Dear Marc, Thank you for your info. Just a quick question though. What do you mean by pilot jet? I only heard about the main jet.
One other thing, I think I've heard about putting 34PICT-3 carb on a 2 litre engine as well. I think there must be some kind of adjustments for that. As a starter, I'll take Dean's approach and put the 130 main jet on the carb. Let's see how it goes. Again, thanks for your help Bob Bkk 71 RHD Yellow Super ----- Original Message ----- From: "marc vellat" <[EMAIL PROTECTED]> To: "Air-Cooled Volkswagen Discussion List" <[email protected]> Sent: Friday, March 21, 2008 7:10 PM Subject: Re: [vintagvw] Stumble engine > The problem below 2000RPM is due to the idle & > progression circuits not being right. You may be able > to improve it with larger idle & pilot jets, although > the largest displacement I've ever achieved > satisfactory results with using a 34PICT-3 carb was > 1775cc. With the throttle shut the carb won't pass > enough air to sustain an idle so you have to crack it > open, and that completely disrupts the transition > off-idle. > At higher speeds you're operating on the main circuit. > The carb is designed to run leaner at mid-range cruise > (for economy) than at high speed (to keep from frying > pistons). A larger displacement engine operates > further to the right on the A/F map - the carb only > knows how much air is going through it, not how large > the engine or the RPM - so the mixture will actually > be RICHER than on a stock-size motor. The carb's still > too small for the engine to make anywhere near its > full potential, but there's no driveability problem. > > > --- Bob_Kai Wongthanavimok <[EMAIL PROTECTED]> wrote: > >> Thank you for your help. >> >> Just a thought though. If the carb cannot keep up >> with larger cylinder >> volume, shouldn't it have problem during high rev as >> well? It only stumbles >> during low rev < 2k rpm. >> >> ----- Original Message ----- >> From: "dan moy" <[EMAIL PROTECTED]> >> To: <[email protected]> >> Sent: Thursday, March 20, 2008 7:52 PM >> Subject: Re: [vintagvw] Stumble engine >> >> >> > Sounds like the addition cylinder volume is the >> problem. The carb cannot >> > keep up with the demands, have you thought about >> dual kadrons? You will >> > more then likely have to change your exahust if >> you >> move to a larger carb >> > setup. >> >> --- On Thu 03/20, Bob_Kai Wongthanavimok < >> [EMAIL PROTECTED] > >> wrote:From: Bob_Kai Wongthanavimok [mailto: >> [EMAIL PROTECTED]: >> [EMAIL PROTECTED]: Thu, 20 Mar 2008 >> 00:59:33 >> -0700 (PDT)Subject: >> [vintagvw] Stumble engineBy way of introduction, I'm >> a >> new old listee (been >> with the list few times many years back) from >> Bangkok, >> Thailand. I have a >> 71 RHD Super with recently mod as follow:Existing >> stuffs:o 1,600 standard >> single port AS case engine with 30-Pict3 carb - now >> replaced with belowo 009 >> dizzy with Pertronix magnetico Bosch blue coil but >> recently changed to >> Hitachi Red (my mechanic said it is compatible)o >> Aircono 831 trannyo Old >> standard muffler Newly put in (~3 months):o New >> single >> 34 Pict 3 Solex (but >> I think made by Bocar) on >> > dual port (was single port before)o New 76mm CB >> performance cranko New >> > 88mm Mahle piston set The two should put me to >> a >> 1,850cc engineo New >> > 044 CB Performance heads (I think 40X37mm valves). >> On 34Pict3, I have made >> > some mod according to Nate from AirCooledTech.com >> by >> plugging the throttle >> > by-pass hole to boost the vacuum so that 34pict >> can >> work with 009 see >> > link: >> http://www.aircooledtech.com/34pict3_modification/ >> Here is my >> > problem, whilst running nicely on high rev, the >> engine stumbles on low rev >> > (below ~1,800 - 2,000 rpm). Situations like this >> normally occur:a) >> > cruising along the road, turn in to cross street, >> shift down to 2nd, push >> > gas pedal while releasing the clutch, stumble >> almost >> the engine is going >> > to stop.b) cruising along, slow down, shift down >> to >> 2nd, same to a)c) >> > cruising, stop on standstill traffic on neutral, >> the >> engine stumbly idle. >> > However, after a while, the engine came back to >> (almost) normal with >> > slight hiccup every minute or so. The symptom is >> a! >> > s >> > if the gas does not come through sufficiently. On >> a) & b), I have to >> > push gas pedal a bit (to keep rpm up) together the >> clutch to hold so not >> > to go too fast. Any idea? My mechanic suspects on >> 2 >> things, (1) bad carb >> > (he is kind of not trusting Mexico or Brazil made >> carbs), or (2) stand >> > muffler cannot cope with such a large engine. >> thought that exhaust cannot >> > come out fast enough. Oh, BTW, >> "sometimes", there were some >> > backfire like single firecracker too. Hope it is >> not >> too long. Appreciate >> > everyone comments. Bob/Bkk/71 RHD Yellow Super >> >> ---------------------------------Never miss a >> thing. Make Yahoo >> your >> > homepage._______________________________________________vintagvw >> site >> > [EMAIL PROTECTED]://lists.sjsu.edu/mailman/listinfo/vintagvw >> > >> > _______________________________________________ >> > Join Excite! - http://www.excite.com >> > The most personalized portal on the Web! >> > >> >> >> > -------------------------------------------------------------------------------- >> >> >> > _______________________________________________ >> > vintagvw site list >> > [email protected] >> > http://lists.sjsu.edu/mailman/listinfo/vintagvw >> >> >> >> >> > ____________________________________________________________________________________ >> Be a better friend, newshound, and >> know-it-all with Yahoo! Mobile. Try it now. >> > http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ >> >> _______________________________________________ >> vintagvw site list >> [email protected] >> http://lists.sjsu.edu/mailman/listinfo/vintagvw >> > > > > > ____________________________________________________________________________________ > Be a better friend, newshound, and > know-it-all with Yahoo! Mobile. Try it now. > http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ > > _______________________________________________ > vintagvw site list > [email protected] > http://lists.sjsu.edu/mailman/listinfo/vintagvw > ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping _______________________________________________ vintagvw site list [email protected] http://lists.sjsu.edu/mailman/listinfo/vintagvw
