XS650SK Carburetor Jetting Confusion

jetmechmarty

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I just dismantled my carburetors. I can't remember the last time I was in them, because I don't keep records. I expect it has been twenty years or more.
Here is what I found. The main jets are #137.5 The pilot jets are marked "30".
My genuine XS 650 SJ Service Manual says Main jet #135. Starter jet #80.
My parts catalog says Main jet #135. Starter jet #42.5.
On the first page of XS650SK 1983 SERVICE DATA the carburetor jetting is listed as 132.5/42.5.
:umm:

OK. The bike is running OE airboxes with K&N filters installed. The exhaust is OE with the baffles knocked out. This bike almost always starts on the first kick, even after sitting for months at a time. Since the top end was pretty worn out, the spark plugs are black from excessive oil. I did not detect signs of running lean. 45 to 50 mpg.

At this point, I don't know whether to leave well enough alone or rejet to the SERVICE data. :shrug:
I have no clue how it came to be where it is. Please advise.
 

GLJ

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I would leave well enough alone for right now. Clean the carbs and use. If it it ran well before it should again. If it doesn't run right then play with the jetting.
 

Jim

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Stock was 42.5 on the pilot and 132.5 on the main. Since your intake is basically stock with an open exhaust, I'd start with 45/137.5 and adjust from there.

BS Carb Jetting.png
 

gggGary

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The BS34 were EPA carbs so were set pretty lean,After consulting with 5twins I usually go up 1 or two on mains and pilots, and use the needle washer mod. I've found these to be really good running carbs with a bike set up about like yours.
650carbspecsreducedsizeey7.png
 

jetmechmarty

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The starter jet marked "30" really baffles me. I know the PO. It was me.

USPS has some critical engine parts held hostage, so I have a little time to get this close.

Open exhaust means I knocked the two disks loose in each of the mufflers. It's still quiet that way.
 

Jim

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Fwiw... running pod filters and EMGO commando's. I'm at 45 pilot and 137.5 on the main with Gary's washer added to the needle. Seems about right for my setup.
Also just thought... I'm running the GN250 iggy retarded to about 35°
 

jetmechmarty

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Marty, there may be some confusion over terminology. The starter jet isn't the same as the pilot jet. The starter jet is the orifice in the enricher valve ("choke") assembly. AFAIK it's fixed.
Thank you! Yes, the PILOT JET that lives under the rubber plug is the one marked "30". I verified with a 10X magnifying glass.

Since this is Covid Times and my wife is here stuck with me, I'm often telling her stuff she cares nothing about and she often reminds me of that. At our last home I worked on a few bikes that belonged to others. So, she asked me, "What would you do if it was Curtis' bike?" Wow, good question. The answer is, I'd put it to stock.
 

jetmechmarty

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Another issue is that I can not remove the float needle seats. The screws won't turn and "somebody" in the past used a #2 phillips driver on them. So, this time, they're going to stay where they are.
 

Jim

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Another issue is that I can not remove the float needle seats. The screws won't turn and "somebody" in the past used a #2 phillips driver on them. So, this time, they're going to stay where they are.
I've used a cutoff wheel on a Dremmel to cut a slot for a flat head screwdriver.
If those o-rings are original, they're most likely the consistency of hard plastic by now.
 

jetmechmarty

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I've used a cutoff wheel on a Dremmel to cut a slot for a flat head screwdriver.
If those o-rings are original, they're most likely the consistency of hard plastic by now.
I was shocked by how pliable the chevron seals on the butterfly shafts are. They were never out before. The float valve, I'm not so sure. The pieces are all going into the ultrasonic cleaner and I hope that helps with the stuck screws.
 

jetmechmarty

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Butterfly Shaft
Have any of you sourced a quantity of butterfly shaft seals? The cheapest I've found are $3+ per each. I'd like to have a bag full of them, or at least enough to have them on hand.

 

gggGary

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Butterfly Shaft
Have any of you sourced a quantity of butterfly shaft seals? The cheapest I've found are $3+ per each. I'd like to have a bag full of them, or at least enough to have them on hand.
BS34 carbs
Throttle shaft seal Suzuki part # 13651-51010 SEAL
I replaced the butterfly shaft seals with these Suzuki seals they fit perfectly. Cost a dollar less than the Yamaha seal .....
http://www.boats.net/parts/detail/suzuki/S-13651-51010.html 5twins tip
 
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Jim

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jetmechmarty

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$1.72 at Partzilla here.
$1.23 at Part Shark here.

If I use Partzilla, my recent experience says it will be March when I get my parts. Part Shark offer Priority Mail or UPS shipping. My current order is lost or detained by USPS. :(

Years ago, before I had internet or computer, I needed Chevron seals of the same style to overhaul my brake master cylinder to my 1966 Ford Thunderbird. I bought the required batch and put kits together for folks in the club. I can't really remember how I pulled that off, but I did.
 
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