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Discussion Starter · #1 ·
Carbs completely rebuilt per Larry's book, ambient temp is around 50 deg f, new oil, air filter, operating temp reached, digital tach reads 1100 rpm +/-50, carbs are sync'd with a U-tube Manometer, to the point where the delta is less than 1/4 of an inch between the water columns;



I increase the throttle and the differential changes between carbs by as much as 5 to 6 physical inches...what are your thoughts? should the levels stay pretty close to those achieved at idle? When I let off the throttle from say 6000rpm, she steadys right up, and the water/dexcool levels match right back up again. vacuum leak somewhere? do I need to tweek the fuel mixture screws up or down a hair?
 

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I wonder of there might be a vacuum leak somewhere,, possibly around the throttle plate shaft??
 

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Vacuum leak or misadjusted valves are the first two things that come to mind.
 

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Balancing procedure if everything else is ok.



I think there are 3 or more schools of carb balancing. I prefer mine balanced at the rpm I use the most. And then test again at idle. If it's off a bit at idle I don't have much of a problems as long as it's good on the up side. The best would be perfect at both sides.
 

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Discussion Starter · #6 ·
I wonder of there might be a vacuum leak somewhere,, possibly around the throttle plate shaft??


This is a good possibility...I thought of leaks too, but had not thought about this. Are there kits for replacing the felt for these shafts? is it felt or brass? Maybe I need new bushings? This is all great feedback...I adjusted the valves, and they seem a bit noisy...I will go over these again.



I went back out to the shop and tightened up all of my hoses to the manometer with clamps, tried to eliminate any possible leaks with the measuring device and it appears to still do the same thing.



I would like to hear more about the throttle shaft seals, and how to tighten them up...thanks all...again, some really great feedback!!
 

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If you suspect a vacuum leak get a can or common carb cleaner or better yet a propane torch (don't light it!) and spray around anything that has to do with the intake side after the airbox while the engine is idling. If you notice a change in rpm then you've found a suspect area.



Don't do this in an enclosed area unless there is no gas heater and it's a large are then still limit yourself, it's much safer to do outside.
 

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I increase the throttle and the differential changes between carbs by as much as 5 to 6 physical inches...what are your thoughts? should the levels stay pretty close to those achieved at idle? When I let off the throttle from say 6000rpm, she steadys right up, and the water/dexcool levels match right back up again. vacuum leak somewhere? do I need to tweek the fuel mixture screws up or down a hair?
Good Morning from Oklahoma! I am new to this forum having recently acquired an '81 GL500 Interstate. The bike had sat for most of its 30 years and has only 2600 miles on the clock. It runs pretty well so I've had no reason to delve into the fueling system. I'm just now into the front brakes as they were a mess and waiting on parts to finish that job. I have no direct experience with these carbs but come from years of experience with BMW boxers. So, Im used to having a couple of feet between them! However, on most twins I've worked on, there are idle mixture (air bypass) screws that are adjusted separately from the throttle butterflys when balancing the carbs at idle and at operating RPM. Is this not true of these little Keihins as well?



Paul
 

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I wouldn't trust water as a medium for balancing carbs.Not viscous enough IMHO.My Carbtune doesn't use liquid so that's not a problem,



http://www.carbtune.com/



I reckon you aren't getting an accurate reading.If the carbs are balanced correctly at the maker's recommended idle speed +/- 10% of that speed they carbs should be balanced correctly all through the rev range.If not as other posters have stated the fault is elsewhere.I don't think you can sort your problem,if there is one,with your manometer.
 

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Good Morning from Oklahoma! I am new to this forum having recently acquired an '81 GL500 Interstate. The bike had sat for most of its 30 years and has only 2600 miles on the clock. It runs pretty well so I've had no reason to delve into the fueling system. I'm just now into the front brakes as they were a mess and waiting on parts to finish that job. I have no direct experience with these carbs but come from years of experience with BMW boxers. So, Im used to having a couple of feet between them! However, on most twins I've worked on, there are idle mixture (air bypass) screws that are adjusted separately from the throttle butterflys when balancing the carbs at idle and at operating RPM. Is this not true of these little Keihins as well?



Paul


Paul, you're among friends here, I'm in OKC & Old Okie is just West of me in Okarche.



