R1100RS rough idle

[earlecj]

The bike is a 1996 R1100RSL with 110K miles. I've had it for 5 years. About 500 miles ago replaced the right side throttle body and did the cam chain tensioner upgrade, and then everything was great until about a week ago when it barely cranked over. Bad battery, I'd been expecting it, and today I put in the new battery (Odyssey PC680) and started the bike. It ran a few seconds, very rough, and died. I guessed that something had come loose from the throttle body job and it needed a rebalance, so I restarted it to warm it up. Would not run at idle; had to keep it about 2000 RPM just to run. Seemed to be missing spark, intermittently. Also blew some oily smoke on startup, but that ended in 30 seconds or so. The Twinmax indicated the TB balance was still good, but the needle jerked to the left when the engine missed, which I guess means that it was missing on the left cylinder. At full temperature (4 bars) it would idle roughly for a minute or so and eventually die. Checked the left side spark plug; it looks perfectly normal. Any ideas what could be doing this?

Chris in Olympia, WA

[MCMXCIVRS]

Check that the throttle cable is not pulled up out of the ferrules. This is pretty common after a fuel tank R&R and throws the TBs way off balance creating exactly the kind of condition you describe.

[boxerr]

Did you do the throttle re-learn before starting after the battery replacement??

May, or may not have anything to do with it, but disconnect the battery again, and before starting, twist throttle from idle to full 2-3 times with the key on, then turn off. See what happens then when you start it.

[dbrick]

Did you do the throttle re-learn before starting after the battery replacement?

I think that only applies to the 1150 motors. This guy has an 1100.

[JimMoore]

QUOTE=MCMXCIVRS;515888]Check that the throttle cable is not pulled up out of the ferrules. This is pretty common after a fuel tank R&R and throws the TBs way off balance creating exactly the kind of condition you describe.[/QUOTE]

This.

[earlecj]

OK, here's the state of the saga:

1. Browsing around on the web I found someone with a similar problem that was caused by an air leak. Seemed plausible since I'd replaced the TB. Sprayed carb cleaner on the rubber manifolds while the bike was idling and sure enough, it was sucked in, causing the engine to rev up. So I loosened the hose clamps and reseated the TB in the manifolds. That improved the situation a lot, but not entirely. I took it out for a test ride this evening and it was still bucking a little at 2-3K RPM.

2. This is completely irrelevant, but maybe interesting; during that test ride I hit and killed a deer. I've never hit a deer before, either with a bike or a cage. It ran out right behind the car in front of me and I had something between one and two seconds between first sight of the deer and hitting it. The pavement was wet so I went for the brakes instead of a swerve, but barely started to brake when I hit the deer square in the hindquarters, doing maybe 40 mph (me, not the deer). I heard its pelvis break. The bike hardly twitched. The deer thrashed for a few moments, but by the time I circled back (after a short break to let my heartbeat return to something near normal) it was over. A little doe, maybe 75 pounds. Damn shame.

3. Throttle cable ferrules fine, but I did completely forget to reset the TPS. Just went out and did that and the idle is now much smoother. Maybe that was the problem, I'll find out on tomorrow's commute. In the daytime.

4. Update 24 hrs later: yep, it was the TPS. Runs great now.

Thanks for that tip!

Cheers,

Chris

[PELON]

after thinking the worst, you got me to look at the ferrules and yes, the throttle cable was out.

thanks

:thumb

[Pauls1150]

It's a moot point now, but I'll say it anyway -

Under normal typical circumstances, if the TwinMax needle pulls left, that indicates that more vacuum is being pulled on the left cylinder - so a problem would more probably be on the RIGHT side.

Just a W.A.G., but I'd venture that the TPS was OK telling the computer what to do on the left side (since that's essentially a "manual" control), but the computer was confused about what to do on the right.

[Zaasu]

I hate to be a moron, but that's who I am.
What is a TPS? :dunno

[barryg]

Throtle position sensor

[Pauls1150]

It's the square black plastic thing on the side of the left throttle body.

Shops will tell you "Oh no don't ever touch it! It's perfectly set at der Holy Faktory!"

There are several articles on the Internet BMW Riders site that describe how to set it correctly; look for "Zero = Zero".

[ANDYVH]

WOW! Glad you survived the deer crash. Now, make sure your front end is still straight and square. It is suprising how much force is applied to the front forks on an animal strike. A couple in my cycle club nailed a large dog dead center, riding two up, on a K1100LT, at maybe 30 mph. They didn't go down, but the impact bent the fork legs back almost 4"!

As to the TPS, if you replaced the RH TB there was no reason to expect the TPS setting to make any difference. If you did nothing on the LH TB other than to route/attach the throttle cable to the RH TB then there should be little to do with the TPS. The TPS is very sensitive and even small changes can result in an engine running MUCH more rich, which can mask other issues. I rebuilt both TBs on my 94 RS last summer. In so doing I had to unmount and remount the TPS, which I simply did with match marks. That was clearly not accurate enough and my fuel mileage was suddenly down in the low 30's and the bike was definitely loading up, plugs were black and sooty. After I adjusted the TPS with my voltmeter all instantly returned to normal.

Air leaks and the throttle cable on the 1100 is a very likely culprit. Also, small pebbles can get jammed in the cable pulley easily if you happen to open it way up just when a pebble is thrown up, as I found out a few years back.

When replacing or rebuilding TBs on the 1100, it is critical to get the RH TB to match the LH TB, using the LH TB as the "base" setting. But I have also found that proper cable ferrule setting at the TBs is critical for idle, for on throttle balance, and especially for accurate/equal TB reaction when you crack the throttle up. Even with my cheapo mercury sticks, if I don't the throttle cables ferrules equal for play and cable tension, then the trottle response is rough and slow to match side to side.

I just fired my RS up Saturday after four months of rest. It started right up on the third crank and warmed quickly to a smooth steady idle. So TB balancing, even with mercury sticks, CAN be done at home if you know all the little extras of getting them set up. Paul Glaves is an EXCELLANT reference for this!

[Happy Wanderer]

+1 on the small pebbles stuck in the throttle cable pulleys on the throttle bodies. Last year while heading down to the 49er my bike began to idle really rough suddenly and for no apparent reasons. Pulled the tupperware off in the motel lot early the next morning and removed two tiny pebbles. When you look closely at the cable you can see a small bump or bulge as it wraps around the spool. Just pop the cable off from the bottom, clear the debris and pop it back in again. Done. Perfect idle restored.

Unbelievably, as we arrived in Mariposa the next day it happened again! Annoying but I smiled anyway since I knew exactly what it was this time. A nice fellow at the rally lent me his Sears battery operated screwdriver with a ball end allen head to take the Tupperware off real quick too!

The bike got a new nickname on that trip. "Rock Collector" :)

[cycleman2]

I think that only applies to the 1150 motors. This guy has an 1100.

Nope applies to the 1100's as well.

[bikerfish1100]

Nope applies to the 1100's as well.

it might, but the only time i have ever done the Motronic re-set was following a chip change. 3 new batteries in 2 different R11S bikes (one stock, one Laser chipped), never an issue.