I've been on a voyage of discovery I could have done without.
Those of you on the New Forest Run will know we failed to get Su's Kwakasicky to run happily.
It would only tickover on choke after lots of effort, and would only rev at all after lots of warming up. When hot, it would run off choke but horribly, with no tickover.
I'd checked the carb over some months ago and it was as clean as a whistle.
I took it off again, blew it all through again, no change. I found a jet not seen before, on the top in a tube, listed in the manual as the pilot jet.
It had a slot in it, wouldn't budge, and splintered up. I wasn't sure if it was a plug, or a jet, as some of the emission control versions have this sealed off with a plug. Anyway, I ended up taking hours with a dremmel, cutting a slot in it, trying to turn it, as each layer broke up, I cut another slot etc. hoping I'd break through a plug and see the jet beneath. I also dripped acid into it, which fizzed and cleared away some of the oxidised aluminium. The assembly is in a vertical tube at the front of the carb, a perfect collector of salty water and road grit. Nice one Kawasaki!
Eventually it shifted, acid heat and dremmel. It was indeed the jet, and I'd taken off about 6mm of it before it shifted, but there was enough left of it to function.
So, another stripdown, blow through, no different.
Out came the engine. I'd set the valve clearances a few weeks before, they were a bit loose and I had to tighten them quite a bit. Also the engine was smoking.
The engine has done about 6000 miles from new. It got a reasonable 3000 mile hammering down to Spain and back last year, but it was looked after and not abused, though ridden hard. Had it taken its toll?
Not a bit of it! Bore smooth and shiny, piston perfect, zero play in the ends, zero play in the valve guides and stem seals.
The ring end gap clearance in the bore is .15 to .30mm. It was at .25. Nearly put new rings in, but at £30 a set, thought I'd leave it for another 5000 miles, Su doesn't do much mileage on it.
Did have a white washer shaped biscuit fall off the exhaust valve, and the inlet and head chamber were sooty.
There was deposits on the seat of the exhaust valve, very hard to remove, after which, we lapped it in.
Re assembled, fired her up, forgot the oil.
Panic. Put the oil in, fired her up, no change, running crap. Tinkered with the Pilot jet screw, as I haven't a clue where it was set to. No luck.To cut to the chase, the rubber tube between the carb and the flange on the head was letting in air, as was the vacuum pipe to work the fuel tap.
There was a backfire and I just caught a glimpse of a jet of fuel mist squirt from each side of the rubber connecting tube, which gave the game away. I was surprised, as I thought the clamps were tight, but obviously not!
It was the cause of all the grief. I have found an awful lot about single cylinder engines that will only run on choke, and a lot of crap printed about it.
So here's my tale, I hope it helps save someone else's sanity.
Ps. The old WD 40 trick did the trick! Sprayed at each end of the rubber, a few revs, and it took off like a jet as it sucked in the WD. Replaced the worn clips with jubilee clips and a bit of a beasting, and now runs fine. New pilot jet, new inlet rubber and two new clamps on order!
POSTSCRIPT: Connecting up the main tank again, (I couldn't adjust the pilot screw with the tank on, so ran from a can) The problem returned.
Long and short of it is, contaminated fuel. Probably diesel. (A senior moment?) So while it's imperative to have no air leaks on the manifold, also try fuel that is known to be fresh and clean! Bikes fine now! (Touch wood....)
.........could come in handy one day......... if only I could remember all this stuff!
