Suffolk punch 43s starting issues

Morning - just to add to this, took air box off and notice that the carb spit fuel back when I turn the engine over on the recoil starter...

Ok - an update. Suspected the intake valve was stuck open - and lo and behold, it was! Cleaned, reseated, and she starts fairly well, with a bit of choke.  

The only thing remaining is for me to fabricate a throttle to carb linkage, as this didn't come with my replacement carb. Does anyone have this carb who could possibly send me the length between the throttle assembly and the carb. so I can make one out of some stainless rod?

Sounds as though the previous owner had issues , hence the damage to the carb.  Taking account of the age of the machine and knowing that their electronic ignition does not age well I would try to check the spark with the plug installed and under compression. A simple in line tester will show up issues with the plug, it’s connector and the electronic coil in working conditions. Checking the spark in free air can be misleading; otherwise, why would your good spark and a wet plug not produce some attempt at combustion ? Yes, a carb issue could be drowning the spark, so you could turn off the fuel , dry the plug, remove the air filter , and spray some carb cleaner or flammable maintenance spray ( not all are)  directly into the carb Venturi. If your investigations lead back to an ignition issue, be aware that there were two systems , each with dedicated coils and flywheels - not interchangeable.

Thanks for your reply. Some great information for me to consider. I didn't realise that a plug under compression might behave differently than in free air. 

After learning the stuck valve up, we certainly fire up - with a good helping of choke! I think I need to adjust the carb idle, as the one I bought was only a quarter turn from fully tight.

I think I now need somebody with the same system to measure the throttle linkage rod thing for me (the thing I have used some solder wire on, temporarily), so I can fabricate one of the correct length.

So update, found some settings for the carb online and starts on choke, then opened out and cuts the lawn! After approx 20 min run time, an attempt to restart 5 mins later resulted in no start. Puzzled!

Just so happens that I recently rescued a Dellorto carb from a scrap machine and it came complete with a link. Something worth being aware of is that different applications of that carb have differently calibrated emulsion tubes. The tubes often have a four digit number which is the part number and a two digit one which is the calibration number. This one came from a Suffolk and is a #75, but back in the day there was a service bulletin suggesting that poor running could be dealt with by a different emulsion tube number and a different plug gap - I will try to dig out the details.

Emulsion tubes do get blocked by stale fuel etc and unscrew for cleaning. They can be a *** to remove and can be ruined by heavy handed attempts to remove  them. You need a hollow ground close fitting screw driver. If it still doesn’t budge, put the carb into a pan of water  and boil it up for five minutes , then try again

Note that the tube has three pairs of obvious cross drillings and a single tiny one between the two threaded bits.

Having issues with the images. Going to save before they all disappear !!

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Thanks you so much for that - especially going to the effort to measure the linkage. I'll be able to get that made up today! Appreciate any details you may find too!

All the best!

Just to add to this, when I got the replacement carb, all three screws were pretty much wound in and was sold as cleaned  (pinch of salt, but looked it) - so I'm not too sure where to start on setting it up properly. I've read that the idea mixture should be about one and a half full turns from fully tight. 

Also, my carb main adjustment is the one with the external screw. I read somewhere 1 3/4 turns back from fully tight too, though I feel if you try to wind it too tight it may 'interfere' with the emulsion tube - it just starts to feel prematurely tight! 

I have searched and searched about a definitive set up for these, so if anyone has seen one it would be great to know. 

I managed a full mow of the lawn yesterday, but would she idle? She would not! I followed Wristpin's advice on another forum to blow out the idle circuit and watch the carb cleaner spray into the venturi. Not sure if I cleaned anything, but definitely managed to get a spray from the idle/off idle holes. 

Like I say - if anyone has setup a Dellorto FHC 2013A on a Punch 43S, I'd love to hear!

So I think I am almost there, but judging by the spark plug on a quick 5 min mow this morning, she's running far too lean. My Dellorto carb seems to have that retro fit external main jet adjustment. Does screwing out richen or lean the mixture, I can't tell?

“That retro fit adj main jet” Image please. Presume that it’s the vertical one under the float bowl that replaces the bowl nut?

Correct jet setting. Is a job for the ears. Undo it until the exhaust goes heavy with a bit of black smoke, then slowly in until the engine just about stalls , then open it half way between the two and then try both directions in eighth turns until it sounds happy.

Don't know why I missed this. Thanks very much for that