Author Topic: '86 K75S mission to accomplish better fuel consumption  (Read 9348 times)

Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #25 on: March 05, 2019, 04:44:24 PM »
If you're referring to a lot of discussion about injectors to be used in the classic K models, that's probably because these are road motos rather than race motos, and many would rather be riding when the moto is running smoothly instead of investing fuel dollars on dyno testing.

Be patient. Somebody will come up with the data, but from what you wrote in your previous post, if you want it to be good data, it seems like you'll need to do it yourself.  :yes

I am referring to the four hole vs. one hole injector debate. Probably you are right, however I have seen dyno tests on various items, including exhausts, so it baffles me, why nobody done it to these injectors, a most vital piece of equipment to fueling. Nevermind though, as I am not planning to upgrade these, only to replace the one in question, as my cash is rather hard earned and I am parting with it only if I really have to :)
  • Budapest, Hungary
  • K75S 1985 model

Offline Martin

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #26 on: March 05, 2019, 04:50:29 PM »
The only problem with doing your own injector testing is you need to use extreme care. You are dealing with explosive vapors and you don't want to set fire to your bike, house, garage or your dog.  For safety sake I used an air powered set up.  As to why there are no dyno tests out there it's probably not in the best interests of the companies selling the four hole injectors. If you had a product that was supposedly superior wouldn't you want to show dyno proof of it's superiority.

 As an interesting aside I had a couple of injectors that wouldn't come clean with various cleaners and injector cleaners these injectors had no flow at all. While getting "O" rings and injector filters at a local European aftermarket car workshop we were talking injectors and I told him about my blocked injectors. He asked me what I was using and I said Wynn's injector cleaner and he revealed that when they clean injectors they use lacquer  thinners. It took about three goes but the blocked ones eventually cleared and showed good patterns. They were given to me by a mate had been sitting for about thirty years and he deemed them totally stuffed.

Regards Martin.

  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #27 on: March 05, 2019, 04:57:08 PM »
the speedometer reading has nothing to do with the odometer reading.  They operate on two separate electrical mechanisms.  A measured run is the surest way to check the tripmeter.  It sounds like yours is running accurately, but a measured run is the only test  I would trust.

Gryph, I was under the impression, the speedometer and the tripmeter are driven by the same stepper motor, that has got the small potentiometer connected to it. If not, that would explain, why my speedo is 5-10% optimistic and the tripmeter is spot on...
  • Budapest, Hungary
  • K75S 1985 model

Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #28 on: March 05, 2019, 05:00:47 PM »
I got some injectors at the car wreckers for one of my spare bricks which seem OK but have only riden around the block with them. The injector and part number are almost identical. (part no. 0280 150 208) They were from a six cylinder BMW 520i 1983 model. Also a net search suggests many 90's models as suitable. Some having 4 holes which are supposed to be more economical.

Dave, I have read, the 318i 1983 uses the same injector, as the K75, so you are probably on the mark with an another 1983 BMW. I am sure, Bosch did not manufacture a VERY specific injector just for these bikes, however form factor, size, securing pin, flow rate, impedance, etc etc has to be taken into account and I am lost with all that data buzzing around my empty head :)

BTW, does anybody has got any ideas, as to what changed in '89 (apart from world order :) )? I might have access to some K100 injectors, but I would need to know, if they are swapable... Flow rate is different, lower in the newer type injectors, but were they changed because of some environmental legislation? (if everything remains the same, including the computer, the newer injectors must have run leaner) Or did they swap to Motronic at that time?

K75 injectors and K100 injectors up to '89 - 13 64 1 460 450
K100 injectors after '89, K1, K1100, K1200- 13 64 1 461 523
  • Budapest, Hungary
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Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #29 on: March 05, 2019, 05:36:40 PM »
Dave, I have read, the 318i 1983 uses the same injector, as the K75, so you are probably on the mark with an another 1983 BMW. I am sure, Bosch did not manufacture a VERY specific injector just for these bikes, however form factor, size, securing pin, flow rate, impedance, etc etc has to be taken into account and I am lost with all that data buzzing around my empty head :)

BTW, does anybody has got any ideas, as to what changed in '89 (apart from world order :) )? I might have access to some K100 injectors, but I would need to know, if they are swapable... Flow rate is different, lower in the newer type injectors, but were they changed because of some environmental legislation? (if everything remains the same, including the computer, the newer injectors must have run leaner) Or did they swap to Motronic at that time?

