TRX "hunts" or "surges" at low rpm and no load.

[WR450FGreg]

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My TRX has done about 25,000km and is running stock gearing. It has Staintune mufflers on it with the inserts removed, which is the way I bought it.
I'm finding that it runs horribly around 2,500 - 3,500 rpm under no load, ie. kinda trailing throttle I guess you'd call it.
It surges terribly until I give it a bit of throttle, then it cleans right up and pulls like a train.

What's the general consensus on this?
I see that many have said in the past that the needle jets flog out to an oval shape and need replacing.
Is that still the popular opinion?
I just want to check before I start pulling it apart and ordering jets.

Thanks in advance,
Greg

[Con Rod]

fueling issue for sure, needle jets isthe most likely culprit, given you will be about 10% throttle I pressume so you are between the fuel screw and the needle

[dicky]

Bear in mind that it is the tubes that wear, not the needles.
I bought a Factory Pro kit and only used the tubes.
The FP needles are very different form stock and I re-used the originals.

[WR450FGreg]

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Thanks guys!

Ok, any suggestions on which needle jets to buy?

[Rod.s]

Well gent the Aust distributor has these kits in stock and at $45 per kit plus postage is a damn sight cheeper than any Yamaha dealer could offer them for
http://www.motorcyclespareswarehouse.co ... -parts-kit

[WR450FGreg]

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Thanks Rod, I'll contact them.

[WR450FGreg]

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Ok, kits ordered.

A bit of advice if possible please, from those in the know......

In view of the fact that I run Staintune mufflers, without inserts, which would no doubt "breath" better than OEM, should I consider running slightly richer than normal?
I never ride it hard or anywhere near max rpm, so I assume the supplied main jets will be fine, but what about the needles, maybe raise them one notch?

[dicky]

Stock TRX runs fairly rich.
You may find that dropping the needle 1/2 a notch (use a thin washer) or even reducing the main jet gives better economy with no reduction in performance.
I'd start by only replacing the emulsion tube (if the needle is still round) and then move on to adjusting the needle height or main jet as needed.
One issue that you will have is a flat spot between 2k to 4k, this is due to the stock ignition ECU.
The best $200 you can spend on a TRX is to replace the stock ECU with one from Ignitech.

[cobbadiggabuddyblooo]

Stain tunes are designed to run with std trx jetting.

[WR450FGreg]

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Update:

I took the needle jets (ok, emulsion tubes!) out and slipped the needles into them to see if they seemed ovaled.
They appear ok to me.
Is the ovaling normally significant or hard to detect?
I don't think I'd get the tips of my vernier calipers in there to measure the ovalness.

I've taken the plugs out too. They are quite black, so maybe the bike is running rich as has been suggested.
I might replace them for the sake of it, while the bike's apart, after gapping them to specs of course.

[Con Rod]

very difficult to see without a large magnifying glass. Replace them and start with the clip in the middle position and go from there.

Make sure your air filter is clean too

[WR450FGreg]

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very difficult to see without a large magnifying glass. Replace them and start with the clip in the middle position and go from there.
Make sure your air filter is clean too

Thanks Paul.
Yeah, I'm replacing everything that came in the kits for the sake of it.
I've got a new filter on it's way. I'm sure it's the original one in there at the moment.

Cheers,
Greg