Just wanted to double check.

[e30 gangsta]

Hey guys I just had a question on jetting. I am using this guide and I am a little confused on the pilot jet.

http://www.xs11.com/forum/showthread.php?t=382

My math for my bike gives me a 147.5 main jet, and either a 45 pilot, or a 47.5.

It says to go up 1 pilot for every 3 jet size increases, which would be 45, but I went up a total of 4 jet sizes. So its a little more than 1 jet size. Basically I want to make sure that a 45 pilot jet will be ok? Thanks.

Bike is a 79 special, with pods, and a 4 into 1.

[motoman]

Hey guys I just had a question on jetting. I am using this guide and I am a little confused on the pilot jet.

http://www.xs11.com/forum/showthread.php?t=382

My math for my bike gives me a 147.5 main jet, and either a 45 pilot, or a 47.5.

It says to go up 1 pilot for every 3 jet size increases, which would be 45, but I went up a total of 4 jet sizes. So its a little more than 1 jet size. Basically I want to make sure that a 45 pilot jet will be ok? Thanks.

Bike is a 79 special, with pods, and a 4 into 1.

IMO, your throwing guessing at it. Even with your set-up, start out stock jetting and check the plug burn before just assuming it needs to to raised up a bit richer(in which case one step up on the pilot, main jets, leave stock and do a plug reading after a long cruise at 4-5K rpm.).

[e30 gangsta]

Actually I just found out the bike is an 1980 xs1000sg. With the newer style carbs so It needs 120 mains and 45 pilots. My question is the main jets, are they the large or small style?

I assume the mains are these

http://www.mikesxs.net/parts/yamaha-...56-14944-24-00

Or are they these?

http://www.mikesxs.net/parts/yamaha-...620-14231-27a0

Thanks guys!

[motoman]

Actually I just found out the bike is an 1980xs1000sg. With the newer style carbs so It needs 120 mains and 45 pilots. Thanks guys!

Original stock jetting for 80-81 Specials is 42.5pilot jets and 110main jets.

[e30 gangsta]

Original stock jetting for 80-81 Specials is 42.5pilot jets and 110main jets.

Yea I figured that out much lol, but now that I am installing a 4 to 1, and pods, Id like to rejet the bike. So I need 45 pilots, and 120 mains. I am just trying to figure out what style mains are in the carbs so that I can order them.

[motoman]

Yea I figured that out much lol, but now that I am installing a 4 to 1, and pods, Id like to rejet the bike. So I need 45 pilots, and 120 mains. I am just trying to figure out what style mains are in the carbs so that I can order them.

The large Mikuni's for the main jets and just Mikuni pilot jets for the pilot circuit. To avoid just chasing your tail getting to run correctly(and it never will anyways), be sure and use Genuine Mikuni jets. To be Genuine, they'll also have the Mikuni curly-q embossed into them(main jets) next to the number size. Pilot jets will be marked accordingly near the top of jet on the side(use a magnifying glass to identify markings on pilot jets).

[motoman]

The large Mikuni's for the main jets and just Mikuni pilot jets for the pilot circuit. To avoid just chasing your tail getting to run correctly(and it never will anyways), be sure and use Genuine Mikuni jets. To be Genuine, they'll also have the Mikuni curly-q embossed into them(main jets) next to the number size. Pilot jets will be marked accordingly near the top of jet on the side(use a magnifying glass to identify markings on pilot jets).

Also, pilot jets need to have the correct number and sequence of side holes in them....(3 2-3 2 IIRC).

[TopCatGr58]

Hey there gangsta,

What Brant/Motoman has stated about getting GENUINE MIKUNI jets is correct. We have seen way too many folks chasing their tails with tuning issues because they used jets from K&L kits, or other generic jets. They are not manufactured to the same metering standards as MIKUNI. The pilot jets were known to have way to large of metering orifice on the end.

For a long time, we got off on a red herring type thought that it was the different # of aeration holes that were in the sides of the pilot jets that were causing the excessively rich conditions...but it was just the main metering orifice that was too large in the GENERIC/K&L jets, and the # of vent holes was immaterial. Since then we have also sliced through the carbs at the jet mounts, and found that the side holes are actually not involve at all!!!! The aeration circuit joins the pilot circuit AFTER the pilot jet. The pilot jet screws and fully seats into the carb body, and there are NO air inlets/ports anywhere around the side of the pilot jet hole...the aeration ports are further down/upstream in the pilot circuit path. The reason for this long discussion is that Yamaha/MIKUNI has offered and sold pilot jets that have NO side holes in them, and they work just the same as the earlier style with side holes.....provided they are MIKUNI and have the proper sized metering orifice at the end. George/GLOWEVA installed the NO SIDE HOLES Pilots on his bike last year, and it responded just fine!