K75 injectors and K100 injectors up to '89 - 13 64 1 460 450
K100 injectors after '89, K1, K1100, K1200- 13 64 1 461 523

OK, to answer my own question, BMW switched to Motronic and 16v at the time (according to Adam Wade's Motorcycle Fuel Injection Handbook)  (...) The LE Jetronic fuel injection system with separate ignition management was replaced by Motronic engine management with the introduction of four-valve cylinder heads with the 1990 K1 and the 1991 K100RS
  • Budapest, Hungary
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Offline daveson

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #30 on: March 05, 2019, 06:07:40 PM »
I did two searches for my alternate injectors for specifications, one almost identical to the originals, the other a bit different. I have put them in my '85 model,  my only registered bike (I have a stack of bricks now)  I will compare them for fuel economy, I think that's a good test for suitability.

Often just looking at injectors is a big help for comparison.
I have some four hole injectors too,  eventually ill put them in as a test also.

I lost my license six weeks ago for speeding, that's going to improve my fuel economy too,  another six weeks to go.

  • Victoria, Australia
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Offline The Mighty Gryphon

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #31 on: March 06, 2019, 09:46:20 AM »
Gryph, I was under the impression, the speedometer and the tripmeter are driven by the same stepper motor, that has got the small potentiometer connected to it. If not, that would explain, why my speedo is 5-10% optimistic and the tripmeter is spot on...

The pulses from the pickup in the final drive are split into two paths in the cluster. 

One path goes to a circuit that converts the frequency of the pulses into a voltage/current that goes to the meter movement in the speedo.  The voltage/current deflects the needle to indicate the speed you are moving at.  The higher the frequency of the pulses, the higher the voltage/current going to the meter movement and the more the needle will swing up the speed scale indicating higher speed.

The other path sends the pulses to a synchronous motor that converts them into rotation.  The higher the frequency of the pulses the faster the motor turns the odometer/tripmeter gears to register distance. 

The calibration of the odometer motor is fixed by the number of poles but the circuit that controls the speedometer needle deflection is adjustable to allow for mechanical variations in the meter movement that indicates the speed.  Because of this, the odometer is always spot on, while the speed readings can be anywhere within the calibration range of the circuitry.  As the bike comes from the factory the speedo is about 8-10% high, but the odometer is spot on. 

While there are ways to calibrate the speedo to an external signal from a soldering iron or Karamba software, I have found that turning the calibration pot all the way to the stop gets my speedometers very close to perfect.  Wish I could remember whether it's clockwise or anti-clockwise.

Bottom line is that regardless of what the speedo is saying, the odometer SHOULD BE accurate.  Both instruments depend on a good signal from the final drive pickup.  From time to time you should pull the pickup and clean the face of it to remove any metal particles that may be on it.  These particles can affect the accuracy of the instruments.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline alabrew

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #32 on: March 06, 2019, 01:59:57 PM »
"I lost my license six weeks ago for speeding, that's going to improve my fuel economy too,  another six weeks to go."

How does it work where you are? Guessing not your first offense?

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Offline daveson

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #33 on: March 06, 2019, 04:31:59 PM »
In Victoria you get penalty points for different offences, twelve points and you lose your license, but if you exceed the speed limit by 25km/h (~16mph), you lose your license  regardless. That's the first time it's happened to me,  although I have lost points in the past for smaller scale speeding. I was doing 130 in a 100 zone. (~81 mph in a ~62 zone) 

Speeding was something that never interested me until about six months after I got a brick, I'm not much interested in doing these "compression tests" anymore. Naturally the fuel economy dropped compared to when I first started riding it. I think bricks are exceptional in being able to do 200km/h and 20km/lt, but they can't do both at the same time.
  • Victoria, Australia
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Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #34 on: March 07, 2019, 03:27:09 PM »
The pulses from the pickup in the final drive are split into two paths in the cluster... 

The other path sends the pulses to a synchronous motor that converts them into rotation.  The higher the frequency of the pulses the faster the motor turns the odometer/tripmeter gears to register distance. 

Wish I could remember whether it's clockwise or anti-clockwise.

 From time to time you should pull the pickup and clean the face of it to remove any metal particles that may be on it.  These particles can affect the accuracy of the instruments.

Gryphon, thanks! I have not seen your answer, as I must have turned off notifications for this thread by accident, or something...

