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First time Norton Owner; need some tuning help #784017 09/12/19 2:54 am
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Andrew Dunham Offline OP
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Hi everyone,

First time Norton owner here. Was able to pick up a very nice (looking) 73' MKI 850 about a month ago.

[Linked Image from i.imgur.com]

Stock air box, stock filter, stock exhaust. Boyer EI with NGK BP7ES plugs installed.

Upon initial inspection after getting it home, it became apparent the carbs needed replaced rather than cleaned. Easy; the new AMAL's seem to work well and I've used them 3-4 times previously. Ordered a couple and popped them on (after figuring out the Commando rite of passage with removal/installation of the carbs.) They came with 260 mains, 3.5 slides, and 19 pilot jets. I figured it was a good place to start as I had seen those specs elsewhere online.

Fast forward to the first start. Bike starts easily and idles (not great, though) so I figure the mixture screws are wrong. I had them at the recommended settings of 1.5 turns out, but the bike seemed to run most efficiently around 2.5-3 turns out. Anyway, the bike would hardly rev at all. I pulled the plugs and they were VERY sooty and black. Not wet, just black and sooty. Figuring it was a horribly rich mixture, I dropped the needle down to the top position. This helped quite a bit, and allowed the bike to be ridden but it would cut out round 4,000 RPM.

Fast forward to today and I've just installed size 17 pilot jets and 3.0 slides per a few recommendations. The bike is running significantly better and now will rev to 5000 - 5500 before just cutting out and returning to idle. Like it will not rev past 5000 or so. Just will not.

Any ideas? I am trying to approach this methodically, but feel as if I could spin out of control quickly here. I am currently thinking the advance is screwy or something. I have yet to check the timing. Hopefully in the next couple of days.

Thanks!

Last edited by Andrew Dunham; 09/12/19 3:02 am.

1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
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Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784027 09/12/19 6:25 am
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kommando Online Content
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Set the fuel level in the float chambers first, assuming these are premier's you have the adjustable stay up floats.

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784033 09/12/19 8:23 am
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Rohan Offline
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Its always worth pointing a strobe light at the timing and verifying that it is somewhere in the ballpark,
or you could be chasing your tail for some time....

With sooty plugs like that it might be helpful to have a new pair ready to try when you know everything is set correctly too.

Nice looking sparkly FireFlake Blue cycle there.

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784091 09/12/19 9:49 pm
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Andrew Dunham Offline OP
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Thanks, guys. I appreciate it.

Kommando, any idea what the float height should be? I checked the fuel level according to AMAL specs and it was very close. I've ordered a new air filter, so having the carbs off to check the float level and change that will be a good time.


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784109 09/13/19 1:44 am
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Andrew Dunham Offline OP
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Interestingly enough, I stumbled across this thread... where C.B.S was having a very similar issue. Even more strangely, I chimed in with the same issue on a BSA!

I'm going to take a good look at the air as well.


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784302 09/15/19 12:07 am
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Andrew Dunham Offline OP
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UPDATE!

Bike is running decently now, but still not quite right. The plugs are still sooty around the end of the threads and top of the ground electrode. The center electrode and bottom of the ground electrode are nearing a nice tan, but still dark.

I lowered the float height to .080" below the surface. They were almost level with the surface when I started. A new air filter and 240 mains replaced the 260's that were in it.

It still cuts out and bogs down around 5,000 RPM but pulls nicely up to that. It is rideable if ridden conservatively, but if I get on it a bit, it breaks up. So I took a look at the timing and here are the results:

At idle, we were seeing 18 degrees BTDC on the RIGHT edge of the boss that the mark sits on. NOT on the mark.
2,500 RPM = 23-23 degrees BTDC
3,500 RPM = 26-27 BTDC
5,000 RPM = Bouncing between 28 and 32, so probably 30-31.

My Dad thought he saw some exhaust gases coming out of the head when it was first started today, so new exhaust seals will be on the way. Hopefully that will solve the backfiring it is doing.

Any other thoughts are welcome!


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784388 09/15/19 10:08 pm
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As we see in chatchat elsewhere, are you measuring the float height or fuel height ?

A #3 slide is enrichening it, the opposite of what is needed, once you get the fuel height ?

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784411 09/16/19 12:08 am
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Hi Rohan,

I had done both, actually. But I think perhaps incorrectly. Initially I had hooked up a hose to the bowl drain, held it up beside the carb and measured the fuel level in relation to the top of the bowl surface joint. This fell between the .17 - .24" spec that I found from AMAL.

