2nd Bultaco won't run

[jofritz]

just started to work on my second Bultaco and don't seem to be more lucky than last time (still working on the 125 Lobito, will post updates however).

The Bultaco starts by kicking. First time using starter-spray. After some time it will still start using no spray... (5 - 10 min. after the use of spray, so none will be left to keep it starting, I supose) but it won't rev up, idles for some seconds (2-5 seconds) and stops. Action on the gas hand won't change anything, kills the engine even quicker...
any ideas? We obviously have spark... could it be to weak? So the first steps could be going through the prozess of cleaning the points, shorten all cables, perfection the contact on engine bolts (...) or rather start on the carb as it seems to be more promissing. It's a dellorto carb and a very quick examination makes me rather confident, it could be something else...
greatfull for any hints or ideas

[pschrauber]

I would in your situation clean the carb, the jets, nozzles, gas sieve and adjustment screws also the gas line and the petcock, then look up for cracks in the manifolds or not thight hoses, last not least replace the plug.

Then I would clean up the air filter and make sure that the air flow to the air filter box is good. 

To the ignition the usual things, points gap, ignition timing, capacitor and how good the wires are connected especially between wire from the coil to the spark plug connector.

Last not least wash out the gas tank tank and use fresh petrol.

I press my thumps that the bike might start and run then. 

[stevem75]

Having followed both of your posts regarding your bultacos I will give my best advice.  
these are very simple engines.  They need three things to run.  Spark.  Fuel.  Compression 

when checking for spark all you need to do is make sure it sparks.  Don’t worry if it isn’t “fat blue spark”, just make sure it does spark.  Compression.  Bultacos are famous for crank seal leaks if they’ve been sitting for years and years. The leaking seals can cause primary compression leakage and this makes starting them very hard, and if they do start, they run so erractically that no amount of adjusting the carb makes a difference.  Another spot to look for air leakage is at the carb manifold and sometimes even the cylinder base gasket 
fuel.  The Amal carbs are famous for wearing out.   But more often than not they will run just fine with a perfectly clean Amal or bing carb.  They need to be carefully disassembled and cleaned.  All the passages in the carbs need to be clear and the jets must also be clear.  
Once you have made certain that the carburetor is clean, that you have good crankcase sealing , then you can go ahead and verify correct ignition timing and set up.  
There’s always tons of what I call useless info out there.  Banal comments like “put a mikuni on it “ or “put an electronic ignition on it “ and your problems will go away is really just lazy.  

these bikes ran perfectly fine from new when they were new.  And there’s no reason they can’t run like that again with some basic maintenance 
cover your basics.   Spark , fuel.  Compression. Once those basics are covered your Bultaco will start and run like your car does everyday 

Steve  

[jofritz]

Thanks Steve... that should be the way to look at it... but as time seems to be the limiting factor, I'd like to do things step by step... starting with the smallest and most promissing step 🙂

That is, what you were helping a lot as I don't realy know if my spark is fat and blue. So I will concentrate on other things first. Starting with the carb and the fuel supply (tank/petcock)

As you have been following the Lobito topic as well: it felt like a lack of fuel, as after tickling it ran for some time, so I checked with an external fuel supply bypassing the fuel tank and the petcock on the Lobito and with this setup the bike runs perfectly fine, reacts directly on slitest and quickest movements with the throttle.

I will take off the petcock and check for obstacles... any better ideas?