GS850 1987 Ekectronic ignition

[welshbird333]

Hi All

I have fitted a GS850 1987 electronic ignition to a GS750. It does not allow me to fit the backing plate, I have lost my timings marks how do I get over that problem. Engine starts and runs at 1500 rpm touch the throttle and the engine dies.

Thoughts and any helps would be great.

 

[Nessism]

Can you time it manually with a degree wheel and continuity light? And did you remove the stock spark advance mechanism when installing the new ignition? The ignitor box that you are trying to use has the spark advance built in.

 

[Steve]

What year 750? Earlier ones had mechanical advance mechanisms, later ones had it built into the ignitor. Your '87 ignitor has the advance built in, so if you are putting it on an '82 or earlier 750, you will have too much advance.

Also, would you mind being just a little more specific with your location? I looked up "Byfield" and found two. One in Massachusetts, the other in England. Since you have an ignitor from an '87 850, which we never had here, I am suspecting you are in England. :-k

.

 

[fastbysuzuki]

What year 750? Earlier ones had mechanical advance mechanisms, later ones had it built into the ignitor. Your '87 ignitor has the advance built in, so if you are putting it on an '82 or earlier 750, you will have too much advance.

Also, would you mind being just a little more specific with your location? I looked up "Byfield" and found two. One in Massachusetts, the other in England. Since you have an ignitor from an '87 850, which we never had here, I am suspecting you are in England. :-k
.

The username Welshbird333 may hold a clue

 

[Nessism]

What year 750? Earlier ones had mechanical advance mechanisms, later ones had it built into the ignitor.
.

Good question. My brain was thinking 1st or 2nd generation 750, but the 3rd gen bikes had the spark curve built into the ignitor, and they also are the ones that had a tendency to fry their ignitor.

 

[welshbird333]

Hi,
I did remove the spark advance which took my timing away. Cheers

Can you time it manually with a degree wheel and continuity light? And did you remove the stock spark advance mechanism when installing the new ignition? The ignitor box that you are trying to use has the spark advance built in.

 

[welshbird333]

Hi 1977 GS750 has point and the early GS850 electronic ignition fitted all worked well then swapped it to a modern electronic ignition form a gS850 1987.

Good question. My brain was thinking 1st or 2nd generation 750, but the 3rd gen bikes had the spark curve built into the ignitor, and they also are the ones that had a tendency to fry their ignitor.

 

[welshbird333]

LOL Yep a welsh girl from the UK..

The username Welshbird333 may hold a clue 

 

[welshbird333]

New one that is causing the headaches!!!

 

[welshbird333]

this is what i took off :

 

[Grimly]

The new one gives you no capacity to set the base timing then? The advance requirements between the 750 and the later 850 won't be all that different, iwt, but in the absence of any documentary details of that, I could be wrong.
You could slot the holes in the mounting plate and retard it a bit, but it won't be very much before you run out of plate.
Was there anything wrong with the 850 ignition system you'd already fitted?
If that was dud, there are three ways to go...
1. Fit a Newtronic (Piranha) system complete - they're still in business, look up Autocar, for a cost of about ?120. I've had an original Piranha system for 30+ years and it was on the bike when I got it. It's done well over 200K miles between engines. You will need the original mechanical advancer and cam points nose.

2. Fit a Dyna system for twice the price and be prepared for it to fail, as these self-contained systems with the pickups and amplifiers are notorious for failing with the heat inside the end crank cover.

3. Build an 2x HEI module, utiilising the original 850 triggers, which will cost about 50 quid all in. I built one a couple of years ago and it worked fine. Google for " HEI modules on motorcycles".