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Old 03-12-2012, 01:38 PM   #1
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Fuel economy issue

Havent been writing for a long time, but I have been around watching and reading . The problem is:
I have R60/7 with Bing slide carbs. Started to ride it last year. And the problem is that it spends to much fuel, around 10l/km. I haven't noticed it before, but now it's starting to feel on my valet.
Things that have been done upon the purchase of the bike: Carbs have been rebuilt (except float bowls, old ones where in good shape) and synchronized (by hand), needle jet set on factory position, timing done, valve clearance done, new air filter, new throttle cables, new spark plugs. I was informed by my mechanic that pistons and rings are in good shape (not perfect), cylinders also.

Now I have an opportunity to get my hands on Bing CV 32mm carbs and with proper adjustments fit them on 26mm cylinder. Will CV carb help to lower this high fuel consumption or will it stay the same? Or maybe it's better to stay with the slide carbs and check everything again (carbs, timing, valves...).

Thanks
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Old 03-12-2012, 02:23 PM   #2
97oilhead
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Have you checked the floats to make sure they are working properly. You could be driving along and fuel dripping out of the overflow.
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Old 03-12-2012, 02:44 PM   #3
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Quote:
Originally Posted by 97oilhead View Post
Have you checked the floats to make sure they are working properly. You could be driving along and fuel dripping out of the overflow.
On long rides I deliberately wore sneakers so that I can see signs of fuel leaks, but nothing. My sneakers were dry. Couple of times left the petcocks open for 20 minutes, again no leaks.
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Old 03-13-2012, 07:24 AM   #4
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Are you saying 10 Liters per kilometer? ???

There must be some mistake!

No, don't try installing different carbs to solve the consumption problem - the R60 runs great with the carbs designed for it.

With high fuel consumption it must not be running very well. Please tell us what other symptoms it's got. Without anything more specific I'd look into all possibilities that would cause this - wrong jets, needles too high, high fuel level...

This is the opportunity to learn what makes your bike tick!
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Old 03-13-2012, 07:46 AM   #5
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Yeah 10 LITERS per KM is like 4+ GALLONS per MILE...

Did you maybe mean 10km per liter?
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Old 03-13-2012, 09:56 AM   #6
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Yes, it's liter per km. It seems that I have been a bit off with calculation, the exact calculation is 8.85 L / 100 km. 260 km drive with 23 liters (tank capacity is 24 liters, and 1L left in the tank). But it still seems a bit high.
I am planing to reinspect the carbs. One thing maybe worth mentioning, the other day during a ride I have noticed that the bike has slightly less power going up hill. Maybe the clutch is worn out, can it effect fuel consumption?
Haven't noticed any other symptoms that I can tell, except the clutch issue.

thanks
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Old 03-13-2012, 11:11 AM   #7
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I wouldn't buy different carbs either. If fuel consumption is a problem I certainly would not go to bigger carbs. Buy the Bing manual for the specific carbs you have about $10 USD from Bing and go through the carbs again to make sure everything is in good condition and in spec. Do it yourself so you "know" what's what and not taking some guys word for it. Is your choke/enricher circuit fully releasing when not needed? I'd suspect you're running really rich or your ign system isn't properly burning the mix. You getting black smoke out the pipes when at road speed? Do a plug chop test and read the plugs. If your clutch is slipping you'd notice it going through the gears not just on hills. It would effect your mileage somewhat but as much fuel use as your experiencing a slipping clutch that bad would be very noticeable and not just a guess if it's slipping. I seriously doubt your problem has anything to do with the clutch. Before you go through the carbs again "yourself" make sure your ignition system is functioning at 100%. If you've got an ignition glitch you'll go crazy trying to fix it by messing with the carbs. You are running stock plugs right? And not some new fangled zowie wowie multi tip super duper save the planet plugs.
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Old 03-13-2012, 11:23 AM   #8
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No one yet mentioned, verify the timing. I would also want to know real compression numbers. In spec?? How weak?? Both of those can cause poor combustion or power efficientcy.
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Old 03-13-2012, 01:26 PM   #9
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So given your new numbers, you're getting 26.6 mpg or 11.3km/l.

That's definitely low, but within the range of tuning I would think.

Does the bike run fine? Do you wind the throttle like a maniac?

Have you verified that there aren't any cracks underneath the tank that maybe leak when the engine heats up?
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Old 03-13-2012, 06:02 PM   #10
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How many miles on the bike?

It's possible the needles and needle jets are badly worn and need replaced.

But still, that bike should get in the 40s to over 50 miles per gallon.

If you're concerned about tuning and fuel economy (at least as a baseline) be sure to avoid hard acceleration and high speeds. Staying in top gear and cruising will get the best mileage - any time lower gears are used, the bike travels less distance per crankshaft revolution, thus worse mileage. Every time inertia is overcome, power is required which means more gas usage.

But even ridden hard, these bikes should get better mileage than 26 miles per gallon!
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Old 03-13-2012, 06:43 PM   #11
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26 mpg could be had out of a R60 running perfectly. That's exactly why I go on about my mileage. To a large degree it varies too much depending on how you ride to diagnose anything from mileage. That bike should get over 40mpg? No it shouldn't since it all depends. Your bike drops 20mpg? That can be simply from riding slightly above the law to way beyond it. Same bike. Same tune. Of course, it could be something up with the bike too but it all depends. Peoples riding habits vary way too much to be suggesting a state of tune by mpg IMO.
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Old 03-14-2012, 01:33 PM   #12
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I am an 'easy rider'
Never gone high RPMs, always around 3k up to 3,5k. Plugs that I am using are NGK BP7ES.
I will give it a nice long ride, and then check everything, from carbs (needles, jets, float bowls), ignition, timing, compresion. So I can compare, before and after.
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Old 03-14-2012, 03:56 PM   #13
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It could be anything or a combination of anythings. Start at the beginning and move on from there and you will come by the reason(s).
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Old 03-14-2012, 04:40 PM   #14
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Quote:
Originally Posted by MaraBiker View Post
I am an 'easy rider'
Never gone high RPMs, always around 3k up to 3,5k.
3000 is really the bottom of what I'd consider to be the usable RPM range. Try revving it up a bit. As for your fuel consumption, I'd look at replacing your needle jets and needles. They both wear.
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Old 03-16-2012, 12:20 PM   #15
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thanks everybody for your comments, cheers
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