StevieB

Hi haven't been on here for a long time - my Gs has been in storage for 18 months due to relocation. It was running before storage with carb rebuild to resolve fuel issues. Took out of storage with drained carbs, fresh fuel, new battery and replaced the coils as thought cause of occasional missing. Replaced with Hendler coils. Now have no spark - tested with all plugs removed, and to test each plug earthed spark plug in ht lead to good earth on cylinder head and cranked over - no tank fitted. Original plugs, new at carb overhaul. Thought unlikely all four fail. Substituted one of original coils (continuity of lt and ht good). Still no spark. Just after advice on electrical testing to find the fault. I'm not an electrical expert but have a basic understanding. Was thinking is it possible to test the lt inputs to each coil (multimeter to each input and to earth?) - not sure if the lt circuit through coils are one continuous loop or separate circuits. The online Hendler coil instructions state the lt wires can be connected either way? Would like to test system logically from someone with better electrical knowledge and experience. Thanks

Cheers - nice to be riding old skool again

It's been a while but the engine is now up and running well. Ended up replacing no4 carb body - all fuel levels good, starts and runs fine. Learnt a few things about gs mikuni carbs getting it sorted. 32 cv carb internals are interchangeable despite different part numbers (in my experience - except mixture screws). Learnt how to balance carbs. Found a good supplier of second hand carb parts - Mikuni man on Eblag - really helpful Vapour and ultrasonically cleaned, carb body and other parts look like new. May help someone else. Thanks for all the advice on here - got there in the end, so nice to get it back on the road.

Continuing carb saga, wrong ones for a kawasaki. Totally different. Good seller - full refund. Managed to get a set of bs32's for a 750 gs from a friend. Stripped down except air mixture screw is totally seized and rounded off. It's soaking overnight in anti seize compound. The number 4 carb for my 550e is listed as part no 13204-47090. Just got a couple of questions - apart from measuring carb intake bore are there any part nos on the carbs? Never been able to see any. And are bs 32 CV carb bodies the same on the 550,650,750 and 850 ? - with just all internal components (jet sizes etc) being particular to each cc model. Just curious as tried all components from my 550 carb into the 750 and they all fit. The throttle butterfly valve on the 550 says 140 and the 750 says 135 but identical in size? If the 32 mm bodies are identical will make sourcing another no4 carb a lot easier if can't get the mixture screw out.

Just found a set of carb bodies on Eblag. Will c what they're like and update progress

Hi just found out after a lot of investigation why my GS is not running on 4 cylinders - and unfortunately as not a quick fix know what the cause of the problem is Ignition and compression good as previous. Looking into carbs fuel supply first. Fuel from tap good. Have now checked fuel level in carbs. With a tube from bowl on no1 and no4 (as 1,2 & 3 cylinders running as they should) and can only get to 1 & 4 carb when on the bike. No1 fuel level at 4.5 mm as specified in manual (as I set them up), but no4 over 6mm (even though previously set at 4.5mm on rebuild). No 4 was the one I had trouble setting up heights as had repair (weld) to one of the float posts previously snapped by a former owner. Anyway trying to cut a long story short - took off the bowl of no4 in situ on the bike - the repaired no4 carb post has given up the ghost and totally snapped off. Explains why it would'nt achieve the fuel level to supply the idle fuel circuit.Mr So I need to find a no4 bs32 CV carb for a 1980 GS550e (or other bike fitment) or a full set. Will post on the wanted site here first as everyone on here really helpful before I start searching Eblag etc. Hopefully someone may know of a source to buy from. Cheers

Cheers. Got fault diagnosis steps in mind - compression,ignition,fuel. Test the compression first. Test ignition - will try the duck oil method, also fit colourtune plug in no4 - run it and visually confirm spark if there is one. Test fuel delivery to no4 carb - check actual fuel level in bowl with clear tubing method as per carb rebuild link from here. This will confirm float and needle. If it's got correct fuel level suspect no fuel through idle circuit. Can confirm by taking it for a ride, using high throttle input so using main jet not idle. The no4 exhaust pipe should give a high temp. That 's my theories! Will keep updated, if my tests work may help someone else. One day there will a posted pic of it running!

