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Discussion in 'Airheads' started by planktonnn, Aug 25, 2009.
Does it start? I'll take it.
Also Grrrrr, akk, narrrr phooahhhhh etc.
hang tuff brother theres a k75 clutch heading you way
Quote- "Will not the sidebulge impact on general fueleconomatics pushing the price of a ride beyond reasonable reach. Plus there'll be an impact on lane filtering functionality impeding ones potential progress = slow journeys with high running costs.
I don't remember signing off on this". Quote
No, you didn't sign off on the Corporate Apparel Solution, planktonnn, because I knew you wouldn't
like the un-aerodynamic properties of the trouser-width....so, I went ahead anyway and ordered 10,000
units from John G******* over at Fuckwit-Fashions in Gay Paree and paid for them with the secret
slush-fund account you were saving for your underground bunker in Barbados. I've already sold one
pair to rightsideup, so the rest should go pretty quick.....
******** asterixs used to save a potential libel court case
Mine did that following a Boyer Bransdon Ignition install, had been fine with the points.
Retarded the timing a bit to where I still have full advance around the 4000 rpm mark, as per their instructions, and it starts a lot easier now.
Mind you, I have no idea what kind of ignition is on your bike........
Is the aperature to the enrichening circuit reservoir clear and unobstructed.
Quite so, it's certainly a distinct proba/possibility & it's very much on the list to find some soft wire + a can of carb cleaner, drop the carbs off (cables in place) & have a spray/gentle prod about. All carb galleries & apertures are of course subject to blocking one way or another*, but I am particularly thoughtful of the fact that I have Petseal in the tank and so theres a remote possibility that this could lead to gumming up now that they've increased the percentage of ethanol in the mix over here in the Former United Commonwealth Kingdoms. Additionally I'm pretty sure I'm running generally toward or a little over the high end of the scale on oil level and the crankcase breather could be misting oil into the inlet pre-carb, adding to the potential gumming of galleries?
Inversely & contrary-wise I think I'm running an early 'one sided' breather outlet venting only into the right carb inlet**, and the right side is always the first to catch when attempting to start, followed by the left, so theres the vague potential any oil mist in that side could be helping keep things clear? Stranger things have been known
I'm also minded that the kind of coughing back I'm getting in the left inlet tract has previously been seen to leave a sooty deposit which could, after much mileage, block/restrict the idle circuit...
The bike is fitted with a round K&N filter in the aluminium (type 1) airbox and although that has only done around 25k miles*** I will be checking the whole of the inlet tract anyway. Ill have a fiddle with the seating of the airbox/filter & test before even releasing the carbs to dangle for cleaning as such a solution would require least work, even if its not first on the list of potential sources for the fault. Im lazy like that, and I dont really have a work space. If I must dig deeper Ill be sure to want to take a particular look at the left side Carb-to-Head rubber, as whilst they were both new at the main rebuild it got tweaked some time back during a previous carb fitting & may have an air leak.
Certainly, once theyre cleaned, setting up would probably benefit from the considerable stockpiled experience of our local Dave. Setting with vacuum gauges may be possible via the previous offer from DBD, tho/ough that would necessitate a place where we could run my barely baffled engine for a nuisance inducing length of time while we fiddle with the carb settings and I dont have access to such a place. I cant help but think that a snippet of the extensive accumulated knowledge of our Local Dave is possibly worth more than any amount of fiddling by me
I've not touched the adjusters he set on the (then new) cables, and the airscrews are as he last set them, which I found gave good starting & a happy tickover when fully up to temperature (if a bit low prior to temp), but the throttle lift screws have been fiddled with, not necessarily to good effect.
Anyway, as far as a stab at diagnostics is concerned, when I pull the sparkplugs after a bit of cranking I can smell fuel from the cylinders, but the plugs arent wet as such. If it wont catch I can see puffs of mixture coming from the exhaust, which if you remember is comprised of just Supertrapp end caps (5 plates) direct on the end of the stainless (front cross over) downpipes. The end caps are sooty, and while I think the bikes set a bit rich theres no more sooty than one would expect the exhaust gasses to be at that point in the exhaust tract i.e. pre endmufflersilencercans. Generally after running the (6k mile old) plugs are a reasonable colour with no hard deposits, but maybe a little soot away from the post & arch contact. I seem to get a good spark, but Im inclined to think that (combined with some loss in the electrical system) theres a mixture problem, and the aperture to the enrichening circuit reservoir does indeed need checking just as you say. On attempting to start I sometimes find that slightly varying the (airbox based) choke lever and/or throttle while cranking can sometimes lead to the right cylinder starting to catch, and if the starter doesnt jump to disengage I can churn it over till it catches & then the left jug chimes in.
