Knocking / rattling inside primary drive case + backfire

[L.A.B.]

Using a degree wheel, you could set the engine at 28 (or whatever you want) degrees before TDC, and mark the stator to match. Then you would have a timing mark to use in the future.

Yes, there were what appeared to be timing marks on the wrong side of the stator before it was fitted correctly.

It's also a (Wassell high-output) RM24 3-phase stator which I hadn't noticed until now.

 

[marshg246]

Along with other parts, get two inner chaincase to engine gaskets. Going back to the rotor-stator clearance for a moment, note that the stator mounts to the inner chaincase and the rotor to the engine (crankshaft).

The three screws are supposed to mount the inner chaincase properly to the engine and the support in the middle of the inner chaincase is supposed to support it, not deflect it.

So, you put the inner chaincase on with one gasket and no shims on the center post, tighten it check to see of there is a small gap between the back of the chaincase and swingarm. If not, put on a second gasket. Then measure the gap between the center post and inner chaincase. Then take the inner chaincase back off put on shims to match the measurement and then reassemble with one or two gaskets as you determined.

On a 750, I've never seen a need for two gaskets. On most pre-MKIII I've had to use two gaskets.

 

[M-Hawk]

Yes, there were what appeared to be timing marks on the wrong side of the stator before it was fitted correctly.

It's also a (Wassell high-output) RM24 3-phase stator which I hadn't noticed until now.

marshg246's theory makes sense. There were indeed some timing markings on the stator.

Ah a 3-phase stator - that explains the 3 wires to it rather than 2

 

[M-Hawk]

Along with other parts, get two inner chaincase to engine gaskets. Going back to the rotor-stator clearance for a moment, note that the stator mounts to the inner chaincase and the rotor to the engine (crankshaft).

The three screws are supposed to mount the inner chaincase properly to the engine and the support in the middle of the inner chaincase is supposed to support it, not deflect it.

So, you put the inner chaincase on with one gasket and no shims on the center post, tighten it check to see of there is a small gap between the back of the chaincase and swingarm. If not, put on a second gasket. Then measure the gap between the center post and inner chaincase. Then take the inner chaincase back off put on shims to match the measurement and then reassemble with one or two gaskets as you determined.

On a 750, I've never seen a need for two gaskets. On most pre-MKIII I've had to use two gaskets.

Thanks, it's all starting to make sense now.

So when we hypothesised that the crank is bent a little causing the reduced stator gap in places (the location of the tight spot moved with crank movement), it could actually be misalignment of the inner chain case instead? In other words, if I make sure the case is perfectly aligned might I find that the stator gap problem is resolved?

marshg246 Do you mean number '5' in this diagram?: https://andover-norton.co.uk/en/shop-drawing/207/chaincases-chains-sprockets-clutch-alternator

 

[kommando]

it could actually be misalignment of the inner chain case instead?

No, you measured a deflection on the crank and saw the tight point move around with the crank moving around. Its common to find this, moving the stator by moving the inner primary will not cure it as you did not measure a extra large gap opposite the tight spot.

 

[marshg246]

Thanks, it's all starting to make sense now.

So when we hypothesised that the crank is bent a little causing the reduced stator gap in places (the location of the tight spot moved with crank movement), it could actually be misalignment of the inner chain case instead? In other words, if I make sure the case is perfectly aligned might I find that the stator gap problem is resolved?

marshg246 Do you mean number '5' in this diagram?: https://andover-norton.co.uk/en/shop-drawing/207/chaincases-chains-sprockets-clutch-alternator

Yes #5, and also get a #53. They can be very hard to get off undamaged and to take the inner chaincase off you need it off.

The standoff (or switcnarm) holding the inner chaincase out can close the gap on the right side (while looking at it)

 

[M-Hawk]

No, you measured a deflection on the crank and saw the tight point move around with the crank moving around. Its common to find this, moving the stator by moving the inner primary will not cure it as you did not measure a extra large gap opposite the tight spot.

Actually, I did notice a larger gap opposite the tight spot. I didn't measure it but the 0.20mm feeler had plenty of wiggle room in there. Sorry, I neglected to mention that detail previously.

Thinking about it, if it was inner case misalignment I guess the tight spot would always be in the same place. It wasn't.

