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Guaire
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Arlington, VA
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Got out on a Maryland state road for a ride last Thursday. The total length was 140 miles. I had added BG 44K fuel system cleaner to the fuel tank. Today I got gas. My mileage is 31 mpg.
The RT is performing well. Sometimes the idle will hang at about 2K rpm. Riding seems to be the cure for the hanging idle. Plugs are showing on the rich side. BP6ES plugs.
I have considered going to a DynaTek coil, but I'm not sure which one would work. Also, I don't know whether to use the resistance or non resistance wires, caps and plugs. I figure that a stronger spark would help the mileage.
I will check the valve gaps. I suspect they will be OK. Total miles on the bike is 23,800.
I would be appreciate any feedback.
Cheers,
Bill

  • right_is_r_89.jpg
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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

Twocams
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The plugs dont look to bad.

The plugs dont look to bad. The right one maybe a little rich, but I wouldnt worry. You dont say how fast you were going. Or if you were using ethanol gas. Both of those can effect gas millage.
I went for a ride on my 92 other day with other guys. We were going 40-50 mph, 140 miles I got 40.75 MPG. And I was bored...last man.
Ethanol gas with additive for water control.

twocams

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Twocams
69 R69S 03 K1200GT
92 R100RT

schrader7032
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San Antonio, TX
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Not sure if you were running

Not sure if you were running the fuel cleaner as part of the 140 mile run. It could reduce the volatility of the fuel, so could knock down the mileage. But an 800cc bike should do at least 10 if not 15 mpg more than that. Could be lots of things:

- valve clearances
- carb health and state of synching
- position of carb floats...they might be too high resulting in rich operation
- tire pressures
- final drive proper for the bike; RPMs might be higher than expected for given MPH

The stock ignition system should be just fine...I'd wait to throw money at this until you're sure of the state of tune. The bike should use zero resistance plugs and wires...the spark plug cap has a built-in 5K ohm resistance. Adding more resistance will make the spark weaker and it might misfire if the state of tune is marginal.

This page:

www.bmbikes.co.uk/specpages/R80RT.htm

suggests that the gas mileage should be in the low 40s.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Guaire
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Arlington, VA
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I added the BG before the

I added the BG before the ride. Riding speeds were from 40 to 60 mph. Using ethanol 10.
First thing I will do is check the valves. It's cheap. Then more after that.
Thanks,
Bill

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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

khittner
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If this was the first time

If this was the first time you filled the gas tank after a winter lay-up, your fuel tank probably wasn't full to begin with, even if you had filled it when you put it away last Fall. There can be a non-trivial amount of fuel evaporation over the course of 5 months or so.

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Konrad

Guaire
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Got the valves

Got the valves checked/adjusted. Left intake had zero clearance. L Ex was OK. Adjusted the Rights. Got out for a 50 mile run. Mileage went up to 31.9 mpg. Looks like it’s carb check time. It doesn’t feel like they are out of balance. When I stop, the motor goes to 2k rpm, then settles down to 1400 @ rpm. That bothers me.
Is there a connector for a carb sync on my Bings?
I saw the spec online. Informative.
I kept the bike running through the winter. I had a good tank of gas for my little trip. 91 octane, fresh.
EUBMW in Alexandria, VA has carb kits. I’ll want to see if anything is obviously amiss before I buy anything. Yes, I should check the float height.

Thanks,
Bill

https://www.eubmw.com/collections/carburetor-kits/products/bing-carburet...

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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

schrader7032
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With the idle RPM so high, it

With the idle RPM so high, it does sound like you need to do a carb overhaul and a synch. The carbs should have vacuum takeoff ports which lets a differential pressure device like a TwinMax attach. Here's a picture of the port on the side of my carb on my /7...the '83 port might be underneath.

  • carbport.jpg
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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Guaire
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Thanks, Kurt. I’ll get after

Thanks, Kurt. I’ll get after the carb situation. At least I don’t have to overhaul 4 of them.

