Scooterotica

Starting a new thread for this.
Completely rebuilt Li 125 engine with SR 185 cylinder, 28/30 PWK carb, gp crank, mb electronic stator ,af flywheel. Jets 32 120
After various setup problems mostly relating to warm starting I took it to a Dyno.
Tuner binned the filter and changed main jet to 120. Got 12 hp with a slipping clutch.
Scooter starts first time when hot and runs great however just won't start from cold.
Shows no sign of starting with the kick start either with or without choke, starts if bump start it with choke on about the 3rd or 4th bump.
Previously it started ok when cold and hot but not when warm. I tried changing the pilot to 34 but made no difference. At loss what to try next, change the timing, change carb for a delorto, ignition problem?
Any help much appreciated.
Tippo



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try a larger choke jet, after checking the chokes working ok

which plug are you using? b7,8 or 9 if its a 9 thats a cold running plug great for long distances but can be a pain when starting from cold sometimes.B8 if its a new set up first off

GTFOMWSC wrote:which plug are you using? b7,8 or 9 if its a 9 thats a cold running plug great for long distances but can be a pain when starting from cold sometimes.B8 if its a new set up first off

Thanks. It's an NGK BP7ES should I try an 8 do you think. Not sure if it makes a difference but average temp here in KL is 28c

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mick1 wrote:try a larger choke jet, after checking the chokes working ok

Thanks! I think the choke is working as only bump starts with it on. Tried increasing the pilot jet from 32 to 34 but no difference in starting .

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Check the carb manifold is tight and check for split rubber and put a bigger choke jet in say 40 check if plug is wet from petrol if not it'll start

tippo88 wrote: ↑Sat Dec 02, 2017 5:27 pm

GTFOMWSC wrote:which plug are you using? b7,8 or 9 if its a 9 thats a cold running plug great for long distances but can be a pain when starting from cold sometimes.B8 if its a new set up first off

Thanks. It's an NGK BP7ES should I try an 8 do you think. Not sure if it makes a difference but average temp here in KL is 28c

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thats a hot running plug should only really use a 7 when you first start it up after the rebuild and the first 50 mile or so at running in speed.Try an 8 make sure you gap it right as well.One other thing to try if you can is,fuel on,no choke,put your hand over carb mouth for a couple of kicks,take your hand off,then try starting it.If it fires up could well be you need a bigger jet in it as you'll be basically sending fuel straight to the head that way.

Thanks guys much appreciatedwill try the above at the weekend.

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I have been using these carbs for years and what I would say is can you definitely see the choke plunger moving? and when at rest I,e closed try and lift the outer out of the ferrule you will see how much slack is in the outer, they are too short for the inner on standard cable. you have a couple of options, 1) adjustable choke cable, the one I had still did not have the required length. they lengthen the inner not shorten it 2)shorten the inner not east with fixed ends, 3)find a longer adjuster(ferrule) I packed out the original with bits of pipe old cable for a while to test the theory and it worked but would not recommend for the long term (air leaks),4) in the end what you have to do is make a new outer from an old cable, clutch will do with a bit of trial and error you will work it out the outer will be about 1 to 2 cm longer than the standard cable

had same issue on someone's bike recently (pwk30), tried everything and no joy so ended up changing stator and fires up first kick hot or cold. try taking plug lead off and check spark while kicking it, a weak spark indicates LT coil on its way out, if you have a spare stator try it....aint got owt to lose