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Post by george1966 on Oct 16, 2015 10:52:23 GMT
sorry should have posted my question here
my px 125 is euro 3 restriction, i know about the exhaust cat,secondary air box,throttle slide and the cdi rev limiter but are there any other parts or devices restricted .I read on here something about the inlet timing?but it wasn't clear or at least not clear to me lol
thanks for the forum and your help
george
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Post by beatnik on Oct 16, 2015 13:28:23 GMT
Sorry not to be able to help, but what restriction is there on the throttle slide? I've only just found out about the CDI rev limiter myself. Still unsure as to whether to bin that or not.
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Post by beatnik on Oct 16, 2015 14:32:19 GMT
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Post by george1966 on Oct 16, 2015 14:33:38 GMT
Hi i believe a vespa px euro 3 has extra air pockets in the throttle slide which makes the mix lean for the cat exhaust i assume this would need to be factored in if you were tuning ,i,m taking the bike to an aprilia 2 stroke race bike tuner ,it appears he,s a bit of a 2stroke guru ,i,m trying to find out if the cdi has a pre programmed advance curve based on mix ratio or is just a simple rpm retard
george
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Post by beatnik on Oct 16, 2015 15:20:58 GMT
Cool. Keep us updated.
I've ordered a Zeus CDI from Readspeed which removes the rev limiter. I have a misfire and changing the CDI is my next port of call to fix it. Seemed like a good idea to try this one. I'll update when I get it.
Using non-resistor spark plugs can fry the circuit board in the post 2011 PX CDI, so I am led to believe. So watch out for that.
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Post by vespasco on Oct 16, 2015 15:59:49 GMT
Not speaking from experience but from what ive read, the inlet timing (or, if you like, 'the hole between carb and crank'), is quite small, or at least smaller than a pre cat PX.
Which will also restrict performance.
Whatever restriction is on the cdi im not exactly sure but i can't see how you could change it.
Everybody talks of it being a rev limiter.
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Post by henri on Oct 16, 2015 16:15:27 GMT
smaller briefer inlet timings , a 7000rpm limit on cdi an a crap exhaust system , an also as above pocketed slide so it runs extra lean at 2000-3000rpm . coincidently just the rev range they do the emissions test at . shades of VW i think . the unlimited cdi's are quite expensive ,for same money you could get a krptronik mappable cdi an let ya aprilla guy play with it . H
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Post by george1966 on Oct 16, 2015 16:37:54 GMT
Hi the inlet timing is that the "transfer port or inlet port or both" do you know where you read this?
and if the cdi has a pre set advance curve based on standard mix ratio ,how could you ever tune,change exhaust upjet ect it would never run right ,and could run really hot
george
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Post by george1966 on Oct 16, 2015 16:44:23 GMT
sorry posted as you were posting lol are you saying physically smaller "transfer port and inlet port?
thanks
george
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Post by george1966 on Oct 16, 2015 17:22:25 GMT
hi just trying to get clarity,the barrel and the crankcases are different on a new px euro 3 restricted?
george
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Post by vespasco on Oct 16, 2015 17:23:14 GMT
If you compare the hole from the carb to the crankcases on yours and an early P range, this hole, the inlet, is smaller on yours so it's not going to flow so much fuel.
Inlet timing is determined by the crank web and the length and positioning of the inlet hole. Between them they control the duration of the the inlet of fuel into the crank case. Or if you like, the inlet timing.
It wouldnt suprise me if the transfers are smaller too, i dont really know tbh.
Changing the inlet timing would involve a full strip down and rebuild
Please remember i have no experience with theese cat'd motors. This is what i read from various forums.
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Post by george1966 on Oct 16, 2015 17:30:10 GMT
Hi just to clarify , is it the carb or engine side that's smaller diameter ?i,m assuming the crankcase side?
thanks
george
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Post by george1966 on Oct 16, 2015 17:31:56 GMT
hi is it just something like a nylon reducer sleeve or the casting itself? appreciate the info
george
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Post by george1966 on Oct 16, 2015 18:07:48 GMT
just looked at the engine configuration ,silly me the inlet on the crankcase ,new bike need to get a spare engine to strip to get a better understanding lol
george
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Post by henri on Oct 16, 2015 19:54:16 GMT
its the actual physical size of the hole in cases below carb thats restricted on later px engines , the barrels are same an transfer ports ,the bit were cases n barrel meet are same . a moment from ya aprilla guy n a dremel/die grinder an hey presto , roberts ya fathers brother ,(bobs ya uncle),H
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Post by george1966 on Oct 16, 2015 20:22:56 GMT
cheers mate you are a star
george
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Post by phattanglo on Oct 17, 2015 9:21:54 GMT
To be honest unless you're gonna re-engineer the engine your only real option is junk the cat exhaust, fit a non cat and go up one MJ size, or fit a Sip road or similar and up 2 MJ sizes and plug chop.
Unless you light enough to get beyond 7000 RPM I wouldn't bother changing the CDI and for everyday riding the carb slide doesn't seem to make much difference either.
I'm a lardy and on the flat I get 55 ish mph and decent fuel economy.
With the cat exhaust I was getting 50 mph on a good day so I would say a change of exhaust does give you a little bit more top end and it does feel more lively going up through the gears.
The guys on here will be able to tell you more about the benefits of a Sip road type as I just went with the std exhaust and a 98 MJ and it's sweet as a nut.
Oh and yes stick to the suppressor type plug the new cdi is not a happy bunny with a std plug.
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Post by george1966 on Oct 17, 2015 9:56:47 GMT
Hi thanks for the info, early start this morning met up with the 2 stroke guru lol very interesting the suggested option its more radical than i wanted to do and thats just to return it to pre euro as you say,inlet port, throttle slide cdi jets exhaust port flow ,the one thing i do understand is its your weakest link thing,changing one thing affects another and requires a lot more knowledge than i have lol the list of possible incompatibilities resulting in flat spots,wrong exhaust charge,temperature increases are what lead to seizing premature wear ect my new px runs really sweet she aint fast but pulls smoothly in all gears and running temperature was spot on and as he said the factory's know what there doing ,they have lots of high tech diagnostic tools probes ect to set the bike up for optimum running
i,ve got a garage and a box of spanners but i do have a digital tyre pressure gauge lol
george
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Post by pxguru on Oct 17, 2015 11:02:19 GMT
The term "restriction" gets me all annoyed. Anything that is a "restriction" would have to come out of my scooter. I would say the same as Phattangelo about the CAT. Get it off and a bigger main jet. Same goes for the CDI for me, another "restriction". Got to go.
Do these two things and if you are still talking to us later, there are a couple of more serious but non-permenant and easy mods that can be done that will get it up to about 65mph every time.
With 2 strokes, if there is no pinking sound coming from the engine and the plug colour is good after holding at 1/4 throttle and still good at full throttle, then it is really un-likely to ever seize up.
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Post by george1966 on Oct 17, 2015 12:34:23 GMT
Hi thanks ,i think if your confidant in what your doing and have the experience its fine ,but i think sometimes all the different suggestions and differing opinions are a little overwhelming
george
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Post by pxguru on Oct 17, 2015 13:01:44 GMT
If you are not confident then leave it all standard. Just have all the normal stuff to worry about then and can thrash it as much as you like.
The one thing you can be sure of with 2 stroke scooters is that everyone has a slightly different opinion!
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Post by george1966 on Oct 17, 2015 13:16:29 GMT
cheers mate that what i,m gonna do i,m not a young man anymore and with all the plonkers on uk roads nowdays
perhaps slower is safer lol
george
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