1971 Single sided swingarm fastback (2011)

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Some will say that the vernier adjustable sproket is another disaster waiting to happen.....an avoidable one
Yes so i have been told, part of the reason i decided to skip it for now.

anyway, I plan on mapping the cam this weekend, Igot the repaired cylinders and new valve back
 
heres a shot of the repaired studs in cylinders. drill and tapped a large bolt, then drilled and tapped for original studs

1971 Single sided swingarm fastback (2011)


1971 Single sided swingarm fastback (2011)


the machinist told me he chamfered this edge because if you leave a sharp corner in combustion chamber the corner will get red hot and cause detonation. --- I had no idea, learn somthing everyday

1971 Single sided swingarm fastback (2011)



new valve has been installed and head is ready

1971 Single sided swingarm fastback (2011)
 
Hello,
So over the weekend I managed to put the cylinders back on. I had that one rouge lifter machined so it wont jamb up anymore. i set up my dial indicator to measure lift on the cam. Intake came out to .390" and the exhaust .346" . Referencing the Norton spec chart shows this as being a Combat cam. I did a very vague measurement of lift duration with degree wheel, but Im not happy with accuracy (mine).
Anyway, i did a dry run with cylinder head. As a torqued head down i continued to watch valves through spark plug holes and in/ex ports. after head was seated I slowly rotated engine....sure enough, valves are still touching as cylinders approach TDC...both cylinders. I removed head and measured diameter of inlet valve head. I forget the measurement at the moment, but these valves are WAY over sized (referencing the stock Dia in Norton spec chart), and must be the reason Im still getting valve contact.
Push-rods are stock length. and I believe there is only one size of rocker for the commando engines

Pictures to follow
 
Yep, I think Splatt has it, valve looks to be TOO oversize, and not matched to the seat.
 
It will make it easier to check for valve to valve or valve to piston clearance if you do a temporary fit using carb springs in place of the valve springs. This way you can lightly push down on the valve stem to sense clearance as the engine is carefully rotated.

Glen
 
Just a note to say thanks!

I am really enjoying reading about your progress of this project. I would love to do a single sided swingarm on my slimline featherbed ES2, but am nowhere near brave enough!!!

Keep up the good work!
 
splatt said:
The inlet valve appears to be to big for the seat ?, sitting up to high
Click to expand...

Splatt and grandpaul, yep, I think thats it...I was kinda suspect of that, but since this is my first adventure into over sized valves, I wasnt too sure. Im gunna take the head to Rabers this week and have Bob look. Because everything else measures up normal. I figure that few thousands that the valve will reccess down from a properly cut seat will be enough for the valves to have enough clearance.

Thanks for the input
 
motoalchemist said:
splatt said:
The inlet valve appears to be to big for the seat ?, sitting up to high
Click to expand...

Splatt and grandpaul, yep, I think thats it...I was kinda suspect of that, but since this is my first adventure into over sized valves, I wasnt too sure. Im gunna take the head to Rabers this week and have Bob look. Because everything else measures up normal. I figure that few thousands that the valve will reccess down from a properly cut seat will be enough for the valves to have enough clearance.

Thanks for the input
Click to expand...

check with Jim Comstock, but....I think you could sit back a while and ask why the big valves and will they achieve what you hope with a relatively mild cam....

They vales are so large you cannot see the seat, they will likely actually inhibit flow around them....go down a valve size and it will drop into the head and with well cut seats (tri angle) you are likely to get better flow and performance that with these oversize units, you don't say what size but a race bike will perform fairly well with 3mm oversize, a road bike should be happy on standard sizes but with maximized flow around them
 
FWIW KPMI Black Diamond valves for Nortons come in standard size with 1.300" ex and 1.500" in, and oversize with 1.360" ex and 1.560" ex. I've found that you can usually fit the oversize intake with no valve interference, even with most race cams, but you can have a problem if you fit both oversize intakes and exhausts, particularly with non-stock cams. As Jim Comstock has pointed out elsewhere, if you need to sink the valves to get enough clearance, sink the exhaust valve, not the intake.

