Jet Kit for 79 xs1100F

[TheRev]

Hello All

My mechanic who is working on my carbs called and suggested that I purchase a jet kit for the carbs. I am running pods with a 4 to 2 mac exhaust. He said he has dialed in the jets but needs new needles. I guess he can't shim the current ones. My problem is dynojet doesn't make a kit for a 79 model. If I purchase the kit for the 80+ would the needles be the same? I don't need the jets just the needles.

[IanDMacDonald]

Why can't he shim the needles? Our carbs have adjustable needles. Stock is middle setting. Honestly Pastor, I've never felt the need to mess with the needles with the mods u have. One size up on the mains, and life was good.

[TheRev]

He said he did shim the needles and it wasn't running well. Perhaps the needles are worn out or bent or something. So are the needles the same on a 1980 as they are on a 79?

[IanDMacDonald]

No, they are not the same. '80+ Needles do not have the grooves & clip in them to adjust them, where-as our's do. Before you go buying new needles (I believe you have to buy the carb kits, as they do not sell them individually) http://pages.ebay.com/motors/link/?n...800391&alt=web, start a new thread with your symptoms. )Even on my 750's, I dropped/raised the clip one notch, and was golden. If he is exhausting the needle clip positions, I'd say it's time for a bigger jet size (main an/or pilot).

[MarkD]

Might help--- this is what I used, but of course, not the jets. I bought genuine Mikunis.

http://www.ebay.com/itm/4-Yamaha-XS1...p2047675.l2557

[TheRev]

Hi Ian

He says that the jets and air/fuel are all dialed in. He says the jet kits have a needle with a different tapered point and are also different at the top of the needle where the grooves are. That is what he is looking for. This mechanic knows old bikes. He ran the second highest rated service department in the country for Triumph for 20 years. He has a few xs's and has rebuilt them both. Currently his son is riding a 78 xs special. Anyhow, I wanted pod filters because I hate the damn air box. He installed new jets and it ran well but not good enough. So he drilled out something but I can't remember off the top of my head what it was. Then it ran to rich and was bogging down, back firing out of the carbs and wouldn't take throttle without dying. He then made some adjustments and regained the low end but it bogged down in the top end. So now he tells me he needs these different needles. That's about as much as I know. I admit I just don't know enough about carbs to follow what he is saying so I thought I would throw it out to you all.

No, they are not the same. '80+ Needles do not have the grooves & clip in them to adjust them, where-as our's do. Before you go buying new needles (I believe you have to buy the carb kits, as they do not sell them individually) http://pages.ebay.com/motors/link/?n...800391&alt=web, start a new thread with your symptoms. )Even on my 750's, I dropped/raised the clip one notch, and was golden. If he is exhausting the needle clip positions, I'd say it's time for a bigger jet size (main an/or pilot).

[IanDMacDonald]

I gotcha Rev, no disrespect to your mechanic, but I'm not 100% convinced he knows these Mikuni's as-much as he should if he is drilling anything (slides or jets would be my guess). I have many XS's myself (Xssesive variety), and each one is configured differently, all wearing Mikuni MKII or BS34 carbs, including the 850 which had Hitachis originally. If you are going to give-in to what he wants, and trust him, buy what Mark posted above.

[MarkD]

Rev-- years ago, I took my first XS to a fairly good and experienced mechanic because me bike broke up around 4000-4500 rpm. Thinking it was carbs, he drilled holes in my airbox. Of course, that was the wrong fix, as it was the very common ignition pic-up wires breakage/stretching. Seems like the best set up ( there are other recent threads on this) is the stock jets with the stock airbox. Saying that, when I bought my 2nd XS 1 1/2 years ago, it had pods. I never ran it that way, I put stock sized jets in and airbox that the PO had. If you want, I could send the jets I replaced so you could try them.

[IanDMacDonald]

Well Mark, The Rev says that the jets are dialed in, so right now he is conquering a needle jet setting, which sounds right. In my opinion, if it comes down to this setting alone, the mechanic must be looking at mid-range power, and something very specific to how he expects the bike to run. Fair enough, buy those kits and see if you can help him get them dialed in.

[crazy steve]

What the guy has done is drill the air bleeds on the carb slides, which was an 'optional' mod if using the Dynojet kits. Those kits had jet needles with a 'special' taper that supposedly worked with this mod, which is what he's after. But as you've already found out, they're NLA.... And the '80-up kits won't work.

Those kits were notorious for tuning issues if the slides were drilled (a non-reversible mod), so at this point you have two choices; find the correct NOS kit which may or may not fix it, or replace the slides with stock ones and start over. These kits are popular with the Harley crowd too, but the drilled slide trick usually resulted in having to buy a new replacement slide.

Not what you wanted to hear, but it is what it is...

[TheRev]

HI Mark

That would be great if you could send me those jets. I would really like for this bike to run well with the pods. I just hate working with that damn airbox.

