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Post by partanen on Jun 10, 2014 11:28:32 GMT
After spending 5 hours online to find solution for this problem, I have to bother you guys again. Sorry.  Vespa PX200 2003. Original throttle slide was number 4. As Sip recommend slide number 6, I tried it, to improve mid range fuel mixture. Now my carburettor works great at mid range. But at low speeds it's four stroking almost all the time. I have turned mixture screw in and it's only one turn out at the moment. I was hoping someone of you have already struggled with these? Should I order smaller idle jet (-s), or go back to original throttle slide? This number 6 gives nice oomph at midle throttle, but at slow cruising it's annoying. Or is there even better throttle slide? Thanks in advance |
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Post by partanen on Jun 10, 2014 18:59:06 GMT
I went back to original 04. Only difference I could see is that 06 has no air pocket under the slide like 04 have.
One other thing came to my mind. If and when I don't have to twist the throttle so much with 06, then oil amount delivered to the engine is lower. As I have oil mixing device in use. Not so good I thought.
From now on I think I try to find another way to get richer ratio at part throttle. Another emulsion tube maybe.
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Post by vespasco on Jun 10, 2014 20:30:14 GMT
Please rwmind me, what wngine and non stock components do you have?
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Post by sbwnik on Jun 10, 2014 23:03:48 GMT
I'd not fret too much on the oil mix, it's not that precise. I can't find the source that I had, but it varies the mix depending on engine revs (IIRC it's something to do with the partial vacuum created - it's actually sucked, not pushed, into the engine. The pump just gets it high enough or something)
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Post by henri on Jun 11, 2014 16:42:07 GMT
rather than changing slides ,the emulsifyer controls the mix more for mid throttle response , the slide is for 1/8th to 1/3-1/2 throttle , but the different emulsion tubes are really too wide apart to be practical to jump from 1 size to next.unless doing a dyno session with exhaust analysis,an prepared to re-jet the rest to suit .your getting into pretty specilised carb tuning waters , people get ultra-fine modelmakers drills an reams an re-size the holes in a emusfyier to suit there particular tune .
i'd stick with ya original 1 , henri
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Post by partanen on Jun 11, 2014 17:59:06 GMT
Drilled air filter, Sip Road 2.0 and MMW cylinder head.
I found that idle jet with smaller air jet works better than stock 55/160. I have now 50/140, and four stroking isn't so bad. There is still some four stroking at transition, so I ordered more idle jets. Let's see how it goes.
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I'm pretty sure that pump actually pumps oil in to the engine. I bought a new pump last winter and I learnt how it works. Shaft turns when engine is running. Throttle position affects how much oil is pumped because shaft goes up and down when engine turns. Looks like it's hard to explain.
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Edit: Main jet is 122 at the moment.
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Post by vespasco on Jun 11, 2014 18:30:34 GMT
Have you experimented with your timing to suit the head and exhaust?
isn't the 50/140 actually richer, this would make sense An even richer idle would probably work even better.
Ive also experimented with si slides a little bit. and you know what, i ended up going back to the no. 4, with the kidney shaped cutouts on top.
I tried the T5 slide but could not get it smooth enough with the limited sources i had.
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Post by partanen on Jun 11, 2014 18:33:27 GMT
Not yet. Timing is 18 (+/- 1) at the moment. I'm trying to hear if it's knocking, but I think it's not.
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Post by vespasco on Jun 11, 2014 18:42:46 GMT
If you dont hear it. Then you aint got it! Which is good  You would very likely hear something quite strange , likely around 1/2 + throttle. |
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Post by henri on Jun 13, 2014 7:53:23 GMT
pinking or pre-ignition isnt really a knocking sound , more of a "tinkling" ,dont know if that translates into finn , its a lighter/higher more tinny sound than say a bearing knock ,usually its most present with the engine under load IE going uphill an 1/2-2/3 throttle.
you will probably find that youve reached the limitations of the dellorto/spaco slab carb for fine tuning , the way from here is a different manifold without the airbox an probably a japanese/mikuno carb an foam filter ,you'd have to lose the autolube an pre mix ,an then there's boost bottles an power-jets to play with .once you start tuning it never ends ,theres always 1 more thing to try/buy/fit/hate n throw away . an none of its cheap either , H
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Post by partanen on Jun 13, 2014 9:36:50 GMT
"tinkling" actually translates well into finnish , by google translater. Yes, that's the sound. I have not heard it yet then. Sierra burned head gasket pretty soon when it pre-ignited.
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