Knocking / rattling inside primary drive case + backfire

It's not a hard job opening the primary up and give it a good inspection, you never know something simple could be wrong could even be a worn chain, some triplex chains sometimes worn lose rollers and if you check the chain you have to find the tightest spot of the chain and adjust to that tight spot, but I be opening it up and look see, clutch housing, rota and Alt who knows till you open it up and lookie inside could be a primary inter cover bolt fallen out and rattling around the bottom of the primary case.
Be also a good time to change the primary oil as well run ATF brand F for smooth clutch running, no more than 7 floz.

Ashley

Back firing could be a timing issue. Open the points cover on the right hand case and see what ignition system you have and post.

My bike is pretty similar to yours. These are a few thoughts on what I have found over the years. Firstly agree with the earlier advice on the primary etc. I also agree that the inline value is a bit risky. Some say they have used them 40 years no problem. Others report ruined engines from no oil. I do not run one. They are installed to stop wet sumping when the bike is stored for a few weeks or more. Some bikes including mine never wet sump. Others do. If yours is one then either ride it more often or drain the sump if it hasn't run for a while.

The screw in clamps on the exhausts are famous for rattling undone. Hopefully the threads are in good shape. My method involves using high temp RTV on the threads and tightening them once or twice after the bike is hot.

I don't know if your familiar with the Amal Mk1 carbs but if not be aware the choke is a bit counter intuitive. When the cable is slack the choke is on. Normal riding position is with the cable pulled fully tight. I think the advert says new levers etc. Please be aware the modern reproduction choke levers are total crap and vibrate to the closed position. I gave up on my new lever and found an original in decent condition and it actually works. So you may find your choke is vibrating to the on position.

The standard top mount under the tank is pretty marginal. There are many upgrades available. I use the Dave Tayler upgrade which is at the lower end of the options. If you do have a repro petrol tank some of the better options eg Norman White or CNW may not have enough clearance.

You have the correct petrol pipes fitted but I find that version prone to leaks. The latter Mk 11 Mk 111 version works better for me.

If your tachometer drive leaks there is a proper seal upgrade available.

There is a special section on rhis site with info on the best modern oil options for the Commando. If the bike has sat a while take off the front tappet covers and pour an egg cup or so of oil down the push rod tunnels. This will keep the cam happy. Don't let the bike idle immediately after start up because that kills the cam. Run it at about 2000 rpm or so.

Commandos can be a bit fussy with handling unless everything is straight and properly adjusted. Check wheel alignment , isolastic clearances and tyres are balanced and running true.

Brakes are not that great. I'll leave advice on the front options for you to search the many threads. I have gone upmarket with a CNW disc. Andover Norton sell a front master cylinder with a correctly designed piston. Personally I wouldn't go with the resleeving options because I feel a 100 % reliable brake is kind of important.

RGM sell upgraded shoes with good linings for the rear brake which are the best I have ever found. But you may need to have the linings arced with a lath to get them to fit properly.

I think the Norton workshop manual is good plus the Clymer manual if you can find one. The Haynes one is not as good.

As above regarding the choke
Slack cable is on full choke
Tight cable is choke off

htown16 said:

Back firing could be a timing issue. Open the points cover on the right hand case and see what ignition system you have and post.

Click to expand...

According to the ad. "New Wassel electronic ignition and coils"

M-Hawk said:

Thanks MichaelB - this tool? https://andover-norton.co.uk/en/shop-details/15499/clutch-compressor-tool-c-4805

Click to expand...

If you get this far in and need this tool I have a spare you can have for the postage
I'm in Harlow Essex

overall, you will be checking the quality and attention to ( sometimes vital) detail that the rebuilder carried out. This can be hugely variable, in the experience of many posters on this forum. The snag is, you have to train yourself to know what you are looking for....

Looking at the photos it shows a bolt welded to the frame next to the side stand bracket. Has this been added as a stop for the side stand? Because it looks like the side stand itself has worn its stops away. Get rid of the valve in the oil feed pipe pronto (the thing with the brass fittings). You WILL destroy the engine if it gets stuck closed on start up, at the moment you are relying on the oil pump creating enough suction to open the valve against its spring. Service the oil pump at the first opportunity to close the clearances up to zero, that will slow down/stop the wet sumping. Try and find an experienced friendly commando owner to look the bike over, he/she could find other stuff that might need attention. The grab rail clips are incorrect at the moment they are cable clips and are not strong enough. The oil filter mounting head bolts haven't had the locking strip tabbed over. The oil feed pipe to the rockers is incorrectly routed and touching the cylinder head fins.

Wow, what an amazing response. So much useful information. Thank you.

I have found and ordered both the Norton and Clymer manuals. I already have the Haynes and found it lacking detail.

I’ll work on removing the oil feed valve, makes sense.

I’ll keep this thread updated as I go. Should get time to do some bits this weekend.

Thanks again all.

A few other minor nit-picks in addition to what's been mentioned.

The 'NVT' speedo and tacho are later 850 Mk3 items.
Speedo and tacho cables incorrectly routed. Both would normally run beneath the lower yoke and then up to each instrument inside the headlamp brackets and not as shown in the brochures.
The side stand would normally be black.
The brake line clip would normally go above the lower yoke (so clips to the headlamp bracket tube) with a second clip below the upper yoke.
The exhaust doesn't have the standard 850 balance pipe and the exhaust rings are not the original 850 types.
The seat cover pattern is technically too early for the Mk1.
The centre stand bolts facing the wrong direction as the bolt heads would normally be on the inside (to prevent the L/H bolt shank from fouling the spring when the stand is raised/lowered).
Amber side reflectors missing from the coil bracket and the spacers between the coil clamps and bracket are not standard.
Rubber-covered grab rail clips are non-standard.
The ad says Hagon shocks but they look more like Emgo or another similar type.
Black sheathing on the switch cluster wiring would normally be grey.
The steering lock is missing.
The clutch cable ferrule doesn't appear to be correctly fitted to the gearbox cover.
The auxiliary power socket is missing.
The rear brake pedal adjustment nut and bolt are missing. If the brake light switch is acting as the stop then it won't last long.
Mk1 cylinder barrels would normally be silver.