You or the PO ever go the the Firelake Casino near Shawnee? If so I've seen your bike, if not it was either traveling through or there's another one in the state that hasn't found the forum yet. Are you going to get more specific than just NE Oklahoma?



Yes, the carbs on these are picky, Larry and a few others on here are carb experts. Larry even has a book now in publication that's by far worth an addition to your library. Also be sure to download the full FACTORY service manual stuff from the google docs site, a link to which you should find easily enough in the sticky notes at the top of the forums.
 

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Paul, you're among friends here, I'm in OKC & Old Okie is just West of me in Okarche.



You or the PO ever go the the Firelake Casino near Shawnee? If so I've seen your bike, if not it was either traveling through or there's another one in the state that hasn't found the forum yet. Are you going to get more specific than just NE Oklahoma?



Yes, the carbs on these are picky, Larry and a few others on here are carb experts. Larry even has a book now in publication that's by far worth an addition to your library. Also be sure to download the full FACTORY service manual stuff from the google docs site, a link to which you should find easily enough in the sticky notes at the top of the forums.
I'm in Bartlesville. Don't know if PO ever frequents casino of which you speak; not me. I've learned much about these interesting transverse V-twins in the few weeks I've lurked on this site. Today, I've pulled the front axle, lubed the speedo gear; removed the rear wheel and lubed splines. Rear brake shoes look good. I've found a replacement kickstand on eBay. Hopefully this solves the "leaning too far to the left" problem I seem to have. I will get some pics posted when I get her back together a bit. Thanks!
 

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As with anywhere in Oklahoma you're just up the street, simple turnpike drive puts me almost right at your front door. I'd almost bet it's the same bike I saw out at Firelake one night almost a year ago, not many around the state.



As far as "leaning to the left" if I recall most people have found that the actual mount is the problem but people have come up with resolutions for that.



Choose your parts wisely, sometimes things that are seen on eBay are still available from a Honda dealer. If it shows up as available on http://www.bikebandit.com then any dealer can get the part. http://www.tasmotorsports.com/ is also oe of my favorite suppliers as they often have a ton of stuff they never list on their website or advertise, just need a cell phone with free LD to call them. Matt will probably answer, tell him Marshall referred you and you're likely to get free shipping as well.



Nothing beats having OEM parts as opposed to some of the knockoff stuff you run into.



Rear brakes are rarely used by most riders thus they rarely wear, if they are noisy it's a simple matter of taking a bit of 400 wet/dry sandpaper to both them and the drum putting a light crosshatch pattern on them.



I had to replace my rears as one of the POs apparently relied on them heavily, I went with the replacement (both front and rear) from Niche Cycle on eBay. Heck of a lot cheaper than EBCs. They're made by EMGO which is a pretty good name brand, slotted and although I haven't ridden it yet since they were replaced I doubt I'll be dissatisfied. I also changed over to DOT 5.1 brake fluid (not DOT5) and I can't stress enough that there is some confusion between the two. 5.1 mixes fine with any 3 or 4 system but has half the viscosity thus response should be far better - especially on release. It's a good idea to change out your brake fluid completely anyway and if you've got a few extra bucks be sure to get one of the stainless hoses from http://www.jdaent.com/ as you'll end up with Teflon over stainless aircraft quality stuff instead of the common crap that you see on eBay. Send him a note and he'll probably already have the pattern as he custom builds every one by hand. As old as the front brake hose(s) are on these bikes they're using half the pressure to swell them and half to apply to the brakes, you can't afford to not have the best brakes you can on a bike that was pretty much underbraked to begin with.



We know most all of the best suppliers for these bikes so before you really buy something it's a good idea to get an opinion from the forum members, many of which seem to be on here 24x7.



Once it gets warmer and I get my paint done I have good reason to believe that Old Okie (in Okarche) and I just may make a little ride up to see you or meet you around Stroud which is a decent halfway point.
 

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Discussion Starter · #14 ·
I wouldn't trust water as a medium for balancing carbs.Not viscous enough IMHO.My Carbtune doesn't use liquid so that's not a problem,



http://www.carbtune.com/



I reckon you aren't getting an accurate reading.If the carbs are balanced correctly at the maker's recommended idle speed +/- 10% of that speed they carbs should be balanced correctly all through the rev range.If not as other posters have stated the fault is elsewhere.I don't think you can sort your problem,if there is one,with your manometer.