 

[marshg246]

Actually, I did notice a larger gap opposite the tight spot. I didn't measure it but the 0.20mm feeler had plenty of wiggle room in there. Sorry, I neglected to mention that detail previously.

I think you said the crank was off by .005" as it turned. If so, then you could have two problems. Often the gap, when averaged is way more than 0.008" so any small bend in the end of the crank won't hurt much - .005" is quite a bit though. Reguardless, the inner chaincase must be right to have any hope.

 

[concours]

Wrong sized key hacksawed badly to size, wonder what other bodges await. A sloppy key plus the loose sprocket could create the noise.

This.
That key has been run loose. Therefore, we know the sprocket has been loose on the taper.
Those two tapered surfaces will no longer provide the needed holding power, OR, the concentric locating ability.

O.P., you have bigger fish to fry.
Sorry.

Edit: JMWO

 

[marshg246]

This.
That key has been run loose. Therefore, we know the sprocket has been loose on the taper.
Those two tapered surfaces will no longer provide the needed holding power, OR, the concentric locating ability.

O.P., you have bigger fish to fry.
Sorry.

That is the rotor key. You may be right but let's see when he removes the sprocket. If that key or keyway is damaged, then it will likely be something he doesn't want to hear.

 

[concours]

The world is full of bodge repairs. I have to deal with the end game on a regular basis. The laws of physics hold fast.

J

M

W

O

.

 

[MichaelB]

With what I see, I would be ordering shims 55, 56, 32 ,33, 11, woodruff keys, studs, nuts, and looking at all the other related hardware.

 

[M-Hawk]

Thanks MichaelB. I'm building my order now.

I've not pulled the sprocket yet. I want to have everything ready to go before I do that I think. If I want to get the sprocket puller, is it this? https://andover-norton.co.uk/en/shop-details/16314/extractor-assy-061037-06-0941-

Also, does anyone know if the woodruff key set includes a rotor key? https://andover-norton.co.uk/en/shop-details/23196 Or do I need the separate rotor key as well? https://andover-norton.co.uk/en/shop-details/16612

Andover product descriptions are somewhat sparse!

 

[kommando]

I want to have everything ready to go before I do that I think.

You need to see the taper on the crank and the sprocket before ordering any parts, hopefully the loose sprocket has been caught before any damage has been inflicted on the crank taper. However its just as likely this was a bodge job that failed to get the sprocket tight on the crank taper as it was already damaged.

 

[L.A.B.]

I've not pulled the sprocket yet. I want to have everything ready to go before I do that I think. If I want to get the sprocket puller, is it this? https://andover-norton.co.uk/en/shop-details/16314/extractor-assy-061037-06-0941-

Yes, (also extracts the camshaft sprocket, etc.)

Also, does anyone know if the woodruff key set includes a rotor key?

As it's the "set" then I would think so, the same as the RGM set.

WOODRUFF KEY (SET OF FIVE)

RGM2WK RGM NORTON WOODRUFF KEY SET

www.rgmnorton.co.uk

 

[mdt-son]

Hi

I'm new to the forum, having just acquired my first Norton - a 1973 Commando 850 mk2a.

I have two issues, that are not related, but would really appreciate any advice that anyone is able to please give about them. I'm desperate to get the bike out onto the open road!

Issue 1
Knocking or chain slap in the primary chain case. I've checked the chain tension and it's about 3/8's (as recommended in the handbook).

My guess is sprocket misalignment, and/or a very worn primary chain.

- Knut

 

[M-Hawk]

You need to see the taper on the crank and the sprocket before ordering any parts, hopefully the loose sprocket has been caught before any damage has been inflicted on the crank taper. However its just as likely this was a bodge job that failed to get the sprocket tight on the crank taper as it was already damaged.

I was hoping you wouldn't say that, but you're right.

 

[L.A.B.]

I was hoping you wouldn't say that, but you're right.

There seems no reason to hold back on this because the engine sprocket is already known to be loose on the taper so may just slide off without having to use the extractor.

 

[M-Hawk]

There seems no reason to hold back on this because the engine sprocket is already known to be loose on the taper so may just slide off without having to use the extractor.

I assume I need to remove the clutch at the same time, or can I just slacken the chain using the adjuster and see if the sprocket releases from the taper?

 

[concours]

I assume I need to remove the clutch at the same time, or can I just slacken the chain using the adjuster and see if the sprocket releases from the taper?

Same time.