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· Registered
129 Posts
Discussion Starter · #1 ·
I see there is much banter online about fuel injection, IAT/sensor mapping and Lambda sensors, but after a quick search there seems to be an awful lot of posts to wade through for a succinct answer- so I will just ask...

If appears that a few days ago on my ride to work I may have experienced real surging on my bike for the first (and at the time of posting- only) time.

The problem began once the bike was warmed up (this is not an erratic tickover problem- Ive fixed that some years ago)- about 3-4 bars on the guage; in 6th at a constant throttle. 4000rpm/ 75mph. The surging seems to cycle every 6 to 20 seconds.
The bike accelerates fine -albeit with a seconds hesitation when opening the throttle on the trough of the surge. It feels like a loss of power- and a dip of a few mph. The surge was noticeable at other revs, but not as severe as at motorway speeds.

Some info on the bike-
R1150RT, 2003 model- twinspark, 56000miles/90,000kms
Last minor service done 54000miles, last major including valves, air filter, throttle balancing and BBAS clean at 48000miles. NGK Super Iridium plugs fitted at the same time. 1000-ohm resistor added to the Intake Air Temperature Sensor to boost open-loop fueling. No problem there. Standard exhaust. Standard air filter. Pink CCP was refitted at time of IAT mod two year s ago.
Fuel filter at 36k. New quick-disconnects on the fuel lines.
Stick coils seem to be good as there is no problem with tickover or hesitation at low revs.
Battery has been low over the last few weeks whilst Ive been off work sick, but has been charged and seems 100%.
The bike has been running fine for months- all weathers- wet, dry, -5degC to +16degC.
Fuel consumption has been slightly higher the past few weeks- from 48UKmpg to 44UKmpg. Id attributed this to a couple of late work dashes and backway blasts.
TPS reset and low battery dont seem to be the issue as the lighting, cranking and throttle response have all been fine since the battery was recharged- I rode a couple of weeks before this surging appeared, and just as abruptly disappeared...

This is the first and only time Ive experienced this on the RT. The bike ran fine on the home run- perhaps a slight momentary surge, but that could have been my imagination.

SO before I go trawling all the forums out there to glean the right info- can any of you advise me on the following?-

1- is this the first signs of a faulty Lambda/O2 sensor?
2- are there other causes I should check for?
3- is the crossover voltage for the Lambda sensor 1V and the upper and lower limits 0.4V and 1.6V respectively (think I read it somewhere)?
4- how quickly should the Lambda voltage cycle with a fully-warmed-up engine?
5- is it easy to access the Lambda plug on the Motronic/ECU, or is it a tank-off job?
6- can the Lambda sensor be removed from the exhaust without removing the downpipes from the bike? I fear rusted manifold studs and ensuing helicoil trauma...
7- read somewhere that NGK are better than Bosch for Lambda sensors- is this still the consensus?
8- what effect does it have on rideability and fuel consumption to just disconnect the Lambda sensor, should it prove to be faulty?

Many thanks in advance for your advice/info...

Oh, and I suppose I should mention we run 95octane without biomethanol additive in north europe...

· Registered
129 Posts
Discussion Starter · #3 ·
Thanks for the link!
From other replies it seems that I may have just had some water in the fuel or maybe carbon fouling on the sparkplug....

Theres been no further problems this week, so it seems (hopefully) a one-off. I will post again if anything else happens.

Thanks again!
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