TB balancing....Revisited
 

Hi all,
As the title suggests I need some more TB balancing advice. My bike is running dog rough at and above 4K rpm in any gear. Iv'e balanced my TB's at idle and at 1500-2000rpm. As soon as the bike rises above 3500rpm things start to get rough and at 4000 its getting unbearable. Have I made a mistake with the balancing? and should I be looking at balancing at higher revs ie 3500 to 4000.

The bikes an 03 twin spark R1100S with just over 12K on the odo.

Large amounts of humble pie eaten here cos I thought I had the TB balance thing licked :confused:

why balance at 1500-2000? that is not all that far above idle. all write-ups on doing a TBS indicate do your basic idle set with the BBS, and then sync at 4k with the cables.
also possible that a cable has lifted off the adjusting ferrule (likely the right one, it just seems the one more prone to doing so).

Joe is correct on checking the unseated throttle cable. Its an easy thing to. Hopefully you will get the problem sorted out easily.

It sounds like more than just TB balancing going on with your bike if the throttle cables are seated properly. My 03 BCP has zero vibration close to 5k rpm and is smooth as silk.

Also, if the valve gap settings do not match b/w sides, the vibration will be greater.

4K on the revs seems to be the magic number for vibration on the 11S. I select gears to avoid it like the plague. TB's are dead on as are the valves. What octane petrol are you using? Mine rides perfectly everywhere but 4K =/- .2K Reminds me of my old O-540 Lycombing that did like 2450 revs.:)

IF you have NOT yet completely removed the BBS's (Big Brass Screws) and cleaned them completely as well as the passasge in the TB they go into....do it now.
I guarantee you you'll find a bunch of crud in both places. This is a requirement for an accurate TB/BBS synch.
word

Ummm... yeah.

I've noticed the exact same thing. I cringe every time I hit 4k. It feels like the engine is going to rattle itself apart. My TBs and valves are all set up properly, so I guess it's just the nature of this beast.

Other than a very precise TB and valve adjustment, using 4 feeler gauges, the next thing to do to smooth out that infamous 4200 rpm problem, is to put a pair of Autolite 3923 spark plugs. They're so cheap, about $2 each, I throw them away every year.
That was the final piece of the puzzle to get mine running as smooth as any oilhead I've ever seen.

I'm partial to the Bosch +4 Platinum 4417. It's three times as expensive as the autolites but hey, at 0.0005 per mile, I can live with it. :D

Hi all,
Its been suggested to me on the uk boxertrix forum that it may be a coil cap on its way out. What do you think? has anyone had this happen to them?.
I,m going to do a tB balance at 3-4K rpm tomorrow, so fingers crossed.

Thanks, beemercobby.

It may not always be obvious, but do ensure all mechanical aspects of the engine and complete support system/s is up to standard before attempting to 'tune through' a broken part or system.

Don't chase your tail.
New plugs.
fresh fuel filter
clean air filter
valve adjustment
intake manifold boot check/seal (use yamabond 4)
FRESH, CONFIRMED GOOD battery. Holds a consistent 13+VDC charged. I can't emphasize enough how a hurt battery can imitate a host of other issues. My $.02

for historical recording purposes, compression test

DO check the quality of your spark (should be bright blue at cranking speeds and ground both plug caps )
examine the plug caps and entire wire closely for cuts, arc-thrus, etc.
IF you are in far enough to do a fuel filter, DO check the condition of the ignition coil visually and with a meter (.5 ohms primary resistance)...does the coil look bulged or smell burnt.

good luck.

and I like the cheapo autolites; my favorite are nology pure-silver electrode plugs (made to order by brisk)

Jony: Just got back from a 150-mile ride up to Turner Falls. These comments about 4k vibration have me scratching my head. My bike (03 BCP) at 4,500 has ZERO vibration, and there's no 4k threshold that I can feel. I get a little -- but not even serious -- buzzing over 5k, then it smooths again at about 6k. I rode about 100 of those miles at a steady speed on the Interstate, somewhere around 4,300-4,500 rpm.

If Beemercobby has done a good TB sync and valve adjustment, and is still getting radical vibration at those rpms, don't you think he needs to look at everything else, from fuel delivery to ignition? Something just seems out of whack.

Hi all,
Iv'e just got off the phone to Motorworks, its a BMW bike parts specialist here in the UK who give good advice too. When I descibed what was happening I was told that if my TB's are in balance and tappets set right then its almost a certain that its coilcaps. These things fail at a rate of every 2-3 years because of their crap design and location. They were fitted to the twin spark to get them through emmision laws and keep the 1100S on the road for another couple of years while the 1200 engine was being developed. My bike sometimes misses a beat at tick over which convinced the guy at motorworks that its probably coils. Not supprised their $108 a pop .
At closer inspection there is some corrsion on the metal part of coil so fingers crossed new ones should do the trick. Their on back order so I won't get any until late next week, I'll keep you posted how I get on.

Thanks to everyone States side.

WOW maybe having a single spark isn't so bad after all.:)

Really though, I just adjust by the book and my 01 is smooth from idle-up. I have put 20k on the s now and I never get surging or vibration unless something is really out of whack.

no, it is not. some vibrato here and there, but "rattle itself apart"? not even close to normal.

Hi all
When JonnyRR said 0.5 Ohms primary resistance accros the coil, does that mean the coilcap itself that fits the primary spark plug. I tested one of mine today and it showed 9.39 ohms. If iv'e tested the right thing then its pretty sure to be gooshed.

Thanks, Beemercobby.

No, primary means low voltage side of coil.