Explain this GS experts!

[Giblet]

Weekend before last I completed my 82 GS1100GK's first valve shim adjustment in at least 20K miles. I also swapped the original 16" (130-90X16 Kenda Kruz 637) wheel with a 17" (Chen Shing 130-90X17 HI-MAX) off an 80/81 GS1000G. The first tank after the shim adjustment averaged gave me 34.8 mpg with the 16" wheel. The second tank gave me 35.2 mpg with the 17" wheel. Prior to this (for at least the last year) I was getting a solid average of 35 mpg. The 3rd tank averaged 36.1, 4th tank was 36.8 and the 4th tank was 37.6 mpg. My daily drive is about 15% city and 85% highway. I have done my best to duplicate route, acceleration and cruise speed. I'm going to work tomorrow and am interested to see what the mileage does. Is it possible the valve train takes a bit to settle into the new shim thicknesses? When I first got this bike 4 years ago it was running between 37-40 mpg depending on how hard I rode it. I was thinking about selling it and going to one of the "E" models but am so much happier with the way it runs and especially \\/ the super improved cornering I'll probably stay with it. It just turned over 40K miles 3 weeks ago.

[rustybronco]

Is it possible the valve train takes a bit to settle into the new shim thicknesses? When I first got this bike 4 years ago it was running between 37-40 mpg depending on how hard I rode it. I was thinking about selling it and going to one of the "E" models but am so much happier with the way it runs and especially \\/ the super improved cornering I'll probably stay with it. It just turned over 40K miles 3 weeks ago.

No it does not take a while for the valve train to settle in, try running some seafoam through the carbs and see what happens, how is the air filter and compression?

[gs54]

I heard much about seafoam where do you get it?

[rustybronco]

i get it at advance auto parts.

[Giblet]

No it does not take a while for the valve train to settle in, try running some seafoam through the carbs and see what happens, how is the air filter and compression?

Figured it was a silly question but this puppy seems to be much more sensitive to some things like fuel/air flow etc than any car I've ever owned. I'm trying to understand as much about it as I can so I can keep it running for a long time. I buy Seafoam at O'Reilly's mostly but Autozone carries it and I think I bought it at Big Lots once. I have a stock replacement K&N air filter, recently cleaned & oiled. Haven't checked the compression but since it has just over 40K (I put well over 1/2 that on it), & runs like a scalded cat I'm thinking it is OK. I need to buy a new compression gauge since my old one disappeared long ago. I guess I don't care why the mileage is going back up as long as it keeps that trend. It has smelled like it was running very rich for some time and now that I think about it that has virtually disappeared since the adjustment plus, there is virtually no pinging now. More Seafoam definitely won't hurt.

[rustybronco]

Figured it was a silly question

Nope its not.

The compression question was asked because i didn't know and it has 40 k on it and you said it hadn't had an adjustment in 20k just wanted to be sure the valves were ok. the thing i find the most on bike engines is DIRTY Carbs and cracked intake boots you said it ran good and the milege was going up so i just thought it might be a good idea to help them along.

[DimitriT]

I am amazed and impressed that you can measure tenths of a mile per gallon. Perhaps you had some crud on the valves which is getting cleaned off now that your valves are actually closing. I would check them again in another 1000 miles.

About nine years ago I spent 3 nights in Caddo Mills. I drove down there to buy a sailplane and did a little flying. Nicest people in the world down there. Very flat country.

[Giblet]

Many thanks. I know it was probably adjusted at least once as 2 shims were installed with the numbers up. These bikes must be tough as mine sat up for several years and I have been working on it for 4 years and have not gotten to everything that needed attention. It had just over 19K when I got it. Can't wait for fall and my next Texas hill country ride.

[Giblet]

I am amazed and impressed that you can measure tenths of a mile per gallon. Perhaps you had some crud on the valves which is getting cleaned off now that your valves are actually closing. I would check them again in another 1000 miles.

About nine years ago I spent 3 nights in Caddo Mills. I drove down there to buy a sailplane and did a little flying. Nicest people in the world down there. Very flat country.

Good idea. Kool. I grew up in Greenvlle, about 15 miles from here and we built on the lot where my wife's folks were living when she was born (early 60's). My youngest wants to go up in a sailplane for his 14th bday. Its all of 2 miles away and YES, its a great place to live, albeit very flat. Welcome back anytime :-D .

[KGB]

You also essentially changed the gearing on the bike by altering the tire size. You added a 1 inch taller wheel and tire.
This will also effect fuel mileage.

Have you noticed your rpm at speeds are different now?

[Giblet]

You also essentially changed the gearing on the bike by altering the tire size. You added a 1 inch taller wheel and tire.
This will also effect fuel mileage.

Have you noticed your rpm at speeds are different now?

Lowering the RPM's was part of my intent. I didn't think it would be much but as gas keeps going up, a little can get to be a lot. My tach has gone wacky the last two weeks so I'm not sure how much it dropped yet. Probably not more than a couple hundred rpm but that can certainly add up over time. The biggest surprise was that it didn't affect the seat height much that I can tell. I was mainly interested in why the mpg seemed to be creeping up. I'm sure the valves weren't closing completely because I was hearing an excessive amount of pinging under heavy throttle especially in 5th gear at highway speed & that has all but ceased since the shim adjustment.

[Giblet]

I am amazed and impressed that you can measure tenths of a mile per gallon. Perhaps you had some crud on the valves which is getting cleaned off now that your valves are actually closing. I would check them again in another 1000 miles.

About nine years ago I spent 3 nights in Caddo Mills. I drove down there to buy a sailplane and did a little flying. Nicest people in the world down there. Very flat country.

Amazed and impressed? Is that because I'm from Texas or what \\/ ? Just kidding, math isn't my strong suit but I do work in engineering and deal in that degree of resolution, not to mention that my dad taught me to do it that way. I've always used it as a tool to keep tabs on my vehichles condition.

[Giblet]

Nope its not.

The compression question was asked because i didn't know and it has 40 k on it and you said it hadn't had an adjustment in 20k just wanted to be sure the valves were ok. the thing i find the most on bike engines is DIRTY Carbs and cracked intake boots you said it ran good and the milege was going up so i just thought it might be a good idea to help them along.

I wish I thought of everything when I was posting. I have also installed new boots between the carbs and air box and new o-rings between the head and intake boots.

[themess]

The first tank after the shim adjustment averaged gave me 34.8 mpg with the 16" wheel. The second tank gave me 35.2 mpg with the 17" wheel. Prior to this (for at least the last year) I was getting a solid average of 35 mpg. The 3rd tank averaged 36.1, 4th tank was 36.8 and the 4th tank was 37.6 mpg. My daily drive is about 15% city and 85% highway. I have done my best to duplicate route, acceleration and cruise speed. I'm going to work tomorrow and am interested to see what the mileage does.

For years, I have recorded gasoline purchases as precisely as the pumps will let me, and have entered the data into spreadsheets and made graphs. The results vary at least as much as yours do, even when riding or driving the same routes at the same speeds. Air temperature, humidity, wind direction and speed, proximity or other vehicles, rain, all make significant differences. Long term trends (over many thousands of miles) and large sudden jumps need to be explained. Variations of +/- 5% are quite normal.