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71 fast back in shropshire

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71 fast back in shropshire

Posted by chrisshrops at May 05. 2017

Hi folks I'm new here ,and new to the world of nortons

I have a 71 fastback that has been of the road for the last 15 years or so ,I am just starting the rebuild .

it had a very weak spark with 20 year old boyer ignition fitted the carbs were replaced shortly before the bike was parked up so I'm hoping they are ok

I now have a new trispark ignition and twin coil kit to fit and see if i can get a nice spark from her,I will give the amals a good old clean out try and get the pilot jet clean and see it I can get it kicked into life .

I am sure I will have may questions over the next few months

 

Re: 71 fast back in shropshire

Posted by Tony Ripley at May 05. 2017

Welcome Chris,

It is good to see another Commando being brought back to life.

We are always ready for questions.

Regards

Tony

Re: 71 fast back in shropshire

Posted by david_evans at May 06. 2017

Hi Chris, Welcome. It would be good to see you at the Shropshire Branch meeting. We are just moving to a new venue, The Bradford Arms Knockin, (second Thursday of the month) We are an un-constituted branch so no membership fees etc.

I too have a 1971 Fastback which I bought back in 1975 for £350. (JS flat slide carbs and Trispark ignition and coil)

 

Dave Evans

Re: 71 fast back in shropshire

Posted by alan_blackhurst at May 07. 2017

Best of luck with the Trispark I tried one it was a rubbish now running a Pazon

Re: 71 fast back in shropshire

Posted by john_holmes at May 07. 2017

The Trispark has the electronics in the timing cover which gets hot, electronics does not like heat, Boyer Mk1 is the same and suffered from failures, the Boyer Mk2 went to a separate remote box to cure these failures.

Re: 71 fast back in shropshire

Posted by christopher_winsby at May 07. 2017

Have a look at Bushmans Amal they have a good mod to help access to the pilot jet from both sides and enables cleaning out crud trapped behind the bush.

Re: 71 fast back in shropshire

Posted by david_evans at May 07. 2017

I struggled with my Trispark for some time, with one cylinder dropping out in damp conditions giving me miserable running most of last year. After fitting a dual output Trispark coil I have to say the bike has never run better in 42 years of ownership. I think the coil resistance is critical with these ignitions and 2 x 6V is no good. There is less wiring and fewer connectors under the tank to give problems. Also stepped output from a Boyer powerbox gave me some problems. I have looked closely at the temperatures involved in the timing chest and it's not that high.

Re: 71 fast back in shropshire

Posted by john_holmes at May 07. 2017

My Commando with Boyer and 2 6V coils suddenly went onto one cylinder a few years ago, after swapping out HT leads coils, Boyer boxes, stators, rotors etc it was cured by adding a dedicated earth wire from the head to the battery +ve terminal. My guess is that the std earth path from the engine broke some strands and would then only conduct enough allow one plug to fire at the same time and it was easier for the one side, never checked the harness to find out. What would also have cured it is a dual coil as there is not need for an earth path out of the engine for this type of coil as the electrons move from one side of the coil to the other. All these wasted spark EI's put extra demands on the original wiring and components, coils are firing twice as frequently, as are HT leads and voltage losses in the harness,switches also add to the problems as do the earth paths.

Re: 71 fast back in shropshire

Posted by steve_adkins at May 07. 2017

Greetings from South Australia, Well I have had a Tri-Spark on my Commando for over 5 years no issues, fit and forget with dual matched coil form Tri-Spark as the lord Lucas coils were well past it. I have used two further iTri-Spark units and they to have performed flawlessly. The latest Tri-Spark version also has on board diagnostic tests too. I also have a Tri-Spark regulator to fit to my Triumph (1964) and have every confidence in their products. Steve Kelly's warranty stands up too. I am not associated with the company or on the 'payroll' but praise when praise is due. Boyer make a good product but its expensive (shipping does not help) and when I have local support 30 minutes away, although to date not needed, is better than support 12,000 miles away.

Your money your choice!

 

Rgds Steve

Re: 71 fast back in shropshire

Posted by chrisshrops at May 10. 2017

thanks for the replies chaps already very helpful

I have a twin coil kit to fit with the trispark ,when i get a mo i will pop it on and see what we get ,re the carbs I have made a cleaner wire for the pilot jets I will let you know ho we get on.

all the best chris

Re: 71 fast back in shropshire

Posted by chrisshrops at June 12. 2017

I am slowly getting there

The old loom has been hacked about a good bit by the looks of it, someone had run a wire from one of the coils direct to the batters at some point

I think I may just buy a new main harness am I right in assuming that rgn ,andover ect are all much the same for looms ?

Re: 71 fast back in shropshire

Posted by john_holmes at June 12. 2017

I bought one from Andover Norton, it fitted well but the fuse holder was badly assembled and there was no pressure on the fuse so intermittent contact to the power, replaced it with a modern 15 amp resettable fuse and no issues since. TMS Motorcycles do good harnesses too and they are made in UK by

 

http://www.autosparks.co.uk/

I have their harnesses on a B25 (installed 1986 and still going well), B44 and T120R. Use silicone grease on all the connections and there will be no corrosion, I first did this on the B25 which was left outdoors for a few years and the harness is still good even now.

The old style fuse-holder is going to always be an issue at some point so I always swap them out eventually.

Re: 71 fast back in shropshire

Posted by chrisshrops at June 12. 2017

thanks John

that is great info,I will place an order

Re: 71 fast back in shropshire

Posted by john_holmes at June 12. 2017

More tips.

If fitting EI I keep as much of the old std wiring as possible and do not cut into the harness but add extra wires using heat shrink wrap or self amalgamating tape to cover them.

https://en.wikipedia.org/wiki/Self-amalgamating_tape

Keep the old harness in place and starting at one end swap the connections and the harness as you go back, work you way along one connection at a time, change all the bullet female connectors to new ones of good quality eg Autosparks. Use silicone grease on all connections including earthing points, the earthing points should all combine inside the harness in a daisy chain but add in extra for any where its relying on the frame eg indicators and run an extra from the head using the head steady back to the battery.

The big 5 double way connector under the tank will be well past its use by date, use 5 doubles and tape them together and they will fit to the available space better than a new replacement if not too tightly taped.

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