Jetting question

[skids]

My 80 and 81''s do have pilot air jets installed in the perimeter of the inlet bell. They seem to have different threads than earlier models. Did your engine eat those pilot air jets??? It is true that the main air jets are pressed in and non removable in 78 through 81's.

Originally posted by MAXIMAN
Thornton,

I derived that list strictly from looking at all the carbs for all year models of XS and XJ. The parts list is at the Yammy official website. It shows the different jets for the different years. best I can tell some of these parts are interchangeable...some are not...as some years had different bodies. This is evidenced by the fact that years '80 and 81 appeared to have no removable air pilot.

I can only assume the air pilots on these models were pressed in or fixed.

I'm not sure if there are any specific marks that would show this. I am certain somebody on this magnificent forum will no doubt be able to answer that.

[MAXIMAN]

NO NO NO...the post before clearly stated I based that list on a parts diagram. I couldn't find the air jets on the yamaha parts schematic. I assume they were not removeable.

Re-read the post. I never said they were missing...I said I assumed they were pressed in.

[MAXIMAN]

Thornton

Read this FAQ for more carb difference inof:

http://www.xs11.com/forum/showthread...=&threadid=867

[RS Thornton]

Maximan,

Here is the final jeopardy question, other than the chrome caps on carbs 1 and 4 are the 79SF carbs the same as the 78E and the 79F? I know the plumbing was changed for the vacuum valve but I think the carb bodies are the same.

I knew things had started to change with the 1980 models, but it seems like the carbs on the first three models are pretty much interchangeable. I'll take a closer look at the parts lists on the yamaha web site for these three version.

Scott

[MAXIMAN]

Here's a quote from Blaine Hoopes XS11 carb FAQ:

Q: Are all of the carbs on all of the XS11's the same?

A: NO! In fact they are slightly different on nearly every model even if they look the same on the outside. Differences I have encountered are:
'78 - '79 carbs are completely different than '80-81 carbs and few parts are interchangable.
Some models had different needle jets on carb 2-3 from those on 1-4 to richen the mixture for the 2 inner cylinders and keep them cooler. '80G & '81H had larger main jets on 2-3 than 1-4 for the same reason, SG & SH did not.
SG & SH had uncovered pilot jets and do not have the hole linking the pilot jet to the main jet. Putting the rubber caps over the pilot jet on one of these carbs would cut off all fuel from the pilot circuit (neither the service manual nor the Yamaha parts fische indicate this and Yamaha will gladly sell you rubber caps and tell you they are required for your 80SG even though they will completely kill your pilot circuit).

It seems to be a common practice to replace a damaged carb with one from a parts bike of a different model and year. I have found carb banks that have been intermixed like this are very hard to sync since one carb may have larger or smaller drilled holes in the carb body and may even have missing holes that cause a mismatch

It would appear that the 78-79 were very similar but still have differences. Whereas the 80-81 models were quite different.

I know the carbon my 1980 Special were a bit different from the carbs on my '82 XJ1100.