Poor idling 650SS

I have recently put a 650 motor in my Dommie with a carb set-up like yours. The carb is an old Mark 1 Concentric jetted the same as the Mercury 650. To insulate the carb from the head I put the Paxolin (2mm) spacers between the head and the manifold. It appears to work for me. The idling is fine.

I would suggest that you check your ignition timing and the auto advance/retard mechanism.

I originally had a carb flooding problem due to the Ethanol in the fuel. I put a Fuel Cat in the tank and this cured the problem. It also boosts the fuel up to 5* and you don't need to lead substitute in the tank anymore.

Hi, just start the bike and spray a water and fairy liquid mix all around the carb gasket areas to eliminate those. if it is taking in air you will notice it by the tick over settling down it will also make a fizzing noise and you will see it slightly bubbling at the joint at fault. its a bit safer than using unlit propane, just thought it might help. Baz

I have recently put a 650 motor in my Dommie with a carb set-up like yours. The carb is an old Mark 1 Concentric jetted the same as the Mercury 650. To insulate the carb from the head I put the Paxolin (2mm) spacers between the head and the manifold. It appears to work for me. The idling is fine.

I would suggest that you check your ignition timing and the auto advance/retard mechanism.

I originally had a carb flooding problem due to the Ethanol in the fuel. I put a Fuel Cat in the tank and this cured the problem. It also boosts the fuel up to 5* and you don't need to lead substitute in the tank anymore.

Yes a fuel Cat is a good idea and two egg cup ful of Castrol R in a tank full of fuel help with the valve lube but think you carburttor is way to big, my monobloc is 1.1/8 inch and that in mm is 28 mm , not 30mm has I just mesured it all up with my Engineers steel ruler with the carbutters I have here, and I a few of them and try runnig of Bosch W7DTC sparkplugs Thats what My Manxman 650 running on from the last 3 years now the ideling realy good, nice slow tick over, yours anna j

Check Mercury sales brochure as attached. Worked for me.

I found that the slide in the 32mm carb on my mercury would start to catch slightly when the bike got hot and cause similar issues to yours. A little fine water paper sorted it out. Have you checked the carb bowl fuel height?

I would agree that a 30mm is a bit on the large side - a 28mm would be better however that shouldn't give you grief. I would check that the throttle cable is free and not frayed and that the throttle slide is coming to rest on the throttle stop with an audible click. It's easy to have the slide hanging on the cable at tickover rather than on the stop. That alone can give problems. So be sure your cable is adjusted properly. The other thing to check is that the throttle return spring isstrong enough to clost the throttle under all circumstances. If your engine is running away up to 2,000 rpm, it's getting a lot more mixtrue in than it should. One last thing - the cable routing. Is the cable hanging up or catching on something? The old MoT test of bars from full lock to full lock with the engine running is worth a try.

Check Mercury sales brochure as attached. Worked for me.

Hello this Brocure is when real petrol was around no this horrble green stuff we Have to put up with now, and smaller carb will over come the constant flooding of the carburettor, Even I down to 280 main jet and still need to be lower or drop the needle one noch, the floats are none setting type so I have file of 20 thou of the body where the float needle housing fits to stop the carb flooding , even modern bikes are having problem with this horrid fuel , yours anna j

Right fellow NOCers thanks for the suggestions, to take them in turn.

Cable routing is fine new cables all round when I bought the new carb from Norvil 3 weeks ago. It doesn't hang up and the slide is right down on the stop even when it is racing. putting my finger in the mouth of the carb stops it, take it out and it idles ok for a short while then creeps up again. Stopped doing the racing bit of the game since I played with the carb settings last time still lumpy and uneven at idle though

Carb size is fine the Mercury had 30mm concentric and I am now going to see if the one I got from Norvil has the right jets and slide in it, I have had no luck in finding that piece of info on t' interweb so thank you for a copy sir.

It was doing similar things with the twin monoblocs on and as they were a pain to tune and never stayed tuned for longerthan the end of the road so I converted it to a single carb.When it is not idling it runs fine and seems to have more bottom end than with the twin carbs.

Float height could be one to check but it is a new carb so I am assuming it is OK but will look at it just in case.

The carb is a premier amal one with the plug to makeunbunging the cross passage for the idle screw easier, why has it taken till now do do that seemingly simple idea, might shove an air line on that see if theres any machining crud floating about in there.

Done all the air leak checks with wd40, soapy water and commercial leak test spray ...nothing no change at all so I think my flatting of the faces and new gaskets etc has solved that one.

Doesn't WD 40 make a lot of smoke on a hot engine !!

