My XS build, need some advice!

[PMKXS11]

Hello all, I've been working on my '79 XS11 Special on and off for about 2 years now and while recently I've finally got her on her wheels again, I'm looking for some advice about what to do with my engine. Specs are as follows:

Bored to 1196 with Wiseco piston kit.
Mild headwork done + 3 angle valve job
Web Cam 110 grind cams (.395/.395) + valve spring kit
Crower connecting rods
I'm currently in the process of building a 4-1 exhaust with a mix of TC Bros header kit for the XS650 (1.5") and a 4-1 collector dumping to 2.5" with 2.5" piping to the middle of the rear wheel. I have a small stamped cone inserted in the 2.5" section to create a little back pressure
Mike's XS 3.3 Ohm dual tower coils, with correct wires, NGK boots and NGK BP6ES Plugs.
Carbs are stock as far as I know, but they have been cleaned and rebuilt.
I will be running UNI pods, as they do not cover the port at the top of the inlet.
I think that's all I've got in the engine, I might have missed something.

After all that nonsense, my question is what to do about my carbs. I'm new to carbs and I really don't know jack about tuning em right. I see Dynojet makes a kit for this bike but I'd rather not spend the $130 if I don't have to. When I rebuilt the carbs, I put them at factory settings, as per the service manual. Float height is per book as well. Jets I believe are stock, but reading up on these bikes I see that jetting was different year to year and Standard vs Special.

If anyone has any advice on how to go about this, or where to start, I'd really appreciate it.

Here's a pic from a few months ago, before putting in a Vesrah clutch and spring kit. Currently sits looking the same, but with exhaust on her.



Thanks!

[natemoen]

Actually dyno jet does not make a kit for the early carbs, they only make kits for the later version of the carbs. That is why they list it as '80-'83 XS-XJ.

They used to make a kit but it has been discontinued for a long long time.

[cajun31]

Pmk

What is the status of the bike. Running or not running? A picture of the carbs would help as well. In order to decide whether rejetting is necessary you need to be able to get the bike running with them. Once you accomplish that by doing the basics.... bench synching, float adjustment (which you have done) and basic idle mixture settings to begin with and then get the bike to crank up. You will then be at the point where you can start dialing them in by reading your plugs under load conditions and then you can synch them with a tool such as a morgan carbtune or some other appropriate sych gauge setup. There are tips a plenty on all of this. By the way the bike is looking good. I will say that everyone on this site swears by keeping the jetting in these carbs Mikuni. Regardless of what you buy make sure the jets are Mikuni original as it is easier to dial the carbs in with them.

[PMKXS11]

What exactly should I take a picture of on the carbs? I bought this bike as a basket case in 6 crates from a guy who owned 4 xs11's at one point, so I'm not entirely sure that all the parts are original to the bike.
All the wiring on the bike still needs to get done. Like I said, this bike has been coming together on/off as there are a lot of custom bits on this bike that take time to make/have made. I also work full time and when I can, I'm out riding the GSXR on the track, which is a never ending project in itself hahaha.
About a year and a half ago, I assembled the bike, and cleaned the carbs, and ran it, just for kicks. It was very lazy to rev, and it would hang before slowly dropping RPMs. I also noticed that the carbs would spit gas back.

[cajun31]

pics

taking a picture of them will give us an idea of what year model the carbs came from. Did they come off of that year model etc... The jetting was changed from the 78 and 79 models to 80 and 81 because of the epa regulations at that time. the actual carbs themselves were redesigned to meet the epa guidelines. if the carbs were spitting gas then I would suggest that you go back through the carb cleaning process. Look under the repair tips for carb cleaning 101 and follow those recommendations for cleaning those carbs again. Sounds like you have a sticking float or floats that is not allowing the carbs to stop gas flow.

You have to start with small steps then we go from there. Easier to diagnose problems if you can get the bike running.

[cajun31]

here is a thread that shows

all the different models and the jetting from each year.

http://www.xs11.com/forum/showthread.php?t=73

[BA80]

The dyno kit isn't really needed with the 79 carbs, if that's what you have, because the older carbs are extremely adjustable out of the box. So to speak.

The jet needles for the mains have 5 settings so basically you have 5 main jets to start with and you can go up or down a size and have plenty of room for adjustment.

The pilots are available in several sizes larger or smaller in genuine Mikuni. Always go with the CORRECT genuine Mikuni or you will set yourself up for ridability problems.