Now, I'll be the dissenting voice regarding your jet sizing needs. When I first got my 81SH, ignorantly I put on a 4-1 set of pipes....headers work better than OEM pipes right!! I ran it that way for 9 years WITHOUT rejetting, and it seemed to run okay, but I had the STOCK AIRBOX. I never tested it with a DYNO, and the plugs still looked okay, perhaps a little lean looking, but not blistered white. I made several long distance rides, like about a 1000 mile 1 day trip, and never burned holes in my pistons.

However, Yamaha had started leaning out the fuel/air ratios after the 78 year due to EPA requirements...and so the 80/81's are already running a bit lean with the 110 mains even with OEM pipes and airbox. The 4-1 pipes and INDY POD filters will contribute to a more leaner condition. The Clymers were wrong about the staggered sized jetting, they did that early on, but abandoned it shortly thereafter despite what the books/specs say.

I have the same setup....4-1 pipes and POD filters, but I also put in a 1179cc big bore kit. I upped my mains to 115 and my pilots to 45.0. I did do a DYNO run with that setup after my rebuild/breakin, and that showed that I could probably go up 1 more jet size for the mains due to the slight drop in the transition zone. A few years later I did up my mains to 117.5, and the plugs have a nice tan color. I also have the Velocity Stack mount mod for my PODS which we have found to also help contribute to straighter airflow into the carb throat similar to the built in velocity stacks of the OEM AIRBOX.

SO...Tuning it can be acheived. Keep in mind that the 4-1 pipes are designed to scavange better and will provide less backpressure, and so that can reduce the low rpm grunt a bit, and moves the power band a few hundred rpms higher. I like to run it in the higher rpms anyways...~3500 or more....others like to cruise at 2K. SO depending on your riding style, it will depend on how it behaves in that you may have to give it a little more throttle/rpm to get off the line, but will power from 3500 on up to 7.5+ just fine.

That's my 2 cents, hope you get it to run the way you want.

T.C.

[BA80]

To be Genuine, they'll also have the Mikuni curly-q embossed into them(main jets) next to the number size. Pilot jets will be marked accordingly near the top of jet on the side(use a magnifying glass to identify markings on pilot jets).

Uh........what culy-q is that Brant?

[e30 gangsta]

TOPCAT, I personally wanted to thank you for your reply. There is so much great information on that post. I wish all motorcycles communities were as helpful as this one. Ive owned an xs for only a couple of days now, and everyone I've chatted with on here is awesome. Glad to be here and thanks again for the info.

So you think 120 mains is too big for my setup? Im located in miami florida, Maybe I should get some 115 mains as well just in case. Also how high can you rev these engines safely while riding them?

[Bonz]

I feel the jetting guide is a bit "aggressive" and you end up with more jet than needed. My question is in the pilots. I run pods and full aftermarket headers on two different sets of carbs for other bikes and stock pilots work fine. I don't understand the need to up the pilots on the XS1100 as these carbs are no different than other CV carbs in function. Start with the mains and work down from there to needle adjustment and then pilots. If no needle adjustment is possible, start with mains and then pilot jets.

With my 80SG I run a K&N filter in the stock airbox and have gone down 1 size in main jets living at 7200' elevation. Very good running bike and supports the fact that I feel the jet guide is goes larger than needed.

Again, the best way to tune a CV carb is get the main jet right first, then the needle height (if applicable) and finally the pilot circuit.

[motoman]

Uh........what culy-q is that Brant?

Sorry for the vague explanation Greg..........just looks 'curly' to me and was the easisest way of explaining it for me.

[trbig]

I agree with Bonz in that the jetting guide goes too far. I can't remember right off hand, but with the pod filters I think it says 2-3 sizes up for that alone. One size up on the mains and stock pilots is what worked for me and kept my plugs burning a nice tan.

[e30 gangsta]

Hey guys so I went up to the 45/120 setup from the original 43/110 setup. The bike is still on stock exhaust and I still get popping under decel with the throttle closed. Does that mean it it still too lean? Should I add more fuel to the main circuit?

All the bike has done is mike xs pods filters. Thanks.

[MadHatter4119]

Have you checked for exhaust (a lot re-use header gaskets) leaks...? What
are your spark plugs telling you...if they are lean...it will show up on the plugs
...if they are white looking...you need to limit how much you run it...keep a fan
blowing on the engine...Good Luck