Alarming or no ?

[DGXSER]

For riding around town, daily travel stuff, I typically get around 34-36. When I take longer rides, a tankful or close to it, I get around 42-44. I have 4-2 without a crossover, factory airbox, stock pilots and 120 mains.

The only 4-1 I owned I sold before I put many miles on it.

[mmaddix]

32mpg was the worst I got when my carbs were out of sync, pretty dirty, my ignition system was weak and not firing all cylinders, and my pod filters were attached to the carbs with the boot it came with so it was blocking some of the air holes on the carb. Now I run the pod filters attached the stock xs1100 boots from the airbox, I cleaned and synced the carbs fixed my ignition system, and I started getting 35-37 and this is with a 4-1 with no muffler. I recently modified my 4-1 so I will actually have back pressure and hopefully get over 40mpg. I will post the mod i did once I see what kinda mpg's it gives me.

[graybird78]

i'm with jetmechmarty,my mpgs on my sg is 32-33mpg. my bike is all stock and has fairing ,trunk and hard begs.plugs are light tan.

[LoHo]

A couple of questions about plug color checks:
1- How many miles of riding would give one an accurate color measure?
2- One should use the "Cut Power at Speed"-method for checking the mix at higher RPMS, right?

[BA80]

I'm with you Marty, I usually get 32 - 36 MPG if there isn't wind to contend with but then I usually run between 75 and 90 on the slab. I got a little over 40 MPG ONCE when I was following Bob Falter through Iowa and he was running 60 - 70.

[donebysunday]

where are the mixture screws on my '80 special?

If your carbs have not been adjusted already I have a method for removing those plugs from the idle mixture needle towers so as to not damage the screwdriver slots in the top of the idle mixture needles. Also easier than just trying to pull them out with a screw although you will still need to use a screw or tap for a small bolt to get them out. PM me if you like.

[donebysunday]

A couple of questions about plug color checks:
1- How many miles of riding would give one an accurate color measure?
2- One should use the "Cut Power at Speed"-method for checking the mix at higher RPMS, right?

Hi LoHo !

1- 10 or more miles of 25-40 mph riding.
2- same mi., but now you want to check the mains, so balls to the walls then pull off rather quickly, shut down, pull plugs and check

[WMarshy]

The pink colored plugs are from different additives in your fuel oxidizing from combustion.

[MPittma100]

White?

I don't understand how you folks are getting nearly 40 mpg. I have fiddled and futzed until my machine is running as good as it possibly can. The ceramic on my plugs is nearly white. The valves are in spec. The timing chain is new. I have fresh oil. I have an airbox with a K&N filter and a four into one header. 32 mpg is the best I can get.

I've been talking to Unca Done and told him he was probably lean if he's getting that kind of mileage. Does the exhaust make that much difference? Done has stock head pipes.

A white plug is definitely lean and lean is good MPG. But too lean is not good especially on an air cooled engine w/o an oil cooler.

My SG has 210 jet and 45 pilot (78E sizes). The check on mileage with these bigger jets was 35 down from 38-39 with stock jets. The performance "feel" is better with the larger orifices and MPG difference is ok with me. Plug colors are light brown. This is with OEM exhaust.

MP

[MPittma100]

My Mistake

I referenced "my SG" in the previous post. Well I lied! I do not own an SG. It is in fact an SF. I stand self - corrected.

MP

[BA80]

That 210 jet is what goes in an 80 - 81. If that's in an E or an SF it has late carbs on it.

[jetmechmarty]

That 210 jet is what goes in an 80 - 81. If that's in an E or an SF it has late carbs on it.

I thought the SG/SH main jets were 110 across. Did I remember that right?

[BA80]

A white plug is definitely lean and lean is good MPG. But too lean is not good especially on an air cooled engine w/o an oil cooler.

My SG has 210 jet and 45 pilot (78E sizes). The check on mileage with these bigger jets was 35 down from 38-39 with stock jets. The performance "feel" is better with the larger orifices and MPG difference is ok with me. Plug colors are light brown. This is with OEM exhaust.

MP

I referenced "my SG" in the previous post. Well I lied! I do not own an SG. It is in fact an SF. I stand self - corrected.

MP

Exactly Marty, that's what I'm saying. MP is saying, as I understand, that's what's in an E and his SF. Isn't that what he said here?

[DGXSER]

He is talking about the pilot air jet being 210 with 45 pilot jets. The stock on an 80-81 (and I believe on the 79 as well) was 185 pilot air jets with 42.5 pilot jets.

There was a lot more to it than just jetting on the 78, different cams, timing, etc.. so I am not certain just jetting it up will get you anything more than less turns out on the mix screws and a little lower millage. But, if you like how it runs with those jets, have fun!!

[BA80]

Ahhhh......I see now. I was thinking mains and saw 110 when I actually read 210.

Ivan has been experimenting with air jets in his SH and seems to have come up with a fair combo. Not sure what it is but posted something about it on the other site.

I went up from a 42.5 to a 45 pilot in my carbs and it seems to have helped the lower end a bit.