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Discussion Starter #1
Sorry for the War and Peace below, but I hope someone can shed some light on this issue...

So a few months ago I heard this constant whistling/whining noise when my 2005 DL650 (clocked just over 50k, regularly serviced) was idling. The mechanic said it might be the fuel filter, but he also said the filter would not catastrophically fail all of a sudden. This sound sort of came and went and since I wasn’t experiencing any other issues or loss in performance whatsoever (not even in top RPM) I didn’t think too much of it and though I’d deal with it as soon as I start noticing a loss in compression.

The whining noise eventually completely disappeared, and the bike was fine. Then, a bit later, it would be idling fine at around 1,100 RPM, nice and steady, and it would sometimes suddenly drop back to around 750 RPM, idling terribly, sometimes even stalling. Still, if I turned open the throttle it would still rev just fine. Just idling was the problem. Just as the problem came, it went, going back to 1,100 RPM – no issues. Back to the mechanic for a service and to get it checked out, but he couldn’t diagnose the problem as it was running fine during the test rides. So I recorded a few short videos of the issue when it happened after the service (from fine, to worse and stalling to barely being able to keep it running).

Up until last month, when it became unrideable. Running inconsistently, little puffs of smoke coming out of the exhaust and as soon as I let go of the gas it would stall. About to take it to the mechanic and now it won’t start at all. Starter motor is turning but that’s it.

Does anyone have any idea what the issue is? Is it the fuel pump, even though I didn’t have a loss in RPM, or is it something else? I uploaded the videos as they give a pretty good impression of what’s wrong. I would love to post them, but I can't post any links as a newbie...

Thanks!
 

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From GW
The TPS is a main causes of failure to idle properly.


TPS Solution::| There isn't a valid TPS test, you replace it if there are symptoms of a TPS problem and the symptoms here indicate it's a likely suspect.:| A bad TPS is heat and position sensitive. It can test okay and be bad. There is no good test procedure. It isn't that expensive and replacement is a good idea if a long enough ride to get it hot causes problems. The tps is the bottom sensor. The one on top is the secondary tps which is rarely the problem. Removing and replacing the fixing/adjusting screw for the TPS requires a Torx T25 security bit. It's a fiddly adjustment. Small changes in TPS position make large setting changes. Warm up the engine, use a wire to put it in dealer mode, and twist the tps body so that the display shows - C00, which is the mid position. _C00 is the lower position. You want to see the dealer mode dash - in the -C00 read out raise to the higher position at about 2500 rpm for the best result.


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At 56K miles it could be both inlet filter and TPS but not really related.

A plugged inlet filter will cause the pump to whine randomly for a few months then eventually constantly. Listen to the whine when you first turn the key when the speedo needles sweep you'll hear it pressurizing the fuel lines in the prep-to-start. If that sound starts to vary and get noisy I'd suspect the inlet sock is starting to plug up. My Gen2 Wee did this last year so I pulled inlet filter and rinsed it in kerosene (I did not have a new filter) and that fixed it for about 9 months. I can hear the pump whine all the time now even while riding but don't have any power loss at higher RPMs but have a filter on order.

If you have a mechanic do the work then make sure he does both Item #2 (inlet strainer $30) and Item #7 (regulator $120) on the parts fiche. The regulator includes a high pressure filter downstream of the pump but pump whine is usually caused by the inlet strainer. These parts are back-order parts so make sure the mechanic orders them prior to the work so your bike is not sitting around in pieces waiting for parts. If you DIY (like me) you can do just the inlet strainer but if you are paying a mechanic just replace both, its a lot of labor to pull the tank, fuel pump and dismantle the pump to get to the parts and if you are paying for labor you don't want to do it twice. Make sure you or the mechanic rinses the tank to clear any crud to avoid plugging the new filters and check for rust in the tank.