Get it running the best it can with the stock jets before you change anything or you may create a problem before you start.

And, change ONE THING AT A TIME not several or you won't know what caused any particular problem you may have.

Experienced advice

[PMKXS11]

Awesome, thanks guys. I just got my parts for my track bike back today, so that's top priority right now, but then I'll jump on wiring the XS and getting the thing running.

I remember having the 5 slots on the needles during the rebuild, was that an early model thing or used throughout the year range?

[BA80]

I remember having the 5 slots on the needles during the rebuild, was that an early model thing or used throughout the year range?

78 and 79 only, after that Ralph Nader was in control.

[TopCatGr58]

The adjustable slide needle was the Early Model carbs, 78-79. A few other characteristics of the early carbs, only 3 small holes in the inlet bell along with the arced vac. slide port, the later carbs had 4 small ports because they put the float bowl vent INTO the bell instead of the side of the carb body=upper "T" fittings are VENT tubes. They also had brass metal floats instead of the plastic ones. The float needle was solid metal, and the seat screwed into the body, the later models had rubber/viton tipped needles and the seats pressed in with O-rings and a "C" type clamp that was screwed down to secure seat. The Pilot jet towers are CAPPED OFF with a large head screws, and there is a connecting tunnel between the main jet and pilot jet tower because the pilot is fed via the main jet....so the mains are larger ie. 137.5 oem vs. the later models that had fully separate towers, so the mains got reduced to 110-120 range.

The early bikes were jetted richer for performance, then the EPA stepped in and they got jetted leaner for emissions, so that's why we say start with the OEM jet size and test/plug throttle chop and see what the plugs look like. Also the carbs will need to be Vacuum synched...that's part of the reason why your idle HUNG and didn't drop back down quickly.

T.C.

[PMKXS11]

The adjustable slide needle was the Early Model carbs, 78-79. A few other characteristics of the early carbs, only 3 small holes in the inlet bell along with the arced vac. slide port, the later carbs had 4 small ports because they put the float bowl vent INTO the bell instead of the side of the carb body=upper "T" fittings are VENT tubes. They also had brass metal floats instead of the plastic ones. The float needle was solid metal, and the seat screwed into the body, the later models had rubber/viton tipped needles and the seats pressed in with O-rings and a "C" type clamp that was screwed down to secure seat. The Pilot jet towers are CAPPED OFF with a large head screws, and there is a connecting tunnel between the main jet and pilot jet tower because the pilot is fed via the main jet....so the mains are larger ie. 137.5 oem vs. the later models that had fully separate towers, so the mains got reduced to 110-120 range.

The early bikes were jetted richer for performance, then the EPA stepped in and they got jetted leaner for emissions, so that's why we say start with the OEM jet size and test/plug throttle chop and see what the plugs look like. Also the carbs will need to be Vacuum synched...that's part of the reason why your idle HUNG and didn't drop back down quickly.

T.C.

THIS!!! I remember everything you just described while rebuilding em. So it looks like I have early carbs and factory jetting. sweet.

Another question for you guru's. What do I do with the vacuum lines? As you can see I'm running a standard tank and standard petcocks, so that eliminates the Octy right? Again, this bike was a basket case so I tried my best to get it semi-together to see if it would even run. I have the hose coming off the advance, where does that go?

[BA80]

The vacuum line for the advance goes to the #2 CARBURATOR not the boot. There is a ported outlet on the carb itself.

The vacuum operated petcocks have a vacuum port (the smaller nipple) that should go to the #2 and #3 INTAKE BOOT.

[WMarshy]

If you want to keep it simple and don't care to retain the vac operated petcocks you can turn them into manual petcocks. You can cap all the taps on the carb intake boots that would normally be use as vac source and lightly modified the chrome plate on the petcock with a dremel that's held on with two screws. Once the tab is gone you can rotate the petcocks lever to the 12 o'clock position. Just mind the end of the lever, it might hit the tank. See this link.

http://www.xs11.com/forum/showthread...ht=petcock+mod

[PMKXS11]

Any benefit to eliminating the vacuum operated petcocks? I had mine rebuilt and powdercoated so I'd like to keep em pretty.

[cajun31]

No real advantage

that I can think of. It just seems that a lot of folks just don't care for that feature especially on the specials with the octy. I do believe that if you eliminate the vacuum feature you have to remember to turn the petcocks off or the gas floods the carbs.