Help a noob? '79 XS1100F

[DiverRay]

Yes, you have it all correct. You may find you need to go up one more size, but not a given at this time. If you DO need to go up on the main jet, you may then need to go up on the pilot jets as well. If you have to go above about 3.5 turns on the idle mixture, you are close to next size up on pilot jets. I do have a few sizes here, as I've done a lot of carb work over the years. Let us know how things are going with the tune, and I can try to send out parts if I have the correct size to swap in.

[jdub89]

Yes, you have it all correct. You may find you need to go up one more size, but not a given at this time. If you DO need to go up on the main jet, you may then need to go up on the pilot jets as well. If you have to go above about 3.5 turns on the idle mixture, you are close to next size up on pilot jets. I do have a few sizes here, as I've done a lot of carb work over the years. Let us know how things are going with the tune, and I can try to send out parts if I have the correct size to swap in.

Another question...I am getting ready to place an order on jetsrus.com. For the XS1100SF(my engine) the website states overall jet length of 8mm and head diameter of 6mm. My jets are 9mm and 8mm respectively which is the size that shows for the XS1100F but my engine VIN is for an SF. Safe to assume I should snag the size they show for SF? Could the PO have swapped the engine and kept the carbs from the F? How much of an impact could this have had on how my engine is running?

*edit..I might have been premature in posting this. Upon further inspection on jetsrus, the jet showing for the XS1100SF is Keihin. Can you confirm the 9mm and 8mm measurements are what I need for Mikuni?

[jetmechmarty]

Another question...I am getting ready to place an order on jetsrus.com. For the XS1100SF(my engine) the website states overall jet length of 8mm and head diameter of 6mm. My jets are 9mm and 8mm respectively which is the size that shows for the XS1100F but my engine VIN is for an SF. Safe to assume I should snag the size they show for SF? Could the PO have swapped the engine and kept the carbs from the F? How much of an impact could this have had on how my engine is running?

*edit..I might have been premature in posting this. Upon further inspection on jetsrus, the jet showing for the XS1100SF is Keihin. Can you confirm the 9mm and 8mm measurements are what I need for Mikuni?

Do you know what carburetors you have? You jet to the carburetors. Excuse me if this was covered. The SF does not have Keihin carbs. OE was Mikuni with aluminum tops and brass floats.

[cajun31]

Another question...I am getting ready to place an order on jetsrus.com. For the XS1100SF(my engine) the website states overall jet length of 8mm and head diameter of 6mm. My jets are 9mm and 8mm respectively which is the size that shows for the XS1100F but my engine VIN is for an SF. Safe to assume I should snag the size they show for SF? Could the PO have swapped the engine and kept the carbs from the F? How much of an impact could this have had on how my engine is running?

*edit..I might have been premature in posting this. Upon further inspection on jetsrus, the jet showing for the XS1100SF is Keihin. Can you confirm the 9mm and 8mm measurements are what I need for Mikuni?

The jets you want are for Mikuni carbs.

GENUINE MIKUNI AIR JET BS 30/97 Jetsrus are the pilot jet types you need. The size needed will be dictated by the type of carbs you have. I asked earlier for pictures of your carbs. We need to see them to identify them for you. Over the years and changes of hands these bikes go through many changes. You asked could someone have changed the carbs...yes absolutely.
MIKUNI LARGE ROUND MAIN JETS N100.604 Jetsrus are the main jet types you need. Again... size will be dictated by the carbs.

[jdub89]

Do you know what carburetors you have? You jet to the carburetors. Excuse me if this was covered. The SF does not have Keihin carbs. OE was Mikuni with aluminum tops and brass floats.

Yes I have Mikuni, but I don't know the carb series on these bikes. When I searched by bike model, jetsrus came up with Keihin jets. Thats why I got confused.

[jdub89]

The jets you want are for Mikuni carbs.

GENUINE MIKUNI AIR JET BS 30/97 Jetsrus are the pilot jet types you need. The size needed will be dictated by the type of carbs you have. I asked earlier for pictures of your carbs. We need to see them to identify them for you. Over the years and changes of hands these bikes go through many changes. You asked could someone have changed the carbs...yes absolutely.
MIKUNI LARGE ROUND MAIN JETS N100.604 Jetsrus are the main jet types you need. Again... size will be dictated by the carbs.

Thanks! The N100.604 is what I thought was correct. I guess I was moreso asking if there were different stock carbs between standard and special based on jetsrus pulling up different brand jets between the two. Mine appear to be stock 78-79 Mikuni carbs based on previous threads I have searched on here. My apologies but I haven't been able to get a picture of them yet.

And to answer your previous question...I believe they were the K&L kits but I cannot remember and yes the jets were replaced. Unsure if they were Mikuni brand. Gonna replace again so I know.

[jetmechmarty]

Yes I have Mikuni, but I don't know the carb series on these bikes. When I searched by bike model, jetsrus came up with Keihin jets. Thats why I got confused.

These bikes have been around a while. Parts got swapped. 1980 carburetors are still Mikuni but different. You need to be sure what you have before you buy jets. Are the floats made of brass?

[jdub89]

These bikes have been around a while. Parts got swapped. 1980 carburetors are still Mikuni but different. You need to be sure what you have before you buy jets. Are the floats made of brass?

Yes. Just got a photo from where I pulled the bowls off earlier.

[jetmechmarty]

Yes. Just got a photo from where I pulled the bowls off earlier.

Okay, those are ‘79 carburetors. Carry on.

[jdub89]

Okay, those are ‘79 carburetors. Carry on.

Thanks for helping confirm. Sounds like I need the N100.604 jets so I will get those ordered. Also have some new choke parts coming from Yamaha cause I lost one spring and both 1/8 ball bearings when I first broke these apart in 2020. No worries, I will get her right.

[cajun31]

Thanks for helping confirm. Sounds like I need the N100.604 jets so I will get those ordered. Also have some new choke parts coming from Yamaha cause I lost one spring and both 1/8 ball bearings when I first broke these apart in 2020. No worries, I will get her right.

Carburetor Facts - Models and Jetting - XS11.club Forums... just in case you haven't seen it.

[jdub89]

Carburetor Facts - Models and Jetting - XS11.club Forums... just in case you haven't seen it.

I did come across that, but thank you! Gonna clean these up, change the jets, and set float height. I'll report back with an update or more questions. Thank you all very much for the help so far!

[red bandit]

The only difference between the F & SF carbs is the choke handle and the emulsion tubes. On the F the tubes are all the same. On the SF the tubes that go in cylinders 2 & 3 have less holes. Less holes is less air making a richer mixture to help keep the two inner cylinders a little cooler.

[jetmechmarty]

The only difference between the F & SF carbs is the choke handle and the emulsion tubes. On the F the tubes are all the same. On the SF the tubes that go in cylinders 2 & 3 have less holes. Less holes is less air making a richer mixture to help keep the two inner cylinders a little cooler.

My concern was maybe the carburetors might have been from an '80 or '81 XS1100. These '79 carburetors have had work. The tees between the bodies are aftermarket aluminum with o'rings.

[jdub89]

My concern was maybe the carburetors might have been from an '80 or '81 XS1100. These '79 carburetors have had work. The tees between the bodies are aftermarket aluminum with o'rings.

Yes, I replaced those when I did the initial rebuild. Mine were heavily corroded and the rubber was mostly all cracked or missing. The carbs looked bone stock when I first pulled them off.