The bike was still running rich, so I thought I would lower the float some. It was previously (at the .17-.24 spec) approximately flush with the top of the bowl. I dropped the TOP of the plastic float so it was .080" below the top of the bowl mating surface. So presumably the actual fuel level dropped fairly significantly when I did that.

At least changing the slide is an easy job... so that makes sense. The cutaway is LESS, allowing less air in... duh!


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784417 09/16/19 12:48 am
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So how is it going now ?
You'd expect that premiers would come in the box fairly well dialled in by now, they've supplied enough. ?

I remember fitting a new pair of Concentrics to an 850 back in the 70s, and they were just wonderful out of the box,
gave it that like-new running. (not that I bought it new).

btw, you have played with the carb syncronization ?
If both slides are not lifting perfectly equal, it may not give its best.
Which is quite an understatement...

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784425 09/16/19 1:51 am
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I didn't get a chance to play with it today, but it starts easily, idles well, both carbs respond to idle and mixture adjustments easily. The mixture is 1.5 turns out to achieve best idle conditions. It is only during riding that the bike will cut out or bog down around 5,000 RPM.

We checked the advance and it appears to be hitting full advance (31 degrees) at 5,000, so I'm fairly confident that is OK.

The next thought is a potential air leak at the exhaust in the head. My Dad thought he saw some exhaust leaking there, so I've ordered new gaskets and will fit them in about 10 days when I return home from a work trip.

That's the interesting thing; I think they probably were fine as is. I have fitted several other Premieres and haven't had to adjust them


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784485 09/16/19 4:59 pm
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when I got my 74 it ran great but had this intermittent miss between 3500-4000 rpm, tried everything, it had a Pazon EI,,replaced it with a new Boyer and all is good..maybe ur Boyer is going bad, not sure how to test..

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784514 09/16/19 8:40 pm
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Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #784797 09/19/19 7:44 pm
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Ensure fuel tank vent is clear, then confirm fuel flow rate from carb (remove float bowl plugs and turn tap on)


71 Commando
73 TR7RV
70 A65
56 A10
68 CB175
Re: First time Norton Owner; need some tuning help [Re: TUC toranna] #784965 09/21/19 3:39 pm
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Fuel rate seems fine; similar on both sides. No blockages in the lines or anything. I am using both petcocks as the carbs aren't connected with a tube. Are the petcocks set to be a regular and a reserve or are they the same? As in is one lower than the other?


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785000 09/21/19 10:09 pm
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Originally Posted by Andrew Dunham
Are the petcocks set to be a regular and a reserve ?
As in is one lower than the other?


That is usually how they are set up, with the reserve on the left.
But no guarantees after all these years.
Ex-factory, there was a little 'Reserve" decal on the tank just above the tap.

Might be worth you having a looksee - or if you don't want to disturb the taps
(and get new leaks) maybe just drain each side into a drum, and see how much
comes out each side - and see what else comes out as well, always worth getting all
the gunge out, rather than it going into the carbs...

If its all clean it can go back into the tank, of course.

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785246 09/23/19 8:56 pm
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Another update:

I removed the stock air filter today and the bike runs just a little bit better; not significant. I did notice the exhaust leak I mentioned earlier, so I've got new seals on the way and I will order the proper tool from Andover Norton to get the nuts tight. I hate to wait that long with the shipping from England, but at least I'll have it then.

I think fixing that exhaust leak is the next logical step.


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785260 09/24/19 12:28 am
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Indeed, if you have any leaks in the exhaust it will cause popping and
banging in the pipes, not to mention some extra blueing sometimes.
I use a little muffler putty on the joins - it bakes solid like a rock and seals
everything upbut can be flexed and cracked off if you need to remove the pipes.

Draining the tank to see what comes out, and what sort of reserve you have
could save a roadside stop sometime, so well worth the few minutes while its inactive. ?

Re: First time Norton Owner; need some tuning help [Re: Rohan] #785262 09/24/19 12:35 am
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Originally Posted by Rohan


Draining the tank to see what comes out, and what sort of reserve you have
could save a roadside stop sometime, so well worth the few minutes while its inactive. ?


Strangely enough, I have had THREE different bikes with saddle-type tanks (no tube connecting the two saddles), where
in each case, some PO installed a standpipe-type petcock in one of the sides ... which means that the fuel on that side can never be used unless you laid the bike on its side and let it run across inside the tank.