Not original but a useful addition would be the brake pedal safety spring:

Edit: Kickstart lever is the later Mk1A/Mk2A/Mk3 type.

baz said:

If you get this far in and need this tool I have a spare you can have for the postage
I'm in Harlow Essex

Click to expand...

Thanks Baz, that's very kind of you but I already purchased the tool from Andover.

Thanks L.A.B. - that's a very comprehensive to-do list, saving me a lot of head scratching!

Front brake wise it looks like it is still on the original bore sized master cylinder (5/8") Be aware that the front brake is not really up to the road conditions/traffic we have now. If you have yet to try the brake in earnest do so carefully. To improve the front brake there are various kits/upgrades available. From replacement discs, calipers, master cylinders, double disc set ups etc etc. The most cost effective i.e. biggest improvement for the least money has to be the sleeve kit from RGM
£49 +vat and get it fitted. That and a pair of pads from AN transform the front brake and it is almost invisible so not altering the 'standard' look.
Adding to L.A.B.s list
Should have fork gaiters
" " " Mud guard flaps
Cloth covered wiring harness, should be pvc tape wrapped.
All of this info is what we have gleaned from the photos, the 64,000 dollar question is what are the engine, gearbox, primary drive internals like?
Get hold of a decent i.e. long and strong, exhaust ring tightening tool and really make sure they are tight and prevented from undoing (the forked washers that are bent to engage with the rings and fins are shite) the better way is to lockwire the rings to each other with a tension spring so the spring live loads the lockwiring . Failure to observe this and the rings coming loose will ruin the thread in the cylinder head = much expense in getting that repaired.

dobba99 said:

Adding to L.A.B.s list
Should have fork gaiters

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A good idea although the full-length gaiters weren't listed for the 850 Mk1 (or Mk2/2A), only the 061115 short (dust boot) 'gaiter'...

...although one factory Mk2A road test bike did have long gaiters so perhaps they were optional by that time...


...and certainly were (according to the market?) on the Mk3.

dobba99 said:

" " " Mud guard flaps

Click to expand...

Mud flaps were not listed for the 850 Mk1...
...but are for Mk2/2A:

"...mudflaps on Interstate..."
("Interstate and Mk2 Roadster" according to the 2/2A parts supplement)

The first thing you need to do is make sure you have a good battery and that it is fully charged. I'm not that familiar with the Wassel but assume it operates pretty much the same as other ei. If the voltage drops below 12 volts they don't like to function right. They work opposite points. Instead of advancing the timing with increasing rpm, they retard it with decreasing rpm, thus the tendancy to backfire. The next thing to do is check the timing. Any automotive style light will work. Power it off another battery, not the one off the bike as it causes interference. Remove the small cover over the end of the crank. You will see a degree scale. Remove the plugs and use a wd40 straw while rotating the engine by the back wheel with the gearbox in 4th to find tdc. At tdc slowly rotate the wheel backwards until a pad shows up on the alternator rotor with a groove down the middle. Highlight the groove with some paint. This is the timing mark. Put the plugs back in and start the engine. At around 4000 rpm the timing mark should line up with around 30 on the scale. As you rev the bike you should observe see the mark smoothly advance and then quit advancing around 4000.

L.A.B. said:

A good idea although the full-length gaiters weren't listed for the 850 Mk1 (or Mk2/2A), only the 061115 short (dust boot) 'gaiter'...

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

...although one factory Mk2A road test bike did have long gaiters so perhaps they were optional by that time...


...and certainly were (according to the market?) on the Mk3.




Mud flaps were not listed for the 850 Mk1...

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

...but are for Mk2/2A:

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.

andover-norton.co.uk

http://www.classicbike.biz/Norton/Brochures/1970/74NortonBrochure.pdf

"...mudflaps on Interstate..."
("Interstate and Mk2 Roadster" according to the 2/2A parts supplement)

Click to expand...

Its a Mk2a we are talking about, your brochure photo shows the bike fitted with gaiters and your info says the Mk2a was fitted with mudflaps. Also on the subject bike, it has a Mk3 gear lever.
AN list the long or short gaiters for the Mk2a. Usually it was short for the american market and long for the Uk and europe

dobba99 said:

Its a Mk2a we are talking about

Click to expand...

303165 is a Mk1.

A rebuilt bike with no miles and sold by the rebuilder is a red flag to me. Too many posts of first time buyers pulled in by the aesthetics of a fresh paint job and the rebuilder cutting costs by not doing the internals over the years. I would be opening up the primary and take a lot of photos and post them here, if it shows shoddy spannering and/or worn parts I would get it looked over by a professional.

L.A.B. said:

303165 is a Mk1.

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Wow, you really must have scrutinized the photos with a magnifying glass, i'm impressed. So why did the OP say it was a Mk2a?
I fully agree with Kommando, a 'restored' bike with no miles on it, is to be treated with caution.

dobba99 said:

So why did the OP say it was a Mk2a?

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In some circles the MK2a is considered the best Commando so he was playing fast and loose to up the price. Today MK3's with the starter command the best selling price but calling it a MK3 would be a real stretch .

If this is a private sale then its 'sold as seen' and no comeback.