It is anti-clockwise, I did it with a soldering iron, but you are correct, potentiometer hitting it's stop is approximately the right amount of correction. I left mine registering just a hair - 1-2kph more, than truth, cops around here are a pain in the arse and they fine you if you are over by a very small amount.  My tripmeter is not smooth, but jumps, hence I thought there is a stepper motor inside, probably something is amiss, however I measured today yet another 30km's and it was again very precise. I might need to dig out the sensor anyway, as it's cable is getting brittle and I fear, it will crack at the most inconvenient of times. 
  • Budapest, Hungary
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Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #35 on: March 10, 2019, 05:36:04 PM »
OK, fuel consumption did not change much since having the injectors done. I have noticed, my header pipes turned blue, before they were more yellow-honey coloured. I have not checked the plugs as yet, will do so tomorrow.

After a 2-300 km's I can now say for sure, 'backfiring' upon coasting is back, I did not have had any of that since changing the muffler fairy dust seal. I also tried to re-balance the throttle bodies, but it was perfect, so it appears, injector cleanliness has got nothing to do with the balance :)

So if the plugs will be good, what else is there to try? Brakes I will check soon again, I do not like their operation especially whilst wet, the front basically becoming half power in the rain and the rear brake must be still dragging.
  • Budapest, Hungary
  • K75S 1985 model

Offline The Mighty Gryphon

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #36 on: March 10, 2019, 05:57:07 PM »
If the plugs look good with a nice tan color on the nose, I would wonder if the engine is running cold and not warming to proper operating temperature.  That could be caused by a thermostat that is stuck open and cooling the engine too much in the cool weather.  Beyond that, I am stumped.  It will be interesting to see if consumption goes down when the weather warms up as summer approaches
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Martin

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #37 on: March 10, 2019, 06:08:01 PM »
I found that in order to eliminate backfiring on over run I had to do the following. 1/ Correctly adjust TPS. 2/ Eliminate vacuum leaks. 3/ Eliminate exhaust leaks at the fairy dust gasket. 5/ Correctly adjust the mixture 6/ Shut the throttle when coasting on overrun. 7/ And the final piece in the puzzle, get the correct spray pattern on the injectors.

Early on when I first got my bike I had the mixture adjusted there times unsuccessfully, I ended up buying my own exhaust gas analyser $300.00 Au I think. Had my injectors cleaned professionally twice no difference, I then built my own cleaning test rig and got the correct flow and pattern which totally stopped the backfiring. However since then I have run with the TPS disconnected as it reduces the jerkiness at low speed and it will backfire occasionally. I'm willing to put up with this due to it is easier to ride at slow speed. Lately I have been thinking of putting a switch into the circuit so I can switch it on and off. The other idea is to reconnect the switch and adjust it so it doesn't work in the early part.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Martin

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #38 on: March 10, 2019, 06:35:17 PM »
You could also be wasting money if you have your injectors cleaned. And you don't make sure your rail is clean, and replace your hoses and filter. Or at the very least make sure you hoses are not breaking down and contributing to blockages. When I cleaned mine I replaced all the hoses and the filter.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline daveson

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #39 on: March 11, 2019, 02:11:45 AM »
Turn the rear wheel by hand,  there will be minimum resistance, then apply and release the rear brake. Turn the wheel again, the resistance should be the same. Check on other occasions also.

The pipes turned blue, that is something to worry about.  It's a sign of overheating. All three?  Think of the things you did before that and reconsider them. Are they the right injectors? I'm thinking it's not a good idea to replace only one injector,  keep them all the same.  Maybe double check the hall sensors (in case they are loose) as wrong timing would effect all three cylinders. I think you pinched the outlet of the fuel return line inside the tank, in a previous thread. Consider opening it up again.

What is the final drive ratio? The standard for your bike is 32/10, that is 3.2:1. From memory this will result in speedo and tacho needles being parallel in fifth gear.
  • Victoria, Australia
  • Current;'86 K100RT Past; '97 Yamaha V Star 650 Yamaha V Star

Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #40 on: March 12, 2019, 10:11:07 AM »
GUYS, thank you very much for your replies. I do not know, how to turn back the notifications for this thread, I thought, nobody is bothered with my ongoing crap, it turns out quite a lot of you are...

