Seem to have lost my TB mojo....

[riceburner]

Bike has been running a bit rough recently, and also tickover has been at about 900rpm (but consistent at that engine speed).
(bike is a twin spark with 78k+ miles, OE plugs/filters etc).

I did a TB balance over the weekend in an attempt to raise the tickover back to 1100, and get rid of the rough running (it manifested as an occasional missed beat).

Did the valves (all were slightly loose, all were tightened to spec), then used my 3-1 manometer to balance the low speed revs. I dialled out the LH BBBA and then matched the RH BBBA in order to raise the tickover revs - was that right? I THOUGHT I'd got it ticking over relatively nicely at about 1150 revs or so (a bit fast, but no matter).

Now, when I use the bike, the tickover hunts between 1000 and about 1600 revs inconsitently. It'll tick at 1400 for a few seconds, drop to 1000, climb to 1600, drop again... etc etc.

Any thoughts?

All the plugs were fine (replaced them last service) and both stick coils appear to be working ok.

[boxermania]

Couple of thoughts based on your post

Set left TB BBS at 1.5 turns from close, do same for the right BBS. Set tickover (idle) speed at 1100 to 1200 rpm.

If idle varies, look for an air leak, either at the gasket between the TB adaptor to the head or the hose that connects to the bottom of the TB and the carbon canister if you still have one.

Check the stick coils.....

[riceburner]

Couple of thoughts based on your post

Set left TB BBS at 1.5 turns from close, do same for the right BBS. Set tickover (idle) speed at 1100 to 1200 rpm.

If idle varies, look for an air leak, either at the gasket between the TB adaptor to the head or the hose that connects to the bottom of the TB and the carbon canister if you still have one.

Check the stick coils.....

When you say "Set idle at 1100 - 1200" - you DO mean "Adjust the BBBAs until manometer is balanced at that engine speed" - don't you?? How else does one adjust idle??

No Carbon cannister on this bike - UK spec.

Pretty sure both stick coils are working - the bike will fire up and run (albeit roughly) with the secondary plug-caps removed.

[boxermania]

Yes, balance with the BBS, normaly a base setting of 1.5 turns out gets you in the ball park with little adjustment on the right side BBS. If there is major adjustment needed, check the TB to head gaskets as I suggested earlier.

Good luck...............

[riceburner]

ok cheers - will have to have another look next weekend then, cheers for the advice.

oh - re cleaning the BBBAs - am I right in thinking that they can simply be completely unscrewed, nothing internal is going to fall out of place if I do so??

[boxermania]

The BBS have a small o-ring that seals against the bore and a tapered end. Suggest spraying a little silicon lubricant between the BBS and the bore so as to soften the o-ring before screwing out.

Once out, clean the taper thoroughly, do not scrape or use anything such as sand paper that can damage the surface. Spray some WD-40 on a Q-tip and use it to clean the bore where the BBS screws on, also spray a little down the bore to clean the threads.

Libricate the 0-ring and screw the BBS back in, carefully, so the threads are not crossed, screw all the way down, once again lightly and back out 1 1/2 turns. Do one side at a time and then proceed with the idle setting.

If you idle was swinging, make sure you checks the gaskets between the TB and the head, air leaks can develop there.

[riceburner]

hmm - ok - cleaned the BBAs out and did another TB balance - things are marginally better - less "hunting" at tickover (although I think I've set it a bit high - no matter).

Still getting missing at higher engine speeds though - so suspecting the stick coils £70 each.... ouch..

[boxermania]

riceburner.....stick oils it is.....maybe you can get them from beemerboneyard (stateside) cheaper

[riceburner]

riceburner.....stick oils it is.....maybe you can get them from beemerboneyard (stateside) cheaper

yeah - will have a look into that.


hmm - bang goes that new bow I wanted....