Thanks Shep; my manometer is filled with 100% Dexcool which is a bit more viscous than water. The tubing I chose to use was 3/8"ID and I have 1/16" diameter holes at the intakes. I think the Dexcool, the larger diameter tubing, as well as the restriction orifice, work together to really help keep the fluid from being so jumpy, and it would appear to be adequately dampened.



It is good to know for certain though that the balance should remain throughout the rev range. My gut feeling was a vaccuum leak as posted by other members. I know I did not remove, or inspect for that matter the felt that is found in the throttle and choke posts. It seems like it would be a simple enough thing to look into, not cost much money, and if anything one area in question to eliminate.



I used the analog U-tube manometer as well as a digital with a built in dampening feature, and they both confirmed the variations in DP.



I think i will use the ol' propane torch to check any suspected areas. Once she is warmed up, the motor idles very nicely and steadily around 1100 to 1130 rpm. It would make sense there is a vacuum leak. I will go out now to grab some pics as I left the manometer hooked up so you all can see my setup.



thanks guys!
 

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The propane method is, and has been, the choice of most auto mechanics for ages. Keep up the good work!

I also see nothing wrong with using Dexcool, if it needs to be thicker common glycerin would also work.



Just got off the phone with Old Okie, he also agreed that Stroud might be a nice place for us to meet. Not much to do around that town though after the tornado leveled their outlet mall ages ago but I know they've got a wonderful lake with camping areas that are rarely used, several nice inexpensive motels and a small bar that, the last time I was in it, was about half cowboys and half Indians. There were also a lot of girls in there looking for company but I was not at the time since I had a girlfriend up in that area who had to go on a trip and I just stuck around town for the rest of the evening. Had I taken any offers I'm sure it would have got back to her in no time.



Home of the Sac & Fox Nation and I think they also built a casino there as well as the two they have down in Shawnee. They're known to have the highest "win proportion" of any of them, in other words you can expect to end up between 85% - 90% successful. At some of the ones we've got near us you may as well take five $20 bills, toss two of them in the door then walk back to your car.



I'm far better playing the horses but of course I've got a ton of experience I've learned from a pro, developed my own system and while I didn't play this year at all last year was probably the first time I actually came out around -$20 for the entire year, for six years running before that I usually came out quite a few hundred $ ahead. Biggest night I ever had I hit a $455 Trifecta with a simple $4 bet: 7/5/1+2. It's not too hard to learn my system but it involves knowing which tracks are best, a lot of paper, a good pen and precise timing before you place you bet. I see all these people with tip sheets, programs and the like - some even have computer programs to figure stuff out in advance - but that isn't really necessary if you understand how the whole thing works. I'll be glad to share the system to anyone that wants it, it's based upon common sense.
 

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Discussion Starter · #16 ·




A pic of my manometer--went together in about an hour.



I went out there tonight...i think it was 20 degrees F!!! ha...anyways let her warm up, and after warming up, I tried the propane around the throttle and choke shafts with no apparant change in RPM. I was looking at the carbs further, and found that I do not have clamps on the rear intake nozzles that connect the carbs to the plenum
how embarrasing!



I guess I never got them from the guy I bought the bike from installed the carbs and never gave it anymore thought. I tried some heavy duty zip-ties, but I think I will need the proper clamps, and i think with the amount of variability I am getting when I run her up in RPM is coming from leaks at this point--funny how these things reveal themselves




I will get some proper clamps and post the results if at all there are any changes.
 

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Looks like a working setup to me!



The CV carbs are very picky on these bikes, so much so that even if you install the airbox cover with it pointing anyway but backwards it upsets the balance. Same thing if you put in anything but the proper paper air filter. Some people put in a K&N (which I love on my cars) but they're able to adjust for it, this bike won't so you've got to richen up the mixture a bit which requires jet changes. Larry can probably explain this better.
 

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As with anywhere in Oklahoma you're just up the street, simple turnpike drive puts me almost right at your front door. I'd almost bet it's the same bike I saw out at Firelake one night almost a year ago, not many around the state.



As far as "leaning to the left" if I recall most people have found that the actual mount is the problem but people have come up with resolutions for that.



Choose your parts wisely, sometimes things that are seen on eBay are still available from a Honda dealer. If it shows up as available on http://www.bikebandit.com then any dealer can get the part. http://www.tasmotorsports.com/ is also oe of my favorite suppliers as they often have a ton of stuff they never list on their website or advertise, just need a cell phone with free LD to call them. Matt will probably answer, tell him Marshall referred you and you're likely to get free shipping as well.



