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M20 Starting tips after very long storred

Hello Again folks

My 1947 M20 had been not used for quite some time. I initially was told not since 1987 but it may have been 2007; either way it is a long time. I am going to renovate it as mentioned in earlier post about oil spring valve issues. I am attempting to get it going initially before renovating but am experiencing difficulties. Is there anything special/difficult about starting a bike after a long time?

Things I have done and checked as follows:

1, Drained oil from sump and tank and replaced in tank to change later when engine hot and flushed out.
2. In combination with above cleaned and checked as best I can the 2 ball valves and engine sieve filter plate on sump.
3. Taken tank off as quite rusty inside to look at de-rusting later (electrolysis /soda or phosphoric acid; not decide yet).
4. Partially dismantled carb and checked main jet looks quite clean. I can see through the main jet OK. Cleaned throttle and choke slides which all move quite nicely. I did not remove pilot jet
5. I filled float bowl with fresh fuel so should be enough to start it.
6. Initially no spark. P400 paper on points and now sparks OK ish as far as I can tell (more on this later)
7. Checked compression (seems loads under foot) but on gauge gives 5 bar or 75 psi. I guess with a 5:1 compression that's pretty close to what I would have thought (5 x atm at 15 psi = 75 psi) so should be ok?

However after all this it just will not start. After multiple attempts and tired legs ! I have tried with and without choke, with advanced and retarded ignition and combinations of. I note that I can smell fuel about the bike and I cant detect even the hint of firing.

It was known to be running when laid up so i guess timing must be OK and cant really change as is set with a gear.

On the spark topic it seems ok but maybe every now and then it may miss one when plug held on head. Plug is ancient NGK B6HS. I nipped to local car parts shop (Halfords in UK) to get new plug but the closest I could find was a BR8HIX which has same reach but slightly different electrode design. I know it's probably incorrect but this does seem to spark OK after gapping it at 0.3 mm ~ 0.012" and I would have thought would be ok to run it?.

Anyway, that's another long blether but if anyone has any re-awakening starting tips it would be much appreciated.

Cheers

Neil

email (option): nlhclarke@gmail.com

Re: M20 Starting tips after very long storred

Hello Neil,
Having fairly recently recommissioned an M20 after a lay-up of similar duration I would say the following.
If it really was running before it was laid up, and has good compression, then the issue is almost certainly one of only two variables - sparks or fuel.
Almost any strength of spark should cause ignition if it’s happening at the right time and the mixture is good. I think my plug is the same NGK as yours and at least 39 years old, it works fine. You should check that the ignition timing is correct, 7/16” btdc at full advance. You don’t need to touch the gear to at least check it.
For fuel, by far the most likely culprit is a clogged pilot jet or airway. These pesky things can cause no end of trouble if obstructed by the tiniest particle, which after several years they are bound to be. Simply blowing through won’t likely remove corrosion or gum. You should go over the carb again, remove the jets and soak them overnight in carb cleaner, and very carefully with a thin strand of copper wire check that all the pilot ways are clear. I bet they are not!
Good luck,
John

email (option): John.childs1 ‘at’ btopenworld.com

Re: M20 Starting tips after very long storred

The 276 carb is very prone to blocking on the pilot air circuits. The only way to clean it properly involves warming the body and removing the jet block from the mixing chamber. It then becomes clear that there are a number of airways which simply can't be cleaned without dismantling.

Re: M20 Starting tips after very long storred

Because electrodes are no longer glazed and modern fuels are conductive at compression pressures, once the plugs get wet usually they will not fire till they are properly dried
Only gasses burn & getting furl droplets to vapourise in a cold UK climate will be problematic
A few tricks to try
1) pour a teaspoon of the heaviest oil you can find down the plug hole, wait 5 minutes then give it a few kicks to promote a proper seal
2) using a HOT AIR GUN warm the carb and in particular the long carb manifold .
If ou have any engine you can pop the plug into ( a mower will do nicely ) run the plug for 5 minutes to warm it up , toss a teaspoon of fuel ( or a squirt of carb cleaner ) down the plug hole slip the plug in , finger tight will be fine & give it a boot

This assumes you have taken the previous advice & checked the timing
A squirt of you favourite dewatering fluid all over the points will not hurt either
Slip the vavle chest cover off & make sure the valves are actually moving
A very small amount of rust on the stems can hold them open

Re: M20 Starting tips after very long storred

Cheers chaps for the many helpful tips. It looks like I've got my work cut out. I'll let you aĺl know what I find. Cheers Neil.

email (option): nlhclarke@gmail.com

Re: M20 Starting tips after very long storred

If you are sure that the ignition timing is correct and there is fair compression and some fuel in the inlet tract it should start. Have you drained the oil from the crankcase, if it's been standing for years the oil tank contents will now be in the engine and it will be reluctant to run so will need to be emptied.(I've just seen this has been done!) Try a squirt of easy start down the carb with the throttle open, and if vigorous kicking still fails give it a push in gear with the valve lifter lever up, drop the lifter when the engine is spinning and get ready to pull the clutch in when it starts. If you have room a tow may be better. When it starts there will be lots of smoke and debris from the silencer. This is not a highly strung thoroughbred, it's a squaddie proof old workhorse and will run! Good luck.

Re: M20 Starting tips after very long storred

FWIW I repair mowers
When presented witha non starter, the first thing I do is pull the spark plug & chech that the piston(S) are going up & down
After that it is off with te rocker covers to make sure the valves are working.
Next check there is oil
Now I know I am not goig to do more damage by cranking the engine I set out to start the engine
A shot of carb cleaner down the plug hole and crank
If the valves are working & the spark is working & timed roughly right the engine should fire
Next it is carb cleaner down the carb throat
The engine should start & run as long as I keep squirting fuel into the carb
If it stops when I stop then there is a fuel delivery problem

Re: M20 Starting tips after very long storred

Remember you can still get a spark if the capacitor has failed in the mag. If you suspect this you can try fitting one externally.

email (option): pes.sales@btconnect.com

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