Twinspark on an R100GS

[DevonianScotsman]

Fitting Twinspark to an R100GS - A myth or reality?
What are the pros and cons?
How does it work?

As you can tell, I'm still young - So need some education in the field of Old-Man Airhead GSing...

Cheers chaps!

 

[(RIP) Proff]

Personal opinion.
not worth it.
Had 2 bikes with it , one ended up with bottom plug'oles filled with bolts, other ended up with new single spark heads, my R100cs..
Never could see the benefit of it, bit like Mike Krausers 4 valve airheads

 

[DevonianScotsman]

Good to hear from you Proff. How was the land of Frogs and half-decent wine?

How exactly does Twinspark work? Is it lliterally just 2 coils and 4 plugs?

 

[45disco]

not good on a gs or g/s that is intended to be ridden off road. the bottom plug wires are susceptible to breakage and can cause ignition system failure(in the middle of no were) and the water thing(shorting), if not check often, on my r100rs i see a great fuel millage increase from 38/40 to 45/50mpg.@ 70 ish mph, but i watch the bottom plugs caps, i have broken them .

cheers

 

[VAL. H.]

We have a very nice, well sorted twin spark, gas flowed heads, forged pistons and gauld knows what else.

SWMBO rode it on Salisbury Plain last week end, and IMO it runs very sweetly indeed. However I should mention here; I've never ridden a single spark GS, but have ridden a couple of 80RT's though this was several years ago, so couldn't say one way or another as to whether it's better with the extra plugs.

From the info I've gained over the years, I would recommend that you get the work done professionally 'set-up etc' as this seems to make a big difference. Ours is a Jim Cray conversion.

Incidentally; Jim did the conversion when the bike had clocked 100'000 miles. It's now done another 30'000 miles, and from what I understand has had no more than regular dealer servicing.

There are a couple of other well respected BM technicians around the country, may-be more local to you. Ask around on here, someone will be along to tell you who the are.

Val.

 

[Voyager]

Have a look here . . :

http://www.gunsmoke.com/motorcycling/r100gs/index.html


And in particular, here . . . :

http://www.gunsmoke.com/motorcycling/r100gs/dual_plug/index.html


The theory behind twin plugging revolves around the fact that the 100GS has an 'over-square' motor, where the distance the ignition flame-front has to travel across the piston crown is relatively large compared with the stroke.

Therefore, at high speed, it is possible for the fuel to be burning well into the power cycle.

Producing two simultaneous flame fronts quickens the burn and produces power earlier in the cycle - meaning less fuel is required (or it goes faster).

In practice, the advantage is minimal at low speed, and brings another set of problems.

A quicker burn means that the auto-advance characteristics need to be changed - which means mucking about with the auto advance unit. This is not for the amateur or the feint-hearted Engineer.

Those of us who have done it (twin-plugging . . not altering the auto advance) end up playing with the ignition timing and usually end-up leaving it standard.

I couldn't swear that my 100GS (or my previous R80RT) run better because of the twin plugs - though I did find starting in cold weather easier.

The cold-starting could probably be inproved by fitting a Dynacoil in place of the Bosch original without adding additional plugs.

I wouldn't do it again, and I'm thinking of going back to single plugs as the 'Timeserts' fitted for the lower 12mm plugs keep seizing onto the plugs, then coming loose from the head


Others will be along shortly


Bob.

 

[DevonianScotsman]

Cheers for the explanation Voyager, and all the tips guys - Much appreciated.

I don't see myself Twin-Plugging my GS - but I am looking for a collector box to replace the Y-piece that was on the bike when I got it... (I'm fed up of the popping and farting and the flat spots in the revs).

Anyone got a spare lying around somewhere?

 

[Steptoe]

the 'Timeserts' fitted for the lower 12mm plugs keep seizing onto the plugs, then coming loose from the head


.

Thats happens a lot - plus had a couple of heads over the years crack between the second plug hole and exhaust port.

I'm with proff, i'd never bother doing it on my own bike.

 

[Beemerboff]

Most tuners , including Jim Cray , will only do twin plugging in conjunction with flowing and squish banding.

However there is a school of thought that says that if the flow and squish are right then there is no need for twin plugs.

The GS seems to like a couple of degrees less advance than the others, 30 degrees works OK for most folks.

The popping and farting from the Y piece are because the aluminum gaskets are not sealing the joints between the pipes , and they are most likely blocking the muffler somewhere.

So pay the huge price for the OEM gaskets , remove the muffler and shake it till all the bits come out - you may need to enlarge the inlet hole a little as the bits fuse together inside the muffler- and reseal with the new gaskets and a bit high temp silicone.

Retard the timing a couple, and unclip the snorkels from the air box.

It should run a treat , with no flat spot a a bit of a kick over 5000 revs too.