Hi just been running it again,swapped plugs and plug leads multiple times. And with original plugs In case us on fit new plugs. No 4 cylinder just doesn't run up to temperature, no matter what plug or lead (1 or 4) is fitted. When the revs have risen uncontrollably I think as suggested that is when it's running on all cylinders. So there's an intermittent fault. Logically I wouldn't think valve clearances as would be constant and on vacuum guages readings across all cylinders the same. But I will do a compression test to eliminate that. Will check no 4 carb bowl for fuel, plug dry. And try fitting clear tubing from bowl drain to check fuel level in bowl. Unfortunately I think the carbs may have to come out again for further investigation. Not what I was hoping but progress thanks to reading the tips on exhaust temp.

"4 cylinder unlikely to be coil fault as fed by same coil as no 1"

Just an update, in the shed making some progress. I have been waiting for my Clymer manual to arrive past couple of weeks - nothing's ever easy. After all that got delivered the wrong book - so another on order. Any one got any use for an American religious book - trial of a mind!! Anyway thought try advice from here - invested in an IR heat gun as suggested by gixer1460 - got a way forward. 350 degrees on 1,2 and 3 downpipe. 40 on no 4. Brilliant. So gonna swap 1 and 4 plug leads and see if fault moves to no1. Thinking if fault on 1 cylinder unlikely to be coil or signal generation as the same coil feeds no1. Will update - but fantastic idea using a thermometer gun. Cheers

Ordered a Clymer manual for the GS. Got one for my other bike and fault diagnosis really good and structured. Gonna start from scratch with all fault diagnosis on ignition, fuel/air and compression. Get it sorted logically without spending loads of time or money. Been ongoing problem for months. Will update when sorted (or any unanswered issues!)

Tried swapping plug leads to start some fault diagnosis (1 &4, 2&3). It wouldn't start! Swapped em back to original - still no start - various choke settings and plenty of fuel in tank. Last time I ran it apart from high revs it was ok started and ran - stopped with ignition switch so there should be plenty of fuel to start in carb bowls. But did prime again incase. So against my initial thoughts of fuel air problem do I have a possible ignition issue as suggested. With plugs removed and ground via cylinder there was only a spark on number 1. Not good but a constant failure should be easier to find than intermittent. Disconnected plug caps - resistance on each 4.5K - 4.9K ohms. Coils primary windings both 3.7 ohms. Measured inner core of each HT coil lead together (think correct way to measure?) for secondary got 14.5K left, 15.3K right ohms. Ignition fuse good and 12V at fuse contacts. So my fault diagnosis is beginning down a different path. Just going through methodically. Was going to clean up all ignition connectors next. And thought could put a voltmeter on each coils feed from loom to see if get 12V when cranked over. It's an American import with factory signal generator so don't how else to test it? Also can you test the actual cdi unit? Don't want to short anything out and cause more problems. I've got a basic understanding of electrics but no expert!

Sorry just thought also - if it was only firing on 2 would it still indicate 4 cylinders on vacuum guages? Would the down stroke piston still produce enough vacuum to register on the gauge even though it's not firing? Got me thinking maybe it is an ignition fault. Cheers

Thanks for both of your replies. Has given me a lot to think about and plan some further fault diagnosis. Curious if intermittently running on 2 cylinders, should be easy to prove if the exhaust down pipes are all hot (simple basics - I hadn't considered). Does make me wonder how people tune by ear if I can't tell between 2 and 4 cylinders running! As been looking into the fault for so long been a bit blinkered - just focused on vacuum leak. Most posts on hanging idle mention running lean or vacuum leak. And the info on swapping plug leads to prove ignition or carbs will be another fault step. Didnt know about wasted spark principle, thought they all fired singly in sequence. It's an American import so Suzuki electronic ignition and no points - so thought ignition issues would be down to coils or leads (tried multiple sets of plugs). So good to get some help from another perspective, will really help trying to pinpoint where the fault lies. I will let you know how I get on. Thanks