Nothing beats having OEM parts as opposed to some of the knockoff stuff you run into.



Rear brakes are rarely used by most riders thus they rarely wear, if they are noisy it's a simple matter of taking a bit of 400 wet/dry sandpaper to both them and the drum putting a light crosshatch pattern on them.



I had to replace my rears as one of the POs apparently relied on them heavily, I went with the replacement (both front and rear) from Niche Cycle on eBay. Heck of a lot cheaper than EBCs. They're made by EMGO which is a pretty good name brand, slotted and although I haven't ridden it yet since they were replaced I doubt I'll be dissatisfied. I also changed over to DOT 5.1 brake fluid (not DOT5) and I can't stress enough that there is some confusion between the two. 5.1 mixes fine with any 3 or 4 system but has half the viscosity thus response should be far better - especially on release. It's a good idea to change out your brake fluid completely anyway and if you've got a few extra bucks be sure to get one of the stainless hoses from http://www.jdaent.com/ as you'll end up with Teflon over stainless aircraft quality stuff instead of the common crap that you see on eBay. Send him a note and he'll probably already have the pattern as he custom builds every one by hand. As old as the front brake hose(s) are on these bikes they're using half the pressure to swell them and half to apply to the brakes, you can't afford to not have the best brakes you can on a bike that was pretty much underbraked to begin with.



We know most all of the best suppliers for these bikes so before you really buy something it's a good idea to get an opinion from the forum members, many of which seem to be on here 24x7.



Once it gets warmer and I get my paint done I have good reason to believe that Old Okie (in Okarche) and I just may make a little ride up to see you or meet you around Stroud which is a decent halfway point.
Thanks, Marshall. I do appreciate the good advice. This bike came from Muskogee. I trailered it home after dark last month and I do believe I bent the side stand when it shifted under the tie-downs. Got home and the entire weight of the bike was on the front wheel and kick stand with the rear wheel in the air! It's a miracle I didn't lose it all. The tang was broken off anyway. The replacement I found on eBay is in good condition and supports the bike much better plus has the tang. I'll slip a hockey puck under the stand when needed. I doubt the brake fluid had ever been changed and the entire system was a mess. One piston on the right caliper was frozen allowing the front wheel to barely turn. I've overhauled the MC and both calipers with OEM kits and installed new EBC pads. Rotors are good and true. Honda no longer provides the brake lines nor was I able to find them through my usual aftermarket sources. I've gone with Goodridge lines/banjo fittings and they should be here any day. After the brakes are done, I'll set the valves, put in new plugs, change all fluids and filters and ride her a bit with some fresh fuel. BTW, where do you attach a manometer to the intake tubes? Does something replace the small screws near the heads?



My oldest son recently moved to OKC. He's an engineer with Chesapeake. So, I do get over that way more often now. Say, is that great little chicken restaurant in Okarche still there? Ishem's I believe was the name of it. That might be a good ride destination!
 

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No idea about the Chicken restaurant but Okarche rarely changes, as with most tiny towns if it's good it's still there, however Chesapeake & Devon own almost half of OKC nowadays. I know a lot of people over there and it's hands down an excellent company to work for. Next time you talk to him ask if he's ever heard of Mustang Fuel or Clearwater Enterprises just for the fun of it.



Set the valves ASAP and be sure to follow the tutorials on this, when you're doing the chain tensioner (perhaps the most important item and should be done first) if you pass a TDC mark do not try to back up to it or all the slack goes to the other side and it won't work.



As far as balancing the carbs,if they're like the ones on my CX there is a screw on each one in the intake side right before they hit the rubber connectors that go to the heads. I don't know the size/pitch but I think they were a fairly common Honda part at one time and just recently someone started a thread that mentioned them so try the search in the individual forums or someone will chime in in time.



You're moving awfully fast on your project for an Okie, you sure you're from here? :)
 

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If you are satisfied that your device is working well then you have to get the levels exactly level,not just close.I know this can be frustrating but it's worth the effort.



The trick to it is getting the levels just a little out so that when the balance screw lock-nut

is tightened it's brings them in.Then a dab of thread-lock to make sure they don't go out again.
 
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