R850R "stumbles" at 3100 to 3300 rpm

[CRazyCam]

Hi Folks.

I've had my 1998 R850R for a few months now, and have fallen in love with it....
but.... it seems to have a funny kind of stumbling when cruising at a stead throttle at 3100 to 3300 rpm.

It feels as if I had briefly come off throttle and then back on to it, but I haven't.

All other engine speeds, it's smooth as silk.

Is this the dreaded "surging"? that I have read about?

Any suggestions to curing the problem, please?

regards,CrazyCam

[omg1010]

Surging can occur at different rpm levels but it always occurs at steady throttle. However the 850 models have been less vulnerable to this than the 1100 models. I suggest you get your bike properly synch'ed. Also you may want to change your spark plugs, your air filter (use the one from K&N) and last but not least the plug in the fuse box which influences the air/fuel mix. There are plugs available ranging from yellow to pink, grey to other colors. Depends on which one is installed in your oilhead to determine which would be the appropriate one to enrich your mix.

Kind regards from Germany
Oliver

[CRazyCam]

My R850R has a yellow plug on the Fuel Injection thing.

Is there a list of these plugs, their colours and their capabilities/applications?

The more I think about it, the stumbling at such a precise rev range does kind of sound like an injection mapping issue.

regards,CrazyCam

[CRazyCam]

Correction to the above.......

The yellow thingy appears to be the starter relay, and I have an empty socket where the plug should be.

Do I need a plug to "tell" the injection that it's an R850R?

regards,CrazyCam

[omg1010]

@CrazyCam
As said previously many of these color-coded plugs exist. There are even 2 different yellow plugs (yellow-gold and yellow-olive). The original US-Version R850R had the yellow-gold plug. If I was you I would try the rose colored-plug (BMW p/n 65 36 8 366 625. The result is a richer fuel-air mix. This plug was used for the R1100R/GS (ECE and US-Version), R1150RS (ECE and US Version) and R850RT (US Version). You can get these plugs for small bucks from companies like beemerboneyard.com or for big bucks at your BMW dealer ...

And by the way the location of this plug is as per this image (http://www.servis.offmoto.com/Manualy/B ... %20Box.gif) under "Relay 1 / Encoding Plug"

Brgds
Oliver

[CRazyCam]

Thanks for that Oliver, I'll see if I can find a pink plug and give it a try.

regards,CrazyCam

[CRazyCam]

OK folks, for anyone that might be interested, I got a pink Cat Code Plug, from my local BM dealership.... $16 Ozzie.

I plugged it in this arvo, pulled fuse No. 5, replaced fuse, and did the ignition on/throttle off to full times 5, ignition off, then started it up.

First impression was that the bike has become even nicer!

I didn't get much more than a few passes to the end of the street and back...... well, I needed a few beers before I was game enough to try brain surgery on my bike.

Will report back with more info when I get some more time riding it.

BTW, running without the Cat Code Plug is supposed to stuff the catalytic converter. My bike has, quite probably, been running with out the CCP for years, so, I assume the Cat is stuffed.

OK what does that actually mean?

regards,CrazyCam

[CRazyCam]

Oliver, mate...thanks heaps!

Road testing today, with pink plug, the bike felt much nicer and smoother.

Stumbles at 3100 to 3300 are gone.

Mid range roll on feels better, too.

Maybe I am losing out on peak revs power, but <shrug> I don't care.

Only other outstanding test is whether I get better than 4.62 litres per 100 kilometres.

I'd love to know why the cat code plug was removed in the first place.

regards,CrazyCam