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TRX850 Problem on quick throttle openings/Low RPM

Discussion in 'Technical and Troubleshooting Torque' started by MV, Jul 29, 2009.

  1. Hi all, having some problems with my TRX, if anyone's got some ideas, that'd really help, cos I'm all out! :(

    It starts & idles fine, (from cold) & is fine with smooth throttle roll on, but when you whack the throttle open, it bogs down. If I back the throttle off & then roll on smooth it works fine. Happens at all revs...

    The other part is, when it is warmed up, the idle will jump every now & then, like you've given the throttle a small blip, & will stall under 3K rpm when taking off. Small throttle opening don't really do anything, to get going I need to rev to 3/4K & slip the clutch a lot.

    It all started when I took the carbs off a couple of weeks ago to give them a clean, (found my throttle cable was frayed, so I ordered a new one) made sure to keep all the parts in their respective carbs etc, my Emulsion tubes & needles seem fine, & as far as I can tell, all of my vacuum lines are intact. Pulled the carbs down again last night, thought I had fixed it, because it was idling beautifully, but when I took it for a spin, no such luck

    Before this it was working fine, so I know it's something I have done, really frustrating.

    I think that's it, hope someone's got some ideas!
  2. Did you set the float level when you put the carbs back together?

    Did you do a balance?

    Both are very important for throttle responce.
  3. Err, no, haven't. (Only because I haven't worked out where to measure the floats from :oops: )

    I presumed they would still be ok, as I haven't changed either & it was running fine before I pulled it apart. Or is that faulty logic?
  4. Yeah you should set them. There is only a little metal tab in there and just getting the carbies onto the bench may be enough to adjust you floats a mm or so.

    Same with the balance. I had a similar thought to you one about balance. Then I did it and the off throttle responce was well improved.

    Now the carbies are back on the bike maybe just try the balance first.
  5. I take it the carbs have a float bowl drain?

    If so, you can connect some clear plastic tube to them and curve it to point straight up. With the drain plug backed out a few turns, fuel should fill the tubes to float level. This gives you an idea of level, and lets you compare them to each other without removing from the motor.

  6. I'll do both tonight & see how it goes, thanks for the advice guys. Hopefully it is just something simple like that.
  7. It's a good tip if your carbs have a spigot off the drain. Many don't unfortunately.
  8. Quote ibast
    It's a good tip if your carbs have a spigot off the drain. Many don't unfortunately.

    True, and hopfully these ones do. You can set yourself up if they don't, by getting a brass hose fitting that replaces the drain screw.
  9. They do have the nipples, should be fine.

    She's in bits at the moment, carbs arre pulled down, can't see anything awry.

    I'll check on the prices of emulsion tube with Yamaha tomorrow, cos they could do with replacing, then I'll check the fuel pump & tap, hopefully something will come of it.

    Tomorrow, balance carbs, check float levels!
  10. Well, I'm about ready to ride it off a cliff.

    Not really, but it's very frustrating. Carbs are pretty close, balance wise, so I left them alone, as far as I can tell the level is about spot on too... I will have to recheck the level tonight, still not 100% sure on where to measure from.

    Leaned out out the slow jet screw by half turn, made it run better low down, so I dropped the needle down one click, that made it worse again...

    Took it for a ride around the block, found out I hadn't seated the fuel line correctly, mainly because it was pissing onto the back tyre, it's a bit slippery that stuff. :shock:

    I drove again today. :cry:

    I'm going to replace the emulsion tubes, but they're a couple of weeks away. If that doesn't fix it, it's going to a professional.
  11. Replace the vacuum hose to the tank. I had a bike exhibit some of the symptoms you have noted. When it got hot the vacuum hose was leaking and letting the tap partially shut. This leaned the mixture, making the bike hot, etc, etc.
  12. Thanks mate, I'll check that out too.
  13. Ok, so I've got some results, I set the float heights PROPERLY, dropped the needle down, & fine tuned the idle jet screw to 1 turn out (I didn't want to go any leaner...), it's ridable now. & I pulled my best wheelie to date! :LOL:

    New emulsion tubes & a Factoy Pro Jet kit should be here next week, hopefully that should sort everything out!

    It's still a bit of pig own low, but a bit of clutch slip & a lot of revs sorts that out.