650SS missing and r.h. cylinder running rich

Previously thomas_newton wrote:

Hi,

Originally both cylinders of my 650SS were running very rich causeing very poor running. The main jets were reduced from 280 too 270 with number 20 pilot jets. The spark plugs were NGK B6ES but have been replaced with Champion NC4.

The bike is running much better now, but still has a miss/feather with the throttle at approx 1/4 open. Picks up no problem on full throttle & also ticks over very reliiably.

The issue which I could do with some advice on is the Right hand cylinder appears to be running rich with a sotty plug when checked after a run. The Left hand is OK plug colour light brown.

Have you tryed Bosch W6DTC you may find there a better plug,

Previously thomas_newton wrote:

Thanks for the info. Anna.

The worry I have is the left cylinder plug looks spot on but the right is very sooted up.

Same type of plug in both & same carb settings. I suppose I coulld turn the pilot air adjustment out to see if I can fine tune one cylinder.

That at will only affect the engine at small throttle openings. It's always difficult to know what the posters level of knowledge is, and hope I'm not teaching you to suck eggs! but I found this article very useful, it's based on a mikuni but the principles are the samehttp://www.iwt.com.au/mikunicarb.htm .

the other thing to think about is wether it was working ok recently, and what might have caused the problem. It might not be carburation.

Fuel level could be too high on one carb,or the float needle not sealing due to grit /fine sediment or disolving tank liner causing it to be sticky ,or just the normal variences between two carbs or different slide cutaways. I would do what many have done and get 20 thou machined off the bottom face of both of the float needle housings.. You could try swapping the carbs over to see if its another issue like poor ignition on one cylinder,bad lead ,plug cap etc.

Thomas, your plugs are correct (Champion N4)

A single carb would eliminate the carb balance issues and give you more MPG. Stay away from petrol marked up as EN228, this will not help.

Since the engine starts, and ticks over OK, and is fine on full throttle, the problem seems to be with the needle and or the needle jet. Have you checked both needles are fitted in the same slots? It is quite easy to be a slot out. Possibly lowering the right hand side, by one notch, would help.

As it happens I have been using "Super" unleaded.

It would be nice to think problem is as simple as this. I will fill up with ordinary unleaded next time.

I am hopeing to go to the Tay Vally Branch Borders weekend which will give me a 120 mile round trip to try things out.

thats a bit heavy 40 to gallon its what your getting you should be in the 50 to gallon even on twin carbs

Thanks Dan. A very interesting articial in laymans terms.

It is maybe not be a "pilot issue" as it seems to feather just at 1/4 throttle open. Just about a pleasent running speed. Picks up fine on acceleration.

I will have to start from scratch again in case I hve missed somthing between the left & right carb.

I have recently bought the bike been a BSA single man most of bikeing life. Single carbare so much easier !!

yes but he talking about Mikuni carbs Not amal there a diffrent thing , and twin carb set up must be in very good condition No warn parts if there is some wear on one side this will give you rich mixture on that carburttor , the twin amal mono bloc should be the right side has no float inside, its a chopped monobloc , linked too the left side carb via a under carb banjo fittings and a short pipe these are Amal 376/288 and amal 376/289 they should have a 3.1/2 cutway side and a 106 needel a 250 main jet for the 650, but you may need a smaller main jet for ethernol fuels thend to run rich, i find yours anna j

I am going to check the carbs again as soon as I get sometime.

Needles were set the same( I think ), but I suppose I need to strip & check again in case the right one is inncorrect.

The concentric carbs look to be new (ish) looking at the condition of them, but I can not be certain. Both are fitted with short bellmouths.

Hello TOM you not said what year your Norton was this just may help us too help you out here, for we are all in the dark and a Model and Year would be nice, Amal concentric did not come out untill 1967 on and Concentric have a diffrent main jet numbering size the main for a 650 with concentics should around a 280 main jet and a 25 pilot jet. cutway slide No3 .107 needel they should be a matching pair with numbers like 930/18L and 930/17R for a 650cc machine, anything bigger is over kill I do have a 60 page Amal Cataloge on all amal carburettors So if it was built before this they should be Amal Mono bloc 376/288 and 376/289 chopped mono bloc and from 1965-66 Amal 376/317left handed blow & 376/318 Right hand blow I have all the data yours anna j

Anna,

All the documents I have (past MOT's, old V5 documents & present V5 state it as a 1965 650SS. Although when I sent the matching frame & engine numbers to dateing officer he came back with it a s a 1965 Atlas. ???

I think the concentrics are quite new & probably retrofitted.

Well want dose the engine and frame number say, Atlas is Stamped 20 650 stamped 18 or 18ss if your machine a Atlas then the Carbs with be a diffrent number to A 650 and in 1965 you should of had a set of mono Bloc carbs 376/318&376/317 for a 650. A 1965 Atlas would be on mono bloc 389/218&389/219 well it look like someone has fitted the wrong set of carbs for that year and the dating officr will be right in his deliverance , Your machine is a Atlas yours Anna J

You are Just going round in circles. What are the frame and engine numbers?. taken from the machine,not the paperwork. If you want it to work, you have to work with what you have,not what bits of paper say .

