I could have bought secondhand carbs off ebay for less than the parts for these ones have cost....trouble is, they could be in need or worse than mine.......I asked one guy how many miles...."5000", but he couldn't prove it, hadn't got a log book or whatever........so I could still have ended up stripping and repairing them. If it was electrical I wouldn't expect it to be intermittent and to be regular.......OK, not always across the rev range, but certainly in the area of revs this was happening. AL.
Now how in h*lls name do I get to the idle and synchro screws, with the oil cooler in the way (carb heater hoses restrict the amount the cooler can move)??? Apart from junking the heater hoses, anyone got any bright ideas? I have made up a selection of screwdrivers all of varying shaft and handle lengths........and I reckon it will be fumble over the top of a hot engine (Ow, ow, ow!!) with a slim screwdriver about 6" long but with a 1" handle......and guesswork as to whether I get the tip of it in the screw slot. AL.
How about a male/male joiner to connect the two cooler hoses together so you can run without a cooler? Or a third middle hose to give the length so you can make a loop?
Funnily enough I was just looking at disconnecting the cooler from it's top unions and turning the left side main hose back to fit onto the top engine union after disconnecting the right side main hose.....basically I need to separate the cooler from the carb hoses.... I know I suggested something like that to Paul563 when one of his main hoses started leaking......but he had a bottom mounted cooler so the hoses were routed differently. And it is slightly over full with oil so it could lose a bit. AL
Al, I have been following your quest for a smooth running bike, dont thump the bike yet, its far too entertaining!!!
Apart from the battery (and the fairings of course) it is all back together.........Tomorrow will see if there are any petrol leaks when the pump gets switched on and then I'll fire it up and see if it runs...... Although I have changed the throttle slides and guides over for slightly less 'worn' ones; fitted new Dynojet needles; emulsion tubes; changed the jet blocks; renewed the floats, float valves and diaphragms; set the mixture screws to what Dynojet say; I haven't touched the idle screw setting or the synch screw.......so with a bit of luck it won't be too far out....................Some hope...but you never know..... Unfortunately I don't appear to have my vaccum gauges anymore, so it will have to be the drop-off method (a la Guzzi) and see what happens. AL.
Update to last night......... Turned on petrol tap; switched on ignition; let the pump charge the carbs with fuel....no leaks or overflow; put the choke on; pressed the starter button.....Vroom, straight away it's running..... ...eased the choke back a bit to drop the revs.......and immediately I could tell the problem was still going to be there...... ....sho nuff, it was spitting in the carb/s intermittently......... .....I let it warm up a bit more and experimented with various throttle openings.....it happens just around 1100 - 1300 rpm generally (never above 2000rpm), but it ticks over as normal......(although idle deteriorated and dropped speed eventually) Susbsituted known working coils and HT leads etc (two pairs)....problem still there...... Substituted known working ignition control unit (each side in turn).....problem still there.... Whipped the air filter off and watched the slides....in general they are pulling together, but when it spits back, I can see a flash of flame in the carb.......It only seems to be the horizontal cylinder that is spitting (or if the vertical cylinder is doing it, it is rare).... So I tried the old trick of pulling off one spark plug at a time (with a blip of both running in between switching over).....both cylinders appear to be able to run quite well on their own with no eveidence of spitting or backfiring....... ......put them both back on, and the problem is there again. Then I went and had a meal.......bear in mind I had seen no evidence of a leak or overflow from the carbs at all; when I went back two hours later, the vertical cylinder overflow was slowly dripping....... if I rocked the bike, it dripped a lot more, so it is obvious the fuel height is too high, but how can that be when I was pretty pedantic about getting the float heights right and I checked them several times.......and the floats and valves are new, so unless a new float has a hole in it. I don't think it can possibly be a synch problem, because each cylinder runs at the same revs when one spark plug is disconnected, plus they appear to be OK pulling together when the slides go up and at higher revs....Besides, although I know the Mikunis can go out of synch, it wouldn't have been by much unless the synch screw has undone itself quite a bit..... It can't be dirt in the fuel...there is nothing in the other in-line filter at the carbs. It's charging the battery OK so I doubt very much if the flywheel has come loose, so maybe the pick-ups have come loose. F-me, whaddavigoddaddooo? Anyone near enough to assist? AL.
Is your reg/rectifier ok? Under/over charging? Have had CBR's doing something very similar under spiked loads, it messes with the timing under certain RPM, the bike then acts like its possessed! Got another you could try?
I have an OEM reg that I could try, but I'm not sure if it is a good one......RR51 is fitted at the moment so I would have to p*ddle about with the wiring a bit......But a bike should be able to run without a functional reg and charging system if the battery is well charged........or so my past experience with bikes and cars tells me. Worth a try I suppose though......still..........today its take the whole lot out again to find out why one carb is dripping from the overflow, even though I know I got the float height spot on. I might even make a small mod to the idle screw, having spotted a possibilty that it could be extended so it could be turned by hand.....I have a spare trip cable that might fit in some way or another. AL.