Probably it would be simplest to buy Astrals K75S**** which has just blown a gearbox, fit the suitable K gearbox I have from the as-yet-unrebuilt Me-MW K75 Rat & do a total rebuild on the Boxer DMW***** I could ride the standard 75S for a suitable period, reconstitute my sorry excuse for a 79 Rat Airhead, and then sell the 75S, ride the DMW & rebuild the Me-MW 75 Rat. Now if only such a thing were possible
* And take into account that while I have the stack filters inside the tank on the tankpetcocktaps I dont run any inline filters.
** I seem to recall there are other configurations that breathe into both sides via a T junction in the airbox? I seem to recall the (type 2 square airbox) 84 R80RT (The Standard 1 see post 1) had a double sided system accompanied by blades on the oil feed pipe to induce swirl in the inlet airflow?
*** The K&N site indicates up to 50k between cleaning/oiling.
**** Which I sold him ages/many miles back.
***** Because, as previously mentioned, the quality of my builds is so poor that they need redoing every three years or so.
The bikes a bitsa on a 79 reg/chassis, and its a Boyer Micro Digital Ignition KIT00086 in a (hacked up) 79-80 loom with early coils etc., running a post 82 block & jugs with late front cam-end so its a late Beancan repacked with a Boyer trigger receiver, with advance weights removed. The Beancan doesnt seem to have shifted since last strobed by Local Dave. Ive no rev counter fitted, but I seem to recall he hooked a line onto an HT lead when setting timing?
Checking the ignition timing is on the to-do list as part of a general spruce up, and may be possible via the aforementioned kind offer from DBD & his strobe, depending on a space to run the engine as required by the process without getting shot at by the neighbours. Valve timing should also be checked given the opportunity to get a running jump at the jobs list. Also Id have to reboot into the personality that remembers how to set the valve timing without undue faff :-D
Asterixualisation very wise :-D Underground Bajan Bunker Fund blown? BLAST!?! As an Executive Director of this here imaginary motorcycle manufactuary you do of course have the authority to initiate such orders, so fair dinkum, and I observe that many a workshop full of spanner monkeys have branched out into the merchandising strand of income generation before theyve even built more than 5 bikes, but may I bring your attention to the recent filing of insolvency papers by OCC Merchandising with a net loss of $300k, and be so bold as to suggest that were this exciting venture to suffer a massive tankslapper then unsold units could be wrapped around my mancave at the Shedquarters to improve insulation & heat retention, thereby going some way toward providing me with a simulacrum of a working space within which to sort out all my shit? Please?
Whatever you've ordered, at least they are sans tassel...
Cheers fella, thanks for your kind help, hope you didnt forget a return address so I can cover postage & a couple o beers I dont expect Astral to part with the 75S* so it looks like rebuilding the Me-MW is going to be my only option of staying on the road whilst refreshing the DMW airhead.
* If he were to feel inclined to accept an offer so that he could finance the ongoing running & repairs to his Robin Reliant & eating 'n' stuff Id have to do it on fortnightly payments, but Id need to ensure there was a little book to keep track of what was paid & exactly when slices were due. Such things can get very messy see past posts way back for tales of the extensive snags encountered when the roles were reversed :-D
Cracked open the airbox, it's an early type 'tube to T piece feeding crank breather' running out into both sides, but not the one with the swirl inducers
Air filter fine, light oil mist on the inlet tracts where the breathers feed in.
Popped the in and out pipes either side of carb, no sign of damage to the inlet rubber on the left side.
Enrichment circuit didn't seem blocked, but as advised in the Big Book of Bings (page 14) I used human puff rather than an air line to blow out the passages. I can see that this gives the opportunity to feel the amount of resistance change if a blockage shifts, but it does of course leave one with the aforementioned petrol breath.
The starting is better now, but not entirely cured. I get the feeling I'll have to do the whole thing again tomorrow with the aid of a new can of carb cleaner, as the one I had was on its last dregs.
The rubber O ring on the right idle screw was chewed up. I fitted the last spare I had of roughly that size, but I'm not sure that it's petrol resistant, and anyway it's a tiny bit slim so I'll need to pop into Local Daves & see if he has one lying around. He quite often does.
I hate carbs.
I've got the whole thing running a bit better, but I simply don't have the intuitive feel that years of carb fettling brings to the game, this is why we go to Local Dave, even if we really can't afford it. I just can't get the tick-over right, and the throttle stop screws are probably way out. I've not dared to touch the cable adjusters.
Spent most of the day stopping in various car parks for a fiddle and then moving on before those thereabouts got too tetchy.
Oh for a medically induced long term coma...
Or somebody could buy me this, though the pricing is, I fear, somewhat on the optimistic side?, and I'd have to swap the bars out... -
All progress yesterday was an illusion. Setting fire to it now.
