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Loss of power/spluttering

Discussion in 'Technical and Troubleshooting Torque' started by ibanez, Sep 5, 2013.

  1. I've got an issue with my Honda vt250c that I'd like some advice on. The issue is the bike splutters/surges and loses power while accelerating.

    It started while riding on the highway when I knew I was very close to having to switch to reserve, the bike started spluttering like it does when it runs out of fuel so I switched it to reserve but the bike never picked up speed like it usually does after going to reserve.

    I filled the bike up and the problem stayed. While accelerating it sputters and has no power. It idles fine and revs fine while sitting in neutral. The problem only happens under load.

    I've checked fuel lines, drained tank and checked tap, looked at the air filter, changed plugs and checked the battery. I tend to believe its electrical and it starting around the limit I get out of my fuel before reserve might just be a coincidence.

    Any advice on the issue and what else to check?
  2. Sounds like a fuel delivery problem, maybe carbies need servicing
  3. when you drained the tank..... did you check the breather hose?

    when it starts to do it... stop, open the tank and see if it sucks in air, then see if it runs properly again... if it does then its probably the breather not the fuel supply line.

    otherwise buggerred if i know im trying to sort out similar issues on my cbr... fuel pump perhaps???
  4. Yeah could be. Carbies are out of my knowledge though.

    Will also do what you suggested trd2000
  5. It's a fuel delivery issue. You might need to back flush the fuel tap (flush from the outlet through to the inlet and out the pickup screen) to make sure it's not silted up. You could also have gotten water in the fuel and/or the carby filters are choked with silt. Fuel system cleaner MIGHT help but best bet is to clean out the carbs manually. Take it to a mechanic if you're not confident.
  6. If it is the carbies does it sound right that in neutral I can rev it full throttle and it doesn't skip a beat. But when in gear riding it splutters and surges while accelerating? I had almost exact symptoms on a previous bike which turned out to be a faulty coil. Just waiting on a multimeter to check coils.
  7. If it is a partially restricted main jet, then yes they will sometimes rev normally in neutral, but will struggle under load. A teaspoon of water in the carb will cause same problem so try just draining the carbie fuel bowls first. You never know, you might get lucky with the draining, and if something is blocking a main jet, it might get flushed out.
    • Agree Agree x 1
  8. Going to have to investigate the carbies more. There is no fuel filter on the bike I discovered. So maybe something down the bottom of the tank made its way down the line and has clogged a jet. What's the best way to check? Pull the carbies apart I suppose?

    Thanks for all the help and suggestions. I thought it was electrical but the more I listen to you guys I'm thinking carby.
  9. To get in to the jets you're really going to need to pull the carbies out. Try draining to float bowls first, it might be all it takes and is far easier.
  10. Will try that. Thanks.

  11. Even though there is no external fuel filter, most bikes usually run fine mesh filters on the fuel tap pipes inside the tank. Because of these filters, I suspect any large particles would most likely get into the fuel bowl via the breather pipes. The fine mesh would not stop water or the really fine silt though, just the larger stuff big enough to block jets.

    There should be a drain screw somewhere near the bottom of each the fuel bowl. Some only need unscrewing half way, and the fuel drains out the overflow pipe. Sometimes if you've unscrewed it halfway & fuel doesn't drain then you need to remove the screw completely & gently tap the fuel bowl or poke a wire in the screw hole, as they can sometimes block up with silt. The fuel tap needs to be off when you do this so that you only drain the fuel from the bowl initially. Once fuel flow has stopped, I will then turn fuel tap back on again for a few seconds while drain screw is still out, firstly so that the fuel from the tank might further flush the fuel bowl, but secondly to check that the fuel actually flows from the tap readily.

    If after doing this the bike still runs poor, then unfortunately the next step is to remove & clean carburetors. One way to test if it is a fuel prob is to start accelerating till problem occurs & then pull choke on. If problem improves with choke on then that is one indication, though not conclusive. Another way is to spray aerostart /start ya bastard/ ether into airbox while problem is occurring to see if it improves. This might be difficult if not dangerous to do, if problem only occurs while riding.

    Your problem may well be electrical, just less likely than a carburetor issue.
  12. Depending on the bike there may also be fine mesh or sintered bronze filters inside the carby. If fitted you usually have to remove the float bowl and take out the float valve, needle and seat to get to it. Not all have it though. These filters can be washed out in a jar of clean fuel or by spraying something like WD40/CRC 5.56 though them to wash out any fine silt. WD40 etc aren't the best spray carby cleaner by any means, but they work for some things.
  13. Thanks Tinkerer I'm going to take your advice and follow your instructions. Thanks also to Dark Angel for your input again

    I'm full on a work at the moment, even over the weekend, leaving in the dark and coming home in the dark. So when I get some time next week i will have a good look at these carbs. I will definitely update you guys that have helped what the outcome is.
  14. UPDATE.
    Bike is fixed. Was dirty/blocked carb like all you guys suspected. Took it to a dealership to be fixed. Before I took it in I had one more tinker, I undid the screw in the bottom of the fuel bowls, one carb fuel came out, the second no fuel till I gave it a few taps. That pretty much confirmed it was dirty in there.

    I was a little disappointed in the dealership though. They charged me for 2 new spark plugs ( I just replaced them when the problem started. They had only down about 10km, from home to the mechanic, surely they still looked new. Secondly they set the idle WAY to high, turned it back 1/2 a turn now its right. Also came back with a screw missing from the air cleaner cover.

    Anyway is all fixed. Won't use that place again. Have since found a guy with a home workshop that charges 1/2 the labour rate. A few mates recommend and vouch for him. Thanks for all your help guys.
  15. I have a similar issue, and My mate who has worked on carbies since he was a young one with his dad helped me, it has helped quite a bit but I still find I get it on cold mornings, like the engine doesn't like the cold air, but definitely try taking them out and giving them the once over. ​
    I might even suggest taking a look at the fuel tap seals and stuff like that if your taking in extra air there then that may do it ​