Ken
 
Steve and Ken,

Thanks for the input, I am going to Rabers tomorrow with the head .... after reading about this subject and making my measurement....and reading your posts, i most likely will be putting the stock intake valves in. It appears that the vakve seats were never oversized ( I bought this head already ike this) personally I have no problem with stock valves as in my other fastback, Im not trying to make a 9000 rpm race motor. This was mainly an oversite of mine...which was caught by another person on this browser thankfully....I would have destroyed my motor.

anyway, Ill update tomorrow and report on the visit to rabers.
 
BTW i made this little bracket that supports the pistons without touching the gasket and sealant while installing the cylinders

1971 Single sided swingarm fastback (2011)


1971 Single sided swingarm fastback (2011)
 
I like your bracket that supports the pistons during assembly....those aren't the dreded slotted pistons are they??
 
cjandme said:
I like your bracket that supports the pistons during assembly....those aren't the dreded slotted pistons are they??
Click to expand...

cj, the pistons were discussed further up in the thread...there are holes under the oil rings we understand, not slots......

I like that bracket too, it has just what you need....simplicity and elegance.....better find some suitable materials :)
 
SteveA said:
cjandme said:
....those aren't the dreded slotted pistons are they??
Click to expand...
cj, the pistons were discussed further up in the thread...there are holes under the oil rings we understand, not slots......
Click to expand...

I still don't like the cutouts. They were done away with for a reason.
 
1971 Single sided swingarm fastback (2011)


1971 Single sided swingarm fastback (2011)


Here are updated pictures of the other fastback, way too much has been finished to list here, but I am really hoping to have it done by end of summer. almost done with tank, and wiring harness waiting for headlight clamps,
 
Looking good. If you watch any of the car and bike build shows on TV, you'd think this sort of project can be knocked out in a couple weeks. The reality is that most of us have to somehow fit the work (and financing) into a normal (more or less) lifestyle. Most of my complete bike projects have taken years, not weeks, to finish. Of course it would help if we didn't end up with multiple projects going on simultaneously. Good to see you heading into the home stretch on this one.

Ken
 
Ludwig, Nice comment, you Germans know your stuff...how do i know...because i have worked for Hans Lingl a German firm 25 years. As you said the course theads are no good at being anti-loose.

ludwig. said:
motoalchemist said:
1971 Single sided swingarm fastback (2011)
Click to expand...

IMO ,the coarse threads on these studs is a mistake .
Your torque nrs are no longer valid .
You will have to recalculate them .
If 16 TPI , add about 50% .
Even then , the nuts are likely to come loose all the time ..
Click to expand...
 
ludwig said:
motoalchemist said:
1971 Single sided swingarm fastback (2011)
Click to expand...

IMO ,the coarse threads on these studs is a mistake .
Your torque nrs are no longer valid .
You will have to recalculate them .
If 16 TPI , add about 50% .
Even then , the nuts are likely to come loose all the time ..
Click to expand...

I have ,since this post, decided not to use these cylinders and have purchased stock commando. Thanks partly to your input
 
lcrken said:
Looking good. If you watch any of the car and bike build shows on TV, you'd think this sort of project can be knocked out in a couple weeks. The reality is that most of us have to somehow fit the work (and financing) into a normal (more or less) lifestyle. Most of my complete bike projects have taken years, not weeks, to finish. Of course it would help if we didn't end up with multiple projects going on simultaneously. Good to see you heading into the home stretch on this one.

Ken
Click to expand...

Thanks Ken, I know exactly what you mean...If I had all the parts I need to finish (whisch isnt much really) and a solid week of nothing but in my shop. I could have this on the road and riding.This project bike was started almost 15 years ago...It has been put on the back burner so many times I just really had to focus to force myself to finish it. Of course many other project bikes have come and gone in the duration.
 
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