Butler & Smith article on Bings: http://www.luke3d.org/bmw/cvcarb.pdf
Via http://www.luke3d.org/bmw @ http://www.luke3d.org/bmw/lubrificazione.htm
Bing on aircraft VW @ http://www.thesamba.com/vw/forum/viewtopic.php?t=203069
Monday, 15 December 2008
Tuning 40mm BING CV carburetors for BMW motorcycles by ear.
Steve Doyle has put together this great and simple guide to tuning your Bing carbs. No need for expensive tuning equipment. So over to Steve...... Any feed back on this How To please email me and I will pass it onto Steve.
There are 3 common methods to syncing the carbs. They will all work
1. Shorting the plugs. http://bmwmotorcycletech.info/synchcarbs.htm and http://www.airheads.org/content/view/216/98/
2. Using a manometer of some sort. Carbtune, Twinmax or home made http://www.airheads.org/content/view/183/98/
3. Using your ears. No comprehensive articles that I could find..
In the spirit of learning to service and tune at home and after lots of reading, I decided that for me the "by ear" technique might be the most useful, as it doesn't require any special tools and can be performed anywhere. There is no risk of electrical damage to the bike or the one doing the adjusting.
It was very difficult to find a comprehensive description of the procedure, so using the combined knowledge and input of many at boxerworks.com, other internet articles, the 3 usual BMW tech manuals and the BING manual, I have put this together.
I have tried to do it for the carb novice...someone in an early learning phase of carb maintenance, eg me. I have used the 40mm carb 'cause that's what I have, but the principles are transferable to other cv carbs.
*Warm up. Minimum 15 minute ride. If not done, you will be left with a high idle once the bike warms up.
*This procedure is done with known good valve and timing settings, and a clean air filter. Ensure no air leaks around the carb connections or at the inlet stub on the cylinder.
*Throttle cables must have free play 2-3 mms. You should be able to slide the throttle cable outer (at carb) up and down in the cable adjuster 2-3mm.
*The jets/carb orifices, manifolds, seals etc are all clean, tight and not leaking.
*All adjustments must be done on the centre stand. Don’t use the side-stand at all.
*Tools. You will need a working pair of ears, a flat end screwdriver, a 10 mm open end spanner and a fan for engine cooling. Do not let the bike overheat. A second person can hold the throttle open at 1500rpm, or use a throttle stop of some sort.
*When assessing equilibrium between the left and right, place your head between the exhaust outlets and listen for synchrony. Don’t stay there too long as exhaust fumes aren't useful to you.
The orange highlights are the basic setting adjustments. Tuning involves ensuring the effect on the engine is equal, and smooth. Everything else is supportive information.
To simplify the procedure, break down the whole procedure into 3 smaller procedures, doing them one at a time.
You must adjust and set-
1. Idle speed.
2. Idle mixture.
3. Cables in synchrony above idle.
1. Idle speed adjustment. Look down onto the top of the carbs. The throttle adjuster is the straight screw head between the carb and head, which sits above the throttle arm. The arm has the throttle cable attached to it. Your aim is to set the butterflies to open simultaneously.
If you are rebuilding or are just about to mount your carbs onto your bike, these settings can be visualized and adjusted easily before mounting. Otherwise, do them once mounted.
On both carbs, if they're mounted, you can use a thin piece of paper between the throttle adjuster screw and where the screw touches the throttle lever. Set equal opening of the butterflies here. Tighten / loosen the screw until it just grabs the paper. 1/2 to 1 turn tighter (clockwise) is about idle speed. That’s where you start to play with a screwdriver and your ears.
2. The idle mixture screw is under the carburetor. Set both carb mixture screws equally, by clockwise rotation in all the way (the leanest), then back out counter-clockwise by 1.25 turns.
***These settings provide the baseline, so if you haven’t already done the 15 minute warm-up ride, now’s the time. It should run, unless there are other problems like blocked jets/orifices, inappropriate float levels, enrichener circuit is bad.
If you plan to further adjust back in the shed, then it’s important to have a decent fan set up ready to switch on once you have parked the bike. The aim of the fan is to prevent overheating. The adjustments should not take more than 6-7 minutes without a cool down ride. Alternatively, go for a ride, take a screwdriver and a 10mm open end spanner, and plan a few stops on level ground to tinker. Leave your earplugs at home.
Making adjustments. For post 1980 bikes aim for 1100 rpm, and 1000 pre 1980. When one carb starts to dominate, that side muffler will start to "pop" more than the other side. Using the throttle adjuster adjust the other side up to match, or back down the "popping" side. ALWAYS USE SMALL INCREMENTS, eg 1/8th-1/4 turns. If you adjust one side up to match the other side, and it runs too fast, then you need to lower the other side to match.
***You may need to do this a few times to get it exact.
3. Setting cables, or the equal movement of the throttle lever, above idle speed is much the same method except you adjust your cables, not the mixture or idle speed screws.
