norton runs so good but hard cold start

my 69 commando s 750 with dual amals new. runs amazing once i get it to start idles down to about 800 rpm. starts first kick when hot. but when its cold its a different story. it doset like to start with choke with half choke and tickled heavily it will start and run for a few second then die. fuel screw is 1 1/4 turns out. has boyer ignition with good battery charge. what else could it be? and has a topped with about 300 miles on it.

sounds a bit like my 850 which has no choke mechanism. I have to tickle it to fload the carbs, then once it has started I have to quickly work at one tickler to keep it running during the first 15 seconds or so. If I dont get to a ticklers quick enough it dies on me. Once the 15 seconds are dealt with it runs ok till it gets a bit warmer then perfectly.
Dereck

Have you tuned the pilot mixture screws at tickover on a fully warmed engine, the 1 1/2 turn recommended is only a starting point. Also have you cleaned out the pilot jets with a #78 16 thou drill, the pilots and the pilot circuit are very susceptible to deposits and I do this yearly as it does affecting starting especially.

I did on a fully warm engine moved them in little bit to see if it would fire off like it used to. I sprayed the pilot circuit out with some carb cleaner. so there's probably a blockage? and it could be further in then 1 1/2 turns if need be correct? I know on mukini and kiehein if the pilot circuit gets blocked they don't like to idle or start. I just thought it was odd that it doesent do it when its hot.

I was having the exact same problem with my Amal Premiers, died after a few second on cold starts.
Also ran pretty badly for first 5-10 minutes after that.
My friend John Schmidt suggested I raise the float levels.
BINGO!
Major improvement in starting and cold running.
Runs great when hot too.

What did you set your float height to? What your settings on the fuel screws?

Screws set at close to recommended 1.5 turns out.
Floats now almost level with edge of bowl.
I just made them a 'tad' higher than what they came set at.
This is British engineering - precise measurement not required. :mrgreen:

Ha I laughed hard at that comment. Also I noticed it's a little lean on the mains so this should help fatten it up across the range then.

Since the idle jet setting works over the lower range of throttle position, it's final position is not a static setting that you set,... statically! My method of setting the idle screw position is to start the bike, warm it up, then at idle I turn the idlescrew in to find the stumbling point, then turn the screw out to find it's stumbling point. Then I set the screw inbetween those two points as a starting point for my adjustment....

Then, with a screw driver on the idle screw, I gently lift the throttle and lower it. I'm listening for the smoothest transition from idle as the rpm's rise. I do this to both sides, then go back and do it again to see if I can make it smoother with a tiny micro adjustment. (all the time I am adjusting the screw, I am raising and lowering the slides slightly looking for the smoothest accelleration...)

There's a wide range inbetween the stumbling points of either too rich or too lean that doesn't make much difference in how the bike idles. The difference in these screw positions shows up better across the lower range of accelleration, so gently raising and lowering the slides as you turn the idle adjusting screw reveals the subtle screw position changes better.... good luck

These machines have personalities that make trial-and-error a good process for solving many problems.
850 vs. 750 / Combat vs. standard / different ignition types / grade of fuel / on and on...

I would suggest raising the float level just a bit, make sure each carb is at same level, reinstall.
If bowl is not overflowing when petcock is on and not running or when idling, probably not too high a float level.
Test ride and readjust if necessary.
Change ONE THING at a time!

tickled it no choke fired up after a few kicks didn't change anything. why dosent it like the choke? the way the guy had it set up before i fiddled with it would start cold full choke one kick makes me sick that i messed with it wish i would have noticed the intake bolt that was backed out before i fiddled with the settings.

Mine wont start right away either when cold.
This is my starting procedure. I tickle the carbs,open and close the throttle a couple of times and give it a couple of kicks through.
All this Before I turn on the key.
One swift kick and it fires up. I have an extended idle screw on one of the carbs so I can set the idle on the fly usually 1000/1100 RPM.
Unsure of the manufacturer but something like the one on the left
http://www.thefactorymetalworks.com...tainless-finger-twist-fuel-and-idle-screw-set
That usually does it.
When hot it starts right away.