The idle could be a variety of things but the main suspect is the TPS as Hitachi suggests. While there is no definitive TPS test some riders have swapped the secondary TPS with the primary TPS as a test to see if that corrects the problem since the secondaries don't wear out the same way as the primary. The most common symptom of a bad TPS is the bike is warmed up and stalls while coming to a stop. Other possible causes are vacuum leak, throttle body idle-air out of sync and ISC (idle-speed control) valve out of whack so these should be checked too. The ISC valve reset is an easy thing to rule out yourself.

Here are the steps from GW;

One thing to try is to reset the ISC valve PRE-SET.

1) Turn the ignition switch to the OFF position.
2) Remove the seat.
3) Put the bike in dealer mode
4) Turn the ignition switch to the ON position.
5) Turn the ignition switch to the OFF position.
6) Then, wait more than 5 seconds.
NOTE:The ISC valve automatically is set at the PRE-SET position.
7) Take the bike out of dealer mode.
 

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My experience with a clogged filter is that the bike runs fine at idle but starts sputtering above 5000rpm.

A friend had staling issues and inconsistent idle rpm.
He changed the TPS, but it was the same, he even took the whole throttle body assembly from another DL650 and CDI but had the same problems.

Finally he had a throttle body synchronisation done and that fixed the problem.
Don't know why he didn't do that first. Would have saved him a lot of time, money and nerves.

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Discussion Starter #6
Thanks everyone for your advice - much appreciated! BTW - it's got 56,000 kms on the clock (35,000 miles).

So I had a tinker today and started off with a Wee that wouldn't start.

I reset the ISC valve preset and had a look for any error codes. Everything appeared to be fine (-C00). When I took the bike out of dealer mode I did manage to start it (it still ran pretty rough, with RPMs all over the place, and stalled). When it stalled, I got an FI code and a flashing red light. Went back to dealer mode and got another -C00. Back out of dealer mode and the bike started again. ran a bit better but stalled again - same FI code and the flashing light. Back into dealer mode and, again, everything appeared to be fine.

Started again, ran a bit better again and left it running for 15 minutes. When the engine was warm I revved it up to 7,000rpm without a problem and it returned to 1,000rpm idling speed. Does this mean that the TPS is likely not the issue? It's still not completely smooth and when opening the throttle suddenly it's blowing out little puffs of black smoke, but at least it's running.

Next step: throttle body sync.
 

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Turning the bike on/off or (I think) switching in/out of dealer mode clears the display of the error code. You would need either Suzuki's SDS tool (not for sale) or a Healtech analyzer ($$$) to pull the code from memory. Leave it in dealer mode and run it and see if you can catch the code. Getting that code is going to be key in resolving this issue. Throttle body sync is not necessary at this point, it is something else causing the problem.

On the other hand, with the symptoms of poor idle, puffs of black smoke, etc it sounds like you have a leaky or bad fuel injector which may not show up as a FI (fault indicator) code. I have two fuel injectors from a 2009 available in the For Sale forum if it comes to that. PM me if interested.
.
 

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Previously I wrote...
A plugged inlet filter will cause the pump to whine randomly for a few months then eventually constantly. Listen to the whine when you first turn the key when the speedo needles sweep you'll hear it pressurizing the fuel lines in the prep-to-start. If that sound starts to vary and get noisy I'd suspect the inlet sock is starting to plug up. My Gen2 Wee did this last year so I pulled inlet filter and rinsed it in kerosene (I did not have a new filter) and that fixed it for about 9 months. I can hear the pump whine all the time now even while riding but don't have any power loss at higher RPMs but have a filter on order.
So I had a chance to install the new inlet strainer/filter on my Gen2 Wee (L4) and I am happy to report that all I can hear now is the fine whine of a Suzuki sewing machine instead of the fuel pump whine ;-) I also notice it seems to start and idles better and on the road seems to be more responsive to throttle inputs but these observations could all be placebo.
 

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Attached is a pix of my solution to have quick access to the Dealer Mode plug. Simply wired in a switch and mounted it where it was out of the way, but yet easy to get to without first turning off the bike.
 

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