650SS Premier concentrics jetting

savingclassicmotorcycles

savingclassicmotorcycles

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Feb 6, 2011
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Hey everyone just curious for those with a 650ss and the new premier concentrics
What jets is everyone running.

Pilot
Main
Needle jet
Needle clip position
Float heights
Slide
Air filter or no airfilter.

Currently I'm at on a 66' last of the mag ones plumstead built
Pilot : 19 went up from 15
Main : 280
Needle Jet : 106
Needle clip position : Middle
Float heights : 2mm below bowl lip
No airfilter 1/2 inch head to carb manifold length in total


Not sure if the year of the SS makes a difference? Any engine changes over the years.

Thanks in advance
 
My 2 cents.....were these supplied by a shop that is knowledgeable about Dommies? Or are they a generic carb leaving the jetting up to you?

The main jet sounds big but not really a problem as you will probably never be running at full throttle. Still, it would be nice to have the correct one. Don't worry about it at this point.

Have a spare set of 107 needle jets. I like to bracket the problem...find out what's too rich and too lean. It is a simple jet change .

You did not mention the throttle slide. Amal supplied either #3 or #3.5. These are expensive things to replace so let's hope the ones supplied are correct.

Pay attention to the fuel level as the carbs are on about a 10 degree angle into the head. This is an area of potential problems so check that the fuel level is actually controlled well. Because I wanted the carbs to remain straight up and down in my Atlas special I machined a pair of Commando manifolds approx 5 degrees off each side and now the carbs have no issues. Nice if you have a milling machine handy. This won't be mandatory however. Many Atlases have amals bolted up as is.

You should have a phenolic spacer between the manifold and head to keep excessive heat from reaching the carb. I have the best luck using the standard phenolic for a commando and sandwich it between two paper gaskets ( usually not available from Norton. Try a Triumph shop or Burlen direct.) I use Yamabond on these gaskets and now they are airtight. Using phenolic against aluminum provides a so-so seal, not entirely reliable. Therefore the jetting can be affected.
 
Thanks mate very interesting got some 230 mains on the way :) going to double check the fuel level with the amal tool.

Were actually supplied by Amal when the premiers first came out

Throttle slides are 3
Current setup is
Gasket
Phenolic (new commando ones)
Gasket
Manifold
Carb with o ring to manifold
Not used anything on the gaskets
One thing I was wondering is the balance pipe manifold to manifold underneath should that be closer to the carb or the head. I've got it to the carb currently :)
 
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looking at your plugs on the other thread, things are looking pretty good. On the Commandos the balance pipe is closer to the carb, do not know if it matters. I use a carb balancing tool...vacuum gauge... to synch everything up. I am unsure if the balance pipe does any real good. I think it was installed to give a bit more life between each carb adjusment. However, when I use the vacuum gauge then reinstall the balance tube the idle jumps and I have to fiddle some more. Currently I cap off the balance tube. It always seemed like introducing a big air leak on each side.
 
Seattles on the right track. And yes those mains sound pretty big. I used 190s on my 500 SS race bike with 52 bhp rear wheel on the dyno on 30 mm Amal Mk 1s. So 280 will be giving you way more gas than you can use.

But every tuning job on a magneto equipped bike should start by checking BOTH cylinders for ignition timing. I imagine you are running somewhere from 28 to 30 depending on CR.

Would be nice for your engine to have some kind of aircleaner on there.
 
johnm said:
Seattles on the right track. And yes those mains sound pretty big. I used 190s on my 500 SS race bike with 52 bhp rear wheel on the dyno on 30 mm Amal Mk 1s. So 280 will be giving you way more gas than you can use.

But every tuning job on a magneto equipped bike should start by checking BOTH cylinders for ignition timing. I imagine you are running somewhere from 28 to 30 depending on CR.

Would be nice for your engine to have some kind of aircleaner on there.
Click to expand...


Do you have a build thread for your 88ss? 52bhp from a 500 is pretty impressive!
 
It was a few years back now in about 2003 before I was on this site. The closest thing to a build thread is on the Britbike forum. I’ll see if I can find it.

http://www.britbike.com/forums/ubbthreads.php/topics/353857/1

This is it. Not a build thread but answers to questions abut how I built my bike.

I went overseas in 2011 and have not done anything since.
 
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You checked the ignition timing on both cylinders right ?

I really recommend this. I ruined two sets of pistons before I checked both sides. Magnetos are electrical and mechanical devices. Just because you have a spark it doesn’t mean it’s at the right time both sides. Errors in the cam ring, the bearing centricity and the shaft alignment can all mean the spark may be 29 degree on one cylinder and 39 degrees on the other.

Don’t even bother to tune carbs until you have checked this. I would have loved to have this advice when I started.
 
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johnm said:
It was a few years back now in about 2003 before I was on this site. The closest thing to a build thread is on the Britbike forum. I’ll see if I can find it.

http://www.britbike.com/forums/ubbthreads.php/topics/353857/1

This is it. Not a build thread but answers to questions abut how I built my bike.

I went overseas in 2011 and have not done anything since.
Click to expand...

Thanks for the link. Too bad some of those folks involved in it have gotten sour and left, taking their knowledge with them. My lady friend speaks of everyone's "baggage to talent ratio". We've all got one, and sometimes it flip flops.

Your bike and your approach sound very well reasoned and thought through.

Back to carb jetting!
 
Johnm is right ...ignition first. You probably will not feel any difference going to 230 mains but at least you'll know that you are very close. I don't think many people know for sure what main jet to use. Who goes down the road full throttle at red line or beyond?
 
Yep good point lads totally forgot to check the timing I'll double check that as soon as this weather clears up!

Good point regarding the main jet as well, bobbing on speed wise an she's only approaching just past the 5k mark in 2nd. 30mph 2nd gear is about 2,700 rpm so wondering if it's overgeared.
 
referring to your other post now 300 + responses. I worked in printing for too many years. Unfortunately all the skills you learned in printing are non transferable to any other occupation. Don't waste any time moving on to something else. Can you imagine all the shops that had mega dollars (or pounds in your situation) invested in big presses and all they can do is haul them off for scrap. A 36" 4 unit Heidelberg now useless rusting in the alley? That's progress. Imagine all the jobs that disappeared with the demise of the print industry and all the other industries that supported it.
 
Yeah I totally get you mate we were running a state of the art Heidelberg XL75 4 LX2 with axis 2 prinect etc luckily I was split between pre press on the macs and the press room + other stuff / managing a department so got a few transferable skills hence me deciding to get out of the industry after a bit of thought had a few offers back in it but want to get out while I'm young enough to do so :) although some print houses are still going it's certainly an industry in demise in the uk truly a shame. I'd class it as a forgotten industry in a way just being allowed to shrink truly a shame.
 
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