Author Topic: 1986 K75c - Fuel Tank Vent Hose Rounting  (Read 30039 times)

Offline Laitch

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #50 on: February 22, 2019, 09:18:59 AM »
Would this extensive test be necessary, if the values measured at the computer are well within specs?
What about the HES? Is there an easy way to tell, if timing is correct?
You already asserted the coolant temperature sensor values at the computer were in spec; I already stated the more complex test was optional.

Wait a minute! You've already set the valve clearances. As far as determining an easy way to tell if timing is correct, describe what seems easy to you and what seems difficult. That will establish your personal baseline.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline The Mighty Gryphon

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #51 on: February 22, 2019, 11:41:56 AM »
Timing is fairly easy to check.  Remove the "T" shaped cover from the front of the engine.  Behind it you will find the plate the HES are mounted on.  The plate and the valve chain cover are machined to provide a cutout inspection hole where you can see the timing mark in the unlikely event you can get your head and a timing light in there.  The opening is about 13mm wide and at the 3 o'clock position on the HES plate.

The good news here is that when the edges of the cutout in the two parts are aligned, the timing will be at factory specifications. This is the way the timing is set according to the factory manual I have.  All my bikes are timed that way and they run well and get 45-48 MPG.

Do you have a temperature gauge?  How long does it take to get to normal temperature?  My bikes can take as long as 4-5 miles in cold weather(0-10C).  If you are doing city trips there is a good chance as much as 80% of the trip is being done with the cold engine enriched mixture.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline daveson

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #52 on: February 22, 2019, 01:57:11 PM »
I was wondering if there was a hissing (esp. under revs) from your exhaust as a sign of a blockage, but after seeing your fuel economy I'm thinking there is nothing wrong with your bike (except return line - burrito syndrome) it's good for a high performance engine in a harsh environment.

I'm thinking your fuel economy should not be improved by the previous owners fuel since the fuel you put in should be measured against the distance that has been travelled, not the distance that will be.

Maybe clean the speedo sensor. In fifth gear the speedo and rev needles should be parallel at all times.

Do you fill your bike while on the centrestand? I fill mine on the side stand,  to the lowest point of the filler neck, so the burrito is above the fuel line. Also, if full on the centrestand, I wonder how much the fuel expands as it heats up,  because that would mean adios amigo out burrito.
  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline Laitch

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #53 on: February 22, 2019, 05:46:38 PM »
As an attempt to thwart continuing misunderstanding of later model Classic K moto fuel tank vent and fuel pipe assemblies, and to help clarify for myself what is going on within these critters, I have modified one of the useful images posted by rbm way-back-when in this thread. Edit suggestions are welcomed.

  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles
I wept because I had no radials until I met a man who had no splines.
https://tinyurl.com/RillRider

Offline mw074

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #54 on: February 22, 2019, 06:14:12 PM »
Well done Laitch, rbm. Thanks.
  • Michigan

Offline szabgab

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #55 on: February 24, 2019, 03:13:46 AM »
Timing is fairly easy to check.  Remove the "T" shaped cover from the front of the engine.  Behind it you will find the plate the HES are mounted on.  The plate and the valve chain cover are machined to provide a cutout inspection hole where you can see the timing mark in the unlikely event you can get your head and a timing light in there.  The opening is about 13mm wide and at the 3 o'clock position on the HES plate.

The good news here is that when the edges of the cutout in the two parts are aligned, the timing will be at factory specifications. This is the way the timing is set according to the factory manual I have.  All my bikes are timed that way and they run well and get 45-48 MPG.

Do you have a temperature gauge?  How long does it take to get to normal temperature?  My bikes can take as long as 4-5 miles in cold weather(0-10C).  If you are doing city trips there is a good chance as much as 80% of the trip is being done with the cold engine enriched mixture.

Oh, that sounds simple enough. Once my boy is in kindergarten tomorrow I will dig in to check, what's what, if I am unsure, I will post some pictures. 45-48MPG is dream territory for me, I am currently on 32MPG according to fuelly, but Laitch and you are correct, a cold engine on short trips will be heavy on gas. However I have taken the bike for a spin of 150-200 miles back in October in balmy 22C, and my fuel consumption did not lower significantly, so in the springtime I will carry on fault finding.
  • Budapest, Hungary
  • K75S 1985 model

Offline daveson

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #56 on: February 24, 2019, 03:46:56 AM »
It seems your getting 6 to 7 litres per hundred km. I'm thinking that's 43 MPG (36 US)

That's not bad for a thirty year old bike.