Bill

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Twocams
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Another thing is the Governor

Another thing is the Governor weights inside the "can" hanging up? Oak had talked about them in one of the Airmail Magazines.

twocams

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Twocams
69 R69S 03 K1200GT
92 R100RT

Guaire
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Two cams - "Another thing

Two cams -
"Another thing is the Governor weights inside the "can" hanging up? Oak had talked about them in one of the Airmail Magazines."

I thought my ignition was electronic. Does the weights problem still apply?

Bill

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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

schrader7032
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The article was in Airmail

The article was in Airmail but written by Ken Tuvman about the bean can on his R65LS. The bean can contains Hall effect sensors...that's the electrical part. In order to advance the ignition, there is still a weight setup inside the bean can that advances the ignition as the engine RPMs increase. Here's the part:

www.realoem.com/bmw/enUS/showparts?id=0332-USA-04_1977_2477_BMW_R_80,_R_...

Pictures of it installed here:

http://redlegsrides.blogspot.com/2010/11/airhead-bean-cans-and-fog-banks...

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

mark_weiss
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If the idle speed drops very

If the idle speed drops very gradually after you have stopped, suspect a vacuum leak. Carb mount spigots to heads are an often overlooked possiblity. With the engine warmed up, loosen a carb to airbox clamp and see if you can use the carb as a handle to twist the spigot. If it is loose, remove, clean and tighten. Using thread sealant compound can help too.

Igntion advance weights hanging up often results in the idle hanging up, then quickly dropping to normal. Getting to the weights is a fiddly process.

If the amount of fuel system cleaner used was at a greater ratio than the directions for use recommended, or was at the 'severe clean' level, that could reduce fuel efficiency.

For reference, my '82 R100 generally runs in the mid 40 mpg range when ridden locally. About 50 when on a highway ride.

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Mark
qualitycycleservice.com

Guaire
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The right carb is off the

The right carb is off the bike.
I believe I found the vacuum port. Looks to be an M3 thread in there. There was a rubber plug over it. The plug had a complete crack running its length. It certainly could have been sucking air. I squirted brake cleaner into the hole and the spray blew into the intake passage.
The float needle valve definitely shows a 'witness line'. I'll have to go for a pair of those.
If the vacuum port screw is an M3, the motion pro carb sync won't fit. SyncPro runs on 4mm, or 5mm and 6mm.
I'll be walking the carb into my hardware store and checking the threads with bolts to find out the size.
The vacuum port should fit something I could buy at an auto parts store.

Bill

  • float_needle_71.jpg
  • carb_r_to_head_67.jpg
  • carb_bowl_intake_70.jpg
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schrader7032
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San Antonio, TX
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The screw comes up from time

The screw comes up from time to time...it's #1 on this page:

www.realoem.com/bmw/enUS/showparts?id=0444-EUR-06_1982_2477_BMW_R_80_RT&...

Should be a 3.5mm with 0.6 pitch thread.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Guaire
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83 cents each!

83 cents each!

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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

Guaire
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Arlington, VA
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I got parts today at Capital

I got parts today at Capital Cycle in Sterling, VA.

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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

Guaire
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One down, one to go.

One down, one to go.

  • carb_1_clean_98.jpg
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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

Guaire
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On went the Motion Pro after

On went the Motion Pro after the carb overhaul. The idling is even. But, altering the throttle cobbles, I could not keep the meters level as RPMs went up. Any ideas from experienced tuners?
The video link shows what happened on my best effort. Shouldn't the levels stay level as the RPM rises?

https://youtu.be/S7S5nZS8oIg

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1983 R80RT, 2014 Royal Enfield Continental GT, 1986 Honda VF500F

schrader7032
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San Antonio, TX
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I wouldn't worry about the

I wouldn't worry about the changing vacuum with higher and higher RPMs. The more throttle, the less impact the vacuum really has. What your checking on the cable synch is that the cables have the same tension on them at low RPM (where vacuum is more noticeable). You want to do this at low RPM, say 1500-1700, because this is the transition point from idle to off idle. You want smooth and even operation of the slides as you roll on.

There's a lot going on with air flow, etc., as you open the throttle to 3-4K RPMs. You're only interested in off idle.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

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