LOve these annoying hard to trace faults, especially on someone else's bike :wink: Just another theory to keep you busy (and stop you going too mad)! Are we talking about an SS with a fuel pump and not a monster type vacuum pump? If so, have a check to see if the fuel return line is blocked/trapped under seat or tank (more common than you might imagine ). Take it off at the tank end and let fuel run into a container, and listen if the pump sound changes drastically. Also check the lines inside the tank are clear. Could be that if it's blocked, the fuel is pressurising the fuel line too much and flooding the carb bowls - when you open the throttle, too much fuel is being initially pushed into the inlet and causing the backfire .... when it's at higher throttle settings, there'd be an outlet for the excess so problem goes away ... until the throttle is closed off again! Don't let it defeat you
Yep, cheers for the idea....normal SS with pump and filter inside the tank.......return flow not blocked......That's the very first thing I checked when it first started playing up....apart from the fact I can hear it running back in, I can see it running back in with a small mirror on a stick (which I nearly dropped inside!). Tank pipes not blocked....nearly full tank, so every time I take it off, it gets sloshed about a bit and p*sses out of the return stub.....all down my trousers (well I tell people it's petrol, but at my age...well....y'know.......) Fuel flow is fine as well.....soon fills the carbs from empty, and it wouldn't run properly at higher revs if the flow was sluggish. Temporary reg/rec change...........no difference, problem still there.... AL
All good fun -- innit? Dripping overflow seems to be caused by a faulty new float valve assembly.....the 'rubber' tip of the needle appears to have a tiny cut in it right where it seats, almost like a pin prick at a shallow angle and the needle seat looks as though is has a hard plastic fraze around the hole...maybe they tie up.....can't really tell, but the needle didn't fall out like I expected it to when it arrived in the post......New one coming. Also got this in email from Factory Pro The fuel level / float height is a tuning setting. 13mm will richen the lowend (mostly the lowend), 14 is pretty usual and 15 leans out the lowend. 1mm is a significant change. The float measurement is different on the rectangular float and the diamond shaped float. I usually use the diamond shape. But remember, the float height is a tuning thing. Marc Unfortunately that appears to 'contradict' if that is the right word; Factory Pro's website info in respect of their float height measuring tool.....because it says measure the rectangular shaped float, not the diamond shaped one; and there is 3mm difference. AL
Drives you mad, doesn't it?.....one new float needle and seat...hard to get a decent photo, but you can just about see why it leaked. Somehow I can't really face taking the hammer to the bike, though...not when it looks like this. AL
Yeah, she's a lovely bike. You'll be dead chuffed when you suss out the problem. I decided to do a cracked cylinder head repair on my old 93 Blade over a winter and had some fun retiming the cams etc. But the feeling I got when it fired up first time and ran as sweet as a nut could not be beaten! Still got the old girl
Still waiting for a replacement float assembly, d*mmit.........Can't believe the supplier was out of stock; me having had the last two and then one of them was defective!!! So while it has been peeing for the last few weeks when I could have been getting it sorted; I've been stuck, because I don't want to go any further until I have tried the carbs on again. But the carbs have been checked and cleaned again.....Found a way of removing and checking the inner air-cut-off diaphragm plus the choke needles without splitting the carbs.......One choke needle was badly worn....but whether that would have caused the problem, I dunno.... Worn = More or Less Fuel??? I am going to check the the pick-ups and the wiring again shortly.......Anyone know what I should expect in the way of a reading? I believe it should be around 90 - 100 Ohms......and does polarity of the pick-up matter when testing? I assume I can test without pulling them off the bike if the battery is disconnected etc etc??? F-me....give me a set of points, a points file, a rotor arm and a distributor any day of the week.......and a couple of Amal Monoblocs (carburettors, not some sort of Class A tablets). AL.
Al my 900 did this quite a lot in pretty well the manner you've described. I've re-read this post again and have a couple of thoughts. The first is the emulsion tube/needle fit. You've mentioned that these have been replaced with "less worn" items. I suspect that if the tubes and needles are from different carbs, then the wear characteristics will be slightly different (anyone please correct me if I'm wrong here) and so will not seal 110% . After replacing both the tubes and needles with FactoryPro items there was a major improvement, but not a complete fix. The second thought is more around the carbs themselves. As these units are CV items I've noticed particularly when the engine is cold you can't seem to hold a steady throttle just off idle, which as I've had it explained to me is where the carb switches air circuits and the power pulses coming back up the intakes interfere with the needle position. I may be talking utter rubbish so please correct me if I'm wrong
Thanks for the thoughts....but........ ......to solve the problem; already fitted......brand new needles, brand new emulsion tubes, brand new floats/needles (one defective), brand new diaphragms...... ......replaced jet blocks from another pair of carbs (one of mine had a casting defect which cut the seal); replaced throttle slide guides from another pair of carbs (one of mine was damaged and looked a bit iffy where the emulsion tube slid in) plus the matching throttle slides (slides and guides showed mariginally less wear than mine did). Replaced mixture screw seals and one spring on one of them (all bunged up with cr*p in the thread so it had corroded and weakened the spring). Replaced main jet seals. Carbs cleaned out three times at least, float height set dead on 14mm (checked several times).... No real cr*p found in float bowls when first stripped and none found in the tiny in-line filter in the tee-piece between the two carbs. But....... it didn't have the running at low revs problem for three years and it just suddenly happened (albeit the drips from the overflows were getting progressively worse).........It seems to be the horizontal cylinder only. Compression tests seem OK, Electrics appear to be OK..... A closer inspection of the manifold rubbers may have yielded an issue.....they haven't been fitted too well or the airbox etc has caused them to compress the internal lips completely flat for at least a third of their circumference, and there are some nicks in them, so I will change them when I can source a pair. When I finally get the carbs back on and get the bike running, I will then see if it still does it and try a balancing act......but I'm not convinced it is balance either.......if it is, the balance screw has done a d*mn good turn (or more) which I can't really see that it could. AL.
