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Worn needle jets?

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MexicanGringo

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Re: Worn needle jets?

PostWed Sep 22, 2010 10:47 am

Im going to have a closer look at the needle jets/needle seats (there seems to be some confusion to what they're called) Does anyone know how to remove without destroying them? Just to be clear im talking about the guide that the needle slides in & out of
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Neosophist

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Re: Worn needle jets?

PostWed Sep 22, 2010 12:01 pm

There pressed in and can't be removed easily, usually without destroying the carb.

The Mikuni 36mm carbs suffered this problem quite a bid, never come across it on Kehins before.

Can't even remember what size the NCxx carbs are.. I read 28mm / 30mm / 32mm for NC21/24.. so somethign around that size?

What do your plugs look like?

What needles do you have in it? it is usually after-market needles that cause increase in needle jet wear.

You may be right but I think your clutching at straws here..

http://www.factorypro.com/tech/needle_jet_wear.html

Factory Pro have a good article about Needle Jet Wear

Small bore engines, used at higher, smoother, more even intake pressure rpms, will perhaps never have enough wear to cause a problem.



Take the slide out and look down into the needle jet you'll soon see if it is worn or not.. no need to remove it.
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /


vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...
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MexicanGringo

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Re: Worn needle jets?

PostWed Sep 22, 2010 12:58 pm

The plugs are black, and just the furthest out tip of the electrode is tan. Needles are 8ZG, are these standard?

The wear looks just like the photos on that page, slight oval and plenty of play for the needles

*EDIT*

Run the bike just now with no filter, no fuel flows from the needle orifice at idle, but the slightest blip of throttle and i can see fuel spurt out on all orifices. This is normal right? the main jet should supply fuel from as low down as 2k?

Heres a photo of one of the needle guides
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Cammo

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Re: Worn needle jets?

PostWed Sep 22, 2010 10:37 pm

MexicanGringo wrote:Needles are 8ZG, are these standard?


No, they're hrc race parts. Certainly contributing to your problem. They're a fair bit shorter than standard needles so there will be more play in the guide compared to std needles.

Sounds like the carbs were set up for a track/race bike (hrc needles, 40 pilot jets). It might be worth checking the the emulsion tubes are standard. Specs of tubes and standard needles are in the jetting guide sticky post.

The main jets really only come into effect at 7-8,000 rpm.

Going back to standard parts will certainly help your running issues. Getting there! :grin:
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MexicanGringo

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Re: Worn needle jets?

PostWed Sep 22, 2010 11:12 pm

Cheers Cam, yeah thats a start now!... Il have a look at the emulsion tubes as well.

Is any fuel supposed to come out needle orifice below 7-8k?
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Cammo

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Re: Worn needle jets?

PostWed Sep 22, 2010 11:22 pm

Not sure mate, but I wouldn't get too hung up on it. Based on your description it sounds like they're working properly to me.

If the right bits are in the carbs and they're not too worn they will work!

When you get the standard parts in the carbs don't try to run it without a filter & airbox, it will just cause more headscratching with strange running symptoms.
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Re: Worn needle jets?

PostThu Sep 23, 2010 12:52 pm

Yep.. fuel will come out of those as soon as you crank the throttle.

They do look slightly worn but as Cammo said.. get them setup as stock first and see how they behave. ( you will need an airbox and airfilter :D then )

Since the race needles you have are a lot shoter than standard ones they allow much more fuel to come out sooner.

Check the emulsion tubes too :-)

I have some race ones for my ZXR.. they only have a couple of extra holes in them but dont' have richen it up...

Race bike at once stage judging by the HRC setup (larger pilots to fix the big hole caused by open airbox / huge jets)
xivlia wrote:i dont go fast on this bike so really do not need a rear brake.. /


vic-vtrvfr wrote:Ask xivlia for help, he's tackled just about every problem u could think of...
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