Anyway, I'll attach pictures of my header pipes and the plugs. Plugs, again, look pretty much the same, probably a bit richer, but still nice tan coloured. There is oil on the threads of one of the plugs, but it could have been oil seeping past rings, whilst bike was on the sidestand.

Dave - there is little resitance and slight dragging at the rear wheel, and the bike is easy to push. But as we discussed in an another thread the brakes must be dragging whilst the bike is on the move, as the rear rotor gets hot to the touch even if not used. I have sourced a low mileage rear rotor for a song, so I will replace that and check, if it is not warpage or such, that is making the rotor touching (as the whole brake fluid path - master cylinder, pipes, caliper etc were serviced very thoroughly 4-500 kilometres ago). I did not replace one injector, I have sourced a original K75 one and I will keep it with me just in case the one with the cracked plastic body bites the dust. I did open the fuel return line, when I had this problem with the burning fuses, even though fuel was flowing just fine with the pinched line. I do not know, where to check the ratio, I had a poke around the final drive, but could not see any numbers anywhere. Probably I need to clean parts a bit more thoroughly :) In fifth gear gauges move in unison, however tach needle is sitting higher than the speedo

Martin - TPS clicks, as it should and upon releasing the throttle rpm drops for a fraction of a second nearly to zero before bouncing back, so I guess it tells the computer to shut of the injectors, as it should. Fuel hoses and fuel filter were replaced very recently, back in September - October time, some 1000 kilometres ago. I did not check rail however, I might do that too in the near future.   

As far as I am aware, I do not have any vacuum leaks anymore, I used to have massive ones, but I replaced quite a few parts and now RPM stays the same, no matter how much starting fluid or carb cleaner is hosed down on the joints. Exhaust gasket too was replaced recently, just when I serviced my clutch splines and the muffler had to come off anyway. BTW backfire is not the right word, it is more like bubbling, or slight afterburn when throttle is closed and bike is coasting. I am not too keen on buying yet another set of specialised equipment but it would be interesting to see my CO2 levels (alongside some other stuff, fuel pressure, compression, etc, but stuff is veeeery slow to arrive from China).

Gryphon - I've never checked the thermostat, so that is another thing to test. It is very balmy here at the moment, as it is unseasonably warm with 15-20C. I would think, this temperature is just about ideal for our engines. Also whilst I had the Tucano installed, bike gone as warm, as it would in early summer, actually making me remember, how it was burning my legs back in August :)
  • Budapest, Hungary
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Offline Laitch

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #41 on: March 12, 2019, 11:26:49 AM »
I do not know, how to turn back the notifications for this thread,
Notification about a thread is the choice of each member. If members have not activated notifications or have chosen to shut off notifications to prevent the onset of derangement by exposure to tedium, repetition or futile hurling, they'll only know what's happening in a thread if they go looking for it.

You'll find Notification options by clicking Profile in the header menu located at the top of the page then clicking Modify Profile.
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Offline The Mighty Gryphon

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #42 on: March 12, 2019, 04:21:06 PM »
Gab, the plugs look very good.  So good compared to mine that they make me envious.  They indicate a good fuel/air mixture.  Are they the correct heat range?  A hotter plug running in a rich mixture can give a good reading while using a lot of fuel.

The final drive ratio is stamped on the top of the final drive near where the drive shaft is attached.  The numbers are not very large and lightly stamped into the casting, so they can be hard to spot.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Martin

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #43 on: March 12, 2019, 04:36:24 PM »
Bubbling, burbling and or rumbling is fine, and is part of the bike character. I personally think it's declaring it's happiness at being out and about and being well cared for. But on the other hand I could be quite mad, MAD, MAD I say OOO HA HA HAR. Sorry about that I'll go take my medication.
Regards a recovering Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #44 on: March 12, 2019, 05:55:01 PM »
Gab, the plugs look very good.  So good compared to mine that they make me envious.  They indicate a good fuel/air mixture.  Are they the correct heat range? 

The final drive ratio is stamped on the top of the final drive near where the drive shaft is attached.  The numbers are not very large and lightly stamped into the casting, so they can be hard to spot.

Gryphon, thanks, that's reassuring (however I am baffled as to why my fuel consumption is not like yours... Oh well, a good amount of things are still to be checked). The plugs are factory standard Bosch X5DC's.

