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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.

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

Thanks, cobbster

Just to confirm that it is balancing I would put the gauges on and increase the revs slowly up to 4000 and back and just see that the columns or dials are rising and falling together. If it confirms that it is balancing I would suggest you have a problem with a cable or such like or possibly a TB itself, maybe the cable splitter box even.
Oh, and make sure the fast idle lever isnt jammed open a bit like it was on mine.

Hi timbox,
With the twinmax at 85% sesitivity at 4000rpm the needle pulls to one side to ~2.5 to 3. At the same sesitivity at 2000rpm the needle stays pretty much in the centre. As the revs increase the more out of wack it goes.
The info iv'e gleaned says to set things up at 1500-2000 revs because thats where the greater margin of error lies, begining to think not.

Thanks, cobbster.

BMW manual states 3000rpm for TBS afaik.

my Tmax on 100% sensitivity moves 1/2 a segment up to 6K.
sounds like you have the throttle cables of doom.

I doubt an out of synch throttle would feel that rough over 4K revs. Even wildly out throttles smooth out at high revs . Also twin maxs aren't the best things for throttle balancing.

Is it a twin spark bike ? Maybe one of your coilcaps is failing

Hi Steptoe,

Yeh my bike is a twin spark. When you say a coil cap is that the supressor cap that fits to the coil located just under the fuel tank?
I'm going to try a TB balance tomorrow at 3-4K revs see if that helps smooth things out.
Thanks, cobbster.

Cobbster wrote:Hi Steptoe,

Yeh my bike is a twin spark. When you say a coil cap is that the supressor cap that fits to the coil located just under the fuel tank?
I'm going to try a TB balance tomorrow at 3-4K revs see if that helps smooth things out.
Thanks, cobbster.

No mate he means the actual spark plug caps(Main plug), they have a coil built into them.

I think it's fair to say that if your throttles are balanced at 2500 then they should be balanced at 3000 and above..... providing the cables are pulling at the same rate. At 2500 you are above the range where the idle jets/control operates.

It sounds like cables or coil trouble to me. Could it be the actual throttle butterfly spinning on the shaft?????


I am sure the experts on here will help.... Good luck

Stuart

you are using the adjuster on the cables when doing the 3000 rpm check not the brass air screws are`nt you?,and the cables are seated right down in the adjuster? ,these are easy to dislodge.
ian

Hi lads,
I'm adjusting the cables for the high rev adjustment and BBS for the idle speed. Iv'e just got off the phone to Motorworks, 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 £54 a pop .
At closer inspection ther is some corrosion 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, Cobbster.

Cobbster wrote:My bike sometimes misses a beat at tick over which convinced the guy at motorworks that its probably coils. .

easy enough to check - you'll likely only need one.
Don't think that because one has failed the other will also be on the point of failing. They have a mind of their own, i've known bikes with 6K miles have one fail, and a customers GS has 118K miles and still on the original capcoils.

Remove the lower plug caps and see if the engine idles on both cylinders.

If it doesn't attach each lower one at a time and see which side it is thats failing.

Hi chaps,
OK, fitted my new coilcaps today, started her up and sweet. Easy tick over and nice and crisp on the throttle. Did'nt have time to ride it but it felt much better, BUT. I decided to put a fresh set of plugs in as the other ones had about 3K on them. Checked the book which recommends NGK BKR7EKC for the primary and NGK DCPR8EKC for the secondary. When I took mine out they were Bosch FR6LDC primary and YR6LDE for the secondary. These were supplied by Motorworks when I changed them at 9K miles. I looked on Motobins web site and according to them the ones I had fitted are for the early 1100S (primary) and the 1150 engine (secondary). Don't know if it makes much difference but I'm changing them anyway.
Does anyone have any recommendations before I part with any Nelson Eddy's?.

Cheers, cobbster.

Hi all,
All is happy in the cobbster stable. New coilcaps fitted, fresh set of spark plugs and a TB balance has sorted her out.
Its obvious now that the coilcap must have been going for some time hence the threads Ive started mentioning vibrations ect. The firing must have been way off.
I tested the coils at work with a multi meter, across the two outer electrodes it measured 1 ohm on both and across the middle and end of the supressor there was a a huge difference. The left measured 3.7M ohms and the right 1.9 M ohms. Don't know which was nacked but a huge diff between the two.
Anyway, bikes good again so looking forward to the seaon.

BTW I fitted the NGK's the hand book recommends.

Cobbster.