Dear Friends any help gratefully received. my m20 has always started ok until we got the petrol with bio additives. Twice now once when i hurt my back and more recently when it was just too cold I've had ageing petrol in the tank. it would fire a couple of times but not more than that. So i emptied all the old petrol and just got some new. Again sometimes it will fire and more often not. I have checked the spark which looks good. Sometimes it seems to get too flooded, the spark plug is soaked so i take it out and dry it. So it seems new petrol is getting in and there is a spark. Nothing else has changed why won't it pick up and run. Could it be the carburettor has got gunged up inside, if so what should i do.Any other ideas.

hope someone can help. all best peter

Peter, have you checked the quantity of oil in the sump ? If it has managed to drain down then the extra drag on the flywheels is likely to be enough to stop you spinning it over fast enough - and once that has happened, it will soon wet the plug.

If the pilot air drilings are blocked then there is no alternative to dismantling, warming the body and carefully tapping the jet block out to clean it properly.

I understand M20s start with plenty of carb tickling, so having a wet plug is probably good. Assuming it started OK in the past and no-one has changed any settings....timing, etc....and there is not petrol dripping constantly from the carb, then best place to start (sorry!) is put in a fresh spark plug as it seems quite common these days to have plugs that seem to be OK but fail to work under load. If that does not work, then its back to going through the usual suspects.....probably firstly the state of the points, then check timing. Check your HT spark plug connector does not have a suppressor in it! Good luck.

Don't over flood it...There's no need to have petrol p****g out everywhere...

Turn on the fuel and then hold the tickler down for a few seconds...

Give it as much advance as it will take without kicking back...If that's fully advanced that's OK...

Don't open the throttle until the engine fires, then 'catch' it with the throttle....They start better on a closed throttle so no 'kick and twist'..

If it's been stood a long time drain the sump...If it's been in a damp garage give the points assembly a squirt of WD 40, cleaning up any surplus with a tissue and clean between the contact breakers with a bit of card...

Check the points gap...It's not unknown for them to close up...

Gap the plug to .018"....

As I've said before many times...I run bog standard pump petrol and have never had trouble starting bikes that have been standing...After I broke my ankle I didn't start my B33 for 18months but it started fine with the same fuel...

Ron starts up the bikes in his collection periodically and I know he also hasn't had problems starting them after lengthy lay ups...Ian

email (option): ian@wright52.plus.com

thanks everyone for the suggestions. I don't think oil has settled much in the sump as it turns over easily,but i will check the oil tank. I will go through the other suggestions in order of effort and see where I get. I will keep people posted. many thanks of now. peter

Modern fuels can short out plugs if they do not strat.
It all depends upon what exactly is in the fuel.
So start with a new plug and a quick squirt of starting fluid.
If you can get it to run then let it run for a while and get nice and hot then pop the old plug back in as it should ru in a warm engine,
When you are finished, turn the fuel off and allow the engine to starve .
In doing this it runs very lean for the last few seconds which burns all the accumulated crud off the plug.
I have been doing this for years and since adopting this system the M20 starts beautifully and generally on the first kick much to the shock of a lot of onlookers.

So fr short stops when the engine will still be hot I decompress to stop.
For long stops when te engine is likely to be cold I starve the engine off.

email (option): bsansw1@tpg.com.au

Hi Peter.

On top of all the above,
Sometimes it is just a bad spark plug.
I would try to replace it with another one, even a good used one,
Even just for testing purpose.

Noam.

email (option): noam10"at"gmail.com

('Modern fuels can short out plugs if they do not start.
It all depends upon what exactly is in the fuel.
So start with a new plug and a quick squirt of starting fluid.
If you can get it to run then let it run for a while and get nice and hot then pop the old plug back in as it should run in a warm engine,
When you are finished, turn the fuel off and allow the engine to starve .
In doing this it runs very lean for the last few seconds which burns all the accumulated crud off the plug...')

Trevors comments about 'fuel', which he has made before, lead me to believe that what is on offer in the colonies must be quite different to what is sold here in the mother country (I think operating temperatures are pretty different as well much of the time ) and as such practical experience there is quite different.....

Running my bikes on normal pump petrol and a Champion modern equivalent of the old plug grade I have no special starting or stopping procedures and have never had plug problems...In fact the whole subject of fuel is a non issue as far as I'm concerned, I don't even think about it...

As mentioned in my last post, fuel deterioration over periods of 18 months or more doesn't happen either in my experience....

Tales of fuel going off in two weeks and the effects of it on starting and running are, in this country at least, more likely to be the misdiagnosed effects of other problems....

At this point in time much of the pump petrol in the UK only has 5% ethanol with some 10% also available....Ian

email (option): ian@wright52.plus.com

Dear All first thanks a lot for all your helpful advice and guidance. So much appreciated. Anyway, i bought a new plug from Russells down the road, gapped it at 018 checked my points and checked the oil level in the tank which seemed ok.

