22 year old and my first norton 650 ss :) from england

On Commandos I usually install 107 needle jets but I am not familiar with what your smaller and lower compression motor would require. Though it adds another $100 to the cost of the premiers it is very good to have a range of jetting on hand. I never treat the manuals or Amal's specs as gospel because of the changes in fuel. Those specs were arrived at in the 1960's with much different gasoline.
Personally, I think the Burlen people should own up to their mistake and replace the #17 pilots either free or at cost. Paying an additional $40 to cover their blunder, not to mention the lost time and aggravation is salt in the wound. I have replaced many of these pilot jets.
 
I'M running 280 mains, no air filter. 106 needle and 17 pilot, 3 slide and does all i want of her, but not a boy racer anymore, so plodding with a odd squirt into the 70's occasionally. Obviously must be getting old cos the old gal is giving me over 50 to the gallon.
 
Cheers lads Appreciate it :) primary is back on clutch is superb now setting off and starting is massively improved with the 19 pilot jet.

Feels a little on the lean side in second hitting around the 5k mark did do a plug chop an it does look a lil like that.

106 needle jets needle In the middle position considering trying the needle one richer clip wise an see how she feels then one day this week.

Massive improvement though ended up at a shade over 1 turn out 1 an half she was struggling for fuel still setting off just goes to show how out the pilot jets were!
 
Few laps round the block on the Norton 650ss an pulling back on the drive current state of play huge improvement from where it was
What do the experienced 4 stroke Brit bike people think? I still feel it could do with going up a needle jet or richer on the needle.
106 needle jet middle position on clip.
19 pilot jet.
280 main.
Premier concentrics.
Longer inlet manifolds.
Air screw just a tad over 1 turn out idling at 1200 rpm + or - 50 rpm.

Pulls good to around 5k then the vibes kick in an she almost feels like it's holding back a little in 2nd gear once she gets to those revs.

Gonna double check the float heights when she cools off tomorrow.

Champion n5 plugs
22 year old and my first norton 650 ss :) from england
IMG_20190806_172456_585 by norton.rider, on Flickr
 
Ref your ‘feels lean at 5k’ ascertaining which jetting may be lean is actually more depend on throttle position than engine revs.

A common aid is to mark 5 points on the throttle body and 1 marker on the twistgrip. The 5 marks should signify closed, 1/4, 1/2, 3/4, WOT.

Then when you’re riding, if you think it feels out at a particular throttle opening, look at your markers, amend the relevant jetting, re test, etc.
 
Cheers guys yeah since the change to n4's it doesn't need tickling an she's starting first kick every kick.

I'd say it was 2nd gear 1/4 to 1/2 throttle opening just approaching where I'd expect the main jet to come in on another bike obviously still learning about the amals.

Good thing is got plenty of footage to watch back so should be able to see what's happening I'll post it up once it's edited tomorrow.

Thinking of going up to a 107 needle jet.

I'd describe it as how the low range felt when it was to lean she's just lacking that roar at the higher revs an feels like it's holding back
 
Well, you might be better ignoring my earlier post...

According to ‘Norton Twins’ by Roy Bacon, the 650ss with concentric carbs should have:

Main 280
Pilot 25
Slide 3
Needle pos 2
Needle jet 107
 
The Roy Bacon main jet size is bollocks. I built my first 650ss in 1981 & built up the carbs to those settings. It ran well whilst running in, but a week later I went to the TT. As the motor had by then loosened up I started to cane it. On anything over half throttle it just eight stroked. I went to a Brit bike shop called Tiger Tims for some new plugs & as luck would have it there was an old Amal rep. in, who upon hearing about the problem immediately told me to try a pair of 240 mains & work down from there. The bike ran great after that. I can't remember what the rest of the settings were but 3 slides, 106 needle jets, & 2 ring needles would be a good start. As for pilots we now have the luxury of the removable type & 19 seems to be the favoured starting point for Norton twins.

Martyn.
 
Matchless said:
The Roy Bacon main jet size is bollocks. I built my first 650ss in 1981 & built up the carbs to those settings. It ran well whilst running in, but a week later I went to the TT. As the motor had by then loosened up I started to cane it. On anything over half throttle it just eight stroked. I went to a Brit bike shop called Tiger Tims for some new plugs & as luck would have it there was an old Amal rep. in, who upon hearing about the problem immediately told me to try a pair of 240 mains & work down from there. The bike ran great after that. I can't remember what the rest of the settings were but 3 slides, 106 needle jets, & 2 ring needles would be a good start. As for pilots we now have the luxury of the removable type & 19 seems to be the favoured starting point for Norton twins.

Martyn.
Click to expand...

Well, the Roy Bacon settings looked rich to me too, but I’ve no direct 650ss experience.

I can’t recall having a 4 stroke with concentrics that needed anything other than 106 needle jets.

Some trial and error required by Norton_rider me thinks...
 
Matchless said:
The Roy Bacon main jet size is bollocks.
Click to expand...

I'm not arguing but apparently it was/is the official Amal specification for a Concentric-carbed (930/17 & 18) '67-'68 650SS (as a '66 would have had Monoblocs).

http://amalcarb.co.uk/carbspec/carburettor/spares/id/5433/

"Product No: 376/100-280
Name: Main Jet - Size 280
Product No: 622/122-107
Name: Needle Jet - 4 Stroke - Size 107
Product No: 928/0603
Name: Throttle Slide - No. 3 Cutaway"

Another list I have states that specification is for "Without air filter".
 
I can only say what worked for me, but as a 750 Commando with 30mm Concentrics & air filter requires 220 mains I think it's unlikely that a 650 fitted with 30mm carbs would need 280s. My current 650ss has Monoblocks & these as you will know are jetted differently, so I can't compare them.
Maybe it would be best to try the bigger jets as at least the engine won't come to much harm, but I would wager they will be too big.
 
Thanks lads appreciate the replies, just been reading Paul Dunstall's book it mentions Jetting in that.

230 or 240 for silencers

270 or 280 for megaphone equipped machines interesting stuff.

What's everyone's take on Concentric's v Monobloc's?
 

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