Rev-- years ago, I took my first XS to a fairly good and experienced mechanic because me bike broke up around 4000-4500 rpm. Thinking it was carbs, he drilled holes in my airbox. Of course, that was the wrong fix, as it was the very common ignition pic-up wires breakage/stretching. Seems like the best set up ( there are other recent threads on this) is the stock jets with the stock airbox. Saying that, when I bought my 2nd XS 1 1/2 years ago, it had pods. I never ran it that way, I put stock sized jets in and airbox that the PO had. If you want, I could send the jets I replaced so you could try them.

[TheRev]

Or I could start looking for a set up 80 and up carbs and then by the correct jet kit. Would that work? What is the NOS kit I should be looking for? Thanks

What the guy has done is drill the air bleeds on the carb slides, which was an 'optional' mod if using the Dynojet kits. Those kits had jet needles with a 'special' taper that supposedly worked with this mod, which is what he's after. But as you've already found out, they're NLA.... And the '80-up kits won't work.

Those kits were notorious for tuning issues if the slides were drilled (a non-reversible mod), so at this point you have two choices; find the correct NOS kit which may or may not fix it, or replace the slides with stock ones and start over. These kits are popular with the Harley crowd too, but the drilled slide trick usually resulted in having to buy a new replacement slide.

Not what you wanted to hear, but it is what it is...

[crazy steve]

Yeah, you could do that... but that still might not be the 'fix'. The Dynojet kit was one of those 'snake oil' mods in most peoples opinion. It did have some popularity with reputable tuners, primarily for that special jet needle (which was the only part most used out of the kit). IIRC, the kit also came with 'special' jets (and the sizes didn't correspond to Mikuni sizes, so if the kit jetting was off it was tough to cross to stock jets), the 'special' drill bit for the slides and special slide return springs. The springs were designed to work with the drilled slides (so he may be missing those too) and the installed 'complete' kits were known for inconsistent performance. These kits had several 'stages' too, and the higher stages really only worked well on modified motors (big bore, cams, etc). The drilled slides were the top stage, and too much for a primarily stock motor.

At this point, finding a good stock carb set may be your best shot, but don't bother with a Dynojet kit. There's no reason a properly rebuilt/jetted set of these carbs won't work with a pods/Mac exhaust combo; there's plenty of bikes out there doing fine with that setup.

One thing not mentioned is your pods; make sure you don't have the ones with the big 'lip' on the inlet bell, as those can partially block the various openings at the carb inlet and cause the problems you're experiencing.

[TheRev]

What he says he is looking for is the tapered needle. I have KN filters without the lip. It started to snow today so my guess is I need to figure this out next season. I will talk to my mechanic and even show him these threads and see what he says. You all have given me some great advise and I really appreciate it.

Yeah, you could do that... but that still might not be the 'fix'. The Dynojet kit was one of those 'snake oil' mods in most peoples opinion. It did have some popularity with reputable tuners, primarily for that special jet needle (which was the only part most used out of the kit). IIRC, the kit also came with 'special' jets (and the sizes didn't correspond to Mikuni sizes, so if the kit jetting was off it was tough to cross to stock jets), the 'special' drill bit for the slides and special slide return springs. The springs were designed to work with the drilled slides (so he may be missing those too) and the installed 'complete' kits were known for inconsistent performance. These kits had several 'stages' too, and the higher stages really only worked well on modified motors (big bore, cams, etc). The drilled slides were the top stage, and too much for a primarily stock motor.

At this point, finding a good stock carb set may be your best shot, but don't bother with a Dynojet kit. There's no reason a properly rebuilt/jetted set of these carbs won't work with a pods/Mac exhaust combo; there's plenty of bikes out there doing fine with that setup.

One thing not mentioned is your pods; make sure you don't have the ones with the big 'lip' on the inlet bell, as those can partially block the various openings at the carb inlet and cause the problems you're experiencing.

[TheRev]

Crazy Steve

I think this is what I am going to do. I spent a lot of time and money last season trying to chase this problem. It seems like others are making their bikes run with pods by changing the jets. So I think I will just by new carb slides if I can find them and start fresh. I should probably purchase a color tune as well. What do you all think?

What the guy has done is drill the air bleeds on the carb slides, which was an 'optional' mod if using the Dynojet kits. Those kits had jet needles with a 'special' taper that supposedly worked with this mod, which is what he's after. But as you've already found out, they're NLA.... And the '80-up kits won't work.

Those kits were notorious for tuning issues if the slides were drilled (a non-reversible mod), so at this point you have two choices; find the correct NOS kit which may or may not fix it, or replace the slides with stock ones and start over. These kits are popular with the Harley crowd too, but the drilled slide trick usually resulted in having to buy a new replacement slide.

Not what you wanted to hear, but it is what it is...