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Hello,

I posted a enquiry earlier but got no replies, so I decided to have a "mess" over the weekend with my PX it would not start from a kick so I put the air mixture and fuel back to default settings and it started after about the 3rd or fourth kick, now if I let it tick over for a while it starts to rev up on it's own, the cable and outer are brand new and I don't think it's fouling on anything, I rode it up and down the street a few times and my mate said he was concerned because there was no smoke, have I undermixed oil/petrol? any help would be greatly appreciated,

thanks

Just been reading thru a few threads on here and things are pointing to an air leak? are these air leaks generally from the carb area or could they be anywhere, (when I restored the engine I put in new oil seals and gaskets etc) could it be that things need tightening up a bit!

Air leaks can be from anywhere, i'd make sure the carb is seated properly first, don't rebuild the carb area useing gasket sealer only gaskets as the sealer can clog the oil way.

how old is the engine,,, it could also be the carb slide is worn, if it has shiny edges or shows signs of wear on the end then that could be the problem.

Then it could be the oil seals, you say you rebuilt but there is always the probability of damage to the clutch side seal when re-fitting the crank.... quick check on the drive side seal is to see if there is either petrol in the gear oil - but after only a short distance then i'm sure there wouldn't be enough to notice, next test is to remove gearbox breather - top of clutch cover - when its running try and place your finger over the hole if the seal is gone then you can fell suction on your finger, also when you block the hole the engine will clean up and rev smoother.

Then the flywheel side seal, only real test for that is to have a look to see if there is any leakage around it.

I checked the oil on Saturday and it was clear of petrol, sorry mate it is an old engine (1979), I also changed the flywheel seal while rebuilding this engine,(mainly to change a worn cruciform) so changed all oil seals, new crank, piston while it was all apart, I will do the checks you mentioned tonight, will let you know how I got on.

Thanks again!

Hello,

Started scooter up last night & did the following: Checked carb was seated correctly, (there was a new gasket fitted to this) tightened up a little bit as it was slightly loose, tried the finger over the breather hole and there was no suction, BUT the slide on the carb was a bit "shiny" on the edges, can I just buy a slide or is it worth just getting a new carb? oh I did start it after all these checks and when it got warm started to rev it's tits off!

how does it run on the road, it may be a fuel starvation problem, not enough petrol getting through making it run lean.

try running it with the filler cap off, this will eliminate that if it is

yes you can get the slides, is it the 20/20 i may have one.

Thanks ME for all your help thus far, I will try the cap off thing tonight,I don't want to annoy the neighbours too much, it seems ok on the road I know it seems strange but it has a little too much power without me throttling it, I don't want to break it as I have to run it in with it having a new piston & rings etc, should I add a touch more oil just to be on the safe side? I had a bit of paper with the setting for the Petrol & air screws (ie default settings) but have lost it, I remembered the ticking over screw ie 1 and turns out but can't remember the petrol one ie the one at the back of the engine, any suggestions? I know some of this may seem really stupid and your probably wondering how I managed to restore an engine etc, all that seemed pretty straight forward it's these niggly little things that I can't get my head round.
Thanks for your patience!

PS the carb is the original dellorto carb!

One last thing, the piston I took out was "holed" so could this of been because of a previous air leak?

TA!

The screw on the back of the carb is the air/idle mixture screw which on a standard carb is normally set at 1 1/2 turns out, the screw on top of the carb is the tick over screw this has no setting apart from what sounds best, your aiming for a nice steady tick over and a clean pick up when you pull the throttle back.

a little more oil when running in wouldn't be a bad thing.

yes the holeing of the piston can be caused by a over weak mixture, but there other factures as well, over advanced timming to high compression ratio.

had you fiddled with it before it holed, did you change the spark plug for a different heat range????

Right,

I bought the Scooter about a year ago for 200 quid off my mate who had it given to him, he said he had done all the body work but couldn't get the engine running, I had a look at some of his handy work and it was basically a mess so I decided to start over, thats when I discovered it was 50% filler, 50% metal, so I took the proverbial bull by the horns and decided to have a go myself, all bodywork done, I turned my attention to the engine, I took the head off and the piston and where there used to be metal there was now daylight, took off the crank etc and replaced cruciform and all bearings and seals, took the crank to local scooter shop because I couldn't get the shim off to replace it, he told me the crank bearings were knackered and had these replaced along with a new piston rings etc, so basically after The Lord of the Rings story above, there must of been a problem for it to knacker the piston previously and I dont want to repeat it, so you have answered my question about the screw at the back of the engine I will try this over the weekend, I am very grateful for you input thus far as I want to be on the road (after 21 years off the scene) again! ( I don't remember things being this difficult when I was 16-18)

Cheers mucka!