pushrod tunnels. Oil can work its way up the crack/stud threads and out under the head washer.nuts, dribbling forward and down, looking very much like a head gasket issue. Easy fix is to use locktite on the studs into the two holes.
Yeah, I used red stud locker on all the head studs. I don't like them coming unscrewed when I lift off heads. Didn't think about cracks/leaks though. Thanks.
As a UK Commando owner & a retired fireman, I laughed at "Green Goddess". Here, that's a 1950's cold war military fire engine which manages about 30mph. "Jugs" is an interesting expression too. Very methodical approach, well done so far & good luck.
Purchased a new a 1974 850 Commando in UK that "blew up" at the end of 6500 miles around Europe in 1974 from stuck value guides. That prevented normal valve operation that inhibited oil flow that blew the oil lines off the head that caused billows of smoke to end our trip in downtown London. Got fixed under warranty and shipped back to the US.
With the rings being stuck like they were when you first removed the jugs, that is probably the source of your low compression. Also, for a fresh engine, that is some shitty cross hatching. I love when a customer comes into my shop saying their engine was just "professionally" rebuilt. That almost always means I am going to have to take it apart and rebuild it correctly. Especially on the old British stuff. The rings not expanding and being stuck in the piston grooves is your "smoking gun". The bike will not run with compression down around 60 or 70 which is what you measured it to be in past videos.
@@fjdelmonte Be sure to confirm the primary timing scale is giving accurate reading...they have been know to be 3-6 degrees off. Use a degree wheel and a piston stop to determine true TDC...then set to your desired advance timing, install primary and see what the scale reads....adjust accordingly.
If the head was missing the underside stud nuts front and rear, then that right there means poor compression. Note ARP makes a nice rear underside 12-point nut, similar to what you have on the other head/block fasteners on this bike. I think it fits the 3/8 stud but uses 7/16 12-point wrench, which gives decent clearance under the head compared to the stock nut. For the valves, did you consider doing a leak test with gas/solvent etc sitting on the valves with the head upside down to watch over 20 or 30 minutes if the liquid leaks past valve seats?
I still have time for the valve seat leak-past test. I will do it. But, the work done so far shows good skills. All the piston/bore/ring gap/ring clearance measurements were within spec. The "rings stuck in the grooves" problems was probably from sitting idle for 10 years without starting. The failure to complete the head installation is quite interesting though.
What's the reason for removing the rockers? Those pistons look like the early type slotted behind the oil control ring instead of drilled If they are slotted they need to go straight in the bin Incase you don't already know the slotted type causes no end of grief when the top of the piston came off That's why Norton changed to the drilled type
The rockers are in the way of the springs and block my old fashioned spring compressor. I will check the pistons for slotted grooves. They are .020 oversize so they are not original.
I found, when recently working on a Commando 850 head, that by removing the front isolastic main bolt, and pivoting the front of the engine down, I could gain another inch or so of clearance to extract and replace the pushrods.
That is a good question. The cam faces show no wear at all, indicating it may be a new cam. And it may be a special performance cam. The only way I know to determine if it is a stock cam would be to measure the lift of the lobes with a dial indicator. I have the tool. And I can probably find the lift measurement. I will give it some thought.
For heating of the rocker shaft removal.... heat the inside end of the shaft seating area of the head, not so much the outer end area, it is the inner seat that is the interference fit.
And, in this case it is not "They Say" that make this statement, it is the original engine designers, their instructions are clearly written in the Workshop manual for these engines.
True and thanks. I will heat from the inside from now on.
Be sure to check for hairline cracks when looking down the two small stud holes in the cylinder block...use a light into the holes and check if light gets into the pushrod tunnels....quite typical on the Commandos from the stud holes being drilled too close to pushrod tunnels. Oil can work its way up the crack/stud threads and out under the head washer.nuts, dribbling forward and down, looking very much like a head gasket issue. Easy fix is to use locktite on the studs into the two holes.
Yeah, I used red stud locker on all the head studs. I don't like them coming unscrewed when I lift off heads. Didn't think about cracks/leaks though. Thanks.
