The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Bob_Roller on April 18, 2007, 06:41:01 PM
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Ordered a full rebuild kit for the carbs today from the Bing Agency in Kansas. I also ordered the Bing factory manual as well. In talking to the owner on the phone, and he stated that after 25,000 miles these carbs need a good looking at, I gues the main jet that the needle valve on the diaphram attaches to, takes alot of abuse and wears faster than you would think. I have noticed my fuel mileage has dropped over the last 2 years, I attributed it to the 10% ethanol content of fuel nowadays. I guess I'll see if a full rebuild brings it back to 45-50 mpg that I was getting when the bike was new.
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Taking the first carb apart didn't go too well. One screw that holds the butterfly plate to the throttle shaft was peened over to the point that there was barely any slot for the screwdriver, I filed all of the screw that protruded beyond the shaft, but the screw head sheared off. I got the remaining part of the screw out but not enough thread left to secure the screw, so it looks like I need a new throttle shaft! But I am using my ultrasonic cleaner to clean up the disassembled carb, we'll see how good of a job it does.
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I forget, if I ever knew, how many miles are on your bike. Why are you rebuilding the carbs? I mean, did you have a symptom to correct, or are you doing it as preventative maintainance? Also, I don't understand this sentence:
"I gues the main jet that the needle valve on the diaphram attaches to, takes alot of abuse and wears faster than you would think"
Um, sorry, I don't know where to start there. :-[
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Ed, the part that I am talking about, is the brass piece that the needle on the diaphram goes into, I have a 1/16 th inch clearance all the way around with the needle inserted into this main jet. This should be a closer tolerance fit. The fuel mileage has dropped about 7-8 mpg in the last year or two as well. The bike isn't performing as well as in the past, it's just short of 80,000 miles. The throttle shaft o-ring was shrivled and not sealing at all. I replaced all of the seals except the throttle shaft o-ring about 9 years ago, and with this desert heat, it's taken it's toll on the rubber parts again, the o-rings were as hard as rocks and brittle. I think this may have a bearing on just passing the emissions test last week. I'm not overly impressed with the cleaning with the ultrasonic cleaner either, I think I'll get some lacquer thinner and see if it improves the condition of the carb.
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The needle on the slide (metering rod in a QuadraJet carb) rides in the main jet in the carb body. Conventional wisdom says these need to be replaced at about 35k intervals as the needle (hard) vibrates inside the jet (soft) and hogs out the hole in the jet. I have read that putting in a new pair of needles and jets can sometimes get you an 8-10 mpg increase!
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I'd agree totally. Did a complete (gaskets/seals, needles, jets, floats etc) on my 65 years ago when it had 65000km on it. Immediately noticed improved tractability, running, crispness, ease of tuning, idle etc etc, and later found an improvement of at least 5mpg (imp) which means I now easily get 350km till reserve instead of 320km.
Well worth the expense IMO.
Bill...................;-)
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I was getting a consistant 225 miles to reserve for about 25 years and if I went easy on the throttle 245-250 miles to reserve wasn't too uncommon, since then it's dropped to 195 miles to reserve. I blamed the addition of 10% ethanol for my mileage decrease, so I guess we'll see if this improves the mileage.
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Bob, I've been extremely surprised but I have not noticed any difference in mpg since our county's federally mandated switch to "gasahol". I can get the MTBE stuff 5 miles down the road but really can't tell the difference except the gasahol crap is about 3 - 5 cents a gallon higher on average... When the switchover was first made the refiners were a bit behind and the alky stuff was 10 - 15 cents higher! :o Then, the local media ran stories for about a week about how much cheaper the other stuff was if you just drove a couple miles and after a few months the prices were within a couple of cents. :P Don't know if that was because the refiners got caught up or the media's fault for pointing out to everybody how much cheaper the gas was across the county line and they just oozed prices up 'cause they could! Bastards... >:(
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I thought that was called the needle jet, and the main jet was lower. Can't remember for sure right now. I just replaced my needles and needle jets a few weeks ago, and I got pretty crummy mileage riding from Hood River through the Columbia River gorge at around 90 miles per hour. I think it was around 32 miles per gallon; 4 gallons of gas to get to Dallas, OR.
