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my v - strom Losing power while driving.

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Hi, everyone.
i have 09 dl 650:)
In the past few months, I come across a phenomenon that I can't fix.
The whole story is like that.
While traveling at an average speed of 70 mph, I feel a loss of power in the throttle and torque of the motorcycle.
This is reflected in the fact that the last third of the throttle does not add power but only noise, but the motorcycle does not add speed.
When I release the gas handle a bit in the half of the throttle, the motorcycle returns to being strong.
I have this phenomenon for several months and after checking with several mechanics there are 2 indications.
What is causing this phenomenon is the change in air / fuel ratio.
What is causing this change is a fuel pump that does not emit enough fuel.
After my mechanic recommended replacing a pump, I bought an excellent Quantum pump, with good recommendations. After assembling the pump inside the pump housing and assembling the fuel tank, the motorcycle feels excellent and strong,
But after a few miles of administrative travel the problem recurs, and again the event becomes weak so that its maximum speed ends at 80 miles per hour.
After disassembly and the pump assembly the fault is resolved, it seems no problem, but again after a few miles there is again power loss.

After replacing lots of lots of money, a new engine imported from the bar, an air box, a fuel pump including a filter, and many other parts (the motorcycle went through a project to come back after a long neglect), I try to figure out what could make this phenomenon go away.
Each time I dismantle the fuel tank and return it, do a fuel quantity check for the pump, get 350 CC, after I return home from 100km ride do the test again and get 280 CC.
Is there a possibility that there is an electronic failure that leads to the pump not working properly after extended work?
What do you think can cause this phenomenon, I would love to hear from your experience, what can be done?

Thank you so much to everyone for every bit of thread that will help me overcome this phenomenon, after doing disassemblies and assemblies and injecting money into vain it is such a frustrating thing to deal with.
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If you open op the throttle, do the REVs increase? You can see this easily from the dial on the dash. If so, you will need to adjust (loosen) your clutch cable. And if this has been going on for a while, you may be suffering from burned clutch plates, who will then need to be replaced.

A fuelling problem would not just increase the noise, but also lead to stumbling/hesitation where the speed actually backs off. You may want to try the external fuel filter mod. External Fuel Filter modification

The cause of this could be rust in the tank that keeps clogging up the filters. See this as well: Sputtering and bogging down with attempt of full throttle issues!
 

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Clutch slip is a possibility, that would account for the noise and no power and as the oil heats up the slip becomes worse.

The cable on your bike must adjusted at both ends for free play and must be done correctly.

Also if it feels like fuel problems try it with your fuel cap open, there could be a blockage in the fuel cap vent, this will stop air replacing the used fuel causing a low fuel problem.
 
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Discussion Starter · #5 ·
Thanks so much for the comments.
The clutch is fine, I will say the fault again,
After dismantling and assembling the pump, after testing, the pump delivers 330 ml of fuel (three times the ignition actuation), after driving for several miles, when the motorcycle loses power, I come home and do the same test again, and the pump delivers 250 ml of fuel.
The noise I hear comes from the engine making a roar as the two butterflies of the throttle house open fully.
Usually this roar is not clearly heard because it reads at high speeds and the wind is very noisy in the helmet, but when the motorcycle does not generate torque it is clearly heard.
Hope I was clear. Thanks:)
 

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Sounds like starved for fuel. But your 3 x ignition cycle flow volume is still quite good. It needs to be much lower to cause problems. My 2004 WEE had 220 - 250 ml for 9 x ignition cycle. It did not rev over 6 k under load.

That being said I would get a fuel pressure gauge setup to verify that your pump gives the required pressure with the engine running. Actual flow volume is pressure dependent. Here (US) you can rent the test kit from an auto parts store. I made my own, was not so easy to find the components.

It is rare but not unheard of that the pump assembly pressure regulator malfunctions.
 

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Discussion Starter · #7 ·
Sounds like starved for fuel. But your 3 x ignition cycle flow volume is still quite good. It needs to be much lower to cause problems. My 2004 WEE had 220 - 250 ml for 9 x ignition cycle. It did not rev over 6 k under load.

That being said I would get a fuel pressure gauge setup to verify that your pump gives the required pressure with the engine running. Actual flow volume is pressure dependent. Here (US) you can rent the test kit from an auto parts store. I made my own, was not so easy to find the components.

It is rare but not unheard of that the pump assembly pressure regulator malfunctions.
Can you send me the details of the jit tgat you build please? Maby it will give me better indicetion
Thanks:)
 

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Something similar to this one:
Pressure Tester
You need to figure out what size you have on your bike. I think Fuel Line Quick Connector for 5/16 In

This is what I bought:
Lang Tools 74484 - 5/16" Quick Disconnect hose assembly with Quick Coupler Plug: Chrysler/Ford $ 27.90
http://www.langtools.com/sku-74484-5-16-quick-disconnect-hose-assembly-with-quick-coupler-plug-chrysler-ford/

Replacement Schrader valve stem 1/8”:
https://www.amazon.com/Control-Devices-Brass-Tank-Valve/dp/B0081TJO72/ref=pd_ybh_a_51?_encoding=UTF8&psc=1&refRID=FN4AM9F8FFPX3WA3A7T5
Control Devices Brass Tank Valve, 1/8" NPT
 

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Try your test again with the gas cap open, a blocked vent can cause your problem.
 

