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Post by knowledge on Dec 30, 2007 23:12:24 GMT
We have just bolted together my son's PK136 engine. Yum, yum. It has an old Polini top end, with a Malossi 58.4mm piston (heavily modified) and a Malossi head. Above is the induction. It features a V-force reed all mounted in a one-off manifold. It will run a Dell'orto 24mm carb and the exhaust is my interpretation of the faithful PM40 pipe. The Polini clutch has been significantly modded. The ali basket has been altered to allow the six-spring PK XL2 item to be fitted. All the steel clutch plates have been modified from the PKXL clutch. The springs are the strong ones from SIP. We think it will be 15% stronger than a similar clutch that has not be assembled in the same diligent manner. On new year's day, the scooter gets the new engine. (Thanks to John at JB Tuning and Tony O'Brien for their advice on this project)
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Post by 225worb on Dec 31, 2007 17:59:26 GMT
yep looks ok.... Being picky but its a Shame about the base plate that bolts on to the case .....Bit small and restricted ....Be interested to see how it works ......
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Post by knowledge on Dec 31, 2007 18:12:12 GMT
Thanks for your response. I can see why you might think that the base plate is restrictive, but I feel I can justify this.
The carb is 24mm, so it defines the cross-sectional area along the inlet tract. This is good to maintain a constant velocity of this incoming charge. Owing to the nature of the reed valve, the inlet tract has to change shape and cross-sectional area considerably in order to pass through the reed petals. However, once the i/c charge has passed the reed, it really should return to an inlet tract with a similar cross-sectional area as when it first passed through the carb. This is what the base plate is doing, and there is continuity of this as it passes through the crank case a reaches the crank.
Perhaps the most interesting aspect of the base plate is the way it diverts 25% of the i/c charge directly into the boost ports opposite the exhaust port. This charge does not enter the crank case at all, though it does benefit from crankcase compression drawing the mixture through.
Martin
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Post by breezer on Dec 31, 2007 19:01:11 GMT
Hmmmm, maybe...but I don't think you are taking into consideration the transmogrified vortex which will create an anticlockwise paradiddle through the overhead flange modifier. AND you've used a rusty old nut on the primary cog
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Post by knowledge on Dec 31, 2007 19:20:49 GMT
....AND you've used a rusty old nut on the primary cog Yup. We lost the proper one and the rusty one fitted. Good news! The correct nut has been found!
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Post by tony on Dec 31, 2007 20:17:29 GMT
hi all, can i just point out that i was/am very confused on martin's inlet idea..its not my advice! But what the hell it may work. I believe my advice concerned port timings Martin? Is that correct?
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Post by knowledge on Dec 31, 2007 20:28:47 GMT
That's correct Tony. You and JB both chipped in about the transfer timing, which have been increased from 114 to 120. As it stood, the exhaust would have had too much lead over the transfer.
You certainly gave me a great deal of help with the XL2 clutch into the Polini gear-up kit, for which we are grateful.
The inlet idea (75/25% split) was our (me and Will) idea. I suppose it mimics the direct route that is now seen in the RB22 (the route from the reed into the main transfers), though it a much more tortuous route. There is a "bleed" that allows the tract between the spacer and the cylinder to fill with fresh charge on the up stroke, before the crankcase is pressurised by the descending piston and the ports open.
Like you all say, it might just work. If it doesn't, we have a three stud malossi reed to bolt-on instead.
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Post by breezer on Dec 31, 2007 20:48:19 GMT
hmmmm...the RB22. So good Ray's had Terry Shepard re-designing the TS
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Post by tony on Jan 1, 2008 17:24:20 GMT
so Martin, have you retracted the "gauntlet" or is it still thrown in my direction!
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Post by roo on Jan 2, 2008 20:15:59 GMT
it seems like the 24mm carb is pretty small for that choice of reed...is that from a kx85(q) i can imagine there are a couple ponies to be gained with a 28mm carb.
out of curiosity, what was the exhaust lead before you raised the transfers(q)
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Post by knowledge on Jan 2, 2008 21:43:21 GMT
so Martin, have you retracted the "gauntlet" or is it still thrown in my direction! Not so much thrown down, as casually tossed in your direction. However, I feel that we are in for a right arse-kicking. Afterall, this is your specialist subject. We've only been doing small frames for a year. Well I guess the choice of carb size is based on soemthing that Norrie said many years ago, about having carbs that suck, rather than spit. The choice was also confirmed by the size of the ali tube that was cut to make the swan's neck manifold. At 25mm ID, it was ideal and FREE. Boosting the carb to 26mm or more would require a new swan's neck manifold and some more work inside the casings, but you can't go backwards, so 24mm seems a good place to start. It may well have been KX85. I would need to check back through my ebay purchases (£36 - a bargain) The exhaust port is in the mid 170's. I haven't altered it - yet.