InterestinglyAnna,Nortons since the war with ally heads do not need hardened valve seats fitted or the LRP jollop on that account I think you have never tried to recut them with an old fashioned hand cutter set, nothing except a commercial valve seat grinder will touch them. Not like triumphs which have cast iron seats. Nor do they need lead replacement jollopif you use super unleaded. Just a degreeor two retarding the ignition if the engine pinks.

Spark plugs.... tried champion against me better judgment already and no better than the NGK's it has had for ages.. Ever since I put a new set in an MGB and took it to a crypton tuning place and the bloke took 2 out and binned them put a set of NGK's in and handed me the 2 good champs... utter crap never go near them. Hmmm Bosch well they are in the never been there bracket I stick with NGK and have always thought that 3 prong end was a marketing tactic to get money out of people for fancy plugs, may work on a new jap engine with all sorts of wizard electronics but i doubt it would do anything useful or noticeable on a trad engine like we use. ,How do you change them to 20thou when there are 2 others getting in the way of the feeler gaugeas they wont be set to the right gap form new.?

Oh and it does the same on both makes. Plugs do look a bit white which has set me thinking it might just be the jets etc .

Ignition timing is one I had not thought of as it improved a bit when I got the oil slick out of the mag but it could be the advance unit as I tightened the chain a bit when I put the mag back, maybe it's too tight now, Yes I have a spare cover with the holes in it to support the spindle when adjusting. Seems like a spanner wielding weekend coming up .or if the weathers nice I will have to stoop to a ride on the Suzuki

Phew ....Thanks all for the help so far will report back in due course.

Regards Gromit

Well I run my 650 on Bosch for last 3 years now and Had no trouble they work well with this E5 fuels we have now the trouble I am getting now it with the Carb float is it a none pre setting float the needel get suck now then so we have sort this out, but the idea behind the tree point plug is there self cleaning and self shelding too so thats makes you engine run cleaner, and easy starting , but its up to you to battel on with the old plugs yours anna j

John, I have a 1964 650SS engine in a slimline frame. Off the road at the moment with suspected big end failure. Perhaps I should have ridden it round to Anna's for fixing but it's the next job up.

Anyway, this engine uses a post 1960 head, not the 650 type, with single carb. The carb is a 30mm Mk1 Amal, though I can't remember the settings. I use Champion N4 plugs and all my bikes run on BP Ultimate, E 0 if you are outside SW England. Why would you use EN228? If you put solvent in your tank you are asking for trouble. My point is that apart from the big end problem, this bike ran like a dream, even with the engine rumbling!

Good luck.

My 650 is running great apart from a little pinking when accelerating hard at low revs. This is probably caused by the 10 to 1 pistons fighting the ignition. Other than this I have no problems starting, idling or running.

However, when I first built the bike and had it running I noticed that the engine sometimes idled too fast or died depending on the position of the front wheel. The cause of this was the throttle cable being cable tied to the headstock. Turning the handle bars resulted in a tighter or slacker cable. The solution was easy......I just let the cable dangle downwards from the twist grip and then gently loop over the front frame rails to the carb. Previously, to comply with MoT rules, it did a right angle at the twist grip and another at the headstock.

John, I have a 1964 650SS engine in a slimline frame. Off the road at the moment with suspected big end failure. Perhaps I should have ridden it round to Anna's for fixing but it's the next job up.

Anyway, this engine uses a post 1960 head, not the 650 type, with single carb. The carb is a 30mm Mk1 Amal, though I can't remember the settings. I use Champion N4 plugs and all my bikes run on BP Ultimate, E 0 if you are outside SW England. Why would you use EN228? If you put solvent in your tank you are asking for trouble. My point is that apart from the big end problem, this bike ran like a dream, even with the engine rumbling!

Good luck.

Hello well How can you now ride your bike round to my place if its now go a big end failure, but a do have my van and a very big workshop , so big we can all get in it, yours anna j

Worth trying one of your old carbs? If that works ok maybe your new Premier has a basic problem somewhere.

John, I have a 1964 650SS engine in a slimline frame. Off the road at the moment with suspected big end failure. Perhaps I should have ridden it round to Anna's for fixing but it's the next job up.

Anyway, this engine uses a post 1960 head, not the 650 type, with single carb. The carb is a 30mm Mk1 Amal, though I can't remember the settings. I use Champion N4 plugs and all my bikes run on BP Ultimate, E 0 if you are outside SW England. Why would you use EN228? If you put solvent in your tank you are asking for trouble. My point is that apart from the big end problem, this bike ran like a dream, even with the engine rumbling!