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Sorry to continue on an old thread but my 2006 v-strom dl650 is doing the exact same thing as the OP's bike. The lesser amount of fuel in the tank, the worse it is but ive just replaced the fuel pump, fuel pressure regulator, spark plugs and air filter. It was completely awesome on the first ride, couldnt wipe the smile off my face but the second ride after 10 minutes was exactly the same as it was. I used a kemso pump, quantum fuel reg, ngk iridium plugs and a k&n air filter.
The bike in the lower rpm is fine and it idles spot on, but you cant rev it past 6 or 7k in neutral and under load you can barely get it past 5k. Bike already had a kemso pump, i didnt find much silt in the fuel tank or in the pump when i removed it to indicate blockages, i originally suspected the pump was failing but 2 for 2 and the problem is still here. Ive had the pump out of the tank before as well, and it was the same with my bike that when put back together it was great for a short time but then goes back to bad. This is what made me think it was pump related in the first place, but new pump hasnt fixed it. Ive checked the vent tube, and its clear also.
 

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Your bike will not have a vent tube just a drain tube, they vent through the cap.

If the problem is there all the time it's not the vent but if it shows up as you burn down the fuel load it could be a vent problem but that should go away again after opening the fuel cap.
 

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Your bike will not have a vent tube just a drain tube, they vent through the cap.

If the problem is there all the time it's not the vent but if it shows up as you burn down the fuel load it could be a vent problem but that should go away again after opening the fuel cap.
Yep, you are correct. Its an overflow tube, not a vent tube. I honestly didnt look that closely at it, i saw it went through the tank to the hole next to the cap and i knew it came out of the bottom and down next to the foot brake lever but didnt pick up on the fact that it doesnt vent from the tank itself. 🤦‍♂️
Anyway, i can 100% report that opening the tank cap does not fix my issue at all because i just tried it. Ive been chasing this issue for a few months now, it still persents as a fuel flow issue to me because its inconsistant like there is something loose in a fuel line and it moves with pressure/flow, except it can never fully block because the bike has never stopped at any point even when its been at its worst. Once i couldnt rev past 3500 rpm it was so bad, but then after i took the tank off and banged the pump around a bit it was like new again for a while. Thats why it now has a new pump, and once again it was like new for a short time but now its no good again. I only did the pump and everything yesterday, and by last night it was no good again. There are no kinks in fuel lines either because i checked that too.
 

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I have only had the problem once, it was while on holidays I got a bad tank of juice, fresh fuel and a new pickup screen fixed it for good.
 

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Look on this forum for the "quick fuel flow test". There's an official one in the manual but it's kinda involved. There's also a quick fuel flow test developed on here that's easier to achieve. That will tell you whether you have a fuel flow problem or not.
 

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I have only had the problem once, it was while on holidays I got a bad tank of juice, fresh fuel and a new pickup screen fixed it for good.
Im about to pull the tank off and completely empty it out into a clear plastic tub to see exactly what comes out of it because right now i suspect its got water in it again. I noticed yesterday that when it was idling that if you crack the throttle a few times the problem cleared and it would clean rev up to redline, but it had a god awful stale fuel smell in the exhaust fumes thats a good sign of water! If this is the case it seems my new cap isnt sealing, and i replaced the whole cap assembly for this reason 6 months ago.
 

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Look on this forum for the "quick fuel flow test". There's an official one in the manual but it's kinda involved. There's also a quick fuel flow test developed on here that's easier to achieve. That will tell you whether you have a fuel flow problem or not.
Its got a brand new pump, and changing the pump didnt fix it. I replaced the pump, pump filter and the regulator all at the same time so i didnt have to pull it apart again but it was only good for about half an hour and the problem came straight back. I also replaced the plugs and air filter at the same time since it was apart and the plugs arent accessible without pulling half the bike apart.
 

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If you think water is getting past the cap you could cover it with a large flat magnet like a P plate.

It would be even better if you used 2, cut one into a ring to go around the cap, this will create a lip to force water around it then the second over the top like a roof.

If you are going to pull the tank off and empty it that would be a good time to test your cap theroy with a hose.
 

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I literally just had this issue on my new-to-me 2008 Wee. Luckily, a quick Youtube search led me to a video on adjusting the clutch which seems to have completely resolved it.
Hmm, if the clutch was slipping i could see that creating issues but this is like it hits a rev limiter at said rpm. It makes power fine up to this point, but then it just doesnt and wont rev either. Bike still does it in neutral as well, so i dont think it would be clutch related with my bike but i will still look at it just in case. Nothing else ive done so far has fixed it, and im running out of ideas.
 
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