Hi All. I’d appreciate any thoughts on the following. My bike, 1979 V50II, had suffered a major loss of power… associated with some very dramatic pinking from the LH Pot. Both sides have strong sparks, she runs nicely, on tickover on the RHS alone…(250 single), won’t run at all on the LHS alone and struggles to run on both and won’t tickover at all. New plug, no difference.
This developed quite quickly… hint of pinking on one ride, next time out… low on power for the first few miles, then all OK; last outing… maybe a bit down on power when I set off and steadily deteriorated, I gave up after 4 miles and limped home slowly and failed to get the bike up our steep drive. It feels like the two pots are fighting each other as if the timing well out on LHS and less do when the revs are high.
I have read somewhere that failed insulation on the ignition pick ups is a good place to start for ignition issues, but I’d appreciate any thoughts on this, before I start to do too much more dismantling. I have the alternator off, ignition pick ups are both correctly and securely located and what I can see of the cables looks OK, I’ve not removed the black outer cable sheath (yet) and don’t want to do too much with the engine running so I haven’t checked the timing.
Are you sure it is ignition? 90% of ignition problems are caused by the carbs!
An easy check is to drop the float bowl and fuel filter off to look for muck and dirt, make sure fuel is getting through by opening the fuel tap briefly. Run some fuel into a jam jar and look for water in the fuel.
Easy one to check, but Carbs have had a lot of dismantling and new bits addd already and we’re certainly spotless c300/400 miles ago; it’s easy to drop the main yet out and see what comes out and good point re jam jar and ??water.
My reason for suspecting ignition is that the Pots seem to be fighting each other with a really loud pinking sound, sounds almost mechanical and the engine goes better with the failing one disconnected from the ignition altogether/or when the devs are really high… hence suspecting electrons are somehow shorting/leaking and messing up the signal to the ignition boxes.
Just a thought. Have you done the valve clearances? Before you do re torque the heads if it has not been done. I know you have put all new seals in your carbs but are they balanced.
Good luck.
Quick update. I’m sure that in the end it was dirty fuel and I ever so nearly got there in the end.
I started with an explore of the pick up wires, which were fine, but not the block connector at the top… which had one odd and ?corroded/disconnected pin, now fixed. At which point bike ticking over like a clock (rare!) and running as a 250 single on either Pot.
Dead pleased, go for a ride, no pull and no revs at all, so float bowls off, pics says it all… so carbs stripped and cleaned again, ditto tank washed out. Running well now, just back from an 20ml ride round the block via Garage and some more E5. Well, running well above a nearly closed throttle, but some more tinkering is required to restore tickover again…
Glad you have it sorted.
As for setting a decent tickover, firstly balance the cable adjusters so both slides click together when you close the throttle (wind the throttle stop screws out before checking this).
Secondly, play with the pilot screws to get it running best on each side. Generally these should be about 1& half to two turns out. You should hear the revs rise and fall as you wind them in and out, set it to the max.
Then set the tickover using the larger screws in the side of the carbs.
Do not try and set the tickover using the carb top cable adjusters, they are just there to balance the carbs. The cables should both have a bit of slack in them when the throttle is closed.
Excellent. Only yesterday I was watching a YouTube video it’s a chap I follow on YT, his Kawasaki 900 was conking out and ignition coming and going, the fuses had corroded. OK he lives near Durham, but even so. His point was why aren’t fuses corrosion resistant?
The above pics show the ‘odd looking’ block connector. The Brass Spade didn’t match the others and was loose in the block… oxidation v. shiny suggested it was just to say ‘connected’… so maybe headed off a future problem…
I am also suspecting the Coils are not original… I don’t think an orange wire is shown on the wiring diagram and my Pals TL600 Ducati from 1981 has the same coils as mine c/w orange wires.
I did such bypass myself. It is 12- or 15-connector block with roughly same diameter wires, but two of them carry beefy +ve and beefy -ve, so +ve is first to corrode, always. Regarding coils, did your bike run properly before? have you heard it? Somebody could fit wrong coils, which have wrong resistances. All the data is in the manual. Worth to check.
Coils good or at least good enough for a strong spark each side and Bike was running fine before this ‘ignition’ failure which I’m sure was actually fuel in the end thanks.
And hopefully to finally close this one out. Problem was Fuel, not Ignition, in the end.
Ended with one remade ignition connection, discovery that at some point the Ignition Pick up wires had been replaced (worth knowing) and still problems… So, both Carbs stripped and cleaned along with the Tank… which was thankfully providing clean fuel right to the bottom. Then had to repeat strip the RH Carb, just thawing out now after 25/30 miles around the Lanes near home and all finally as it should be. I thought I may have reassembled the RH Carb incorrectly, but all in order. My money re why RH wasn’t correct, and I am not 100% sure, is that this Carb doesn’t seem to cleanly seat in the Head ( new gaskets in place), on second fitting a good waggle just as the manifold bolts had some tension caused the Carb to jump inwards by a mm or so, and presumably seat itself properly this time. Oh well, continuing to learn.
Only yesterday I was watching a YouTube video it’s a chap I follow on YT, his Kawasaki 900 was conking out and ignition coming and going, the fuses had corroded. OK he lives near Durham, but even so. His point was why aren’t fuses corrosion resistant? 
