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Post by db971 on Sept 3, 2013 20:39:03 GMT
I am looking to tune up a spare engine I have. The casings are stripped down and cleaned ready to reassemble. I have the following parts available and was wondering what primary cog & basket (27/69 or 29/68) & xmas tree (DRT runner 20-17-14-10) I should fit and if there is anything else I should consider while the casings are split?
Current primary: 63/22 Cylinder -POLINI 133 cc Evolution kit Mazzucchelli racing crank 45065000 Polini banana racing exhaust 20020250
Looking to fit 4 speed gears, although only have a 3 speed set up (is it worth purchasing the gears separately and changing type/teeth ratio)
Need carb and was looking at 24mm Dellorto
Appreciate any help :-)
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Post by jonnysnatchsniffer on Sept 3, 2013 22:16:37 GMT
erm, it will be pretty much unrideable on 22/63, i use 29/68 on my evo with a drt runner tree, tho i use a franz pipe, 4 gears is really the way forward as is a bigger carb when the case is apart mill the gasket face 1mm or so, so you can take advantage of the bigger transfer area, using a packer to get things where they are meant to be, i think your choice of pipe/carb will restrict the motor by quite a lot id say a proper pipe and 28mm carb would be better suited to the kit
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Post by db971 on Sept 4, 2013 23:52:47 GMT
Thanks jonnysnatchsniffer. The 22/63 I know I need to change. What is the difference between the 29/68 and the 27/69? Also is it the surface where I have highlighted in the pic that should be skimmed by 1mm
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Post by jonnysnatchsniffer on Sept 7, 2013 18:12:02 GMT
yes mill about 1mm of there to get it nice and flat, including the top of the labyrinth seal, bolt the case together when this is done you will need to enlarge the sealing pad on the inlet as much as it will allow leaving 1mm of the pad to seal the 29/68 has a 2.34 ratio meaning that 2.34 turns of the little cog turns the clutch primary once and the 27/69 is 2.46 wayne has a brilliant gear calculator that lets you compare 2 gearsets side by side, id also be a bit wary of using the small taper crank, even tho its a "racing" crank its likely it will snap the taper, its not an if but a when. unless you have a very light flywheel its not worth the risk i dont know your budget but if i were you id have this as my set up for the evo polini evo, which you have runner tree , which gives you a shorter 3rd and 4th and matches the standard loose gears polini 28 manifolda 28/30 mm carb of you choice a decent expansion pipe at least a pkxl2 clutch, or similer a 4 speed gear selector to match the loose gears, either oem piaggio or drt along with an uprated indent spring not that your intended set up wont work,
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Post by amazombi on Sept 7, 2013 18:17:06 GMT
I personally think the Polini Evo would be wasted with the Polini banana pipe.
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Post by Juan on Sept 7, 2013 19:08:49 GMT
Chances are the gearing you're looking at could be a touch too long, probably better sticking with 2.54 or 2.56. I'd agree it'd be better with a proper expansion and a 28mm or above carb with an Evo, 24 or 25 with the banana would work well enough with the normal Polini.
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Post by eean on Sept 7, 2013 19:12:09 GMT
Does Polini not make a dedicates pipe for their own kit?
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Post by Juan on Sept 7, 2013 19:17:00 GMT
Yeah but the first Evo pipes were shite, not sure if the newer versions are better or if they've been tested against whatelse is out there. Gut feeling is they'd still be shite as I can't remember seeing them anywhere other than on Polini's own demo 50 Special.
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Post by eean on Sept 7, 2013 19:25:36 GMT
Mad isnt it, if youre going to make your own pipe why make a shit one especially when youre a successful outfit like Polini
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Post by jonnysnatchsniffer on Sept 7, 2013 20:09:24 GMT
i know eean and its taken them 25 fucking years or more to update the kit, and still it needs work on it. they probably give the smallframe pipe making to some retard that they have to employ under some weird european directive, malossi are just as bad, loads of hp out of the autos but a wank kit for smallframes. i use 29/68 dave and it still revs out in 4th with the runner tree, which with a 300x10 tyre is the same final ratio, give or take a knats cock as the standard primmy primarys and gearbox the franz gives it a good wide spread of power with a good kick up the arse from 6500 to 8000 reving to 9500 in 4th (head down cos im a fat cunt at 16.5 stone), under 6500 its just like a standard ets even with loads of inlet timing mathias will say get a pm40 but hes wrong there
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Post by amazombi on Sept 7, 2013 20:25:32 GMT
The reason may be that designing pipes is not as easy as it may sound, and that you sometimes end up doing quite a few before you get on that works like you want it to work. I remember reading that the guys who did the development work on the Aprillia RSA did 200 pipes over time. Which may be more than you'd do for a humble scooter pipe, but expecting to hit it the first time isn't very realistic.
