MOTOBRICK.COM
MOTOBRICK.COM => Welcome To Motobrick.Com => Topic started by: bitsa on May 04, 2023, 08:27:24 AM
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Hi all, first post just to introduce myself and my new toy/money-pit/nemesis/pal (will delete as appropriate when I know lol).
I'm new to Beemers (at least 2 wheel variety) but had & loved 80's shafties for years (Honda maggots, Yam XJ's and the like). Been out of the saddle for about 10 years now but found what seemed to be a good deal on Ebay so took a punt and won what was described as a 1986 K75S in pieces, which had been turned into a cafe racer & latterly a scrambler before PO bought and dismantled with the intention of restoring.
On collection I'd describe it more as a rat/survival style, lots of flat black/rough sanded tank, hacked wiring and enduro tyres. Still, not terrible for £310 if the engine was good I could at least get my money back in parts. Anyway, first order of business was to loosely assemble it far enough to see if I had the basis of a decent running bike. Before the post gets too wordy, it's decent enough & deserving of some love to make it into a reliable (if still ratty) summer toy. Main issues currently are the L-Jet & the hackery perpetrated to make it run/idle somewhat with leaking intake boots.
Basically instead of popping the plenum and TB's off & cleaning/resealing the intake boots, someone in the past has well & truly mallealated the throttle bodies. Initial settings are thus-:
Idle speed screw - completely missing, along with the stop plate
TB "Don't touch" screws - 1/2 nearly all the way in & 2/3 barely poking through, locknuts loose on both
Bypass screws- virtually falling out, barely hanging on the o-rings
TPS- all the way anticlockwise, acting as "idle stop"
Airbox - MIA, replete with AFM just shoved into the plenum's mouth with a bit of old boost pipe as a spacer, plastic cover loosely siliconed on so presume been tweaked internally, CO screw 12 (twelve) turns from seated.
I don't know what's more impressive, that the bike started at all (and ran as reasonably as it did) this way, or that somebody thought all that tweaking was necessary/advisable/easier than actually sorting the intake leaks.
Where it is now, with the intakes sealed up it starts well cold without "choke" and idles richer than Elon, gradually dying out as it warms. Crack the throttle and it goes lean to the point of cutting out. So now I've actually managed to confirm it runs/rides and is worth my time, it's time to get on stripping it and un-fudging the mess.
My intention is to find/make a new idle screw & stop, strip and clean TBs and verify TPS function then sync the TBs as close as possible using light oil & timing how long it takes a set quantity to drain through each throttle body & then once they're close enough throw the thing back together and hopefully get a more realistic reading on the vacuum gauges next time of asking (it had so little vacuum on first look, I honestly thought the intake valves were leaking or the HES was turned miles out of time).
OK huge ramble over, TL;DR Hello I'm new here and have a complete basket case of a K75S lol
Dan
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(https://www.motobrick.com/data:image/gif;base64,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) Well done—an exemplary introduction! Consider going to the Photo Guidance section and deciphering the instructions for making a personal photo gallery and posting photos from it. You've got a lot to share. Use the Motorbrick Workshop for posting queries about any challenges facing you. Good luck with this project!
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Another approach with the TBs might be to look for a good price on an unmolested set of TBs on Ebay.
Example:
https://www.ebay.co.uk/itm/165097068352
Those are a little rusty but if you keep your eyes open K75 TBs come up often on Ebay. (All K75 models and years use the same TBs.)
Or make a WTB post here. (Want To Buy)
http://bit.ly/new2kbikes
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Welcome! It is nice to hear that someone is reversing a Mad Max "custom" job.
Instead of using the oil, get four ball bearings about 6 or 7mm in diameter. The goal is to adjust the butterflies so they all drop at the same time. The easiest way is to put a block under the idle adjust screw and and set it so the ball just drops for the main throttle body butterfly(I think it is #2). That is the one the others are sync'd to.
Leave the throttle in that position and then, using the screws that must not be disturbed, adjust the other butterflies until their balls just drop.
This will get you a decent sync at mid throttle where acceleration is just beginning.
