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Stock Carb Rebuild Kits (Read 160 times)
DragBikeMike
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Stock Carb Rebuild Kits
01/02/22 at 16:54:57
 
I thought I would start off the new year with a post that may prove useful.  A few weeks back, B-Will did a post on a carburetor problem he was having.  The title of his post was “Just Idle Talk”.  He eventually figured out that the wrong mixture screw was installed.  

I was looking for a PWK carburetor kit and I noticed there were a ton of kits for the stock LS650 Mikuni carburetor.  I constantly see posts where members are having issues related to bogus carburetor parts.  I saw a kit that looked pretty good, and it was only $10.64.  I figured why not order one of these cheap kits and see what’s up.  I have no plans to rebuild my stock carb, but the kit was so cheap that I thought it would make an interesting project.  I will try to point out the important features to be aware of.

I ordered the kit from eBay (seller “All_About_Carburetor”).  It arrived in my mailbox about seven days later.  So far so good.
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DragBikeMike
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Re: Stock Carb Rebuild Kits
Reply #1 - 01/02/22 at 16:55:53
 
The kit came packaged in a nice cardboard box, but there was absolutely no information that could connect the kit to a manufacturer, distributer, or seller.  Always a bad sign.
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DragBikeMike
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Re: Stock Carb Rebuild Kits
Reply #2 - 01/02/22 at 16:56:36
 
Even the return address on the mailer provided zero info as to the origin or pedigree of the contents.
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Re: Stock Carb Rebuild Kits
Reply #3 - 01/02/22 at 16:57:51
 
This kit comes with a lot of parts, and zero instructions.  If you purchased all these parts from an online Suzuki parts distributer, it would set you back about $203, and then you would have to add shipping charges.  Lord knows what a local Suzuki dealer would charge.  The Big-Ticket items are the needle valve assembly (OEM $70.45) and the needle jet (OEM $40.45).  The OEM bowl gasket alone costs $10.45.

Just look at this sack of parts.  What a bargain.  Only $10.64 for the whole shabang.
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Re: Stock Carb Rebuild Kits
Reply #4 - 01/02/22 at 16:59:12
 
There’s an old saying.  If it sounds too good to be true, it must be too good to be true.  

I view a carburetor “Rebuild Kit” as an item that will restore the mixer to factory specifications.  A rebuild kit should have parts that match the design, dimensions, and quality of the original equipment parts.

So, now I have this rebuild kit with all brand-new parts, and I also have all the matching OEM parts.  Let’s do a comparison and see how the kit stacks up against the genuine parts (design, dimensions, quality).

We’ll start with the part that gave B-Will headaches, the idle mixture screw, identified on the illustrated parts breakdown as “piece 41, screw, air, P/N 13269-37400, $10.39”.  I started with this part because it’s a dead giveaway that will identify a worthless kit.

Look at this jewel, complete with a plastic cover to protect the needle tip.  Totally top-notch stuff?
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Re: Stock Carb Rebuild Kits
Reply #5 - 01/02/22 at 17:00:29
 
This picture shows the OEM screw compared to the new kit screw.  The OEM screw is the shorter item, the one on top.  When you look at pictures of a potential rebuild kit, if it has a mixture screw that looks anything like the screw on the bottom, STOP, don’t waste any more time or money.  The kit is junk.  You want a screw that looks exactly like the screw on top.
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Mix_Screws_Stk_Top.jpg

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Re: Stock Carb Rebuild Kits
Reply #6 - 01/02/22 at 17:01:13
 
Not only is the kit screw a lot longer, it also has a different size tapered needle tip, and the straight shank portion where the o-ring normally rides is not straight.  So, the needle tip isn’t gonna throttle fuel because its only half the diameter of the OEM needle tip, and the o-ring won’t seal the shaft properly.  It’s complete junk, totally no good, unsuitable for this application.  Check out this close-up of the needle tips.  Good on top, bad on bottom.
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Re: Stock Carb Rebuild Kits
Reply #7 - 01/02/22 at 17:01:59
 
If you have a carburetor with a mixture screw that looks like this when it’s bottomed out, then you probably have one of these bogus mixture screws.  See how it’s almost flush with the carb body, that’s no good.
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Re: Stock Carb Rebuild Kits
Reply #8 - 01/02/22 at 17:02:42
 
The correct mixture screw looks like this when it’s bottomed out.  It’s well down into the carb body.  B-Will pointed this out in his prior post.  Great observation.
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Mix_Screw_Bottomed_Stock_Normal.jpg

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Re: Stock Carb Rebuild Kits
Reply #9 - 01/02/22 at 17:03:34
 
Next, let’s look at the jets that come with the kit.  The early models came from the factory with a #155 (.061”) main jet and a #47.5 (.019”) pilot jet.  Then, in 1995 the jetting was changed to a #145 (.057”) main jet and a #52.5 (.021”) pilot jet.  The new main jet and new pilot jet that came in the kit have no markings.  You can’t tell what size they are unless you measure them.

Oh my!  The new pilot jet is only .015”.  That’s equivalent to a #37.5 Mikuni pilot jet (at least 4-sizes too small).  That’s gonna be tough to dial in.  Note that the .015”pin-gage is skewed, the only sloppy workmanship I found on all the parts in the kit.  The jet looks just fine at first glance, but inspection indicates it’s not suitable for this application.
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Re: Stock Carb Rebuild Kits
Reply #10 - 01/02/22 at 17:04:52
 
The main jet is also grossly under size.  It is .045”.  That’s equivalent to a #115 Mikuni main jet (at least 13-sizes too small).  A one-way ticket to melt-down.  At least the pin-gage isn’t skewed.
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Re: Stock Carb Rebuild Kits
Reply #11 - 01/02/22 at 17:05:49
 
The kit comes with another jet that has the correct geometry for pilot air jet number 1 (piece 12 or 46 depending on model year), located in the top of the carburetor.  That should be either a #70 (.028”) for the early LS650s, or a #45 (.018”) from 1996 on.  The jet provided in the kit was .052” which is equivalent to a Mikuni #132.5.  I suspect that would make the afterfire akin to a July 4th celebration.  Chop the throttle and KaBooooomerooo!
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Re: Stock Carb Rebuild Kits
Reply #12 - 01/02/22 at 17:06:44
 
OK, so none of the new jets are gonna work.  We can live with that.  Maybe we can use them on a pit bike or a lawnmower.  The air jets don’t wear out or get plugged up, so they can usually be reused.  The fuel jets are readily available from Sudco or Jets-R-Us, we know the correct sizes, and they are cheap.  Forge ahead.

Howzabout the needle valve assembly?  It’s identified on the illustrated parts breakdown as “piece 19, valve assembly, needle, P/N 13370-24C80, $70.85”. The filter, piece 20 and it’s associated o-ring, piece 21 cost an additional $15.  Do the parts provided in the kit meet expectations?  The needle & seat assembly looks pretty good.  I put the needle into the seat, and it passed the “blow with mouth” test.  Should hold fuel.
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Re: Stock Carb Rebuild Kits
Reply #13 - 01/02/22 at 17:07:28
 
The needle has a soft tip and it’s not screwed up.  The little springy pin works smooth, and the spring inside is springy.  It looks exactly like the OEM needle.
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Re: Stock Carb Rebuild Kits
Reply #14 - 01/02/22 at 17:08:11
 
The screen looks good.  That part alone costs $9.60 if you get genuine stuff.
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