What year/model? What am I missing?

fastback has distinct styling
the fastback covers are unique to that model, tank, seat & tail combo

same deal with interstate

roadster type cover is common to the rest


typical roadster

(can't fix m typo)

interstate

scroll down for yr/variants
(looks like a buncha errors with these folks)

Thanks all.

Frame number is 138261. Everything I’m seeing says that’s a 1970 fastback with the more square looking covers except for LAB’s post. Correct?

macvittiemotorcycles said:

Frame number is 138261. Everything I’m seeing says that’s a 1970 fastback with the more square looking covers except for LAB’s post. Correct?

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Probably is a Fastback although the Fastback never had the central oil tank and the Roadster was in production by 138261.

macvittiemotorcycles said:

Thanks all.

Frame number is 138261. Everything I’m seeing says that’s a 1970 fastback with the more square looking covers except for LAB’s post. Correct?

Click to expand...

it's up to you, which way u wanna go, fastback, roadster, interstate, or mixing it up like interback etc, some bits mix, others don't but may mod up, then the sidecovers need to matchup

Ur fuel tank is prob fiberglass & can't be used with ethanol, prob can get in steel but i'm not sure

sounds like u are staying with the fastback look. Here's a interback, with roadster covers & ss high pipes

looks like the 1 year only, 69 r, also used the fastback covers, along with a roadster tank

(have to copy/paste these nxt 2 links)
https://ogden_images.s3.amazonaws.com/www.motorcycleclassics.com/images/2016/02/11091228/3_R-jpg.jpg


along with the 71 production racer
https://ogden_images.s3.amazonaws.com/www.motorcycleclassics.com/images/2016/02/11091236/7_ProdRacer-jpg.jpg

Got it. Thanks. As long as both cover options fit the frame I have then I’m good to go. I may switch to an alloy fuel tank

Just a note, but the Fastback used a different tank

macvittiemotorcycles said:

Got it. Thanks. As long as both cover options fit the frame I have then I’m good to go. I may switch to an alloy fuel tank

Pardon Our Interruption...

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Just a note, while you can make the others work, the Fastback has its own style oil tank that is different from that of the other machines (Save the rare "R").

if possible, you should get hold of the seat off the Commando in the background, the 'ears' on that seat fit into the lower rear sides of the petrol tank. Good project shaping up there.

74ok said:

T

Thread 'Frame checking'

Oct 29, 2024

Further to my 'Something's bent' post, I have removed the tank, cleaned the frame's spine tube of all crud / inuslating tape goo etc and put a straightedge on the top. It's straight from the steering head to the point where the tubes are welded each side (and the narrow tube from the steering head is welded beneath). From this point rearward, the angle changes slightly. If I put a 12" steel rule so that 6" is forward of this point and flat on the tube, the aft 6" has a gap of about 1/16" at the end of the rule.

I'm guessing the spine tube should be dead straight all the way along?

• Tigernut
• Replies: 34
• Forum: Norton Commando Forum

T

Thread 'Something's bent'

Oct 24, 2024

Just got my 850 MkII home and onto the lifting bench. Noticed that the rear wheel is tilted at an angle of several degrees when viewed from the rear (top is to the left, bottom to the right). Measured distance to centre of spindle from deck of bench and the right side is approx 17mm higher than the left. It isn't that the centrestand is bent and the whole bike's leaning - the bike is pretty well dead vertical. So the swinging arm at least must be bent. The whole engine/gearbox/swinging arm cradle could be bent but there's no sign of any stress marks when looking around with a light. The...

• Tigernut
• Replies: 44
• Forum: Norton Commando Forum

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Frame looks pretty good but I will check all this, thanks!

Here is the oil take I’m working with. I think I’ll try the fastback “square” covers and go from there.

Next up is adding an oil filter. Because I will have a fresh rebuilt motor I want an oil filter at least for the first few hundred miles. Searching around the forum the “full flow” oil filter kit seems like my best bet.

macvittiemotorcycles said:

I think I’ll try the fastback “square” covers and go from there.

Click to expand...

The early Fastback doesn't have a cover on the RH side, that's the oil tank.

macvittiemotorcycles said:

Here is the oil take I’m working with. I think I’ll try the fastback “square” covers and go from there.

Next up is adding an oil filter. Because I will have a fresh rebuilt motor I want an oil filter at least for the first few hundred miles. Searching around the forum the “full flow” oil filter kit seems like my best bet.

Click to expand...

Before you decide on that oil tank:
1) You need the matching battery tray and side covers - part of the side cover mounting is the battery tray on both sides.
2) You cannot use the oil tank as it is with a reed valve crankcase breather as you'll have a lot of oil flowing into the air cleaner. The central tank must be modified or replaced with one with a separate vent and breather connection. To understand, start reading beginning at Nov 18, 2022 here: https://gregmarsh.com/MC/Norton/Blue69S.aspx

macvittiemotorcycles said:

Here is the oil take I’m working with. I think I’ll try the fastback “square” covers and go from there.

Next up is adding an oil filter. Because I will have a fresh rebuilt motor I want an oil filter at least for the first few hundred miles. Searching around the forum the “full flow” oil filter kit seems like my best bet.

Click to expand...

As I have mentioned previously, I have a '70 model. It shares a lot of the components that you have. I've done a lot of modifying to add some better ideas to that platform. I use the central oil tank, and I mount a transmission filter in the return line in order to filter oil, instead of adding the late model oil filter kit that many people add to early bikes that did not originally have an oil filter... Here's a link to my set up....


