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SaltyWalrus

Stupid newbie needle jet question

14 posts in this topic

Bought a new left-over 01 XR650R for $3999. Very excited! Bought Baja Designs dual sport kit, uncorking kit and Uni filter. 15 years ago, I had an 87 XR600 so kinda familiar with uncorking. Question: the needle jet (not the needle itself, but the jet with one tapered end that goes in under the main jet and needle jet holder) does not fit. It is too big for the diameter of the appeture it is going into and will not go in far enough to allow threading of the needle jet holder. Did Baja Designs send me the wrong needle jet? Do I have to increase size of appeture? I half remember seeing something about using a drill to increase size of the hole. Thanks for your help!

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I believe you should have received a new Needle Seat with that kit. It comes with the Honda part. Try going direct through Honda. I've heard those pre-made kits don't always work out.

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Yes, that is the thing that doesn't fit. The needle seat (or needle jet). So it should fit without any tampering, huh?

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Have you removed the carb or are you trying to do this with the carb still on the BRP?

I had a problem doing this with the carb on the BRP and had to remove the carb to get the needle jet to drop into the cavity correctly.

Editing: P.S. The needle jet goes in small end first.

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Idealy fit without tampering...Can someone answer another question...It may save you some trouble if I remember correctly but I want someone to verify first.

I thought I remembered someone saying that the needle jet doesn't change and that even with honda part the needle jet is same as stock...its the needle taper that changes they just send a needle jet with it but it doesn't have to be switched out?

Its been a few years and I don't remember I know I changed it just because and didn't know the difference but it was also before I started reading on TT.com.

JT

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You are correct. I compared them when I got the Honda Hop-up kit and they are the same.

So SaltyWalrus can use the old one.

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Cool. That saves some trouble. I appreciate all of your help. Now if I had only been smart enought to order the gasket kit and the 68s pilot, I could put her back together!!!!

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Just an FYI, I talked to Baja Designs (who I haven't been overly impressed with, but this guy seems to know whats going on) and THEY said both the needle and the needle seat (or needle jet) and the needle are different.

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Question: the needle jet (not the needle itself, but the jet with one tapered end that goes in under the main jet and needle jet holder) does not fit.

Something wrong here as the jet needle actually slides in and out of the needle seat but it is not under the main jet but rather it is on top of the main jet.

It is too big for the diameter of the appeture it is going into and will not go in far enough to allow threading of the needle jet holder.

something wrong here also. The new hop up needle is actually tapered thinner than the stock jet needle. If you were to use the old needle seat it should slide in easily as the hole should be the same size or too big. Also some folks have reported using the stock seat with the hop up needle with successful results.

Also what do you mean by

threading of the needle jet holder

the needle jet is held in place and adjusted by a clip and is not threaded on in any place at all. It has grooves and clip positions.

Do I have to increase size of apperture? I half remember seeing something about using a drill to increase size of the hole.

Do not drill any hole larger. I think perhaps you have something installed incorrectly. Are you trying to put the jet needle into the main jet hole?

Think of things this way the main jet is at the bottom and it sucks gas into the airstream from the float bowl. The jet needle and seat sit on top of the main jet and plug off this flow of gas forcing the pilot jet to feed the motor at idle. As the throttle is opened the jet needle is pulled off of the needle seat and starts to allow gas to flow from the main jet into the airstream. This is where the taper of the jet needle contols the flow of gas between it and the sides of the needle seat. This is why the jet needle controls the jetting from partial throttle to about 3/4. This is also why adjusting the clip position of the jet needle changes your air fuel mixture and it leans or riches it. At full throttle the jet needle is no longer restricting the flow of gas from the main jet and it flows into the airstream unimpeded.

Pretend you are the little dutch boy with his finger stuck into the dike plugging the leak. The water on the other side is the gas. The hole in the dike is your main jet. The front edge of the hole is the needle seat and your finger is the needle. As long as you hold your finger in the hole tightly no water comes out. If you pull your finger out just a little bit the water starts squirting out around your finger but you are still restricting the flow. the more you pull it out, the faster the water flows until it is out all of the way and then the water squirts out as fast as the hole will allow.

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Thanks for the lesson if fluid dynamics. Perhaps I was not clear enough in my hasty posts. You confused many of my comments about the needle jet (or seat) with the needle itself. Yes, the needle jet is "above" the main jet, but when installing, the carb is held upside down. Drop the needle jet in and secure by screwing in the needle jet holder which in turn receives the main jet.

Anyhow........there must have been a slight imperfection in the needle jet. After making sure it was a Honda part with correct part number, I very lightly chamfered the outer diameter of the needle jet with emery paper and it dropped right in. Thanks everyone!

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Hey SaltyWalrus,

Did you happen to compare the two Needle Jets? What did you see in the way of differences?

Glad you solved the install problem. :D:)

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I didn't really notice any difference. The new one may be a bit more narrow near the tip. I didn't compare for more than a couple seconds as it is cold in my garage and I was trying to button things up.

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shoyz28,

Are you an old TTer with a new name or a new TTer?

If new then welcome. If returning to TT then Welcome back.

Thanks for bringing that picture along from the Pig Pen. Eric Foster is a great person and has an amazing personal story.

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