Another reason may be that for some reason Polini has once again tried to dance to more than one tune at the same time even with their latest beed of kits. The lamelare is pretty good as it comes out of the box, but the crankcase inducted one lacks exhaust port time to actually perform. As it comes out of the box it works ok with non-expansion chamber type pipes. Not much better than its cast iron predecessor though. My personal opinion is that either you modify the exhaust port on the Evo, or you save yourself the money and buy the old kit. The difference with the type of pipe you mention is mainly in the price, I think.
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Post by daisyb on Sept 8, 2013 6:55:17 GMT
I've fitted a rotary induction evo kit, opened up the transfers fully and increased the size of the frankly tiny exhaust port flange to match my GF Project race pipe, 30mm delly & lots of inlet timing but left all other port timings as standard - basically I'm disappointed, got 16 hp (just)on Jahspeeds dyno it's a pleasant enough drive but lacks the punch I was expecting. Mathias/chaps, any suggestions as to what I should take the exhaust/transfer timing to in order to make it sing?
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Post by amazombi on Sept 8, 2013 8:47:42 GMT
I'm not familiar with the GF pipes, but 16 or thereabout is pretty much what I'd expect the kit to put out in standard form. I do suspect that it lacks blowdown though. What I like to do is leave the head gasket out (which works with most of them Polinis, you want to make sure the head sits properly in the cylinder's recess. If it does so leave the gasket out and drop the barrel to get around 1mm of squish clearance. Once you've done that measure transfer timing. It should be around 125 or so. Exhaust port probably is under 180. With a Franz for instance I'd shoot for 190ish exhaust port timing. Depending on the quality of the inlet tract I'd expect the engine to make around 20 then. The funny thing is that, contrary to traditional belief, power will go up ALL OVER the rev range when you do that.
I suspect that, when looking at the graph, you'll see that there is an early peak with a comparatively steep rise and the power tailing off slowly after that. On the road that would give you a nice kick in the back at first, but it probably feels a bit flat after that.
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Post by eean on Sept 8, 2013 8:48:32 GMT
Youd need to measure what port timings in degrees to know where your at with it now reallyto start making any improvements on it. I would not be able to say as Im not experienced enough but Mathias and Jonny are :-)
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Post by daisyb on Sept 8, 2013 10:26:22 GMT
Cheers chaps. Mathias that is exactly the power curve I'm getting, head is already running without gasket, .98 squish. Eean, I'll stop being lazy and take it apart again to get the timings. Though it'll have to wait until after Cadwell. I'd just kind of hoped that finally I could bolt on a kit without doing too much work, guess experience should have told me otherwise.....
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Post by amazombi on Sept 8, 2013 11:53:47 GMT
It is a bit of a bummer, I agree with that. It's not that much work really though. You've done most of the work already, the exhaust port is a matter of an hour or so, given the right tools. The Evo Lamelare makes a lot more sense in that respect. As do the Parmakit SP09 versions, both the single as well as the bridged exhaust port ones, if crankcase induction is your cup of tea. To be honest a decent rotary has quite a few advantages over a crankcase reed engine, it's a whole lot more work though.
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Post by jonnysnatchsniffer on Sept 8, 2013 14:14:06 GMT
a few photos of mine exhaust port, done by mathias, nice and straight walls and i think only at 186 degrees as it was originally done with a small sealing pad in mind, when i rebuild it ill omit the head gasket and raise it a little, tho worringly ive got a .5mm ring gap after 3-400 miles, which may be down to a rusty tank inlet in progress and showing my butchery, the inlet walls on the finished article are straight from the manifold to sealing pad, the difference between the large and small pad is more than i expected and it has more torque and power all thru the rev range pad roughed out, it ended up with about .8mm left all around, .5 in places where exuberence go the better of me transfers on the case, there not polished its just my camera skills are shite manifold and some various food items not to be confused with scooter parts lol barrel transfers well thats it and im pretty sure it has more than 16hp, im gonna sort the clutch and get it on the dyno
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Post by daisyb on Sept 8, 2013 18:03:44 GMT
Ha! I recon our engines could be twins Jon, apart from the exhaust port inside. My inlet ended up looking like that, would have been easier to get it welded first. I think one of the problems with the barrel is the roof angle of the exhaust port - if you look at any performance 2 stroke its about 7 to 15 degrees down rather than the 30 (I may be exaggerating!)on the Polini. I almost wish they'd done the port flange higher even if it meant a new manifold. I do like a bit of rotary, reed seems like the cowards way out - perhaps I'll mention that to Woodsie as he pulls away from my group 4 Lamy (although I can catch him on the corners!)
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Post by amazombi on Sept 8, 2013 18:16:17 GMT
The angle is not a problem really.
JSS: You could raise it quite a bit now. If you want to and can spare it for a couple of days get a shipment with the usual bribes on it's way. Or go ahead and do it yourself.
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Post by jonnysnatchsniffer on Sept 8, 2013 19:39:36 GMT
trouble is with weld is its needed on the bearing seat and i wasnt gonna do that so just used loads of epoxy putty. exhaust port shape makes quite a bit of difference im told so i got mathias to do it as im a little impatient and a hamfisted fucker that cant/wont really follow intructions. im quite impressed with mine tbh
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