www.boxertrix.com

Had the 11S back for a few days now and I'm starting to notice some hesitation with the engine. I've noticed it before but its getting worse now. With small throttle openings at low to mid revs the starts slowig down then suddenly picks back up again. You can stop it slowing down by winding the throttle on but by the time it reacts you have twisted the throttle quite a bit and it lurches forward.

Any ideas on what it could be?

Hi Tom it's the old surging issue again probably the best course of action would be, set tappets and cam end float, then throttle body sync at tickover and at about 4000 revs you should find this will help massivly if you cant ballance the throttle bodies it's probably an air leak either from the intake rubbers or from the throttle bodies themselves spray wd40 around to find any leak. if it's the throttle bodies you can get a repair/overhaul kit from Dan Cata [see my sig] Set the TPS i'm running mine at .385

If you have no cat fitted you could try disconnecting the lambda sensor under the tank and the CCP in the left hand pod [worth trying on a catted bike but over time it will suppodesly[spellin] ruin the cat

If you have a catted bike or not the accelerator module mod works and is cheap and easy to fit
http://www.sol2.be/Performance/ENG/Home/index.html

Hope this helps Dai

Dai wiskers wrote:, set tappets and cam end float, then throttle body sync at tickover and at about 4000 revs y

I find High speed sync is best set at about 2000 rpm - the engine is pulling more vacuum at these revs as the butterflies aren't open as far - makes the vacuum differential more pronounced and setting up more accurate

DaveH wrote:

Dai wiskers wrote:, set tappets and cam end float, then throttle body sync at tickover and at about 4000 revs y

I find High speed sync is best set at about 2000 rpm - the engine is pulling more vacuum at these revs as the butterflies aren't open as far - makes the vacuum differential more pronounced and setting up more accurate

Listen to this man he knows his stuff

I did forget to mention change the plugs first then delve deeper

Maybe worth a quick look to make sure the vacuum rubber caps on the bottom of the injectors are ok and not sucking in air !!
just a thought
Ned

ned1 wrote:Maybe worth a quick look to make sure the vacuum rubber caps on the bottom of the injectors are ok and not sucking in air !!
just a thought
Ned

Good point Ned

Mine used to blow these off if it kicked back on starting

something i forget about now i have a pipe accross the two with a inline tap fitted to the right hand side makes for easier conection to vacume gages for me [all done from the right side with no worries of melting vacume gague pipe on exhaust]

mine did this recently, I replaced them with 2x 1" pieces of rubber tubing with a screw in one end to seal it and attached with a cable tie to ensure they don't get spat off. Seems to be working fine

slparry wrote:mine did this recently, I replaced them with 2x 1" pieces of rubber tubing with a screw in one end to seal it and attached with a cable tie to ensure they don't get spat off. Seems to be working fine

Mr Parry
I'm suprised at you you'll be matt blacking it soon [make the left one long enough to pass through the bike infront of battery then it's easier to rig up your vacume guages

Dai wiskers wrote:

slparry wrote:mine did this recently, I replaced them with 2x 1" pieces of rubber tubing with a screw in one end to seal it and attached with a cable tie to ensure they don't get spat off. Seems to be working fine

Mr Parry
I'm suprised at you you'll be matt blacking it soon [make the left one long enough to pass through the bike infront of battery then it's easier to rig up your vacume guages

I have got a pair of the OEM plugs brand new but being honest this works better

I have wondered about getting a small vacuum gauge set mounted permanently

slparry wrote:

Dai wiskers wrote:

slparry wrote:mine did this recently, I replaced them with 2x 1" pieces of rubber tubing with a screw in one end to seal it and attached with a cable tie to ensure they don't get spat off. Seems to be working fine

Mr Parry
I'm suprised at you you'll be matt blacking it soon [make the left one long enough to pass through the bike infront of battery then it's easier to rig up your vacume guages

I have got a pair of the OEM plugs brand new but being honest this works better

I have wondered about getting a small vacuum gauge set mounted permanently

I think the vibration would kill them in double quick time
However you could make a ball bearing type manometer and fix it permanently to the bike but with the two pipes on one side of the bike it's just as easy to connect and disconnect when needed

.. got some rubber thingies from a local car shop..
.. the're diesel pipe caps or something or other.. 20p each
Just go into a car shop and describe what you want.. I did and he said.. would these do.. and I said .. Yes!

Never thought of that, last time I checked the were both looking a bit worse for wear but didn't think it would be a problem as the ends were still intact. Definitely worth a look.

Had a look they are both brand new. Garage must have done it when the did the clutch.

Tom

Part 1
The motronic on these things is stone age. I have an air/fuel gauge on my bike and I can see it working at small throttle openings and moderate engine speeds. This is the range where the bike runs 'closed-loop' i.e. the motronic reads the exhaust gas via the lambda sensor and then adjusts the mixture to get the ideal air/fuel ratio. The motronic is no kilohertz affair! the needle on the a/f gauge pulses just two or three times a second as the motronic adjusts, and then readjusts the mixture. The pulsing on the gauge occurs at the same speed as the surging that you sometimes feel.

Part 2
This is a twin cylinder bike with just one lambda sensor. Bad Germans! If one of the cylinders is running slightly rich (maybe out of balance throttles) then the combined exhaust gas will indicate rich and the motronic will lean things off including the 'good' cylinder' (the injectors are wired together as one). Leaning off a spot-on mixture causes an engine to race, so the 'good' cylinder races as a result of the motronic's efforts to correct what it sees as a rich mixture.

Don't waste your time re-reading this post, just do all the things already mentioned in this thread as a means of getting the cylinders as balanced as possible!

Disconecting the lambda sensor will take the closed loop out of the system so it will be at all times open loop