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Post by lan on Oct 29, 2007 19:43:45 GMT
the more and more i look on here the more i want a smallframe vespa so i will probs get one after ive finished my T5, i was wondering tho ive seen a lot of direct reed induction cylinders for smallframes and wanted to kno how much work these are eg. what happens with the crank induction, id also like for someone to show me exacly what this polini twin induction is i kno its both reed and rotary but what cylinder reed etc does it use and where can you get it from??
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Post by Juan on Oct 29, 2007 20:51:56 GMT
Taking things one step at a time.
Direct induction is a piston ported motor which means you need a full circle crank to work in the ideal conditions.It many still work on an inducted model but it'll never work as it should due to the loss of crankcase compression.
The TI is slightly more complicated although fairly simple when thought through.It retains the crank induction as the rotary is still in use and the reed to the barrel is a secondary or scavanger boost.If afraid I can't be more scientific than that just now and the inlet timing is still a bit vague to me although I suspect Minikin can give you a more techinically satisfactory decription on the mechanics of how they work
The Polini TI is still widely available in Italy or from SIP and perhaps the other German shops.
TBH,the question you should be asking yourself is what type of motor you want at the end.Is it purely a fun bike to thrash on occasional days or something more flexibal you can use whenever the mood takes?
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Post by hank on Oct 29, 2007 21:10:11 GMT
it would be interesting to know what difference in power you get between a reed valve full circle mallossi setup as opposed to the polini TI.
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Post by lan on Oct 29, 2007 21:32:25 GMT
TBH,the question you should be asking yourself is what type of motor you want at the end.Is it purely a fun bike to thrash on occasional days or something more flexibal you can use whenever the mood takes? some thing thats racey but not too expensive u could say the best of the non parmakit - falc - quattrini super expensive cylinders as nice as it would be to own one of them my wallet isnt big enough, so the best possible setup but with none of them cylinders |
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Post by Juan on Oct 29, 2007 21:58:47 GMT
I love my TI but I'd love it more with a dcent carb/pipe/etc,depends where you're cut off point is.
A totally fun,thrash bike for me with a semi reasonable budget would be a malossi 132/whatever induction/Simo D&F and half decent drive train.
I prefer Polini SI or TI for a road bike but it's horses for courses.
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Post by lan on Oct 30, 2007 11:27:20 GMT
what sort of crank would you use with the ti?, and assuming any direct intake only cylinder has to have the rotary inlet blocked how would you go about that?
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Post by unreliablesc on Oct 30, 2007 15:16:38 GMT
what sort of crank would you use with the ti?, and assuming any direct intake only cylinder has to have the rotary inlet blocked how would you go about that? The Malossi kit comes with a plate for blocking the rotary inlet. This works, but you gain some crankcase compression by blocking it off properly. I used liquid metal on my old 136, and it worked great. |
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Post by lan on Oct 30, 2007 16:07:17 GMT
correct me if im wrong but is the malossi a 180deg rotated cylinder?
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Post by unreliablesc on Oct 30, 2007 17:06:16 GMT
correct me if im wrong but is the malossi a 180deg rotated cylinder? It's whatever you want it to be.... You can rotate it, but it's supposed to be mounted the normal way out of the box. All off-the-shelf manifolds places the carb under your seat. |
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Post by MiNiKiN on Oct 30, 2007 19:15:51 GMT
To start with a possible setup for you Ian: go for a Malossi direct with reed valve, 25 mm Dello or better PWK or Mikuni 28mm.
You do not need a full circle because generally on Vespas the crankcase compression is to high anyway. it seems that the full circle cranks are of better quality on the other hand.
As mentioned elsewhere, the polini Ti has some advantages on non widened casing ports. To get good flow you should consider "smoothening" the crank and widen the ports as much as possible.
The manifold splits in two, the direct inlet is controlled by a single reed plate. Unfortunately the piston skirt is a bit to long so you have piston and reed controllin your timing, which is anything but clever. shorten the piston on the inlet side or make an additional hole in the piston to run the cylinder inlet fully on reeds. Etc.
Where about are you from?