You need to open the thread to understand it better because there are 2 hoses in the picture that are not oil lines. They are hoses that are part of my dual reed valve breather modification... yes dual breathers and they work better than one breather...

And the oil filter is a fine filter which will catch particles 30 microns and larger with a magnet inside it to collect any magnetic particles of any size.. Just a different and inexpensive way to add a filter and retain the central oil tank and it's related parts (battery tray, etc)

marshg246 said:

Before you decide on that oil tank:
1) You need the matching battery tray and side covers - part of the side cover mounting is the battery tray on both sides.
2) You cannot use the oil tank as it is with a reed valve crankcase breather as you'll have a lot of oil flowing into the air cleaner. The central tank must be modified or replaced with one with a separate vent and breather connection. To understand, start reading beginning at Nov 18, 2022 here: https://gregmarsh.com/MC/Norton/Blue69S.aspx

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Interesting. How do I know if I have a reed valve crankcase?

macvittiemotorcycles said:

Interesting. How do I know if I have a reed valve crankcase ?

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What Greg is saying is not about your crankcase. He's talking about where the breather hose from the crankcase enters the oil tank.

The early bikes had 2 slightly different "central oil tanks". IF your tank has the breather tube inlet entering the oil tank in the "froth tower" bulge in the top of the tank,.... then the crankcase pressure shoots an air and oil mist into the froth tower. That froth tower in the oil tank exists so a breather straw inside the tank that vents the pulsing air pressure from the crankcase can be well above the level of the oil in the oil tank so it doesn't vent oil when it's venting air. Later central oil tanks (like the one on my bike) moved the crankcase breather port off the froth tower, so the oil tank breather vented MUCH less oil with every pulse and the oil mist was shot down at the oil, not straight at the vent pipe. (crazy right!)

On all bikes with the central oil tank, the oil tank's breather exits in front of the oil tank which is inside the (stock) air filter. ( but not mine since I have a non stock K&N filter)

Below is a picture of the 2 oil tanks. The one on the left is the oil tank that's problematic which Greg is talking about... If yours has the crankcase pressure port on the froth tower, you should get a later oil tank or modify the one you have to be like the later one...

macvittiemotorcycles said:

Interesting. How do I know if I have a reed valve crankcase?

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A reed valve is something you add. If you have a hose connection on the drive side near the front of the engine, you have the standard breather. Later bikes had the crankcase breather in different locations. The reed valve, when added, controls the pressures inside the crankcase and reduces the possibility of leaks and blowing out the drive side crankshaft seal. You may have and I missed it, but a picture of the drive side of the engine would help.

Thanks for the explanations. Looks like I have the later style central tank and a hose connecting from the oil tank breather to the front of the engine drive side. Therefore looks like I’ll have to add a reed valve?

So,..... as crazy as this sounds... Both your engine and mine have this primitive crankcase pressure relief system in place on the end of the hollow camshaft. There's a stationary disc in place in the recess of the camshaft port. That stationary disc has 2 out of 4 "pie shaped" cut outs in it.... weird right??? There's another disc that sits against that first disc and has 2 teeth that fit into slots on the camshaft, so it turns with the camshaft. That second disc also has "pie shaped" cut outs in it...

So the way it works is the pie shaped cut outs on both discs align when the pistons are going downward to let the compressed air from the downward stroke of the pistons exit through the aligned discs, and when the pistons are going back up, the disc holes don't align so the mechanism tries to block the air from being sucked back into the crankcase... That was the primitive breather that norton tried on the early bikes and later abandoned. Part of the problem is that the "Pie shaped discs" mechanism is certainly a theoretical answer to releiving crankcase pressure, but in practice it's not up to the job... It can move the air out, but doesn't seal well or really have a performance that is "tuned" to high rpm's...

Reed valves are up to the job. The reed is very light weight so it moves easily at high speeds and it seals well... I put a Jim schmidt camshaft port reed valve on top of my discs just to make the sealing of the port more efficient. I already had another reed valve on the timing side of my engine crankcase, so I was just improving the sealing quality of that port with his reed valve. You could remove the discs if you do a complete rebuild and use Jim's camshaft port breather and it would work better without the discs in the way...

You have the good central oil tank, so your set to use the Jim schmidt camshaft breather and port it right into the oil tank port with no issues..

macvittiemotorcycles said:

Thanks for the explanations. Looks like I have the later style central tank and a hose connecting from the oil tank breather to the front of the engine drive side. Therefore looks like I’ll have to add a reed valve?

Click to expand...

OK, that's original. The oil tank picture is a little hard to tell - does the breather connect to the side of the froth tower (the part sticking up) or to a hose connection in the top of the tank. If the top of the tank, then no problem. If the froth tower, then you can't install a reed valve without adding a connection to the top of the tank.

When installing a reed valve, the current breather hose connection to the front of the engine is eliminated.

When you rebuild the engine, you should leave out the timed breather parts. Parts 84, and 85 here: https://andover-norton.co.uk/en/shop-drawing/451/engine and make sure 83 can't come out.

If I were rebuilding that bike, I would install the crankcase breather from JS Motorsport which includes eliminating the original breather. Edit: And I would either find a oil tank with the breather hose connections to the top (not froth tower) or add one for the breather to the top of the oil tank.