Some say you should warm up your bike, some say you shouldn't. I'm thinking one minute is plenty but takes me two to shut the garage door and gear up. In that time the bike may have pumped about 100 litres of oil,  surprisingly.
  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline szabgab

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #57 on: February 24, 2019, 06:24:49 AM »
It seems your getting 6 to 7 litres per hundred km. I'm thinking that's 43 MPG (36 US)

That's not bad for a thirty year old bike.

Some say you should warm up your bike, some say you shouldn't. I'm thinking one minute is plenty but takes me two to shut the garage door and gear up. In that time the bike may have pumped about 100 litres of oil,  surprisingly.

Dave, that probably would be the case, if everybody else would be getting similar stats. All my other bikes - calculating in my weight (70kg), my ridding habits and after some TLC were getting consumption in the lower half of the average and I was kind of expecting that with this bike too. I know, riding a 750cc touring bike in the metro is less than ideal and I knew, I will have to pay more for fuel than I would have had with a 125cc modern scooter. However the absolute best, I have gotten with this was 40MPG, that is way below average as the median on fuelly looks to be more like 42-45MPG. Warming up is another hotly debated topic, I do not think, one harms the bike, if it gets nearer operating temperature before loading it, I give it two minutes or so too... Anyway, once I really do get everything done to the bike that is to be done and the weather clevers up I will see, how things change...
  • Budapest, Hungary
  • K75S 1985 model

Offline szabgab

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #58 on: February 24, 2019, 06:45:45 AM »
As an attempt to thwart continuing misunderstanding of later model Classic K moto fuel tank vent and fuel pipe assemblies, and to help clarify for myself what is going on within these critters, I have modified one of the useful images posted by rbm way-back-when in this thread. Edit suggestions are welcomed.



Laitch this is brill!

I have done, what was suggested, and bent the pipe yesterday. Carefully was a no-go as there is no room to get in a pipe wrench or proper tools, also one can do anything only by feeling around, so at the end I managed to get the end of the pipe somewhat squashed. It is not restricting fuel flow, so I left it like that and attached a fuel pump breather hose, as that was the only submersible thing, the BMW place had in stock. Being impatient, I bought a metre of it. Got it on the pipe as far as I could spraying the tube with brake cleaner and pushing it on, whilst wet. It is steady, time will only tell, if it is steady enough in the long run. Routed it to the pump and through the hole, that is there for the breather hose specifically but did not attach it to the pump, as I do not have the filter basket with the nipple on. The secret waterfall, or the league of critters immediately left my tank, all I can hear is the quiet high pitched noise of the pump.
  • Budapest, Hungary
  • K75S 1985 model

Offline daveson

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #59 on: February 24, 2019, 07:54:03 AM »
There are a few quick easy tests you can do. Are the needles parallel in fifth gear? Mine are, we have metric here but I don't think that matters. You might have a non original final drive. Is the speedo accurate?

It seems to me roughly say 6.5lt/100km, looking at that metric  graph, I googled that to 43MPG, maybe my maths is wrong or something.

The final drive ratio is usually stamped on the top, near the swing arm.

I'm thinking, be sure your fuel economy is bad before looking for the cause.
  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline The Mighty Gryphon

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #60 on: February 24, 2019, 09:13:34 AM »
I cannot think of any reasons why your plugs look so good with the fuel efficiency you say you are getting.  They should be black and sooty with the amount of fuel you say you are using, certainly not as clean as yours look. 

Are you absolutely sure your trip meter is running properly?  It is driven by a small electric motor that is speed controlled by some electronics and the rear wheel sensor.  I think it is possible that it could be running slow because of drag in the gearing and not registering distance accurately.

I would suggest taking a ride on a motorway with km markers and checking your readings against them.  a minimum 25-30 km trip should tell you if everything is accurate.
  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline bocutter Ed

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #61 on: February 24, 2019, 10:39:58 AM »
I'll use 5L/100km when on longer out of town rides at 80 to 120 kph. In town is another story. My workshop is 1km away and my clients, groceries, banking, beer, etc are all within a 5km radius. I'll use 7.5L/100km in town.
  • Toronto, Canada
  • '61 Puch DS60 - '66 Puch 250 SGS - '87 BMW K75s

Offline szabgab

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Re: 1986 K75c - Fuel Tank Vent Hose Rounting
« Reply #62 on: February 24, 2019, 11:35:05 AM »
Guys, I created a new thread in Classic Motobricks, as not to completely hijack this one. I have replied to your comments there and would migrate everything from Laitch's brilliant picture onward, but I do not have the rights :)
  • Budapest, Hungary
  • K75S 1985 model

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