It sounds like a problem in the idle circuit(s). Either at the jet (one or both carbs) or on the way from the jet to the little ports in the floor of the throat behind the slides. . It sounds like it doesn't want to pull up fuel even when choked. Dr. "hobot" used to describe some insoluble crystal formations from zinc or something in combination with "booze" in the gas. Perhaps that is what's happened.
Lance

Had the same problem with my 70, 750, with single Mikuni and Power Arc EI. Changed to Trispark, and now its a 1-2 kick starter, cold, hot, every day.

ZRMiller said:

my 69 commando s 750 with dual amals new. runs amazing once i get it to start idles down to about 800 rpm. starts first kick when hot. but when its cold its a different story. it doset like to start with choke with half choke and tickled heavily it will start and run for a few second then die. fuel screw is 1 1/4 turns out. has boyer ignition with good battery charge. what else could it be? and has a topped with about 300 miles on it.

Click to expand...

re; "fuel screw is 1 1/4 turns out."
as mentioned elsewhere it should really be 1 1/2 turns out, and the tick over shouldbe a least 1000 rpm.

To get the pilot air screw absolutely spot on buy a secondhand Gunsons Colurtune and with a warm engine use it at night in the dark for beast results –you might find an improvement in throttle response for your troubles, that is, if you have the standard pilot jet e.t.c.

ZRMiller said:

tickled it no choke fired up after a few kicks didn't change anything. why dosent it like the choke? the way the guy had it set up before i fiddled with it would start cold full choke one kick makes me sick that i messed with it wish i would have noticed the intake bolt that was backed out before i fiddled with the settings.

Click to expand...

re; "why dosent it like the choke? "
Don’t look too much into this, if you have tickled the carb floats then that may be all that is required… I have a 301 twin that I virtually never use the choke at all, come spring, summer, autumn or winter- it needs a higher revs from cold once started, but once warm I set the tickover back to normal

How would YOU like being choked ! :shock:

Dam*ed Automobiles , if you fit a Ign. on/off seperate frome the ' self starter ' ,
Clamber in , switch Starter 'ON ' , observe Oil Presuure , at full cold , engage ignition . Switch OFF Starter , promptly .

The Ba#!*+^s primed the Chambers , oiled the works , and is awake without a murmur .

if your buisness is urgent , switching off , & flooring Throttle , imediatly switching ON , And Off 1.00 below redline . ON , OFF at Redline , Engageing Gear & Switch back to on simultaeneous with letting out clutch ,
propmtly , will have you underway , with all haste .
im not sure this method is applicable to motorcycles . youd want to be sure of your traction & equilibrium .

This is essentially the method utillised by V V V S on 30 second alert , to clear the boundary . And ensures ALL Plugs are Clear & Max immediate Chamber Temps , for immedite combat engagement from cold .
( though the Engine would be run up , to operating temperature , perhaps every 30 minutes , to ensue the lubricants wernt frozen . Had to claer the airfield boundry inside 30 seconds at full combat power -
as on call from outposts 1 Min flying for nazi raiders besieging the cities . Many factories were withdrawn to Siberia when in shelling range of faschist invaders. Typically MiG3 , Yak 1 , 7 & Lagg 3 Temp @ minus 30 )
I suppose this is what Norton Had In Mind , when they introduced the COMBAT , some inexperiance and ineptitude by the riders might have led to the odd spot of bother .
So practise perhaps is best not on public areas . :wink:

Different engines respond differently, and each one seems to have a sweet spot when starting. My buddy's 72 Combat and my brother's 71 Roadster both start one kick cold after tickling with no choke. My 850 wants the choke until it warms up. If I shut the bike off and let it cool down to "luke warm" it wants the choke again but no tickle. Go figure. Each bike is unique and the rider must learn its idiosyncrasies over time.

Same bike as Maylar, from cold, flood both carbs, kick it through. Usually starts first or second time.
Hot, no flood and it can be tough to kick but same first or second kick.
Varoooooooooom and ride.

I think Hobot is correct about the effect of alcohol in carbs. I use straight methanol fuel, and immediately after running bike, I always take the jet cover caps out of the bottom of the bowls to let them drain and allow any remaining fuel to evaporate. The material of manufacture is mainly zinc-based, and zinc oxide can form as a white slime. I allowed this to happen once with a T250 Suzuki two-stroke I raced. It locked up while on full noise at the end of a straight.