Would even the frame and engine number give the answer? Is it possible that a 650 top-end could have been fitted to an Atlas bottom end, hence why it is registered as a 650? Don't ignore the clues, Watson.....

Previously thomas_newton wrote:

As it happens I have been using "Super" unleaded.

It would be nice to think problem is as simple as this. I will fill up with ordinary unleaded next time.

I am hopeing to go to the Tay Vally Branch Borders weekend which will give me a 120 mile round trip to try things out.

Tom. Neil was suggesting not using ordinary unleaded, which is EN228, 5% ethanol. Stick with super unleaded. If you are in the north, best use BP Ultimate super unleaded, which is ethanol free. It has been suggested that Esso super unleaded is also ethanol free. Don't use Shell, or supermarket super unleaded.

We have accertained that the machine is a 650ss with the orriginal engine (accepted that we dont Know whats inside!). Its fitted with concentric carbs(float chamber undeneath!) that are not normally a std fitting and may have come off a late Atlas,it would be helpfull to have the carb size to work out the settings ,its also possible the carbs came off a Commando .

Both engine & frame numbers are: 18/112360 so I think the dateing officer may have been mistacken when he thought it was an Atlas.

I relise the carbs are not original.

Hello you relise the Carbs are Not original you can say that again there Not even in my Amal cataloge , there Reproduction carburettors and not the right ones for the year 1965 Norton 650ss Plumstead model ,thay should be Mono bloc. Not Concentric and it looks like one of the needel valves is not seating right and letting that bit more fuel into one side, try resetting the floats you need to take off the carb's undo the float blow screws take off the blow and turn it upside down so you can see the movement of the float and the needel valve then take mesurements of the float too the under side of the carb it should around 25mm they both have too be the same carbs are very finikey you have too have them set just right , And its not like the dating officer too get things wrong but he has this time, well were all human !!

If you have a problem with the spark this will also give a very sooty plug because it's not burning the fuel correctly. You appear to have done a lot of work on the carbs perhaps it's now time to have a look at the plug, plug cap, ht lead and mag pick up or dare I even say it, the mag itself.

Anna,

I have just recieved the Bosch plugs you suggested trying.

I was not to sure about the reach or how to set a gap with the three electrodes, but tried them in & turned the engine over very slowly at first.

Seemed OK so gave them a try & I can not belive the improvement. I have only rode it for a short distance as pressed for time, but wil give it a proper run to the Tay Valley Branch/Borders weekend tomorrow. (weather permitting)

Previously anna jeannette Dixon wrote:

Have you tryed Bosch W6DTC you may find there a better plug,

Hello thanks for the feed back I been trying to get members to give them a try out, but they all on NGK and its NGK this that and other, But no one dose not what to give so other Spark plug a try out and you find your fuel will go farther than it did, I been runing My Norton anxman 650 on them for well over 3 years now on the same set of plugs the bike even start easyer , in fact Bosch are the worlds oldest spark plug manufacturer and there spark plug are qualty made plugs, hears the Bosch plug chart yours anna j PS have a nice time on your ride out,

Thanks Anna,

I will hopfully have some time at weekend to check as you say.

As a matter of interest how difficult is it to get a single carb manifold, & maybe use one of the carbs ?

Hello tom well i use RGM Motors and they have some in stock do not cost a fortune, and you should get it on the next day delivery there good on delivery times, Yours Anna J

Look out for numbers 92 & 93 - I'll be riding a '59 B31, my son my '51 Star Twin BSA. My Atlas is a bit of a handful to ride in the trial but son and I have both competed on it successfully on a number of aoccasions. It does look a bit out of place in amongst all these pre '65 trials bikes!

Hi Anna, As you are a mine of information ,perhaps you would like this challenge, I have been given a box of bosch plugs, described as Super4 ,the insulator is marked R6 and 791, the steel body are marked FR78 GERMANY,It would be nice to use these but I can't find any reference to them to work out the heat range ,They seem to work ok in the 99.I think they were bought for a VW Golf 1.8 gti.

Anna - haven't you checked the Wikipedia article on spark plugs? Your hero, Mr Tesla, is credited before Mr Bosch!It credits Bosch with the magneto in 1902 but then says rather inaccurately that the spark plug was not useful until that. But the 1902 bike I run has total loss ignition - partly because the mag had not been invented, and partly because it does not really have enough power to drive a magneto anyway!Mr Lodge was in there are about the same time as well. The spark plug was not really an invention - and not by Bosch - more a device whose time had come. I think Lodge do modern jet engine ignitions nowadays - are they still going?

Well its nice to know that all sparks started with Nicola Tesla , where would we be with out his knowledge and the Tesla coil hes one man I would of loved to of meet did you know he could speak 11 languages and do algorithms in his head genius or what , yours anna j