R100GS - After half mile, or 4k Revs plus, Engine Dies

[DevonianScotsman]

Righty, mrjonesybop's brother posting on behalf of.

R100GS starts fine, runs ok at idle, but after about a half mile of sensible riding, or as soon as you blip it to over 4k under load it backfires, then gets really sluggish, then dies. If you ignition off, then leave for 30 seconds, it will restart and continue for another half mile.

I've checked the plugs, one is slightly sooty, the other is slighty white, but TBH they've only been in 5 minutes.

I've had the carbs off, and stripped them both from the bottom. The RHS main jet has considerably more restriction when you blow through it with the carb assembled than the LHS one has. I cant strip the RHS carb from the top, as one of the screws is already stripped, and i cant be assed to drill it out.

Oddly also, the floats dont drop to the same height with the bowls off. This looks to be because the hinge on the RHS carb is considerably looser than the other side, allowing the float pivot to move forward slightly, and drop down further. How far should they drop?

Both fuel taps really empty fuel out at a rate of knots, so no problems there as far as i can see.

Before i drill the screw out, and spend £35 on a carb refurb kit from Motorworks, is there anything else we should be looking for? Its all a bit more straightforward from my Kwaker, so throw any thoughts in!

Cheers!

 

[(RIP) Proff]

Most likely to be the coil..
Happened on mine several years ago, same symptoms.
I used 1 coil off a K100 set up I bought off ebay for £20
still got the other one somewhere
I now have genuine g/s spare so pm me if I can help

 

[DevonianScotsman]

Certainly worth a go!
How much for the coil?

 

[(RIP) Proff]

PM me your address or come and fetch it, I'm in Okehampton...
You'll have to modify the bracket and knock up a connector, but the one I did years ago is still on Gertie going strong
Took less than an hour to do ..........

 

[DevonianScotsman]

When's good to collect?
Where is the coil mounted on the GS?

Cheers!

 

[(RIP) Proff]

under the tank on the top tube with both plug leads coming out of it..
looks like the top one of this pic,,
Bottom one is a dyna coil, a good mod but I can never remember iof its the 5 or 3 ohm resistance whatever you need

Collect whenever, just pm me your phone number tomorrow

 

[Rob Farmer]

It's the brown dyna coil for the gs (1.5 Ohm). I've got one on my Mono and is a worthwhile mod.

 

[(RIP) Proff]

Thank you o lord and Master

 

[DevonianScotsman]

So does that mean that coil is the wrong one?

Easily confused, me

 

[thornley]

Same problem on my 1988 R100GS. Early coils were prone to cracking giving the symptoms you describe. Beg or borrow the later coil, the guys on here will sort you out. Eventually it will take longer and longer to start and end up like I did with a knackered starter motor!

 

[DevonianScotsman]

Cheers for the advice - nice to know i'm not the only person ever to have this problem!

Proff, you have PM.

 

[Rob Farmer]

So does that mean that coil is the wrong one?

Easily confused, me

No. The Dyna coil is an aftermarket upgrade. It costs the same as a new BMW coil.

 

[DevonianScotsman]

Cheers Rob

 

[SJRoome]

Hi

I agree that this sounds like an ignition problem, but you may as well sort out the partially blocked main jet as well.

You dont need to remove the top of the carb to sort out the main jet. Take the carb completely off the bike and take out the main jet and the atomiser and clean them and their airways using plenty of carb cleaner fluid. A socket is less likely to damage the jet than using a spanner.

When cleaning and reassembling the carb be very careful not to bend or damage the needle. Hold the slide open to keep the needle out of the way.

Steve

 

[John Armstrong]

No. The Dyna coil is an aftermarket upgrade. It costs the same as a new BMW coil.

http://www.motorworks.co.uk/bmw/pro..._20&header_text=&header_text_image=0&spPage=1

So is the single spark dyna coil the same price as the BM bit? And is it really so much better than the OEM one?

 

[Beemerboff]

The Dyna coils have different resistances, and are colored to match.

So the red one is wrong for the GS - the brown one with 1.5 ohms resistance is the shot.

The earlier point bikes use the green 3 ohm one, but I dont know what a red is off.

According to Boyer , Dyna coils are the best they have tested.

 

[(RIP) Proff]

The Dyna coils have different resistances, and are colored to match.

So the red one is wrong for the GS - the brown one with 1.5 ohms resistance is the shot.

The earlier point bikes use the green 3 ohm one, but I dont know what a red is off.

According to Boyer , Dyna coils are the best they have tested.

Covered by Rob on post 3.
the red ones are fitted to my FJ1100
VRRROOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMMMMMMMM

 

[Rob Farmer]

So is the single spark dyna coil the same price as the BM bit? And is it really so much better than the OEM one?

John the Motorworks price if for a pair of Dyna coils so they are £51 each. The standard coil used to be around the £65 mark but are now £82.80

Get one of the other guys to go in with you if you just want one Dyna coil. The Motorworks coils do not come with a mounting bracket you would need to make one. I got mine (with a bracket) from http://www.motoelekt.com/ignition.htm in the states for £65 delivered following England Kevs recommendation, the Motoelecktric coils do come with mounting brackets.

 

[John Armstrong]

I got mine (with a bracket) from http://www.motoelekt.com/ignition.htm in the states for £65 delivered following England Kevs recommendation, the Motoelecktric coils do come with mounting brackets.

Thanks Rob does the bracket they supply mean that there's no longer a need to move relays and amend the bracketry in the area as they seem to imply here:

http://www.airheads.org/content/view/283/98/

 

[Rob Farmer]

The bracket allows it to be a direct replacement using the original mounts. This is England Kevs pictures on Advrider Kevs Post