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MPG on an 1985 r80rt

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Richard W
(@wobbly)
Posts: 2549
Member
 
Posted by: @john-young

@tpeever  Can you share with me the location of the fuel enricher disk? Bike seems to run very well, but my gas mileage has not improved. I just turned the reserve on both carbs while running with aprx 125 miles on the trip meter. 

  John Young

John -

The enricheners are disks that are mounted into the side of both carbs, under the square cover, on the engine-side. This this the device inside the carb that the "choke lever" rotates to add more fuel for starting. It is literally a round, flat disk about the size of a penny into which slots are cut to control fuel flow. 

There are 2 common issues with these disks...

  • Because the carbs are mirror images and so very similar, the Left disk can be installed into the RH carb by mistake, and vise versa. And this leads to all sorts of issues. Some say that the disks are marked L and R for identification. 
  • On both the earlier engine-mounted-lever and the handlebar-lever type, control cable adjustment is critical. The early engine-mounted style has to be adjusted to make the disk hit its stop at the same instant (or a fraction before) the enrichener control lever hit its stop. 

Check it !! Your mileage sounds awful.

Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.

 
Posted : 08/26/2021 13:49
Tobin Peever
(@tpeever)
Posts: 40
Eminent Member
 
Posted by: @john-young

@tpeever  Can you share with me the location of the fuel enricher disk? Bike seems to run very well, but my gas mileage has not improved. I just turned the reserve on both carbs while running with aprx 125 miles on the trip meter. That is with ethanol free gas. Probably the least amount of miles before turning on the reserve. I'll check the plugs again tomorrow and see how they look. Bike starts right up and idles smoothly.  I'm not bogging the bike and keep the rpms around3500 to 5000. Thanks in advance and for replying.

  John Young

Sure! It is #47 in the attached diagram. I may not be using the correct term but it is a hollow disk that is part of the enrichener (choke) circuit. I assume you have Bing CV carbs on your bike as well? You should be getting easily 200 miles from a tank of gas. I also have the 22 liter (5.8 US gal) tank and generally get about 200 miles before I hit reserve.

 
Posted : 08/26/2021 15:00
Tobin Peever
(@tpeever)
Posts: 40
Eminent Member
 
Posted by: @wobbly
John -

The enricheners are disks that are mounted into the side of both carbs, under the square cover, on the engine-side. This this the device inside the carb that the "choke lever" rotates to add more fuel for starting. It is literally a round, flat disk about the size of a penny into which slots are cut to control fuel flow. 

There are 2 common issues with these disks...

  • Because the carbs are mirror images and so very similar, the Left disk can be installed into the RH carb by mistake, and vise versa. And this leads to all sorts of issues. Some say that the disks are marked L and R for identification. 
  • On both the earlier engine-mounted-lever and the handlebar-lever type, control cable adjustment is critical. The early engine-mounted style has to be adjusted to make the disk hit its stop at the same instant (or a fraction before) the enrichener control lever hit its stop. 

Check it !! Your mileage sounds awful.

Yes, great advice. Check to make sure that both enricheners are completely shutting off when the lever is in "off" position. It could be that one of your enricheners is not shutting off completely or that the disk is in backwards, or both. Both of these will lead to rich running.  My enrichener cables took a bit of fiddling to get both to shut completely off. The choke cables should be in solid wire to allow them to "push" the enrichener disks into the closed position. 

This post was modified 3 years ago by Richard W
 
Posted : 08/26/2021 15:07
David Elkow
(@4949)
Posts: 306
Reputable Member
 

@john-young Hello John.  Yes, if you are only getting 30-32mpg, something(s) must be out of sorts. I know you said this R80 is new to you … have you had other airheads?  I’ve had only 2, but number 2 has been with me for 41 years. It’s a great old motorcycle!  I don’t want to say things you already know, so take this only for what it is worth.

If I were trying to tune/diagnose a “new to me” running airhead, I would, in this order;

1.  Set valve clearances.  
2.  Check compression.  
3.  Set ignition timing/confirm advance.  
4.  Tune and balance carbs. 

This is the right “pecking order” to tune the engine, and uncover issues. I have a feeling (at 30mpg) there may be carb/carb tuning issues, but you have to confirm 1, 2, and 3 before getting to 4. 

The compression check is something that you would only do with a “new to you” engine, to confirm it's condition. After that, a tune-up would be 1,3,4. (You might check the compression again in 10 years, or 20?)  That’s to say, you may be able to borrow a compression tester. Some might say this check is unnecessary, but, it would give me assurance that all is ok with the rings and cylinders, and the valves are sealing. 

 
Posted : 08/26/2021 18:47
John Young
(@john-young)
Posts: 45
Trusted Member
Topic starter
 

 Updating post:

 I have been away for awhile, but wanted to get back and re ignite this posting with where I am regarding my MPG issue.

 I have removed the carbs and purchased rebuild kits for them. I have the right hand carb apart and cleaned everything with Gum-out. It was a bit dirty, but didn't look as though it would cause the low MPG. However, things I have found along the way with the help of suggestions here is that the carb enricheners on mine are in fact marked L and R for each side. They are located correctly. Upon closer inspection I also found the idle jet on both my carbs is a #50, however on all the info I could find they are suppose to be #45. I am in the process of reassembly of the right carb and then I'll do the left. I also purchased new plugs. I will return back with an update when I get it all reassembled. Thanks for all the help.

 
Posted : 11/06/2021 14:01
Richard W
(@wobbly)
Posts: 2549
Member
 

> And what plugs did you buy ? The latest NGK chart shows a plug that is far too "cold" for proper combustion. You should be using something in the NGK "7" range, such as BP7ES.

> Yes, a #50 slow speed jet would waste fuel through the entire RPM range. Good catch there.

> Another place to look is the needle heights. Most carbs will allow you to see the needle clip, and thus the clip position. On the Bings the clip is concealed leading to 2 errors...

1. A very common mistake is to have the needles in different clip positions. You can most easily check for mis-matched clip positions by measuring the length of the exposed portion of the needle.

2. To check for correct clip slot, all you can do is remove and count while reinstalling.

Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.

 
Posted : 11/07/2021 07:10
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