grrclark Posted February 12, 2018 Report Share Posted February 12, 2018 How is the carb inlet for air temperature? A common issue on VW Bugs running modified carb's was that the fuel air mix became too cold and the fuel would condense out, a common cure is to add a velocity stack to effectively increase the size of the chamber for mixing fuel and air and also to draw slightly warmer air from the bottom half of the engine into the air cleaner. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 12, 2018 Author Report Share Posted February 12, 2018 Inlet will be just above ambient temperature I think. The carb sucks air like a trooper, my exhaust is also larger and heavily modified, I did think about a venturie type stack for air flow, I fell the bigger dellortro will work better as it's more suited to my exhaust. Im after speed with torque. Had a few vw's my favourite was my t25 2.1i Quote Link to comment Share on other sites More sharing options...
Velocette Posted February 12, 2018 Report Share Posted February 12, 2018 This will tell you all you need to know,,, http://www.amrca.com/tech/tuners.pdf Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 12, 2018 Author Report Share Posted February 12, 2018 Thanks, I've been following an American two stroke tuner,he specialises in the puch and Moby, two strokes are quite complex to tune, I'm currently working port timing and tuning and how many degree's to take them to. Quote Link to comment Share on other sites More sharing options...
grrclark Posted February 12, 2018 Report Share Posted February 12, 2018 48 minutes ago, Albert 888 said: Inlet will be just above ambient temperature I think. The carb sucks air like a trooper, my exhaust is also larger and heavily modified, I did think about a venturie type stack for air flow, I fell the bigger dellortro will work better as it's more suited to my exhaust. Im after speed with torque. Had a few vw's my favourite was my t25 2.1i I believe a stack improves the airflow so improves the mix, i think it makes it more turbulent, but maybe it's the other way round. I suspect that your right, the bigger carb may well better match your higher flow exhaust. Quote Link to comment Share on other sites More sharing options...
TIGHTCHOKE Posted February 13, 2018 Report Share Posted February 13, 2018 (edited) Many years ago when tuning car engines, in simple terms, we always wanted more cold dense air to allow more fuel in to the cylinders and a better spark at the right time over the correct gap. I remember having 16 different gapped NGK Spark plugs, Drive hard at 120 mph, pull in to a lay-by, lift bonnet, put gloves on. Plugs out, next gap size in, bonnet down and off to do two runs and back in to the lay-by. Found that a certain gap (40 thou) allowed the 2 litre engine and gear box to pull like an absolute train in 3rd. Top speed was very high too, but fuel economy was poor! The cold dense air was delivered through a K+N Filter. The ECU was remapped electronically. The spark from NGK's wonderful plugs, good fuel and correct tyre pressures. I could drive long cross country distances at great speed. (before the advent of the Speed Camera's). An interesting thread, the smooth air / swirling air debate has always gone on, I went along the smooth route and it worked for me. Albert, I hope you find the magic set up. Good luck Edited February 13, 2018 by TIGHTCHOKE Quote Link to comment Share on other sites More sharing options...
Velocette Posted February 13, 2018 Report Share Posted February 13, 2018 Smooth air into the carb ,,,turbulent towards the cylinder or indeed in it,,,remember the swirl head design? Quote Link to comment Share on other sites More sharing options...
Dunkield Posted February 13, 2018 Report Share Posted February 13, 2018 I have built and modified a few 4 stroke motors but never touched a two stroke so I am following this with interest Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 13, 2018 Author Report Share Posted February 13, 2018 I rebuilt a 280cc ktm exc-f, it was originally a 250. Little auto 2 strokes can be dismantled stripped and fully rebuilt in a couple of hours, if you have all the bits. Quote Link to comment Share on other sites More sharing options...
Dunkield Posted February 13, 2018 Report Share Posted February 13, 2018 Looks like super minis are all the rage http://www.returnofthecaferacers.com/2017/12/express-mail-xtr-pepo-mobylette-sp-90.html Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 13, 2018 Author Report Share Posted February 13, 2018 My dream build is s mobylette, too much going on on them for me at this point in time,they have variators and loads of other stuff I don't understand yet. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 13, 2018 Author Report Share Posted February 13, 2018 (edited) New 19mm phbg carb, 60 choke,45 starter,262 atomiser, 95 main jet, w7 needle second clip up. Starts ticks over and revs up great, 38mph max boggy as hell running very rich, going to drop the pilot to 40-42 and go from there. My intake froze it sucked that much cold air in. Edited February 13, 2018 by Albert 888 Quote Link to comment Share on other sites More sharing options...
grrclark Posted February 14, 2018 Report Share Posted February 14, 2018 (edited) It is evaporative cooling with the fuel/air mix inside your intake that will cause it to freeze, as well as sucking in very cold air just now. That will cause the fuel to drop out the mix. Can you fashion a hood to take some of the warmer air flowing around the cooling fins from the cylinder and direct it over the intake, without it looking rubbish of course? Edited February 14, 2018 by grrclark Quote Link to comment Share on other sites More sharing options...
