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B650 - Engine surges at low rpms

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kowalski

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Hello everybody,

I really love my 2007 650 engine (FI), but when I travel at low rpms (say, from 3000 to 4000), at constant speed, engine surges slightly. The strange thing is, the surging stops abruptely, as I shift into 6th gear... in all other gears (especially in 4th and 5th) I get this come-and-go feeling.
At first I thought of a faulty gear position sensor (my neutral light works no more), then I put a switch that sends the ECU to a resistor emulating a fixed 6th gear... in this way engine runs perfectly smooth... but this mod gives me bad idle, and on/off throttle response, then I'm not that happy with it.

Did anybody here had the same issue?

thanks,

WK
 
Start by fixing the gear position sensor: http://kewwibike.blogspot.co.nz/2010/12/gear-position-indicator.html

Once you have done that, see how it goes. Best outcome is Dale Walker's setup. Search the forum for surging. The 650 water cooled models have the same EFI as the 1250, so you will find the usual comments about lean running stock.

At present, your gear position switch is probably mucking up the ECU signal about what mapping to use, so start there. All you need is a can of contact cleaner
 
kewwig said:
At present, your gear position switch is probably mucking up the ECU signal about what mapping to use, so start there. All you need is a can of contact cleaner
Click to expand...

I thought it was the GP sensor, I cleaned it with WD40 and alcohol, but the problem remains. I measured the GP resistance as I shift through the gears, and it seems normal.
The problem now seems to appear even in 6th gear... maybe I just need a throttle body alignment? Never done that in 30K kms.

thank you,

WK
 
kewwig said:
Search the forum for surging
Click to expand...

Did that... I read here of a lot of mods to fix the surge: pair removal, secondary butterflies removal, ecc. But to be honest I didn't hear anybody telling: "I did THIS, and the surging is gone". Plus I don't want to mess with pair and the like, since where I live the law says I have to pass an EURO 3 test each 2 years.

ECM reports no error, I checked every sensor with a multimeter, and everything looks within factory specs. The only thing I didn't do is sync the throttle bodies... do you think I should try this?

thanks,

WK
 
kowalski said:
Did that... I read here of a lot of mods to fix the surge: pair removal, secondary butterflies removal, ecc. But to be honest I didn't hear anybody telling: "I did THIS, and the surging is gone". Plus I don't want to mess with pair and the like, since where I live the law says I have to pass an EURO 3 test each 2 years.

ECM reports no error, I checked every sensor with a multimeter, and everything looks within factory specs. The only thing I didn't do is sync the throttle bodies... do you think I should try this?

thanks,

WK
Click to expand...

Yes. Sync them as they are often out when the bikes are as new, and it affects low speed driveability. There's a few ways to do it. I have a step by step on my blog: http://kewwibike.blogspot.co.nz/2011/06/tuning-suzuki-bandit-1250.html

That way requires a dealer switch. Another way is to cut the no. 4 carbtune line about 10" from the engine and put a "T" in and use it to pull vacuum on the ISC controller. Tried this recently and it works well. Definitely worth syncing the TBs
 
UPDATE: yesterday I made some new tests...

1) ISC valve: it's ok and even disconnecting it the problem remains.

2) secondary butterflies: they stand still when the problem happens, so they can't be blamed.

3) PAIR: I plugged the air hose that feeds PAIR valves, but the problem remains.

4) lambda probe: I connected a multimeter to read lambda signal:
0,05 V in downhill (throttle closed), 0,90 V in uphill (throttle wide open).
When the problem happens (3000 to 4000 RPM, 4th or 5th gear, constant throttle opening), the V go up and down quickly between 0,15 and 0,75... ECM seems to go mad for a while, until either I shut the throttle, or open it wider.

Engine perfectly running, no error codes in ECM memory.

any idea?

thanks a lot

WK
 
With out riding the bike, and doing a pile of diagnostics on it in person, I can only suggest the following, in this order:

Check your TPS (throttle Position Sensor) make sure its calibrated correctly.

As suggested, do a throttle body synchronization
(I prefer dial gauges 'w proper dampening adjusters vs the vacuum stack type)

A S-TRE would be a good idea as well (Smart-Timing Retardation Eliminator) it will not affect idle as it reports neutral when you are in neutral (no timing advance in neutral).

And, a Fi-Tuner Pro is almost mandatory, its a very easy install, works very well together with the S-TRE, and it will get rid of lean spots in the fuel map (smooths out part throttle 3-4k rpm response among other things)

The Fi-Tuner Pro can also run 2 maps, and you can switch between them. You can use a Zero map (no adjustments) to pass your emissions tests.
I would also strongly suggest pulling the O2 sensor wire as the Fi-Tuner instructions will tell you to do (you can extend this wire and connect it again when it comes to emissions test time, or try and see if the bike will pass with out the O2 sensor)

I had the above mentioned mods and maintenance done on my Bandit 1250 and it had wonderfully smooth throttle response at all rpm and throttle openings.

EF
 
Easy Flyer said:
I had the above mentioned mods and maintenance done on my Bandit 1250 and it had wonderfully smooth throttle response at all rpm and throttle openings.
Click to expand...

I made some other tests... here the result: the bike is all right, the surging is due to ECM working in closed loop mode, with a bad designed map, proof is that if I simply disconnect the oxygen sensor, the surging disappears immediately.
I would be happy to put one of those ECM-fooling resistor in place of the oxygen sensor, but I'm afraid that it would make the bike run richer, and over time this would harm o2 sensor and catalytic converter... I have to pass an emission test every year!

How many kms did you put on the bike after the mods? Did you pass the emission test?

thank you,

WK
 
Problem solved! I put a 15K resistor on the pink wire of the gear position sensor. In this way, your ECU thinks you're always in 6th gear, and uses only the 6th gear ignition map: hesitation disappears, engine runs smoother, throttle response is quicker, AFR is about the same (and fuel consumption should remain the same too).

Best,

WK
 
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