Scooterotica

The piston is below the Exhaust port. Its a bog standard Muggy kit that was replated. I was thinking it was blow back past the rings but the ring gaps are pretty good. I must say the piston has a couple of nip points if i turn it round in the bore. But not in the position it runs. I measured the old piston and its damme near the same as the one fitted. Again I thought me being a skinflint and re using an older piston may have been the problem.
I only had wire circlips for the 150 kit so wont risk my mates prized standard pacemaker kit. (round clips in a square edged slot not good)I will get some standard circlips and try it tomorrow. It may be a bit noisy as I wont be fitting the JL. I should be able to just change the main jet to a 118 instead of a 124 for a test.
As for the tank I drained it dry. The fuel I drained off tonight seems normal no water fuel separation that I can see. But the spit back was milky.

Which atomiser are you using ? By the way I am in Altrincham.

The 26 mm has the alstyles drilled out one. 50 choke 45 pilot 124 main
The 22mm has a jetex mistry one that has been in it since I got it. They dont do stamps very well. To be honest this carb was on my Casa kitted LI but I just changed it for a home made reamed out 26mm that was on when the scumbags pinched the bike.
The 22mm went on the series 1 and had done 3K miles.
Im looking at getting my mates 150 kit on it just to try it. If thats playing up I may take you up on your offer.

Well The old pacemaker 150 kit started 3 kick sounds great with only a u pipe. ticks over perfect and the carb sucks and doesn't blow s**t out. No other changes other than I fitted the 22mm carb with a 122 main jet. Now to find out why the muggy wont run. Its got to be the old piston....

What about a theory that this problem is inlet port timing related and has always been there but just (partially) masked by something else. Flooding problems do seem to crop up quite a lot on mugellos on scooter forums. I too had such problems several years ago. I put them down to carb issues which I eventually managed to jet out. However I recall once seeing a post which essentially said that piston ported engines with an inlet timing over around 150 degrees do suffer in this way.

Just a theory but maybe worth looking into.

storkfoot wrote:What about a theory that this problem is inlet port timing related and has always been there but just (partially) masked by something else. Flooding problems do seem to crop up quite a lot on mugellos on scooter forums. I too had such problems several years ago. I put them down to carb issues which I eventually managed to jet out. However I recall once seeing a post which essentially said that piston ported engines with an inlet timing over around 150 degrees do suffer in this way.

Just a theory but maybe worth looking into.

That was my experience too with my Mk1 Muggy, never did get rid of the spitback and used to have to turn the petrol off before switching off or it was a bugger to warm start

from what i can see thats more than just spit back- its actually dripping out of the carb like its continually flooding.

Does it drip like that with the engine not running and the fuel tap on?

Chris

bristolmod wrote:from what i can see thats more than just spit back- its actually dripping out of the carb like its continually flooding.

Does it drip like that with the engine not running and the fuel tap on?

Chris

No dripping at all, to be honest I have never turned off my fuel when stopping or I grind to a halt after 300 yards
I had convinced myself at one point I must have got someone elses ported barrel back. Im sure its not as one of the 3 extra studs for the cylinder head had stripped and I had replaced it with a 8mm stud. I dont know what the port timings are on this kit I think its a version 3 the one with the bridged inlet port.
But its done 3 K with the same carb and pipe. It was only when I replaced the piston last time that I decided to try the M Tech to see if variable timing would help it to run cooler. It ran well with the M tech fitted started well from cold and 1 or 2 hot. But it dropped out of the pipe range on 3rd to 4th. I then started to try the 101 settings available when I relented and went back to 17 static. Then I found it was harder to start cold and a sod when hot. I then found the spitback and the wandering timing. New Stator and CDI timing is now constant.
THe 150 kit runs sweet. not even a breath of anything dripping out. But I know a very standard italian kit has 1 or 2 less ports than the muggy kit.

Well it was hot in the shed today.
Barrel been away and classed as OK. Replaced the piston for a new one that had no nip pints?? but could find no problems with the barrel compared with a new one
Rebuilt the top end again.... 5 times now with the original muggy setup.
Timing still wandering 10 degrees. Spit back OK I thought but because I was running with no air box I was on choke. Choke off spitting but not as bad?
I had fitted a new BGM stator and a BGM CDI and still had drifting timing on tickover it goes from 17 at revs to 10 ish at tickover.
Replaced the stator for one of my 2 originals same.
Replaced the CD for a Ducatti one from my running Imola set up seemed better only about 5 degrees shift
Replaced the flywheel from my Imola a little bit better 3 or 4 degrees shift towards TDC
Is what I'm seeing Normal on a standard scooter. I expect STATIC timing to be just that.
Each component I have changed seems to change the timing a bit 5 or 10 degrees. In the past I have changed stators on the road and simply put them to the same scribe marks of the old one and carried on.
After 3 stators 3 cdis , 2 flywheels, 2 carbs all I want to see is the timing at 17 degrees and stay put. is it too much to ask?

Monty wrote:.....Is what I'm seeing Normal on a standard scooter. I expect STATIC timing to be just that.
Each component I have changed seems to change the timing a bit 5 or 10 degrees. In the past I have changed stators on the road and simply put them to the same scribe marks of the old one and carried on.
After 3 stators 3 cdis , 2 flywheels, 2 carbs all I want to see is the timing at 17 degrees and stay put. is it too much to ask?

I'd say no, it's not normal, my static timing is pretty much just that, maybe 1 degree flutter at tickover but steadies as you rev it. I think at this point I would be looking to borrow someone else's strobe, just to be sure it's not that which is leading you up the garden path