I have to be honest I kicked and I kicked. I was getting tired and feeling like giving up. Then 7 fires in a row and then it caught. Hurrah i can't tell you what a lovely feeling! i don't need to, you know. and then i let it run a while and then switched off petrol so it died empty. left it a short bit and then kicked again and it started 2nd kick. Its back to work now unfortunately.

I just hope the story is the same tomorrow!!!! thanks a bundle everyone. this site is so helpful as well as so nice to have. peter

Result!!!

Not meaning to pinch te thread but yes the slop we get down here is atrotious.
I have a sneaking feeling that down here the oil companies buy all the scrap hydrocarbons world wide and blend them into something that will go bang if you are lucky.
I have bought fuel that stank like paint stripper and took some into a lab of a mate. It was 45% tolluene , 45% benzene and 10% ethanol.
seems Tolluene was available every where really cheaply and the service station operator was cutting his fuel with tolluene only problem the fuel supplier was running the maximum allowable tolluene content of 20% to start with.

Eventually I got all my fuel from Burma Oil till they got pushed out of the market.
Not particularly good but at least it was consistant as it came directly from Burma and was simply stored in the BP depot then delivered to the servos.
Coles eventually leased the tanks so Burma had no where to store their fuel so they exited the market.
Even now if I tip a liter of fuel into a dish in the sun, after an hour it will have reduced in volume about 80% and what is left is a foul smelling geasy slime that will sit in the dish for months.

Don't forget we just had a record Feb hot spell, 22 days of 35 deg C and 80% relative humidity, a touch different to summer in the Old Dart.
Fuel tanks get so hot you have to put on gloves to open the fuel cap and that is without the bike running.

The brother of an ex Prime Minister runs one of the ethanol distilleries and the party he once led is legislating to make it illegal to sell fuel without ethanol
If that gives you some idea of what is going on down here.
I think the heavy oils come out of solution at cylinder pressures then deposit on the plugs. This oily deposit is highly conductive, so people go gar gars blaming the #*^%# spark plugs when all the time it is the #^*# fuel.
The fuel companies have the governments by the short & curleys.
We have no standard for "fuel" it was dropped in the 60's
We simply have a lomg list of what is not allowed to be in the tank plus another list of the Maximum amounts of various volatile solvents.

email (option): bsansw1@tpg.com.au

Interesting stuff Trevor...How do you manage with high compression engines and such variable fuel?..

Sounds like your temperatures at 35 degrees aren't too far out from your ignition timing... ...

Our February hot spell peaked out at about 8 degrees.. ....Ian

email (option): ian@wright52.plus.com

You don't.
Everything gets flat topped pistons.
Commando owners run premium fuel (20% dearer) and add some anti knock addative and for some octane improvers. Premium 98% octane rating is substantially better but actually gives worse fuel economy than plain unleaded in the M20 and often is very stale right out of the pump.
The boys with the fast bikes usually run flash lube which is supposed to be an upper cylinder lead replacement .
Don't know about that but it dose confuse the anti knock sensors in the van.
I run it in the gas vans and it makes a big difference to the fuel economy as it stops knocking so the computer just keeps on advancing the ignition till the temperaure sensor backs it off.

We have an absolute maximun speed of 110kph so there is no point in running 10.5:1 pistons any more and a lot of the off roaders run avgas or avgas blends.
To enforce that there are roadside cameras now run by a private contractor who gets a cut of the "take" , anphometers, aerial survalence, marked & unmarked police cars.
Every police car is fited with a front & rear camera which are hooked into the computer which runs speed determinating softwear and anything over a threshld triggers an automatic pull over.
Running from a police car automatically doubles the fine & demerit points. For trucks over 4 Ton there are cameras that read the number plates and do an average between then for the entire trip and these are capable of doing the same with car & motorcycle number plates, the government is just waiting for a roadside "tragdey" to justify adding another nice little earner.

Thus the M20 has become the favourite ride and the B2 , L29 & S29 are all in rebuild mode while the B44, B40 & A65's are rotting away in the shed.

email (option): bsansw1@tpg.com.au

With high temperatures fuel volatility becomes an issue, for example in Saudi the fuel (all grades) had a reduced volatility otherwise you couldn't start hot engines.
As a result it was considered as a very 'low grade' fuel.

I know from my past experiments, Toulene is low volatility - it is reluctant to burn

In the desert we ran AVGAS in the bikes so we could restart them - nothing to do with detonation/knock/pinking - simply survival.
They started fine first thing (3-4am) but by midday in 35-40DegC you simply couldn't start the damn things and you cannot bump start a XR500 on a sand-dune, however steep!

AVGAS is specifically designed to have low volatility (as well as a lower calorific value) to allow engines to operate at altitude.


back to the question -
It you are certain its carburation ............... it will be the ignition (and visa versa)