Good luck.

Hello I disagree with post 1960 head singel carburettor fitting

fitment

ie 30mm mk1 carburettor so spark plugs would of been Champoin N5 or something like , but with E5 ethernol fuel you need a different spark plugs ,

to siut the ethernol fuels like the three point ground electroid thses are self shelding and self cleaning , give a direct spark colonel , witch make for better starting , your all still going by old data the Fuels have NOW Changed How many more times do I have to put this on the NOC web Threads Read this the Fuels are No longer Based on Crued Oil Has the World is running Dry of Crued oils these are the real facts there subituting the oils with Plam oils and sugur cane oils , and Shenut oils , this is why there cutting down the forrist in the world to grow plam colonels and she nuts for oils , were all now slaves to the oil industry, and the time will come when this is no long sustianable and Free energy devices with come out the sooner the better, the reason they are keeping things going on oil is its a multi trillion dollor industry witch every one is a slave too, but where going to have to change all this if we need to live on this planet any longer, has the polution from oil based fuels is slowy killing this planet, And our selfs too, and I am Not a Greenie,! its a engineering point of veuie and we need to do our part in all this like it or not, now this may make you all laugh , I am looking into Cat litter has a exhuast cleaner , has cat litter is highly exorbant even with gases like exhaust gas and can be chainged out if this fitted in the silencer end in a cage type vessel , now that just one mad idea ! but you all need to now realist things are changing fast, and the spark plug data is Now Out of Date, and needs up dating , were now looking into this to we keep you all posted yours Anna J Dixon

Richard, I agree with you and I should have suggested that another 30mm carb be tried. Sound advice, they do work well on the 650.

Anna, hope this doesn't set you off:

1) My 650 has covered 132 miles before I laid it up, too late for you now as it's the next job after the 99.(Almost there)

2) Outside of SW England, BP Ultimate remains Ethanol free, therefore Champion N4 plugs are right for the 650. Incidentally, my restored 99 will run on Champion N5, same as my Model 50 and ES2. Never had a problem with Champion. D9 in my 16H for good measure!

3) The world is awash with oil. The palm oil you mention, much of that is at the expense of tropical rain forests and used to a large extent to make bio diesel! We need to challenge the extensive use of bio fuels, not use it!

If you want to continue this one (Bio diesel) open up a thread in the off topic section so there are no complaints as there are no diesel Norton's (Yet!)

My 99 runs with Champion N5 plugs

My 650 with N4.

My Commando has N7Y and so does my Mercury engine which has the same head casting as the Commando. In my manual I am informed that N4 plugs should be used in my Mercury....Why not the easier to clean N7Y.....? Can anyone help with a sensible explanation that does not go off-topic please? My German grape vine is doing well again this year.

My Commando runs GR8 with Champion N7Y's too.

Why is the book always right?

"The idling is hit and miss, it will sometimes happily settle to an even idle and then at the next set of lights it will stall or run faster " Quoted.

Hello Gromit, this sounds to me like a typical problem caused by the auto advance/retard not returning the timing back to retard when you come to a stop. Idling the engine at full or partial advance will cause the engine to run faster. Check the return springs, new ones are readily available.

Paul

Previously anna jeannette Dixon wrote:

Previously Phil Hannam wrote:

I have recently put a 650 motor in my Dommie with a carb set-up like yours. The carb is an old Mark 1 Concentric jetted the same as the Mercury 650. To insulate the carb from the head I put the Paxolin (2mm) spacers between the head and the manifold. It appears to work for me. The idling is fine.

I would suggest that you check your ignition timing and the auto advance/retard mechanism.

I originally had a carb flooding problem due to the Ethanol in the fuel. I put a Fuel Cat in the tank and this cured the problem. It also boosts the fuel up to 5* and you don't need to lead substitute in the tank anymore.

Yes a fuel Cat is a good idea and two egg cup ful of Castrol R in a tank full of fuel help with the valve lube but think you carburttor is way to big, my monobloc is 1.1/8 inch and that in mm is 28 mm , not 30mm has I just mesured it all up with my Engineers steel ruler with the carbutters I have here, and I a few of them and try runnig of Bosch W7DTC sparkplugs Thats what My Manxman 650 running on from the last 3 years now the ideling realy good, nice slow tick over, yours anna j

Just reading this thread and I am astonished to read Anna, that considering you are supposed to be an engineer you refer to a measuring instrument as a ruler? It is in fact an engineers rule. A ruler is a King or Queen.

Just being pedantic.

ATB. Paul