Hard Cold Start

I have a '73-750 that has been totally done over. She is giving me fits upon cold starting when she has been sitting for a few days. Single Mikuni, Boyer electronic ignition and I keep the gel battery plugged into a Battery Tender as I know how low voltage can cause issues with a Boyer.

I turn on the Tap, Push down the choke lever, find TDC and kick. She sputters and passes gas (makes wind as our UK friends say) then nothing. Have to kick and kick and kick. Turn everthing off, wait a few minutes and try again. Eventually she starts. Cold blooded beast, has to warm up at least a couple of minutes before I can ride away.

Once riding for a while it is a one kick process as long as it it warm. When it cools off (three beers) I have to use choke and wait at least a couple minutes before I can ride away... ...... Gets embarassing when I try to take off too early and she craps out on me in front of a crowd!

Suggestions please!

I don't recall ever having these problems with the original Amals, maybe I should have kept them..... Maybe I will go back.

Sounds about right. What my brother told me to do is tickle the carbs (or in your case depress the lever) and kick through at least once with the key off. Key on and kick. Then let it warm up before taking off.

You also may be wetsumping.

is wetsumping likely after just 3 beers?

gory said:

is wetsumping likely after just 3 beers?

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Three beers and my wet sump was full, had to drain before departure.

I must say i've never had any starting problems hot or cold with my 850. Put the Amal's back on I say Steve!
To be a bit more constructive though i'd say maybe it's running too weak, no air leaks between carb and manifold or head I suppose?
Dave.

Make sure you don't open the throttle too far when you kick start her because the cold start system won't work. However, if the cold start system is too rich try an initial start without it, if that fails try with it on and give her more throttle.

Best of luck

Cash

Steve
Any chance you have the throttle open a little or start to crack it open as soon as it starts to fire.
The Mikuni "enricher" circuit only works when the throttle is completely closed.
I have to resist a little throttle when I start mine, let it settle for a few seconds then roll in some throttle as I turn off choke lever.
I've set my throttle screw so the air valve doesn't snap shut when I take my hand off so I set it at about 1800rpm and leave the bike while I finish putting on gear and in 2-3 minutes ready to go.
Sorry if I'm saying everything you already know.

Bob

Hi Steve,
Let me ask, after you get it started (cold with the choke lever on)) does it seem to be running rich enough or somewhat lean. The mixture (lean/rich) of the choke (actually enrichening circuit) can be altered with the small jet located in the wall of the float bowl. Some of them are screw in, but mostly they are pressed in. My Mikuni flat side that was purchased from Ebay ran far too rich (on choke) I had to drill a small hole in the bottom of the bowl (later tapped and plugged) to press out the starter jet which I then soldered closed and then re-drilled to .022 inch. It could be that your bike could benefit from a little more fuel at start up, but first check to see if your starter jet is partially plugged before you go drilling it larger. Its kind of hard to beat those old Amal ticklers when it comes to getting some start up fuel in there, at one point I had even considered hooking up a snowmobile primer device, it would not be that difficult, but would just look a little weird.

GB

rx7171 said:

Steve
Any chance you have the throttle open a little or start to crack it open as soon as it starts to fire.
The Mikuni "enricher" circuit only works when the throttle is completely closed.
I have to resist a little throttle when I start mine, let it settle for a few seconds then roll in some throttle as I turn off choke lever.
I've set my throttle screw so the air valve doesn't snap shut when I take my hand off so I set it at about 1800rpm and leave the bike while I finish putting on gear and in 2-3 minutes ready to go.
Sorry if I'm saying everything you already know.

Bob

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BINGO!!! That is EXACTLY my starting technique! From days of yore, I had the habit of opening the throttle just a tiny bit when coming down on the kick start lever. With the Amals, I recall this working great. I can imagine with the 1/4 turn throttle I have on there just exacerbates the problem with the Mikuni. I will have to re-train my muscle memory, being as my muscles have alzheimers, this may be an issue.......

Thank you all so much, I bet this will help a bunch.

For a cold start, I flood the shit out of the carbys, choke on and kick, with throttle just cracked ( Amal 930's plus Boyer ).

Is it possible your bike is running really rich ?.

Josh Cox said:

For a cold start, I flood the shit out of the carbys, choke on and kick, with throttle just cracked ( Amal 930's plus Boyer ).

Is it possible your bike is running really rich ?.

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Worse, it's running a Mukuni.




:mrgreen:

I cannot even imagine a Norton starting with only an enricher or choke flap. Mine on Amals, needs a good gully womper when cold to fire on one kick. Even when warm from a ride, after a rest, she needs about three seconds of tickle. For initial fire up it is a ten count or until the fuel runs out the air cleaner. My bike can sit for months and fire on the first go with a full wet sump. She doesn't mind.

Hi Steve, Is this a new problem, did the bike used to start OK, with the Mikuni.? or...
Has it never been right.
Don't give up on it yet. Mikuni carbs have been fitted to non Japanese bikes for 40 years or more for good reason.
The problem is I think that in the old days, experts were fitting them, now every second Bike shop
wants to sell them but doesn't know anything about them.
If your engine won't run at a fast idle when cold, then the Idle circut is lean.
If this is a new problem, then we can probably blame a blockage, Check the air passage located at 3 o'clock at the rear.
This is the sole supply of mixture to the motor, with the throttle closed.
If this has been a problem since fitting the carby, then we can say that it's never been right.
If you need the choke (enricher) to start, (cold engine), then it should be able to be turned off within seconds,
or, partially turned off. Your engine should start to 4 stroke and blow smoke, if left on.
It should kill or almost kill a warm motor.
The next circut, is the Idle (pilot) jet. Possibly too lean also, if it's OK on a warm motor, but not on a cold one.
Your Norton should start and idle sweatly with a mikuni. As it should with tight Amals or PWKs' or what ever.
Remember,.. No throttle, kick, start, idle, slight revs, choke off, fast idle if necessary.
If it spits back through the carby, it's too lean.
You could also try... turning mixture screw in, clock wise = richer. NB.If this is less than one full turn out from being right in, you idle jet is too small.
Lower your idle speed if you have your bike idleing FAST...
If all else fails... raise the float level by 1/2 mm.
Hope this is of some help. It takes me so long to type, you have probably fixed the problem.
AC

aceaceca said:

I cannot even imagine a Norton starting with only an enricher or choke flap. Mine on Amals, needs a good gully womper when cold to fire on one kick. Even when warm from a ride, after a rest, she needs about three seconds of tickle. For initial fire up it is a ten count or until the fuel runs out the air cleaner. My bike can sit for months and fire on the first go with a full wet sump. She doesn't mind.

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I push the tickle until the first drop of gas comes out the tickle hole. You don't won't it coming out the air filter.

I'll film my start up procedure one of these days (maybe Friday…)

mikunis dont have tickle holes, just women and amals.

I'll take the Amals over a bitching and moaning woman any day, take the bin out, you're not watching football again tonight are you, didn't you buy a carton of beer just the other day.............

Josh Cox said:

I'll take the Amals over a bitching and moaning woman any day, take the bin out, you're not watching football again tonight are you, didn't you buy a carton of beer just the other day.............

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Sounds like a re-training program :lol: wife calls to collect beer on way from work, takes out the rubbish, makes tea and demands i have sex ...well we can DREAM :!: ...but see doe's make tea...only because i dont cook well