• the idle speed is set, or at least both carbs at the paper "pinch" point
• the twist grip is fully closed
• throttle cables follow a nice path with no tight turns or impingements.
• 2- 3mm free travel of the outer cable over the inner cable.
If you don’t have movement of the cable outer, the adjuster is screwed up out of the carb too much, you have a tight turn in the cable route or you may have a frayed cable inner. To increase the free play, loosen the lock nut and screw the cable adjuster in. Loosely "tighten" the lock nut ready for further adjustments.
***You must have that free movement of the cable outer. If the rpm increases when the handlebars are moved lock to lock, then your free play may be to little or the cables aren't positioned freely.
Set the cables with the engine just above idle at about 1500 rpm, kneeling at the back of the bike and listening just as in setting the idle speed.
You'll read a variety of opinions at which the rpm should be set, and I have chosen 1500 because it represents something like the most common opinions. It worked for me, however the cable sync was the more difficult procedure and did require multiple adjustments. Use the throttle stop screw, or something between the right grip and throttle housing to maintain the 1500rpm. A helper is otherwise useful here.
How do you assess your settings?
Idle. Your ears between the exhausts will hear synchronous, glorious harmony, if you're lucky the first time! Listen for difference and make adjustments accordingly. If you’re deaf, another method is to observe the bikes vibration, feel the muffler exhaust pulses simultaneously or have a clear cup with water fastened to the tank or seat. Watch for the smoothest movement of the water whilst adjusting. They are boxers, so don't expect absolute smoothness of water.
A ride when you think you're done will confirm how you've done.
Cable synchrony. Take note of the transition from idle to higher rpm. If it's smooth then your good, but if there is vibration or shudder, then you need to revisit the cables.
After a long ride, let the bike cool then inspect the plugs, looking for an even light gray color. The colour of the exhausts at their tip should also be light gray and even.
The BING manual, page 13, suggests a different order of approach starting at setting the cables first, at 1200-1300rpm with a free play of 1/32 inch (about 1mm would be close).
The manual describes setting the idle speed next, followed by the idle mixture screw adjustment. The manual describes clock-wise (in) rotation of the mixture screw until the engine all but stops. Then take your screwdriver with you on a ride, stopping occasionally to tweak each screw ccw x the width of the screwdriver blade (they call that a notch). Expect the performance to bog for at least 2-3 minutes (until warm) before starting adjustments. When the bogging down disappears is ”the point the idle mixture is as lean as the machine will tolerate, yet provide smooth transition. Anything further ccw would be a waste of fuel.”
You may need to reset the idle speed. Repeat step 1 as described above, using very small increments when turning the screwdriver.
"Its not your average BMW: this shocking BMW 4219Eli was created for a four-year-old boy by the companys design team in an online competition. Its a 42-wheeled sports car powered by 19 engines, each developing 459 horsepower. A total output of 8,721bhp makes it roughly eight times more powerful than the worlds fastest car, the Bugatti Veyron."
nice motor. Don't think it will fit in any parking spaces round here
There must be somebody based in the headquarters pictured above for whom the sole & single purpose of their employment is to find me & sponsor my mechanicalistic misanthropy? Could I not at least be written off as a tax deductible loss?
And so to ongoing woes. Battery charging here at The Place is troublesome, as availability of access to an relevantly placed & reachable power socket is very limited and understandably awkward to arrange. Because The Place is an outpost of a large housing association there are policies, and that means that rather than simply asking to plug in & plugging in, I am instead required to conform. You will know I am not very good at this. It's certainly not the fault of the 'coal face' staff, but simply another exemplar of the way that policies don't fit the ground they're written to operate on. And so I'm left with a limitation on how much I can rejuice my battery between my hamfisted attempts at adjusting the carbs.
Having done what was done in post 3727 I achieved little except rendering the machine unable to start at all, with just the occasional kick but no catch. And tho/ough I will read & reread the material referred to in post 3733 that still won't give me a deep seated & intuitive experiential understanding what the fuck I am doing. The electrical power point access issue is relevant because again I am forced into jabbing & churning the engine over in an attempt to get it to fire between adjustments, and then constantly hitting the brick wall of 'Nil Starterandum'. I've a horrid feeling that I'd manged (sic) to get it reasonably set for the temperature at which I was adjusting it in post 3727, i.e. warmed thru/ough, however this was not a good set-up for starting from cold and I was again forced to crank the high demand starter motor between fiddles, depleting the battery to the point of clickety starter relay time. When it comes to carbs I really don't know where I am ...
I am currently seated pretty much exactly where the A points. This is the site of The Place before the place was built, as its predecessor was being knocked down.
There is no solution to the not charging here at The Place issue, and so the only option is to borrow enough batter kick to get it running & high tail it over to The Previous Place (sometimes called 131, or My Home) to cadge a little more time in the former Shedquarters, where I can at least fiddle and charge simultaneously.