1972 t120rv starting problems

[thunderace1]

Dear All,

New to this forum, but could do with some help (from far more experienced owners) with my oif 1972 t120rv and its non starting!

I have tried everything using my limited knowledge but no joy. The problem is that the bike just will not fire up and I cant see why (it has sparx electronic ignition fitted). I have replaced the battery (runs at > 12.6v), new plugs, checked earth (same voltage), static timing okay, carbs cleaned and checked, fuel in tank!, engine turns over okay etc. etc but no joy. Looking at the book one thing it says to check is the voltage between the -ve terminals of the ignition coils and earth (when the ignition is on) and I get no reading. Does my electronic ignition wiring affect this or do I have some problem with coils etc? How can I safely check that there are sparks at the spark plugs and is there anything else obvious that I have missed?

Thanks for the help

[step2534]

Thunderace, Does it need a choke??? Look at my post Step2534

[thunderace1]

Dear step2534.

The bike has new concentric mk1 amal carbs with choke fitted. I have checked float levels, cleaned them thoroughly and replaced the slides with brass ones, checked balancing and cables etc. I might be wrong (and probably am!) but I feel that my problems are electrical rather than carb related.

Best regards

Thunderace

[L.A.B.]

Looking at the book one thing it says to check is the voltage between the -ve terminals of the ignition coils and earth (when the ignition is on) and I get no reading. Does my electronic ignition wiring affect this or do I have some problem with coils etc?

Yes, that test probably won't work with the Sparx electronic ignition, also the two 6V ignition coils should now be wired in series for the electronic ignition. 



 

How can I safely check that there are sparks at the spark plugs and is there anything else obvious that I have missed?

Remove the spark plugs, refit them to the plug caps, and then rest the plugs on the cylinder head. If you switch the ignition on, and turn the engine over with the kickstart, both plugs should be seen to spark together once for each crankshaft revolution.   

[thunderace1]

Dear L.A.B.

Good to have your advice on this , yours is a name I recognise from the classicbike.net site.

I will try your suggestion re checking the spark plugs tomorrow.

Best regards

Thunderace (my 'modern' bike!)

[L.A.B.]

Are you sure you have set the Sparx ignition timing correctly?

A common mistake is to set electronic ignition timing using the wrong timing mark on the alternator rotor so the firing point ends up 180 degrees out.

[Rex]

On another tack, when I fitted two new Amals the pilot jets were blocked with swarf. I know that Amal (or whoever makes them these days) were supposed to be addressing the QC problems, but maybe it's worth checking them anyway?
Squirt some neat juice into the pots and see if it fires.

[thunderace1]

Dear All,

Further to the responses I have tried testing the spark plugs as LAB said and they didnt work! One of the end of the cable connecting the two coils had come off, attaching it I now have spark plugs working so thanks for that advice. However the bike still wouldnt start and so I tried to clean out the carbs, they seem okay but still no joy on starting. I had ordered another sparx kit for my t140e (which is my next project) and I even tried swapping over to the new coils and starting unit but still no joy. I think that the battery is okay, spark plugs now okay, carbs okay, the engine physically turns okay on the kick start but it refuses to fire up - anything else I could try or I have missed. Next stop for me is to sell the damn thing on ebay!!!

[yosemitepaulmill@aol.com]

can you tell us what work has been done since the bike last run i.e has it had a rebuild
things to check are
ignition timing  Does the sparx ignition give a spark on both cylinders at the same time? if not try swapping over ht leads
next I would try fuel  simplest would be to squirt some fuel into the cylinders either through carb air intake or through the plug holes be careful use only a little to minimize risk
can you feel the compression on kick start if not  check the valve clearance if these are ok you could do a compression test
if compression is ok check valve timing although if the bike has run since these have been changed/ reset as in a rebuild then it is unlikely to be the cause
is the engine turning over on the kickstart? the clutch could be slipping enough to stop it turning past compression but allowing it to turn with the plugs out (not very likely but still a possibility)
hope this gives you somewhere to start
Yosemite

[thunderace1]

Dear yosemite,

Thanks for your detailed suggestions.
When the bike was running previously it was running very rich (and was difficult to start then as well) and I had only done about 1000 miles on it. When I bought it the bile had been in a scrap yard since 1978!; needless to say it took a complete rebuild, a couple of years of my life and more money that I would ever admit to my wife! My current work was to take the head off and clean the chambers and valves etc of the carbon deposits and thoroughly clean the carbs, rockerboxes etc.

I will check that the spark plugs fire together, I think that the sparx kit fires both spark plugs each time.
I will also try your suggestion re squirting fuel
I have a compression guage and so I will look at this, previously I seem to remember that it was about 100
I did redo the value clearances when refitting the rocker boxes but I will have a look again
The engine does turn over on kickstart but I do have to free the clutch plates before I try and kick start it

Busy day tomorrow!
Regards Thunderace

[L.A.B.]

I will check that the spark plugs fire together, I think that the sparx kit fires both spark plugs each time.

Don't bother checking, as it is a wasted spark system so both plugs fire together.

[yosemitepaulmill@aol.com]

Thanks l.a,b never used a sparx ignition unit before so I wasnt sure
If everything checks out ok a couple of other things to check, check that the throttle cables arent holding  the new carbs open  as this can make starting nearly impossible also check that theengine is not flooding (are the plugs wet with fuel)
yosemite

[thunderace1]

Taking the rocker covers off I discovered that the tappets have become undone (or have become loose) damaging the threads on the rocker arms and the tappets themselves and letting the pushrods come off. I am sure that my tappet gaps were correct and locked in place. Anyway new tappets and tapped rocker arms (5/16 CEI if anybody is interested, it also means that my t120 has unf,unc,cei,ba,metric and whitworth bolts etc!).

I have now put the rocker boxes back on with new gaskets and ensuring that the pushrods are on correctly (leaving off the carbs and rocker covers). The problem now is that there is compression on the left side but virtually no compression on the timing side even though everything seems in place. Any suggestions as to what might cause the loss of compression on the right side of the engine only?

I seem to spend far too much time in the garage than on the road!

[L.A.B.]

I discovered that the tappets have become undone (or have become loose) damaging the threads on the rocker arms and the tappets themselves and letting the pushrods come off. I am sure that my tappet gaps were correct and locked in place.

To avoid confusion, I think what you are referring to as "tappets" are in fact the rocker adjuster screws? As the tappets (or cam followers) are located within the tappet blocks at the lower ends of the pushrods.

 

Anyway new tappets and tapped rocker arms (5/16 CEI if anybody is interested, it also means that my t120 has unf,unc,cei,ba,metric and whitworth bolts etc!).

Triumph begun a major change-over from British Standard to Unified (UNF, UNC etc.) threads from the 1968 model year, however, they didn't get around to changing the rocker adjuster threads to Unified until 1978 apparently, and there shouldn't really be any "metric bolts" as standard, and certainly very few-if any, Whitworth threads by 1972.  And don't forget the fuel tap threads-which are BSP.

    

[thunderace1]

Dear LAB,

Yes you are right I do mean the rocker adjuster screws.

With the different threads it does seem to me (first time that I have done anything like this) that whatever was lying around in the factory at the time went on to the bike! The metric bit is that one crankshaft main bearing is imperial and one is metric, the whitworth bolt is the centre 9th cylinder head bolt on my model.

Any thoughts on why one side of the engine has little compression and what I can do to check any potential problems?

Thanks