You'd have to be pretty dim to just say "Oh, this is the RESERVE side, I'll put a RESERVE-type petcock on there", when those are clearly meant for a bike where the two sides are connected.

Luckily, the little filters screw off and the standpipe is brass and can be sawn off in a few seconds .....

Lannis


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Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785267 09/24/19 12:55 am
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The Owners manual for several bikes I've owned mention that in times of great need
(ie when you have run out of juice) that the tank can be removed, and a small reserve
of petrol can be sloshed to the t'other side of tank, and a few more miles eeked out.
I've used this strategy, several times, successfully - and also near laid the bike over in the dark to achieve this,
when it was otherwise too dark to see what you were doing.
Knowing the drill to remove the tank AND having the tools helps...

My current Commando project has 2 reserve taps on it, and I've been known to carry a
litre bottle of 'benzene, essence, etc' etc, so we will see how this strategy works out.

(I also have an Interstate tank on the shelf, so this may be plan C - or is that D ? for me)

P.S. Its been mentioned places that commandos may need both taps open if you are contemplating
warp speed - or a tap may be functioning as the main jet size.... !?

Re: First time Norton Owner; need some tuning help [Re: Lannis] #785269 09/24/19 12:58 am
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Originally Posted by Lannis

You'd have to be pretty dim to just say "Oh, this is the RESERVE side, I'll put a RESERVE-type petcock on there", when those are clearly meant for a bike where the two sides are connected.


Nevertheless, thats how Nortons did it with the Commando ?
The fuel pipe may be connected between the 2 carbs, but the 2 sides of the tank are not interconnected.

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785275 09/24/19 1:47 am
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Another update here (I've got questions just about everywhere right now trying to solve this!).

My Dad suggested that the black soot on the plugs may simply be a symptom of the exhaust leak(s) and that fixing those could solve a lot of the running issues. The exhaust gases getting sucked back into the engine and onto the plugs. I'm hanging my hopes on that for now; because it seems to make a lot of sense. I've got 4 gaskets on the way since I've read some guys need to double stack them for some reason.

I ran out of time to drain the taps today, but will try to do that either tomorrow morning or Wednesday evening. I like the idea of each petcock feeding each carb for the sake of simplicity. I'm pretty religious about refilling the tank after 75 miles or so. It may be way to early, but somehow my brain believes multiple $3-6 fill ups is better than a $9 or $10 one. Don't ask why!


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785280 09/24/19 2:49 am
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Running out of fuel is never convenient - and can be downright dangerous. !
If the fuel pipe is not interconnected, you have to be careful one carb doesn't run
out of fuel before the other, or it may run lean long enough to stress one cylinder.
And you'll have a bike that only half runs - Nortons interconnected the carbs for that reason ?

Popping and banging in the exhaust is a sign of leaness (all that extra air in the exhaust system).
The exhaust gases come out under high pressure, so there is no going back once they are out.
That black sootyness isn't a sign of oil burning, is it ?
You looked for exhaust smoke, particularly visible at night.
If the rings or valve guides are worn, they can smoke (lightly)
and the only sign is that fluffly black sootyness on the plugs.
And the whiff of oil in the exhaust/air.....

My 1st 850 had an oil seal on an inlet guide that had come adrift,
and the plug on the rhs was always lightly black.
New guide seals cured that completely, and the plugs ran clean.

Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785285 09/24/19 3:15 am
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I could fit the dual inlet banjos to the float bowls again; I have no problem with that. Then I'll have both petcocks working both ways (in theory.) That's an easy job and should eliminate any unnecessary issues of lean condition on a single side or similar.

The exhaust gas I saw leaking from the head was white in color, so I don't believe that indicates oil burning. I also don't smell any oil burning. I checked compression and it was around 180 (I think?) on both sides.

I'm going to pull the top end off this winter to replace some gaskets, so I'll take a look at the head and see if it does need to be rebuilt.


1961 BSA Super Rocket
1968 BSA A50
1969 BSA 441 VS
1970 BSA Thunderbolt
Re: First time Norton Owner; need some tuning help [Re: Andrew Dunham] #785443 09/25/19 10:35 pm
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[quote=Andrew Dunham I checked compression and it was around 180 (I think?) on both sides.
[/quote]

180 psi both sides would make it as good as a new one.
Did I read someplace you may be giving it too much choke ?
That could explain a lot.....


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