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Post by unreliablesc on Oct 30, 2007 19:29:59 GMT
The manifold splits in two, the direct inlet is controlled by a single reed plate. Unfortunately the piston skirt is a bit to long so you have piston and reed controllin your timing, which is anything but clever. shorten the piston on the inlet side or make an additional hole in the piston to run the cylinder inlet fully on reeds. Etc. Do you have any photos of this piston modification? Looks like it's the TI for me, and I would like to make the most of it. |
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Post by hank on Oct 30, 2007 19:44:10 GMT
You do not need a full circle because generally on Vespas the crankcase compression is to high anyway. it seems that the full circle cranks are of better quality on the other hand. surely its still better to run a full circle crank with a reed setup? |
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Post by lan on Oct 30, 2007 20:52:11 GMT
To start with a possible setup for you Ian: go for a Malossi direct with reed valve, 25 mm Dello or better PWK or Mikuni 28mm. You do not need a full circle because generally on Vespas the crankcase compression is to high anyway. it seems that the full circle cranks are of better quality on the other hand. As mentioned elsewhere, the polini Ti has some advantages on non widened casing ports. To get good flow you should consider "smoothening" the crank and widen the ports as much as possible. The manifold splits in two, the direct inlet is controlled by a single reed plate. Unfortunately the piston skirt is a bit to long so you have piston and reed controllin your timing, which is anything but clever. shorten the piston on the inlet side or make an additional hole in the piston to run the cylinder inlet fully on reeds. Etc. Where about are you from? Btw its Lan i kno it looks like ian cos of the lower case l but yeh  and im from chester |
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Post by Juan on Oct 30, 2007 21:31:37 GMT
You do not need a full circle because generally on Vespas the crankcase compression is to high anyway. it seems that the full circle cranks are of better quality on the other hand. surely its still better to run a full circle crank with a reed setup? Depends really,there's huge arguement between the full circle and special lip cranks on reed motor.Oz likes a full circle,Curare prefers a special lip. *Lights blue touch paper and stands back.* ;D Marcus,gimme some tips on modifing the TI too as I'm gonna strip the fucker shortly.  |
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Post by MiNiKiN on Nov 19, 2007 12:07:25 GMT
Will do - unfortunately I haven't taken pictures of the recent mods when the engine was split for overhaul (  ). Generally speaking I opened the transfer ports, and opened the boost port to the reed inlet with a radius around the "corner" inlet port timing is 120deg and exhaust port timing 186 deg. I.e. barrel raised by 1.0mm and skimmed on top by 0.8mm. Exhaust port width is 67%, which results in a piston ring life-span of ~1000miles ;D (ergo too much, better 65%). Piston skirt is partly shortened on inlet side to give a theoretical inlet timing of 250deg (enables the reed to work independent of piston). No more additional piston aperture, just the standard one modified so it directs the mixture upwards into the bost port. Rotary inlet timing currently is ~200deg. All this with either a 28 or 30 mil Mikuni on an enlarged and modified inlet manifold with 0.3mm carbon reed. compression is somewhere between 11.5 and 12:1, with a squish of 1.2mm. No Dyno results yet, I am just bedding in - then we'll see. But runs rather nicely compared to before. Since i changed from standard 2.54 helical to RMS 2.56 straight cut primary I face some clutch dis-engagement problems.  |
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Post by adspeed on Nov 19, 2007 19:43:17 GMT
Lan just for your info I have a tuned Malossi on the garage shelf and a Simoni D&F, oh and a 25mm dellorto all jetted ;D The build is documented on here somewhere under.....Malossi!! Let me kow if its of any use... |
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Post by breezer on Nov 19, 2007 19:45:08 GMT
thought you sold all those bits Ad?
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Post by adspeed on Nov 19, 2007 19:51:59 GMT
Nah people were wanting it for silly money, the whole lots done less than a couple of hundred miles!
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Post by unreliablesc on Nov 20, 2007 19:22:36 GMT
Will do - unfortunately I haven't taken pictures of the recent mods when the engine was split for overhaul ( ). Generally speaking I opened the transfer ports, and opened the boost port to the reed inlet with a radius around the "corner" inlet port timing is 120deg and exhaust port timing 186 deg. I.e. barrel raised by 1.0mm and skimmed on top by 0.8mm. Exhaust port width is 67%, which results in a piston ring life-span of ~1000miles ;D (ergo too much, better 65%). Piston skirt is partly shortened on inlet side to give a theoretical inlet timing of 250deg (enables the reed to work independent of piston). No more additional piston aperture, just the standard one modified so it directs the mixture upwards into the bost port. Rotary inlet timing currently is ~200deg. All this with either a 28 or 30 mil Mikuni on an enlarged and modified inlet manifold with 0.3mm carbon reed. compression is somewhere between 11.5 and 12:1, with a squish of 1.2mm. No Dyno results yet, I am just bedding in - then we'll see. But runs rather nicely compared to before. Since i changed from standard 2.54 helical to RMS 2.56 straight cut primary I face some clutch dis-engagement problems. Had a look at a 130TI thread on GSF, and found some pics. I know you have seen them before minikin. Is this what you are talking about? wont the piston be very unbalanced?    |
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Post by Juan on Nov 20, 2007 20:48:40 GMT
Cheers Brede,that helps clear it up.
I was beginning to wish I'd never asked. ;D
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). 
