60mm crank in PX200 disc

Can any one give me any more advice with my 2001 PX200 disc. I am running a 60mm crank with standard barrel and piston with a skimmed Pinasco head, the gap is 1.5mm from the crown of the piston to the head. The pipe is Taffspeed. I am running a standard T5 carb with no air filter a 138 main jet and a 50/100 pilot. timing is set to 19 Deg BTDC. The problem I’ve got is that it will not stop pinking I have messed with jetting, timing. even looked at the springs on the pipe and stand to make sure that there was no rattle there. I 've changed carbs heads barrel and piston nothing works. it was doing it before I put the 60mm crank in when I was running a Pinasco kit with a standard crank. I sold a good 75mph T5 to get a P200 and I do not Know if I have done the right thing anybody got any ideas[:drink:]

I’d deffinitely try it.

I can’t figure out why your piston is not hitting the head if it’s a standard barrel and piston, long stroke crank and skimmed head (if you mean skim the sealing surface to raise compression and not ‚open out‘ to re-profile).

The pack plate ‚should‘ adjust your port timings and make it run better, of course it will also lower the compression and increase the head volume again. Both squish and cylinder head volume are interrelated…you can’t look at one alone (see note below).

Whatever,given what described as your set-up, it won’t hurt to fit the pack gasket, especially as pinking is often related to too high compression… Because what you’re describing does not really stack-up (perhaps you are not certain about any adaption to the con-rod, barrel or piston that has prevously happened?), I would recommend getting the Norrie Kerr book on Vespa Tuning…This has all the info and methods of checking your top end measurements, as well as abundle of good tips about what works well.

NB I measured my squish (Malossi Kit and Taffspeed head) and it was 2.6mm. All the recommendations are for 1mm …after making a few adjustments to the carb and timing having melted a piston, my bike now runs pretty good (82mph on the dyno)


In = leaner, out = richer

I’ve usually settled at the 2 1/2 turns mark. Is the T5 slide richer (smaller cut-away)?

You can ajust the mix screw, try a smaller idle jet, or a leaner slide to work on that closed to 1/4 throttle richness. (I would try in that order as I am a lazy git and that = easiest first)

A 135 main jet still sounds way too big…but if it ain’t broke, then don’t fix it Ie.If the plug looks right …

[:D] thanks for the post I have got a 1.2mm base pack piece from Taffspeed would this put the port timing back in line do you think.[:rotate:]

[:drink:] Thanks for the post
I have ordered an air filter so will put that on when it comes, I have plenty of jets to mess around with on the main jet. The head was skimmed by a local firm. I do have a base pack piece from Taffspeed do you think I should start by putting that on though I have read that this will increase the gap between the piston and the making the scooter slower, what do you think?

[:drink:] Thanks for the post Vespandy
I know what you mean I could not understand why the piston did not hit the head but a guy I Know who ran vespa 200s in the 80’s has said they used to run 60mm cranks with no packs at all?. I have messed with the carb again this weekend, I 've put the P200 carb back in with the T5 slide with the air filter back on I’ve come down to a 135 main jet and a 55/100 pilot and the pinking has stopped (touch that wooden thing over there) and it’s flying it is a bit rich bottom end, do you know what the air screw should be set at on a standard P200 carb? and if I want to make the mix leaner do I screw in or out.
Cheers VespaPaulo2[:dance3:]

I’d do as the man says: Put the airfilter back on as taking it off dilutes your mix with air: The bigger main jet alone will not compensate fully or properly alone. You will then need a smaller main jet the range recommended sounds very safe to me,

The 60mm crank is 3 mm longer than standard…therefore a 1.5 mm packing plate is normally used to re-adjust cylinder hight and the port timings, added to which the head is skimmed: Your compression would therefore be abnormally high: A primary causing of pinking (pre-ignition). The NEW Pinasco heads are reknowned for having having highy compression already (Did Taffspeed carry out all the top end modification work …or did you assemble bits & pieces from different shops?)

[:drink:] Thanks Mate
I will try messing with the air screw to see if I can get it a bit leaner I have it set at 2and a half turns at the moment, I put a 50/ 100 in to test it on my way to work today, did a plug chop when I got to work (mostly useing lower throttle) and the plug looked a bit light but useing the 55/100 yesterday the plug looked too dark almost black. I have phoned Taffspeed but Ian said there is nothing really inbetween the two. Anyway I would rather use the richer jet and play with the air screw. The T5 slide is richer than the PX200 slide, I got that bit of info from Ian at Taffspeed as well, top man give load of advice over the phone for nowt. I agree the 135 Main does seem a bit big but I will do main jet tests and plug chops on longer faster runs to try to see if I can get it down a bit. I could change the slide back to standard PX200 but that would almost take me back to where I started. that’s it for now I’m feeling dizzy.[:dance3:]

[:smile:] hello and thanks to all the people who gave me advice on this topic. Just thought I’d post what I have done with the PX200 since last time. To cut a long story short I still had pinking problems all over the rev range depending on what speed I was doing and how warm the motor was I got really fed up with it so I bit the bullet hammered the plastic and got a malossi 210 with head to match from Taffspeed put a 1.5mm pack piece under the barrel with the malossi gaskets at the base and the head. I have just done 250 miles the scoot is pulling like a train I have to hold back off the throttle because I’m still running in. If anybody need a full spec leave a post and I will be pleased to post it.[:drink:]

not 100% sure but by using a 60mm crank and standard barrel/piston you will be putting your port timings way out, ie ports partly closed off at BDC which doesn’t give enough time for a decent amount of fuel/air at high revs, this could be the cause of the pinking. I’d also put the air filter back on and downjet to a 125/128, 138 is way too big for a standard barrel/piston.[:dance1:]