If you are really fussy, you can get a finer tune by following up with a Carbtune while the engine is running at 4-5000rpm.
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I'm shocked to read it started and ran!
Bless you for rescuing the poor thing.
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Thank you all, for the welcome & some good advice also. I'm way too cheap to spend even modest sums on parts which aren't strictly necessary (the TB assy. isn't physically broken, although they tried!) so will give some consideration to the ball bearing method, that sounds like a decent plan with less clean-up required.
I've never been good with getting photos of stuff (have good intentions to get them but just end up getting on with stuff and forgetting, generally) but will at least try and post up a couple from the Ebay listing and some from where we are now sometime over the weekend.
Speaking of just getting on and doing stuff, I actually jumped in and did some work yesterday to see how things can be improved. Basically found a suitable idle screw from some old carbs in a junk box (hoarder things...) & fudged up a stop, then using calibrated eyeball gauge and a bright sky got the TB's a lot closer than they were. Reassembled again & made a better sealing solution for getting the AFM plumbed without an airbox for the moment (one part I pretty much have to purchase, not a fan of pod filters on anything of any quality/value. Think there's more filtration potential in an old sock!)
Also, since there's a clean looking unmolested AFM in the boxes of bits I've given the rough opened one a tweak to try and reconcile the rich idle/lean on throttle issue which seems to have helped a lot & now it actually stays running long enough to where the thermostat opens which is nice!
Anyhoos, thanks again for the welcome & I will endeavour to take photos of the whole mess as it currently sits.
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As far as the rich idle, have you reset the idle air screws to 1 1/2 turn out from lightly bottomed?
Also, there is an idle air bypass in the AFM that is opened and closed with a 5mm Allen key. The adjustment is on the top to the right of the intake as you look down the throat of the AFM. With the air box out of the way, it's a pretty easy adjustment to make.
Have you tried contacting the bike breakers like James Sherlock? I suspect that for every engine you see that is for sale, there is an air box that has the potential to be binned as they are not parts known to fail. I am guilty of tossing one that came my way a couple years ago because it took up a lot of space and the potential for needing it was less than zero.
As for being a cheap bastard. You are amongst your own here. I know it was the reason I started riding these wonderful beasts, and I Know there are many others who lurk here.
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As for being a cheap bastard. You are amongst your own here. I know it was the reason I started riding these wonderful beasts, and I Know there are many others who lurk here.
Speaking for myself, I started riding my wonderful machine because it's a reliable conveyance to dependable sources of butter croissants, profiteroles and key lime pies that, I might add, don't come cheap. :laughing4-giggles:
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Speaking for myself, I started riding my wonderful machine because it's a reliable conveyance to dependable sources of butter croissants, profiteroles and key lime pies that, I might add, don't come cheap. :laughing4-giggles:
Hence the need to spend as little as possible on your trusty steed.
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Hence the need to spend as little as possible on your trusty steed.
Au contraire, mon ami. The Brick gets whatever it needs but it doesn't want much except tires, regular lubrication, fresh fuel, long riding and occasional intimate fondling. Where I save all my cash is by not purchasing razor blades or haircuts.
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Au contraire, mon ami. The Brick gets whatever it needs but it doesn't want much except tires, regular lubrication, fresh fuel, long riding and occasional intimate fondling.
Exactly my friend, the moderate demands my machines place on me are the reason I got them in the first place. Still, I don't see the need for being extravagant with maintenance expenses. Controlling the price of what they need helps minimize the cost factor in deferring what needs to be done. I prefer to spend my money on fuel.
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The adventures of bitsa are continuing in the Project Custom Motobricks section as Reincarnation of a Rat (https://www.motobrick.com/index.php?topic=15177.msg135252#msg135252).
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hi m8
like you i am new to this site and like you i also bought a bit of a rogue! mine runs ok, good compression and had the tb's balanced
but its a bit of a shed!|! the guy that "converted" this bike had a penchant for cable ties! everything is cable tied, the coil pack, the motronic etc and it has more choc blocks than Cadbury world!
i never bought it to return to original, not my thing so will persevere wdown the Cr route!
will watch with interest on your build
cheers
ming