As a UK Commando owner & a retired fireman, I laughed at "Green Goddess". Here, that's a 1950's cold war military fire engine which manages about 30mph. "Jugs" is an interesting expression too. Very methodical approach, well done so far & good luck.
Purchased a new a 1974 850 Commando in UK that "blew up" at the end of 6500 miles around Europe in 1974 from stuck value guides. That prevented normal valve operation that inhibited oil flow that blew the oil lines off the head that caused billows of smoke to end our trip in downtown London. Got fixed under warranty and shipped back to the US.
How can stuck valves inhibit oil flow?
The head has oil drain holes at the front and rear
How could it blow the oil lines off?
With the rings being stuck like they were when you first removed the jugs, that is probably the source of your low compression. Also, for a fresh engine, that is some shitty cross hatching. I love when a customer comes into my shop saying their engine was just "professionally" rebuilt. That almost always means I am going to have to take it apart and rebuild it correctly. Especially on the old British stuff. The rings not expanding and being stuck in the piston grooves is your "smoking gun". The bike will not run with compression down around 60 or 70 which is what you measured it to be in past videos.
I'd consider replacing those pistons... they are what I refer to as the 'pop top' pistons. If they fail and come apart ka-boom!
Interesting! I did not know that! I will examine them immediately. Thanks.
They are .020 so they are not original. But I will look closely anyway. Thanks
I am suspecting the cam timing is off given the fact that whoever built that motor did not really know what they were doing
I will be checking it today. It could well be off.
@@fjdelmonte Be sure to confirm the primary timing scale is giving accurate reading...they have been know to be 3-6 degrees off. Use a degree wheel and a piston stop to determine true TDC...then set to your desired advance timing, install primary and see what the scale reads....adjust accordingly.
Good thought! Thanks.
Back off the bloody tappets!!
Huh?
If the head was missing the underside stud nuts front and rear, then that right there means poor compression.
Note ARP makes a nice rear underside 12-point nut, similar to what you have on the other head/block fasteners on this bike. I think it fits the 3/8 stud but uses 7/16 12-point wrench, which gives decent clearance under the head compared to the stock nut.
For the valves, did you consider doing a leak test with gas/solvent etc sitting on the valves with the head upside down to watch over 20 or 30 minutes if the liquid leaks past valve seats?
I still have time for the valve seat leak-past test. I will do it. But, the work done so far shows good skills. All the piston/bore/ring gap/ring clearance measurements were within spec. The "rings stuck in the grooves" problems was probably from sitting idle for 10 years without starting. The failure to complete the head installation is quite interesting though.
What's the reason for removing the rockers?
Those pistons look like the early type slotted behind the oil control ring instead of drilled
If they are slotted they need to go straight in the bin
Incase you don't already know the slotted type causes no end of grief when the top of the piston came off
That's why Norton changed to the drilled type
I really hope you read my earlier comment about the slotted type pistons
If they slotted they should be binned immediately
@@nickmarshall9192 when you say "slotted" are you referring to those odd shaped holes just under the rings?
The rockers are in the way of the springs and block my old fashioned spring compressor. I will check the pistons for slotted grooves. They are .020 oversize so they are not original.
What about the oil rings?
All the rings appear to be new and in good condition. Now that the rings are free in their grooves I am going to reinstall them.
get rid of the slotted pistons
Those valve spring caps look non-stock....some kind of hi-tech material (Titanium)? Agree, not worth it on a road bike of this vintage.
Yeah, but they really are cool. The springs may be extra heavy-duty also. And the cam may be hi-perf. So many unknowns. The fun continues . . .
I found, when recently working on a Commando 850 head, that by removing the front isolastic main bolt, and pivoting the front of the engine down, I could gain another inch or so of clearance to extract and replace the pushrods.
Ohhhhh! Good idea! Thanks.
Frank how can you determine what cam is in it?
That is a good question. The cam faces show no wear at all, indicating it may be a new cam. And it may be a special performance cam. The only way I know to determine if it is a stock cam would be to measure the lift of the lobes with a dial indicator. I have the tool. And I can probably find the lift measurement. I will give it some thought.