Jet type for 1978 XS1100

[WMarshy]

well I personally HATE pulling carbs off these things and doing multiple times does not appeal to me. While I am changing the jets, I have a caliper that I an measure the float level just like I measured the header primary tubes earlier. I know my mechanic checks those things as he has commented on some of the junk I have taken to him before having the levels out of whack.

Dont you have the air box off the bike still? I dont know how much easier it could get... Like Motoman said, there is a slight trick to it and once you do it 2 or so times in a row you will start to figure it out.

IDK... maybe your mechanic is the best person to be working on them... should'a asked him what jets to get I guess.

BTW, if you dont want to buy 137.5 in fear they will be the same as what you have in there then try 135's... be prepared to buy several other size jets and pull the carbs many more times if the float height is off.

[motoman]

Dont you have the air box off the bike still? I dont know how much easier it could get... Like Motoman said, there is a slight trick to it and once you do it 2 or so times in a row you will start to figure it out.

IDK... maybe your mechanic is the best person to be working on them... should'a asked him what jets to get I guess.

BTW, if you dont want to buy 137.5 in fear they will be the same as what you have in there then try 135's... be prepared to buy several other size jets and pull the carbs many more times if the float height is off.

.......just the 'nature of the beast', or ANY older scoot, not just the XS's. If your gonna own them, learn how and BECOME willing to do the work on them........just part of the satisfaction factor.

[IanDMacDonald]

Okay, there are a few things I know about (bending valves) and Mikuni carbs. I've had a half dozen XS Yammies all with Mikuni's and tuned them all with pods and factory boxes. First thing to do is get rid of those crap pods and go K&N, Ape's, or go factory aie box. Secondly, there was a night doing some tuning where I had to remove my carbs 13 different times. Trust me, you get good at it and u'll never sweat it again.

Do not shy away from factory spec jets. I cannot remember if these have the adjustable jet needle on them (XS750's MKII's do). But, there was a set-up I had where everybody on the forum was like "abide by the jetting guide", and I can tell you that it's baloney. I had a 3-in-1 exhaust, K&N pods, and never upped the mains. All I did was drop the clip one setting and re-synced them. My gut is possibly a bad float needle, or poor height adjustment. There is no way you're running as rich as you are with stock jets.

I love the "ventilated pistons" comment, lol.

Also, talk to your local bike shop. Everyone has their tackle box full of Mikuni round jets.

[natemoen]

Also, talk to your local bike shop. Everyone has their tackle box full of Mikuni round jets.

No, everyone has their tacklebox full of generic knock off jets....

My local stealership tried to sell me R&D jets for $5 each and I argued with them.that they are not the same and that I wanted real Mikuni jets. Parts guy finally pulled out the big book-o-parts and saw they were only $2.50 each and he just kinda shut up.

[motoman]

No, everyone has their tacklebox full of generic knock off jets....

My local stealership tried to sell me R&D jets for $5 each and I argued with them.that they are not the same and that I wanted real Mikuni jets. Parts guy finally pulled out the big book-o-parts and saw they were only $2.50 each and he just kinda shut up.

sounds all too familiar.....

[motoman]

BTW, presuming those are the early carbs, what position is the clip on the metering rods? Would definitely check before doing any main jetting change, specially dropping steps. Again, ventilated pistons WILL ruin your day.

[DGXSER]

HERE is a great guide on how to tune the CV Mikuni carbs.

[brharris27370]

Update

ok, took the carbs off over the weekend and shot some pictures. First my float height appears to be 23.5mm and not 25.7 like someone mentioned earlier so my floats could be a tad high.


but to the dilemma that probably makes all this a moot point anyway. I found 1 carb that has the mounts for the floats broken. My mechanic apparently patched it and I didn't notice that carb running over or anything but really don't like that.


then finally, the main jets look awful. Even with a magnifying glass, the corrosion had taken its toll on that numbering and I could construe those numbers as darn near anything but if I have to get a set of carbs that's going to be an issue either.

So, currently I am watching a few different carbs setups on ebay. 1 of which is a 1980 XS1100 set of carbs. Are there any other carb setups, I should look for such as a KZ1000 set or specific MM size or does someone have a carb from a broken set. I know my broken one is one of the inners. Don't remember off hand if its a left or right one though.

[bikerphil]

It looks like the #2 carb is the one with the broken float post. It can be repaired with a little do it yourself machine work. I would stay away from any other Mikuni carbs than the ones for an XS11, many carbs for other bike makes/models will have slight differences. Jets are cheap and can be easily replaced.

[brharris27370]

Would like to see if any members just have a 78-79 number 2 carb rather than spending money at the machine shop for something that may or may not work.

[bikerphil]

If you do decide to fix it.....

http://www.xs11.com/forum/showthread.php?t=38769&highlight=broken+float+post

[brharris27370]

If it were just one post then I would feel better about that mod but both posts are gone. I found a number 2 78-79 body on ebay for $35 and so I will likely get it and order some new Genuine mikuni main jets for this thing but I will wait and see what some members might have lying around.

[motoman]

It looks like the #2 carb is the one with the broken float post. It can be repaired with a little do it yourself machine work. I would stay away from any other Mikuni carbs than the ones for an XS11, many carbs for other bike makes/models will have slight differences. Jets are cheap and can be easily replaced.

Actually, carb bank flipped over, looks to be #3 carb. (the "evil" carb)

[bikerphil]

Actually, carb bank flipped over, looks to be #3 carb. (the "evil" carb)

The #3 carb is the one all the way to the left in his picture, see the idle adjustment screw tang off the side of the carb?

[brharris27370]

I assume we are numbering carbs from left to right with number 1 being the left most carb. Since those are on there top they are in reverse order and number 1 is the right most carb in the picture with number 3 being on the far left and number 2 the one I have that's broken in the center.