Cold Starting Problem

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colin davie

colin davie

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Hello all .i have a mk2a 850 with new amal mk 1 premier carbs , tri spark ignition , standard engine apart from inlet tracts opened out to 32 mm and running on bell mouths , carbs set up as standard , problem being i can not start it without full choke and about 15 good kicks !!.
the spark looks yellow and weak to me but i am told this is so with tri spark as it is a "longer spark", am i talking tosh or what ?
the motor is in good order otherwise , once warm starting is a one kick affair , any advice welcome ,
thank you Colin
 
Try 19 pilot jets instead of 17, the premiers come with 17 pilots as that is the same size as the old 25 pilots but they seem to give a weaker mixture for some reason and seem better with the 19's.
 
There has been some chat about the new carbs and the pilot jet they come with, I think people are putting in slightly bigger ones. I don't know anything about TriSpark, at a guess fuel mixture cold is giving you grief. Do you tickle the carbs? Have you tried less than full choke? Also maybe after the 10th kick pull a plug and have a look, wet or dry?
 
Also just noted you saying, 'running bellmouths, carbs set as standard'. You will have more air in the mix without the air cleaner.
 
Forgive me for asking...are you tickling the carbs? If you are not familiar with starting a Commando, you depress the "tickler" button on the carb until fuel leaks out. Without this it is hard to start cold.

Russ
 
Definitely the pilot jets as Komando says...

Change the 17s for a 19s it will transform the low rpm cold running as well as starting.
 
using the choke simply enriches the mixture for starting, you still need to crack open the throttle when kicking in order to lift the slides in order for the mixture to get drawn into the combustion chambers
- tickle until gas comes out then choke on and open throttle while kicking, two good kicks should do it
 
I have similar setup... Amal premiers and trispark in my 750.
No choke installed.
My cold start routine which almost always starts one or two kicks:
Tickle until gas overflows out both bowls.
One kick with throttle closed
Quick tickle both carbs for 1-2 seconds
Ignition on
Kick with throttle open 1/4 to 1/2
VROOOM!
Keep throttle on and do not let rpms drop below 2k or will stall.
 
thanks all for your replies , i am familiar with cold starting a norton , normally flood carb , tiny bit of gas , two kicks and away !
i will change pilots as suggested and go from there , my old 750 running on points way back in the early eighties had no chokes and was a good starter ,i will try all your suggestions ,many thanks again
Colin
 
Assuming you are not using them already, Colin, I'm obliged to suggest that you try some Champion spark plugs, see if you can get that yellow spark to turn blue.
 
Regarding that yellow spark...what are you using for a coil(s)?
 
oneup3down ,you were spot on !.this is a lesson in not looking at going back to basics, perhaps i spoke to too many people ,the trispark was questioned and various other things , it can lead you down the wrong road !,which is where i have just been ,
thanks all , Colin
 
i will change ngk for champion plugs ,i can not get them locally only on ebay , but will do , another thing is it is reluctant to rev past 5500 maybe 6000 at a real push in third or top , it runs great otherwise no coughing or spluttering , i have checked speed settings , 4000 is 73 5000 is 90 and so on , i know it aint no rocket ship but i would hope to get up to 6500 in top , do you think richen up carbs ? or needle settings ? ,
cheers Colin
ps i will enclose photo of my norvill commando when i sus out how
 
What jets are in it now. MK2a's came with 230 mains, I run 260's with the std air cleaner but peashooter silencers that you can see through. Needle jet and position are unchanged. As you are running bellmouths I would expect you to be running bigger than 260's as long as you have free flowing silencers and not the black cap originals.
 
Reluctance to exceed 5K cd indicate poor flow rate from the petcocks or some obstruction in the tank/filters.
Easy to check.
 
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