Jaymo Posted February 14, 2018 Report Share Posted February 14, 2018 Good old carburettor icing- nearly had me in a field back in my Instructing days. Even diligent use of the ‘Carb Heater’ didn’t stop it forming that time- fortunately a low level circuit inside the airfield boundary got us back onto a piece of tarmac. Carb icing is the reason that cars such as the early 911 and VW bugs had a bellow system that automatically directed warmer air- only down side is that warmer air is less dense, and so less power..... back then, I know which I preferred Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 14, 2018 Author Report Share Posted February 14, 2018 (edited) I didn't know of carb icing on carbs, my mate a work told me about the old kawasakis and the slides used to stick open.. 8 hours ago, grrclark said: It is evaporative cooling with the fuel/air mix inside your intake that will cause it to freeze, as well as sucking in very cold air just now. That will cause the fuel to drop out the mix. Can you fashion a hood to take some of the warmer air flowing around the cooling fins from the cylinder and direct it over the intake, without it looking rubbish of course? I have made another manifold it's shorter so will be a lot closer now. Just picked this up today,no compression, big end rattling and main drive bearings goosed, now my plan is to have this new red one as a general runabout suspension lights all the mod cons, then use my gold one as a sunny day bike,so I'm going to be buying more performance bits to go on the race bike and use the stuff I already have for the red one. Edited February 14, 2018 by Albert 888 Quote Link to comment Share on other sites More sharing options...
grrclark Posted February 14, 2018 Report Share Posted February 14, 2018 8 hours ago, Jaymo said: Good old carburettor icing- nearly had me in a field back in my Instructing days. Even diligent use of the ‘Carb Heater’ didn’t stop it forming that time- fortunately a low level circuit inside the airfield boundary got us back onto a piece of tarmac. Carb icing is the reason that cars such as the early 911 and VW bugs had a bellow system that automatically directed warmer air- only down side is that warmer air is less dense, and so less power..... back then, I know which I preferred That's one of the main reasons why I dropped the performance carb' off of my Bug, it is just far too fickle to try and maintain a reliable mix. Gone back to the traditional oil filled air cleaner as well where the intake air is a little bit warmer, it does lose power as less air is being sooked into the engine, but it's a worthwhile sacrifice to keep the car drivable all across the rev range. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 14, 2018 Author Report Share Posted February 14, 2018 Only problem is your proberbly towards 100bhp. Standard I'm 2hp,very rough estimate I'm 4.5 - 7.5bhp I need everything optimum. Quote Link to comment Share on other sites More sharing options...
grrclark Posted February 14, 2018 Report Share Posted February 14, 2018 13 minutes ago, Albert 888 said: Only problem is your proberbly towards 100bhp. Standard I'm 2hp,very rough estimate I'm 4.5 - 7.5bhp I need everything optimum. Absolutely, the two are not really comparable at all, other than icing is to be avoided in all cases. It would be interesting to know how much difference it would make if you were doing this tuning in the summer where the air is warmer and much less moisture laden. You might well have to make changes to jet sizes and spark gaps as you get into the warmer weather. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 14, 2018 Author Report Share Posted February 14, 2018 Looking at other tuners,it matters alot even altitude. Im a novice willing to learn and experiment. I thought at first, just stick a bigger cylinder on and away you go,not the case. Quote Link to comment Share on other sites More sharing options...
Wb123 Posted February 15, 2018 Report Share Posted February 15, 2018 There was a two speed manual puch maxi sold in europe (I have one in bits), that would give you a bit more flexibility. The yanks had a two speed automatic. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted February 15, 2018 Author Report Share Posted February 15, 2018 I'm sticking with the e50 automatic for now,I will get to 50mph on the flat,they do a 3 speed also. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted March 20, 2018 Author Report Share Posted March 20, 2018 (edited) Nearly finished, 74cc airsal piston port cylinder and head,21mm dellortro phbg carb 45pilot 60 choke,w7 needle 2 clips up 98 main jet,hpi cdi mini rotor -timed at 2mm btdc with auto retarding,domino fast action throttle, all cables shortened,wires hidden. Strengthening bar added,holes and stuff not needed deleted and welded,frame and wheels powder coated,gearing changed to 18:40. Just need some good weather and for the salt to disappear then I can tune and jet correctly. Hoping for 60mph. Other bike is awaiting paint,that will be standardish. Edited March 20, 2018 by Albert 888 Quote Link to comment Share on other sites More sharing options...
Dunkield Posted March 20, 2018 Report Share Posted March 20, 2018 Sweet I was wondering what had happened to this project, good luck with speed attempt. Quote Link to comment Share on other sites More sharing options...
Albert 888 Posted March 20, 2018 Author Report Share Posted March 20, 2018 20 minutes ago, Dunkield said: Sweet I was wondering what had happened to this project, good luck with speed attempt. Thanks, Waiting for glass blasting then waiting for paint,out of my hands that part. Also the herendous weather isn't helping much. Will soon have both done. Quote Link to comment Share on other sites More sharing options...
mel b3 Posted March 21, 2018 Report Share Posted March 21, 2018 (edited) I never dreamed that a puch maxi could be so cool ,absolutely top marks mate? Edited March 21, 2018 by mel b3 Quote Link to comment Share on other sites More sharing options...
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