305 running rough at low rpm

Hi folks, I'm close to retiring my little KZ because I know she's just not right. I know it needs new rings again and maybe new pistons (both unobtanium) because I never got rid of that smokey condition.
It always runs pretty rough from cold but lately it's become very 'surgey' down at low revs, it's a bit of a pain to ride to work when it's obviously not happy. It's only a 10 minute ride which I don't think suits it well either.
I cleaned the carbs again last night, I removed the tube under the secondary main for the first time. They were both partially blocked with crud so it was good to get them clean. Everything thing else was clean and in good condition - diaphragms are new etc.
The one thing I need to replace is the carb intake boots. They are cracked and in pretty bad condition. I've tested them many times by spraying carb cleaner on them but I never get an increase in revs so not too sure.
Yes I am running pod filters and I know that makes me a dick but cafe racer style is what got me into motorcycles and KZ's in particular so I have to live with them now. I'm running bigger main and secondary main jets, pilot is stock. It runs fine with the throttle open so it's really just the pilot circuit I think.
Any thoughts or suggestions?

Surging is usually caused by a weak mixture, so if you had dirt in your carbs and possible air leaks on your carb boots they would all be likely causes. What do your plugs look like? if the cylinders are that bad are you getting oil in the bores and on your plugs? or is the compression so low it's struggling to run at low rpm.

Is there definitely no other source for pistons and rings, items from another model or the like? perhaps someone knows. For example a KZ650 is 62mm bore as opposed to 61mm on the 305, but I have no idea if the pistons are remotely the same.

When was the time you adjusted the valves?
Steve

I did the valves maybe 6 months ago. I'm confident the carbs aren't the problem, they're clean as inside although I could check the float levels. The boots looked ok, I glued up the cracks in the outer surface and used a gasket sealer against the engine. I'll check the valves. Could it be a points /timing issue? Plugs look lean.

Low rpm surge and plugs that look lean is carbs or intake boots or both.
Fuel level could be the culprit.
The sealers you used on the boots MAY have worked, at least where the sealer is. They could still leak where the carbs mount. It doesn't take much of a leak to screw up the low speed mixture.
Ignition timing will not affect the mixture, but it should be checked anyway. Once you have eliminated all other possibilities, what remains, no matter how improbable, will be the answer.

When I took the boots off the cracks were mostly between the rubber and the metal mounting plate. None of the cracks went right through, the inner surface looked in perfect condition. I was surprised I thought they would be in much worse shape. I used basically super glue, it's hand grip glue for dirt bikes but it's awesome stuff glues rubber like a dream, I fixed my shoe with it and has lasted very well. Then I used a Permatex non permanent gasket sealer on the mating surface of the boots and engine. I carefully wiped away any excess within the intake ports so I think the boots should be sealing perfectly. I'm wondering if there could be a blockage in the pilot circuit somewhere? I did blast carb cleaner through every orifice I could get to but I'll check the carb diagrams in the manual to see if there is something I missed. Also the rubber plugs that sit between the pilot jet and float bowl are hard and might not be sealing correctly but I would expect that would make it run rich. I was running hotter plugs to compensate for my short journey to work and I'm pretty sure a few months back I was running too rich and fouling plugs! Another reason why I went hotter. Anyway the stock plugs are back in now.

I used the permatex too. Made it better but when I put on my new ones, everything changed.
Steve

I have checked the float bowl levels with the clear tube test. It's supposed to be 1.5-3.5mm below the join. My right carb is at 6 left at 9, when I get time, probably in the new year, after our family camping holiday, I'll sort that out and double check the valves. Meanwhile she's parked up. Have a good Christmas everyone!

Rustyhama wrote: I have checked the float bowl levels with the clear tube test. It's supposed to be 1.5-3.5mm below the join. My right carb is at 6 left at 9, when I get time, probably in the new year, after our family camping holiday, I'll sort that out and double check the valves. Meanwhile she's parked up. Have a good Christmas everyone!

Those numbers, 6 and 9, would be enough to cause a lean condition in every RPM range.

Hey KZ pals! Happy new year to you all. I managed to get a 3 week summer holiday camping in a place called Totaranui - beautiful, no motor bike time though...

Luckily I re-read my post from late last year re the float levels. When I took them off the bike 1 was fine the other was at about 9mm. They are both perfect now at about 2mm. I rechecked the valve clearances. The intake valves were a little tight so I adjusted them. That got it running better but still surgey at low RPM. So tonight I decided to check the timing. I rotated the mounting plate about 2mm clockwise (I think that would retard it slightly) and that made it much smoother at lower revs. I took the mounting plate right off so I could inspect the timing advancer - I think this could be part of the problem. Both sides of the mechanism are floppy and the whole thing feels loose. I would expect it to feel much firmer to hold the timing steady until the RPM increase sufficiently for it to start to rotate. It looks worn where the springs attach and where the tangs meet the notches in the shaft. Can anyone confirm that this should be firm? Does anyone have any tips on refurbishing these or does it need to be replaced?

Cheers
Hama

any pics of the advancer?

I got one for another bike and switched parts. No more wandering idle and crisper throttle.
Steve
kzrider.com/forum/2-engine/600671-ignition-timing#703561