I have found the ratio stamped on, it is very faint indeed, but it shows 32/10, so as Dave pointed out it is the correct one for my bike.
  • Budapest, Hungary
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Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #45 on: March 12, 2019, 06:03:54 PM »
Bubbling, burbling and or rumbling is fine, and is part of the bike character. I personally think it's declaring it's happiness at being out and about and being well cared for.

Haha, I never thought of that sound being a K75 purring, but I will not bother myself anymore with it then :) Same as for the whistle of the fuel pump, first it drove me crazy, now I do not hear it anymore (especially since the cicadas left my tank)...
  • Budapest, Hungary
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Offline The Mighty Gryphon

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #46 on: March 12, 2019, 08:28:48 PM »
Personally, I wouldn't get too wrapped up in final drive ratios.  My experience is that they don't affect fuel efficiency that much.  I don't think a dragging brake will reduce efficiency as much as you're experiencing either.  If it was, I would expect the rear end of the bike to be bursting into flame.

Have you checked valve clearances?  I can't recall if you have.  I have to admit that I'm grasping at straws right now.  The only other thing that I can think of is a slow leak.  A leak of 2-3 liters per tankful is unlikely, but possible.  Leakage rate, if that is the problem, would be on the order of 1/2 liter per hour of operation.  If it is coming out the vent hose you may smell and/or see some fuel around the swing arm and final drive following a ride.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Martin

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #47 on: March 12, 2019, 08:41:02 PM »
Gabe you are starting to get it, embrace the 75's uniqueness. It is unlike any other bike and the better for. I've had mine for 21 years, while mates swap bikes every couple of years. I'll stick with mine to the end.
Regards martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline daveson

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #48 on: March 13, 2019, 05:34:31 AM »
I think it's important to reverse whatever caused the pipes to turn blue.

Find the cause of the brake disc getting hot,  even when not used. Turn the wheel, is there any binding? Brake pedal fee play correct? Brake lever free play correct? Check also while hot.  Wheel turns freely when disc hot?

Your bike may be over reving. You should have 4000RPM at 100km/h Maybe your clutch is slipping. I suppose you have the right tyre. Do you have 75mm inner clutch cable length at gearbox? Correct free play at lever, adjusted from push rod? If so,  in fifth,  foot hard on brake pedal,  2000RPM, let clutch out; the engine should stall.

Do the test only as a last resort.
  • Victoria, Australia
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Offline szabgab

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Re: '86 K75S mission to accomplish better fuel consumption
« Reply #49 on: March 13, 2019, 10:24:10 AM »
I think it's important to reverse whatever caused the pipes to turn blue.

Find the cause of the brake disc getting hot,  even when not used. Turn the wheel, is there any binding? Brake pedal fee play correct? Brake lever free play correct? Check also while hot.  Wheel turns freely when disc hot?

Your bike may be over reving. You should have 4000RPM at 100km/h Maybe your clutch is slipping. I suppose you have the right tyre. Do you have 75mm inner clutch cable length at gearbox? Correct free play at lever, adjusted from push rod? If so,  in fifth,  foot hard on brake pedal,  2000RPM, let clutch out; the engine should stall.

Do the test only as a last resort.

Dave - the only thing, I could do to reverse this to source some dirty injectors and run them instead of the freshly cleaned ones :)

Rear rotor I replaced today morning before going on a trip of +/- 15 miles. Needless to say, I forgot to test the brake, so a non operational rear brake surprised me a bit down the road, fortunately in a non-catastrophic situation... Anyway, once I pumped it a bit and lightly dragged the rear brake for a while the pads embedded themselves to the new rotor and brake operation is restored to normal. It appears to me, this rotor + pads combo works better, than the old one, as the rotor is not getting too warm after a ride, also it feels like bike is easier to push around. The old one was an ABS rotor, the 'new' a non-ABS one (I have no ABS installed on this bike), it should not make a difference, but it most likely does (however I will report back after a tankful or so, as we all new, how subjective these things are).

4000RPM is 81-82 km/h on the adjusted speedo. Clutch operation is faultless, cable length, free play all set to factory standard. Clutch is not slipping and I have tried your last resort incidentally yesterday, in rush hour traffic I was coasting towards a hard turn in fifth gear, forgot about it and let go of the clutch whilst already maneuvering into the curve at 5-10MPH. Bike stalled, nearly dropping me off, fortunately I managed to squeeze the clutch, saving the bike and my butt :)
  • Budapest, Hungary
  • K75S 1985 model

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