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Post by knowledge on Jan 2, 2008 21:44:38 GMT
hmmmm...the RB22. So good Ray's had Terry Shepard re-designing the TS No, the RB has no connection with Terry Shepherd. There are some similarities, but there are as many differences.
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ozzy
Automatica
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Post by ozzy on Jan 2, 2008 22:24:35 GMT
martin, i reckon your inlet idea is over complicating and is just going to obstruct. surely that bar bit sits right in the line of sight of one set of reed tips? and as the ports open and the CC presure starts to blow down surely the CC gases would have to flow back all the way up and around the divider??i reckon you'd be better off with a clear passage. the RB style conection works because its a additional duct into the ports not the only duct; the CC pressure blows down mainly the traditional transfer ducts and then when the diffuser pulse starts lowering cylinder pressure to the point that the atmosphere starts pushing through the reed, the additional duct offer a quicker route into the barrel for more gases.. are you going to dyno it against an open one? if i were building this i'd just make a nice clear smooth run into the boost port and leave it at that, good luck, o
p.s. duuurrrrr, sorry i don't want to sound like a div' talking about things like i know somthing... arn't i wrong, as isn't there a port in the psiton that feeds the boost? if so then why the sperator at all?? it just seems unessercary........
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Post by knowledge on Jan 2, 2008 23:07:27 GMT
Fair comment O, but you've got to try these things.
BTW, the bar in the inlet tract lines up with the point of one of the reed valves. One reed of the four reeds fills the "boost" ports, and the other three reeds serve the crankcase. We have built it it so that the bar does not obstruct the in-coming charge. There is no doubling-back of the flow (if I have correctly interpreted your words).
I'm not sure my RB comparison is helpful, and I apologise if I have misled anyone by suggesting this. The only RB similarity is that the fuel/air mix can enter the top end via the boost ports without ever entering the crankcase.
I am also relying on the resonance of the expansion chamber to draw fuel through the boost ports, as it reaches peak power. As I am sure you know, a correctly proportioned expansion chamber will suck fuel/air mixture regardless of crankcase compression (or lack of it). The problem is that this state only exists over a very limited rev-range.
This phenomenon has been used successfully on two stroke engines that run at only one speed, such as aeriel drones.
Sorry if I'm teaching anyone to suck eggs......
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Post by knowledge on Jan 2, 2008 23:25:33 GMT
Here an image that might clarify the routes a little. The blue flow goes through the crankcase. The red does not, though it is affected by primary compression.
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ozzy
Automatica
Posts: 4
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Post by ozzy on Jan 3, 2008 0:40:38 GMT
i still don't get why you think theres theres any advantage in having the division??
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Post by adspeed on Jan 3, 2008 1:17:27 GMT
Edited due to not really being that constructive.....lol. Soz Juan
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Post by tony on Jan 3, 2008 3:24:30 GMT
it will just restrict Martin. It would be far better without it as long as there is a direct clean feed into the crankcase. If this idea worked then you'd see race motorcycle engines with it on. By the way, what is the scoop out of the spigot for?
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Post by breezer on Jan 3, 2008 6:34:11 GMT
hmmmm...the RB22. So good Ray's had Terry Shepard re-designing the TS No, the RB has no connection with Terry Shepherd. There are some similarities, but there are as many differences. Yeah I KNOW that. That's the point... the TS1 has been out how many years? without any modifications to it, despite terry stating right at the start that he could have improved it. The RB kit has come out, supposedly giving however many BHP out of the box and within less than a year Ray is paying Terry to re-visit the TS - now call me cynical, but that tells me that the RB kit is NOT the panacea to all ills that has been claimed. I've also heard rumblings from trusted fellows in the trade that there are several design issues with it. As such I'd be dubious about copying any of it's qualities.
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Post by roo on Jan 3, 2008 16:38:33 GMT
hmm.. didn't norrie use 30mm carbs on rotary motors back in the day it's great to romanticize about ye good ole days, and to quote great figures from the past, but it's absurd to not acknowledge the present . you are throwing away horsepower using a 24mm carb. strange that you go to all that trouble making a manifold, but neglect the basic fact of adequate carb size in the equation.. the cutout in the spigot looks like it's for the 'boost' feed from the inlet..but that inlet looks way over(under)thought to me... you can achieve the same thing, with more area in just one hole.. who knows, maybe it will turn out to work well like this! but isn't the piston skirt in the way of that boost feeder while the boost ports are open up in the cylinder(q)
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