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Discussion Starter #1
Hi guys, have not been able to find a match for some symptoms my ST2 is presently exhibiting.
Coming back from a 300km ride, on getting back to the crawling traffic, the ST2 kept stalling at the slow 1st gear traffic speeds when the clutch was pulled in.
At trailing or light throttles, the bike seems to hesitate or feels like it's stopping.
It doesn't seem to me to be a tuning issue since the problem came on suddenly. It even cleared on a brief ride a week later.
My first thought was some sort of fuel blockage.
Have cleaned fuel filter (use a K&N, external of tank), cleaned, replaced Jaeger Temperature senders with Bosch units, swapped out plugs, swapped relays 1 and 3 under seat.
Checked and cleaned CPS, looked OK. No fuel leaks. I'm out of ideas.
Do these symptoms ring a bell with anyone? Any solutions that worked?
Thanks!
 

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Even though it came on suddenly, I would still run through a tune. Check the throttle body walls, clean off any crud that may there. Keep us posted!
 

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It appears you've ruled out alot of fuel possibilities, as I once did with similar ST2 symptoms - until i discovered many frustrating months later the far less likely cause: random electrical breakdown, especially when moisture was in the air, via oxidized wiring joints. The main culprit was a large junction box right down in the belly of the bottom fairing: full of dry jointed powder. I cleaned and applied dielectric grease to every joint, and happy days! Worst that can happen is you'll rule that out for a very long time. Good luck.
 

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What Belter said. Having that external fuel filter is probably a nice convenience for replacement every year or two. It would unfortunately encourage you ignore the fuel pump's sump screen (pre filter) and noticing / cleaning out tank sediment.
 

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Discussion Starter #6
Thanks for all the quick replies guys!
Belter, I had to POR15 the tank some years ago after discovering my immaculate ST2 having a rust sludge filled tank. (after a blocked fuel filter that stopped the bike revving over 6.5K). SS904, wasn't aware of a fuel pump sump screen, worth a check - it feels like a fueling problem.
There goes next Saturday! Thanks again.
 

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Make sure the signal from the TPS is clean--no rashy "noise" spots. If there are any, replace the TPS.
 

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I vote for Fuel Pump screen (pre-filter) or even a leaking or partially split high pressure hose inside tank. Only a thorough inspection will clear up. Steve
 

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I vote for Fuel Pump screen (pre-filter) or even a leaking or partially split high pressure hose inside tank. Only a thorough inspection will clear up. Steve
I don't think so. If it were at big throttle settings, then maybe. But he's talking lower rpm, "slow" traffic.
And the bike runs great while giving it a fist-full of throttle, correct?

Maybe try some Chevron Techron. It's the best thing (fuel inj. cleaner) I've used on my Saab's with IMMEDIATE results in smooth running. I've used it on my FI Ducatis, but for no reason other than I know it's a great product for keeping the FI hardware clean.
 

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Did you double check the TPS signal? My buddie's ST2 had some lower speed running issues, and it turned out to be the TPS.

I was going to accuse the temp senders, but I see that you have already replaced them with Bosch senders...
 

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Discussion Starter #11
Hi guys. Finally got the bike running again. Took out the fuel pump, found a 25mm x 10mm sandy residue in the bottom of the fuel pump casting, under the fuel pump filter, but not in the filter. The filter had separated from the pump and the pump was not snugly fitted in the alloy casting but was a little loose. Thought the filter edge might have obstructed the pump inlet. Anyway, broke the O ring trying to re-install - have re-used it before. You have to really get that pump housing to slide EVENLY into the tank hole. Had to wait for some new O rings.
Anyway, back together, test rode it - no fix,symptoms remain. Sometimes she idles, sometimes not, tends to stall pulling up at an intersection with the clutch in. On trailing throttles,around 3000rpm feels like she's stalling, or wanting to.
How do you check the TPS signal Stick, in the ECU somewhere?
 
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