80 XS1100 main jet sizes?

[vintagemcyclegu]

I have a 1980 XS1100SG and I noticed the parts list shows for the main jets 2 125's and 2 120's as the main jets. Yet when I took my carbs apart there were 4 110's. What is stock, What gives, I am confussed. Thanks.

[MrOzz]

I have a 1980 XS1100SG and I noticed the parts list shows for the main jets 2 125's and 2 120's as the main jets. Yet when I took my carbs apart there were 4 110's. What is stock, What gives, I am confussed. Thanks.

The 110s are stock for the 1980SG.

[Bonz]

Ditto. 110's across the board for an 80 SG.

[jetmechmarty]

I believe I have 110-115-115-110 in my SG. I thought it was stock.

[crazy steve]

According to the factory manual, 110s are OEM for a SG....

[Bonz]

I've heard in the forum over the years that some Specials in 1980 (not sure about other years?) had the 110-115-115-110 set up in the carbs from the factory, however my factory shop manual calls for 110's across the board for the Special.

At the Colorado Rally this year, 3Phase shared with me that even between the 80 Standard (G) and 80 Special (SG) the taper of the needles is different, so regardless of what jets the bike came with, the Special and the Standard have different jet sizes relative to one another to take into account the taper of the needle within the same model year. The taper affects how quickly/how much fuel is used through the main jet based upon how the needle comes out of the seat when throttle is applied. So at the same throttle opening, all things equal, the needle taper is a decided controlling factor in how the bike runs. I guess they wanted a shorter taper on the SG for more spirited acceleration (if I remember what 3Phase said) and the G has a longer taper which would lead to more smoothness as the throttle is being manipulated. Hope I didn't get that backwards...

From what I hear, the old addage of a larger jet in the middle cylinders is not doing much if anything to cool the engine down appreciably, as that is the main reason I have always heard for going with the larger jets in the middle.

Anyway, just what I was told, and it makes sense.

3Phase, you out there? Lend a buddy a hand?

[3Phase]

Bones, you got it right on the head!

As far as I can tell, Yamaha went lean and mean for the stoplight/bar hopper Specials for fast acceleration and power at the expense of some engine life but went richer for the long-haul Standards so they didn't burn up engines.

[Bonz]

Thanks for the assist, wasn't sure if I my oxygen depleted brain remembered correctly, as we were standing at closing in on 10,000 feet of elevation having that discussion...

[3Phase]

Thanks for the assist, wasn't sure if I my oxygen depleted brain remembered correctly, as we were standing at closing in on 10,000 feet of elevation having that discussion...

Yeah, but it was fun, wasn't it!

I think my XS did better at that elevation than I did but I'd do it again in a heartbeat. The engine, carburetion and final drive never gave me a lick of trouble and after Lizard Head there was -- Trout Lake!

[motoman]

and after Lizard Head there was -- Trout Lake!
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.......but had just three legal "keepers".

[Bonz]

My bad, I didn't ignore the first post about trout lake, just LMAO for a minute then forgot to respond...

Some MIGHTY fine trout at that lake...