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Post by jellerby on Sept 17, 2017 14:27:49 GMT
Just started my engine after rebuilding it, choke and petrol on, let choke off after having it ticking over fine, switched ignition key off and it started revving really fast and high... Ignition switch maybe wired wrong? I used sealant on the exhaust and head and cylinder is torqued? I'm not sure what that could be?
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Post by mijapxman on Sept 17, 2017 17:30:43 GMT
Jellerby, does the engine stop if you pull the sparkplug cap off? ( Try not to get an electric shock, use insulated pliers or equivalent).😉.
My instinct is to say you have an air leak somewhere maybe: cylinder head, carb ,flywheel seal or clutch side seal, I'm not saying strip the engine yet, do a visual check first for leaks and petrol in the gear oil.
Maybe someone else, can think of another reason?
Good luck.
Mij.
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Post by mijapxman on Sept 17, 2017 18:03:38 GMT
Jellerby, I just did a Google search,in case you needed a quick answer and to see if my old brain's still working, if you wish to, Google " vespa px revving after ignition is switched off" and check out what came up👍.
Good luck.
Mij☺
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Post by jellerby on Sept 17, 2017 18:15:34 GMT
Hey Mij, it will stop after I've pulled the ht lead cap off the sparkplug but not with the ignition switch, I swapped some wires as I thought I put them on wrong but still the same situation. I put two base gaskets on the carb which I changed back to one, same problem. It will tick over and rev fine with the choke out, once it's in it will start to tick over higher.. vespamaintenance.com/fuel/carbtune/ - I used this to get the turns for the carb screws, may have gone to far with the idle screw, I don't know.
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Post by ironsloth on Sept 17, 2017 19:28:43 GMT
Get it running again and wind the mixture screw right in. Then slowly unscrew it, should be able to get it running fine by ear. Did you skim the cases while they were apart?
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Post by jellerby on Sept 17, 2017 20:21:07 GMT
Just cleaned the casings using some wipes to get a nice clean surface for the gasket and sealant. The cylinder was rebored with a new piston. I don't want it damaging if possible with the idle getting high without the choke on. I'm going to spray around some areas with WD40 tomorrow.
Runs fine with choke out but not with it in? How would screwing and unscrewing the idle screw out slowly help? I don't think you'd notice a difference would you?
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Post by mijapxman on Sept 17, 2017 20:55:59 GMT
Jellerby, it may be a partial blockage of the idle jet, try cleaning it, while your at the jets, you'd be as well giving the rest a quick clean, mate,after that, start it and see if it's fixed, if your sure of no leak at the carb, if it's still revving high,Double check for leaks from the cylinder head and base of the barrel, then start the engine again and see if it's fixed.
If the above doesn't work I would suspect an air leak at the flywheel side crank seal.
Good luck.
Mij.☺
P.s I assume you checked checked if the carb was warped, when you changed it back to one gasket? Mate.
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Post by mijapxman on Sept 18, 2017 16:40:30 GMT
Cheap leak down tester? For a vespa you could use the carb manifold for a 28/30mm big carb.
I know sime66 used one on his but can't find the posts.
Anyone like to post or links to how to find leaks? To help jellerby out as I believe I saw him asking mista freak moped in the comments section of one of his videos, but don't know if he got an answer, hope he does, tho👍.
Ride safe
Mij☺
P.s can anyone think of anything else it can be, apart from an air leak?
M.
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Post by jellerby on Sept 18, 2017 17:47:25 GMT
Just rebuilding the carb again Mij, after cleaning and blowing out all the jets, will see if that helps
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Post by jellerby on Sept 19, 2017 18:58:55 GMT
Didn't help.. Sprayed around engine with some carb cleaner in places, (Cylinder head, exhaust) got to the carb and it sounded like the revs got lower and then it cut out. Think that could be it?
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Post by mijapxman on Sept 19, 2017 19:44:48 GMT
Jellerby, yes, sounds like the carbs leaking try loosening the nuts or bolts ( whichever your engine uses) and gently tighten each one alternating between them till they are near to tight, then tighten to the correct torque. Torque settings in link bellow 👇 modernvespa.com/forum/topic156286Good luck Mij☺
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Post by mijapxman on Sept 19, 2017 19:57:16 GMT
If that doesn't work the carb body may be warped.
To find out,remove the carb and place the base of it on a mirror or pane of glass or anything else you know to be flat, to check if it's flat.
If it's not flat, tape a sheet of 400 or smoother to your flat mirror or whatever, and rub the base of the carb in a figure of 8 to get the carb flat( others may do it differently 😉).you will see the rubbing marks on any high spots first, rub it till the marks are even across the carb base. Refit as previously mentioned and start your engine, to see if that's fixed the problem.🙏
Hope that makes some sense, as it's harder to write about than do. Feel free to PM me, if you have further questions.
Good luck.
Mij☺
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Post by jellerby on Sept 19, 2017 20:29:06 GMT
Cheers Mij, hope that's the problem. I tightened both the nuts down equally alternating between the two but didn't have any luck. Will check to see if the carb body may be warped and use the sandpaper. It makes sense, I previously did it with the head as it wasn't perfectly flat. Ive never torqued the carb bolts down on this scooter and never had any problem with any air leak, maybe that's where I was going wrong and didn't tighten both equal. Cheers Mij, will report back tomorrow
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