Ok I have a jetting question about 120 jets on my 79 Special

[JeremyL]

I didn't see where it said 79 on the frame, I just made sure the vin matched and the title says 79.

I didn't realize the motor internals were different in 79 vs 80. hope that doesn't make this a nightmare. We just had a baby so I'm barely having time to clean and slap the carbs back on let alone spend lots of time tuning this thing. Might have to just buy some 80+ carbs if it's going to be a big mess. I just hate to have to do that too.

Not sure what to search for either... Trust me I tried but am not sure what to type in. What I've tried doesn't show much that helps.

[foreda]

No worries!

Don't sweat it, the carbs will still work! You will just need to dial them in with the proper jets which would be 137.5 mains for the older carbs.

[DiverRay]

You will need BIGGER JETS than 137.5 unless you fix the exhaust! These bikes run best with some back pressure! I would use 140 mains to begin with, and you may have to up the pilot jets as well.
Check with some of your local bike shops and see if they have a baffle that will fit, or go to a muffle shop and have them put something inside the baffle, like a cheap "resonator".

[foreda]

Don't sweat it, the carbs will still work! You will just need to dial them in with the proper jets which would be 137.5 mains for the older carbs.

137.5 mains are for stock exhaust. You will need bigger with after market headers.

[JeremyL]

Thanks guys.. I'm going to pickup some jets tomorrow and I"m not sure what to get. I have a MAC replacement baffle coming tomorrow, but I got the "Competiton Baffle" instead of the stock one. I figured since I got kinda used to it being open and super loud that the stock MAC baffle would be too quiet. So I will still be running a 4-1 but this time with a baffle (although it's the comp).. so maybe 140? I think everything else is stock... didn't see holes drilled in the airbox or anything.

[yamahansolo]

140s is a good starting point. I am still curious though if the Von number on the frame matches the one on the motor if not is the frames Von number a 79 or 80. Thus will help you to know. Could have been an early 80 and they stuck 79 carbs on it... no telling. Mine was one of the 1st 500 79s built in 78. And the jets are closet to the 78 than 79.

[petejw]

while u have the carbs apart,
u might want to check that the float heights
are correct as they are different between early and later
model carbs.

early carbs 25.7mm
later carbs 23mm

jat.

[JeremyL]

140s is a good starting point. I am still curious though if the Von number on the frame matches the one on the motor if not is the frames Von number a 79 or 80. Thus will help you to know. Could have been an early 80 and they stuck 79 carbs on it... no telling. Mine was one of the 1st 500 79s built in 78. And the jets are closet to the 78 than 79.

Yeah I haven't really thought of that. I need to find that page again with the engine serial numbers and stuff.

[JeremyL]

while u have the carbs apart,
u might want to check that the float heights
are correct as they are different between early and later
model carbs.

early carbs 25.7mm
later carbs 23mm

jat.

Good idea. I really don't want to have to pulls these off again. That's why I was wanting to skip a 137.5 too so I hope I'm close to running good when I put them back on.

[JeremyL]

Ok I finally checked my vin on the frame. So looks like this is what I got:

Frame: 1979 XS1100SF 3H3-000101
Engine: 1980 XS1100SG 3J6-000101

What's the difference in SG and SF? Is the SF the Special?

[natemoen]

Ok I finally checked my vin on the frame. So looks like this is what I got:

Frame: 1979 XS1100SF 3H3-000101
Engine: 1980 XS1100SG 3J6-000101

What's the difference in SG and SF? Is the SF the Special?

if the letter designator is a single letter e, f, g, h it is a standard. Each letter is a different year, e is a 78, f is a 79 and so on.

If it is a special then the letter s get put in front of the year letter i.e. sf for a 79 special.

Once the midnight specials came out then instead of the s they used an L i.e. LG for a 80 MNS.

[yamahansolo]

Interesting both end with 101. That means it was a really early 79 frame. Maybe since it had 79 carbs you got a weird combo. What are the odds that the motors is a 101? Has to be astronomical ...

[yamahansolo]

Hey... wait a min.... if your is 101 then you have the first special made... if you look up by the steering head you should see a label and also an etched number... I know you said your tittle says 79 but I have see the titles be wrong.
Could it really be you found the number 1 special?

[JeremyL]

Sorry it's not really #1 lol. I wasnt thinking and just copied and pasted the spot from the engine Id link. I was mainly concerned with the first three numbers/letters and didn't even look at the actual serial number spot. And no, they don't match at all...

[JeremyL]

Ok I ordered some 140 jets today. Figured with the 4-1 that has the newly installed "competition" baffle (came today) that I should prob go ahead and go up from stock. I'd hate to slap these back on and it still need a little more jetting so I'm lazy and am skipping ahead to 140.

But I also decided to look at the ignition wires tonight and I didn't pull out my multimeter but I stretched the wires and wow they're just like gummy and stretched out really far. I expected them to be hard and brittle and maybe break. I pulled them out maybe an inch or two so it's gotta be arcing or not even going at all. So I'm kind of excited. New proper jets, baffle installed, and now the ignition timing advancer deal will be fixed, it'll be like a new bike. I can't wait. Sanding and repainting the entire exhaust and gonna change the oil while I'm at it. Guess I need to start reading about the ignition stretchy wires fix. I'd rather do some soldering than work with carbs.

Thanks again guys. If it wasn't for this site my bike would never run right. The service manuals are so overwhelming but this site gives you information a little more organized and personal. Anyways I'll definitely be donating some.