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foxz

best aftermarket fuel/air mixture screw

30 posts in this topic

Ive been told a number of times that the zipty are crap so what after market gives you the best accuracy... id like too adj on the fly and stocker you cant.. ive seen eddie talk about the brass one made by merge.. any one else have any sugestions?

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I use the Zip-Ty and had no problems with it. I do put a little silicone on the threads so it doesnt back out.

I found this out with my sons bike. We lost that one at a track last year. The bike would idle. We did have a spare seal, spring, washer and screw.

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Best screw is the Merge Racing one. Brass screw with a plastic paddle handle. Perfectly machined tip, cannot burn your fingers and easy to turn.

Next best is the Kouba brass. Identical screw to the Merge (though I think the machining quality on the Merge is higher), uses a roll pin as a handle.

James Dean is now making a screw and I have not gotten one yet, but I suspect it is as good as the Kouba, mabe even the Merge.

Next on the list is the Kientech. This screw is identical to the Kouba but the screw is made from stainless steel.

There are a few others that are supposed to be good too but as I have never had them, I cannot say either way.

I prefer a brass screw. Material is the same as stock, is more compatible with the brass seat.

Mosdt of the alloy ones generally should be avoided. I am no machinist, but it has been expalined to me (reasons I do not fully understand) but the tips tend to be slightly tapered. This can cause the tiop to become 'wedged' in the seat. Being soft alloy, the tip can easily break off. I muist hear about a few carbs turned into paperweaights every month because of it. Finally, because of the tapered tip, the metering provided is not the same as a stock or one of the 'good' screws on my list. Because of this, many have hasd to go down in pilot ket one or two sizes to compensate. I prefer to run a large pilot vs. a small one as a larger one is less likely to get clogged.

My $.02

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I have no problem with either of the two Zip-Ty screws I have, BUT...

I use the original Yamaha spring instead of the one provided with the screw. The ZT spring is not strong enough to hold the screw, the stocker is.

Some AM screws are made somewhat differently at the tip than the original, and may meter poorly because of it. But anyone seating a fuel screw hard enough to stick it into the seat is doing things wrong in the first place. All you need to do is find out where the bottom is, not tighten it. Even with a brass screw, this runs the risk of distrorting the tip of the screw and the seat.

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from the zipty unit i have from the threads up, its shorter then stock, the tip is machined diff its skinnier adn shorter...and the second little unit b4 the tip isnt tapperd i dono if that makes a diff... i think i got a shitty one lol

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for the merge units.. there isnt a bike kind too pic..granted its for fcr im guessing... are they all the same... my 01 426

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All FCR's use the same EXTENDED screw.

Was just thinking, a lot of companies make the same part, must be good margins in them.

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All FCR's use the same EXTENDED screw.
Actually, not.

All FCR-MX units do, but the earlier FCR used on '98 400's used a different length screw. The length is different from thread to tip.

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So Gray, all the information I have gotten from all the manufacturers is wrong, that the fuel screws are not all interchageable on all the FCR's? That there are two different length screws and they are not interchageable?

If so, I would think there'd be a lot of complaints from people and I have never heard of any.

You know me, I love being right and I love being corrected so next time, I am right! :)

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I like my R&D FlexJet screw. Its really easy to get to and make changes that are repeatable and fast.

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So Gray, all the information I have gotten from all the manufacturers is wrong, that the fuel screws are not all interchageable on all the FCR's? That there are two different length screws and they are not interchageable?

If so, I would think there'd be a lot of complaints from people and I have never heard of any.

You know me, I love being right and I love being corrected so next time, I am right! :)

The details escape me temporarily, but I distinctly recall there being an issue with the very early FCR as used, I believe, on the '98 model being different from the rest. It seems to me that it affected so few carbs that from a practical standpoint you would be right, but I'm sure that it has come up and been discussed here at least once.

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