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Ed, if you have the needle set too high it will richen the cruising mixture and ruin your mpg. Or, maybe you got the wrong jet and needle?
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Same numbers as the Bing book specifies, and the same as the old ones. I also made sure the new needles poked out of the slide the same distance as the old ones, as I did not find it intuitively obvious how to feel how many turns down I was going. I think I have it right. But then, I only ever got 40 miles per gallon before.
For what it's worth, the Columbia Gorge is famous for being very windy, and for my normal commute, I rarely have the opportunity to go over 90, so in a way I was kidding. With my Windjammer, those speeds are very comfortable. I should ask my friend on the R100GS what kind of mileage he thinks HE got.
My spark plugs always look faintly gray, not too white, but obviously not fouled. I let them go the full 10,000 miles the book specifies, and they work fine.
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The needle on the slide (metering rod in a QuadraJet carb) rides in the main jet in the carb body. Conventional wisdom says these need to be replaced at about 35k intervals as the needle (hard) vibrates inside the jet (soft) and hogs out the hole in the jet. I have read that putting in a new pair of needles and jets can sometimes get you an 8-10 mpg increase!
BINGO! I have seen this with these carbs before. Another symptom, if you have access to a gas analyser, is a tremendous jump in emissions from Idle to part throttle. the brass jet wears and if you look very closely at the needle you may find that it has developed a double taper right where you hold the throttle the most. Bummer about the butterfly shaft. you did index the butterfly discs before removing tho? they are not symmetrical and need to be positioned/centered in the bore before tightening the screws.
rich
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I marked them them with a vibro-etch tool, so I don't install it incorrectly. The throttle shaft is $14 from Victory BMW, so it isn't a real big deal. I think the person that peened these screws had 'issues' at the time and his therapy was to whack the crap out of these fasteners!
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I was just thinking...did I peen over the screws on my rebuild? Hmmm... Can't remember whacking them. Think I used blue Locktite and then gave them a little crush with vice grips. Just enough to deform the brass screw a bit. I'll probably need new shafts myself on the next go-round.
rich
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The screws that I removed were steel, and they were significantly deformed, almost to the point to what a rivet looks like. I think the screw may have expanded in the threaded area that contacts the shaft, and thats where my problem came from.
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The carb rebuild kit was waiting for me when I got home today, you don't get a lot for $118, but I can tell the needle jet ( you were right Ed!) was significantly worn compared to the new one. Also if you are mystified about the theory of the carbs used on our bikes, the Bing Agency has a factory manual that is quite informative, along with trouble shooting tips, and if you modify your engine or exhaust there are tips and charts to help you get the rejetting right, and it's about $10 plus shipping. This manual recommends that the needle valve and needle jet be replaced every 25,000 miles due to the wear that occurs on the brass jet.
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I got 45 mpg last Saturday where I rode about 300 miles. Not much interstate stuff, mostly county roads. I was really happy to see 243 miles on the odometer when I filled up the second time that day.
Unfortunately, the last time my jets might have been replaced was when I dropped off my bike at a Honda dealer in Williamsport, PA to have my carbs rebuilt (pre internet...), so I don't know exactly what bits were replaced and which were not. I know the bike ran a lot better afterwards! Good mechanic.
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Rob, it seems like I get the best fuel mileage if I keep the speeds in the 55-60 mph area. But with highway speed limits at 75 mph here in Arizona, my mileage drops quite noticeably at 75 mph. About 15 years ago, I tried this test on a long stretch (30 miles) of straight country back road, I would set my speed, wait for the .0 to come up in the trip odometer, and turn off the fuel at the petcock, and see how far I could go until the engine first sputtered. If memory serves me correctly, I think 45 mph got me the farthest with this test, hardly scientific or controlled, but it was informative. Now I need to test how far I can go on reserve at different speeds, to see what kind of range I really have, if I get into a situation that I didn't plan for.