R1100s TB's sync - surge? help

[Ro Co]

Hi All,

I was doing some tuning yesterday on my 02 R1100s (new to me). New air filter, plugs, set the valves and then took off for a ride to warm it for a TB sync. I completed the idle sync but when I tried to sync at 2k rpm things went a little sideways. The balance was way out off idle and trying to get it a a steady 2k was not possible. The bike would come up as normal but after a second or 2 it would cut back to just above idle and then back up 2K and continue this cycle. (2K for a sec drop back to idle for a sec, up to 2k). The bike didn't sputter or stumble just switched between the two ranges like someone was flipping a switch. Making adjustments when I could I noticed that the closer in sync the TB's the further up the rpm range the cut back happens.

TB's are now sync'd at idle and 2K and the bike is much smoother. Cut back still happens at ~ 4K.

My question is this. Is this the surging issue that people talk about? and should I try the zero=zero adjustment as a fix?

I have never really noticed a surge on acceleration but have felt this same cut of rpm when slowing down, coming off cruise speed.

Other notes -
Bikes is stock with 38k KMs
Old plugs were a touch chaulky white
Bike pops a little on decel
Choke is now 100% better after sync

Any advice is appreciated. Thanks, RoCo

[ATA]

Potential suspect to unsuspecting punter as what I had?- injectors dirty perhaps?
Try swapping them around, tuning throttle bodies on a "dead spot" see if it helps.

[SergioK]

Did you take the Big Brass Air Screws out completely and clean them up? I'd count quarter turns before they seat fully, then unscrew completely to clean every 6k. Lots of gunk on those.

[Groceryrun]

Just to confirm... after the big brass screw idle sync, you're adjusting the throttle cables for the 2000 RPM sync.

[Ro Co]

I didn't think to clean the bbs. I'll give that a shot tonight. Not sure I follow the the injector swap idea though. Both cylinders seem to be affected equally.

[Ro Co]

Just to confirm... after the big brass screw idle sync, you're adjusting the throttle cables for the 2000 RPM sync.

correct, started with the RHS only but had to tweak the LHS cable to get enough adj on the right.

[ATA]

Could be even simpler- timing- on LHS "Carb", mark, where you are, release two screws,move forward by 5 degrees- idle should improve, BUT if you move too much it will run over' well on idle, slug'ish on a actual run.

[wswartzwel]

gunk on big brass screws will cause that symptom, as Sergio stated.

[Chris Canning]

Originally Posted by Groceryrun

Just to confirm... after the big brass screw idle sync, you're adjusting the throttle cables for the 2000 RPM sync.

Ditto and on a TwinMax the revs need to be a lot higher than that,and just moving the locking nut can send e'm miles out.

[JGard]

On top of everything else people have suggested, one thing I recently did to my S which made a HUGE difference all around was to clean up all the electrical connectors that I could.

Notably the connector from the Hall Effect Sensor to the ECU, Throttle Position Sensor, and the injector connectors. Spray some quick-drying electric cleaner spray in them, then dab some dialectric grease in each little contact.

No matter how much I tried to adjust my valves and sync my TBs, nothing was ever quite right. Once I did this my idle smoothed right the hell out, starting was quicker, and my fuel mileage improved significantly.

Just another option is all

[Drews323i]

I always sync mine at 4k rpm with just the right throttle cable. Smooooth.

[Ro Co]

Lots of good advice. I'll see what damage I can do tonight. Thanks guys.

ps. no twinmax, just using my home built "cro-manometer"

[SergioK]

My home built mano served me perfectly fine. It does the job in very simple terms


Also, what's the ambient temps when you are doing the TB sync? Do you have fairly large fans cooling the jugs? How long is the engine running, total time, during a TB sync?

The times it took me more than 15 minutes to do everything is when engine temps start climbing and the ECU starts doing weird things, just like you describe, oscillating RPMs up and down. These air cooled engines don't like to be parked without air flow.

[Ro Co]

It was fairly cool yesterday, about 15C (60F). I did not use a fan as I only had it running for about 5-7 mins then out for another ride and back on the stand for maybe another 5 mins. I'm pretty quick at it, the set-up is similar to my R90. I'm not sure if that timing would put it over the top temp wise? I'll use my floor fan tonight just to make sure.

[Ro Co]

I cleaned up the bbs, they were not so bad, black but no gum. Checked the electrical connectors, everything looks good there. Things have improved, I still have the surging but not to the same extent. The drop in rpm is not nearly as much.
Below is a link to a you tube video of the surging. (excuse the mess in the shop)

R1100s sync issue - YouTube

After I shot this a decided to try a mixture adjustment. Initial TPS reading was 0.353, I've bumped it up to 0.396. It sound healthier now and another improvement in rpm drop but the drop is still present.

Not sure where to look next? I might pull the tb's and give them a good clean. Maybe a fuel filter too?

[brentw1]

I had some similar odd behavior
one bike had a loose throttle plate
the other throttle body and plate was dirty and cleaning made a big difference,

[Chris Canning]

Originally Posted by SergioK

My home built mano served me perfectly fine. It does the job in very simple terms


Also, what's the ambient temps when you are doing the TB sync? Do you have fairly large fans cooling the jugs? How long is the engine running, total time, during a TB sync?

The times it took me more than 15 minutes to do everything is when engine temps start climbing and the ECU starts doing weird things, just like you describe, oscillating RPMs up and down. These air cooled engines don't like to be parked without air flow.

Yep +1

Quickest way is with two pairs of hands,one holding the throttle at 4000,the two one hold the knurled thread on the cable and the other with the locking spanner because when you tighten the locking nut it only has to go one flat too much and the sync will be miles out,in actual fact many years ago on another forum a guy made an add on for the throttle cable so you could get more purchase on it

[ATA]

Again,
Watched the vid, very similar to what I had on my bike and it was caused by contaminated/old fuel, blocking fuel filter also clogging one of the injectors at much lower revs.
Weird stunbling at 1500 revs

[Ro Co]

I got back to fooling around with things this past weekend. Work completed is as follows;
- replaced fuel filter
- changed plugs to NGK Iridium
- removed and cleaned the TB
- performed the Rob Lentini zero=zero adjustment TB adjustment

I'm happy to say that things have improved greatly but I do have two smaller issues / questions

1. when I did the zero=zero adjustment I'd set the closed TB at 0.010 volts but when a rotated the throttle and returned to the closed position the voltage would change to ~0.025. (the cables are completely slack) I reset to 0.010V and brought the stop screw in until 3.80V. Again a twist of the throttle and return to stop yields a higher voltage, 4.20 is this case. I reset everything a number of times but still have a voltage change. I finally decided to set to 0.010 adjust to 0.380 on the stop screw without playing with the throttle. I started the bike a got a voltage of 0.343v at idle? After some thought I decided to adjust to .380V (via TPS adjustment) while running. I synced right side using throttle set screw (at idle) and set the idle with BBS. All seemed OK. The question is do I have a bad TPS?

2. I adjusted the choke and throttle (at the grip) cables to 2mm free play. Then adjusted the LS TB cable to 2mm free play. However, I can't get any freeplay adjustment on the RS TB cable? With the adjuster fully seated I get a fraction of a millimeter. I triple checked all visible cable seats, no issues. Before I pull the tank again to check, can anyone tell me if there is a adjustment at the cable junction? Is it possible not to be seated here?

Again, any thoughts are appreciated.

RoCo

[bikerfish1100]

no adjustment at the Bowden box. good thing, as it's a pain to access.