Start problems on my Norton Commando fastback 750 1970

Anonymous

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I have problems to get my bike started. It looks like it doesn't get enough fuel ? I had problems getting it to run OK, but after changing both plugs and coils its OK after I get it runing. But when it is cold it will not start :evil: That is, after 20 - 40 kicks it will start eventualy.
Any Idees ?
(I have a mikuni carb and a boyer ignition.)
Regards
Vidar from Oslo, Norway.
 
Joined
Sep 14, 2003
Messages
12
Sounds to me like a carb problem you need fuel and spark if your boyer is sparking then it has to be fuel I would take a good look at your carb for the problem
 

Anonymous

Guest
Probems getting the Norton commando 750 1970 to start ?

Roger said:
Sounds to me like a carb problem you need fuel and spark if your boyer is sparking then it has to be fuel I would take a good look at your carb for the problem
Yes I do agree. I suspect the mikuni carb to give to little fuel when using the chocke. Would it be better to use original Amal carbs ?
 

Anonymous

Guest
I have the stock carbs 900 series amal concentric and have had the same since 1985 when I first purchased my NORTON I have no experience with anything else. I have spent no money on them aside from gasket material I use when I clean them.They have been very good to me, an ajustment a good cleaning easy to work with. Now as for anything else over the years I have come across a few guys I met and road with who had made the switch to one carb or another and I found they had frequent trouble. Now I suppose that if your into tweaking your engine looking for more power and performance this is why some guys change from the stock units.I like the 932's I have I like I can adjust each cyl seperately for fuel and a nice even tick over they are almost maintenance free I dunno maybe I've been lucky
 

Anonymous

Guest
Anonymous said:
I have the stock carbs 900 series amal concentric and have had the same since 1985 when I first purchased my NORTON I have no experience with anything else. ...
Is it hard to get the bike to run proerliely with 2 carbs ? I have the original parts from the old carbs, like the manifoil etc. Can I use these part on a set of new amal carbs ?

regards
Vidar from Oslo Norway
 

Anonymous

Guest
Vidar said:
I have problems to get my bike started. .
The bike is running like clockwork when I get it to start. My work around for the moment is to push the bike.
It puzzels me, when I get it to run it doesn't want any Chocke, I have to turn the chocke of, then give it just a bit throttle, than a bit chocke, then throttle. Usually at this moment the engine is begining to get warm and i can keep it alive with just throttle :!: :!: :!:
Any good idee's what it can be :?:
 
Joined
Sep 29, 2003
Messages
5
Hard Start

Hi Vidar!
You are facing the same carb troubles most of us had with the Norton when first starting to get it properly running. The Mikuni is not a bad carb and will most likely be less trouble than 2 amals. Something is not properly set up in the carb for you to have that much trouble and it might be something as simple as your idlescrew setting or air mixture screw adjustment point. If cold, may be necessary to turn up the idle screw until warm and then reduce it after the engine is hot.
On mine, it is necessary to use the choke and then starting is extremely easy with no throttle applied at the handgrip when kicking. Are you using an air filter? Mine is a K&N filter. Here are some guidelines for Mikuni settings:

MIKUNI CARB JETTING
750 with a single 34mm Mikuni,
main jet 220 needle jet 159 po needle 6DH3 idle jet 35
Slide # 3 idle air jet 2.0

750 with dual 34mm Mikuni's
main jet 230 needle jet 159 p8 needle 6DH2 idle jet 35
slide # 2.5 idle air jet 2.0

850 WITH SINGLE 34 MM MIKUNI
main 240, needle jet 159, p2 needle 6DH3, idle jet 40
slide # 2.5, idle air jet 2.0

850 WITH SINGLE 36MM MIKUNI
main jet 240, needle jet 159, p2 needle 6DH4, idle jet 45
slide # 2.5, idle air jet 2.0

E. Spaghetti
 

Anonymous

Guest
Re: Hard Start

eddie spaghetti said:
Hi Vidar!
You are facing the same carb troubles most of us had with the Norton when first starting to get it properly running. ....
:D
Thanks.
The bike is now stowed away for the winter, have no time to look at it until summer. I have a bitt trouble understanding your data on the carb.
Could you explain what they mean :
main jet 220 needle jet 159 po needle 6DH3 idle jet 35 ?
Slide # 3 idle air jet 2.0 ?
K&N air filter ?
I'm using the airfilter that was delivered with the Carb.

Sorry, I'm a norwegian that's very proud at the moment.. Petter Solberg
won WRC today... YESSSS
Regards
Vidar
 

Anonymous

Guest
Mikuni jet numbers

Vidar, you will need to get a strong magnifier to look at your jets close enough to see the tiny numbers stamped on them. Thats what those things refer to. The Liberty Library mikuni tuning guide for British twins shows pictures and locations for these items and has much information about properly determining your jetting needs.

Check out "Mikuni Tuning for British Twins" at the following link. It's
listed about 40% of the way through the page. $12 bucks well spent.

http://victorylibrary.com/books1.htm
Eddie
 

Jerry Doe

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Joined
May 21, 2003
Messages
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Carb info

Eddie
Thanks for the useful Mikuni carb, info!

That's hard to find..

Vidar - What altitude are you at? If you are in the mountains you might need leaner jetting.

Jerry
 

Anonymous

Guest
Eddie, you're the man :!: :!:

Thanks for the information ... and I didn't even ask yet :D
 
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