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Post by potatopl on Feb 14, 2014 13:01:58 GMT
I'm starting the work on the second engine for my '86 PK50XL. The name might be a bit exeggerated in comparision to yours machines , but that's what I can afford now and still hoping to get a decent sporty engine. The planned specification: - PK50SS 3-stud casings ( medium length selaing pad, needs small repair) - STOFFI's ETS 51mm crank - Polini cast iron 130ccm raised 5mm - GS piston rings - Dellorto PHBL 25mm - DIY 25mm intake manifold - lightened flywheel - 2,54 helical cut primaries - standard PK 4-speed gearbox - Proma snail exhaust The only thing I'm missing right now is the clutch. I've got some standard SF one spring clutches, is there any chance it won't slip (with stiff spring use). I've got an XL2 clutch cover and push plate as well so maybe an XL2 clutch would be a better choice? What would you recomend here?
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Post by madmax on Feb 14, 2014 18:10:28 GMT
That set up looks quite good. However, sell me the xl2 cover as you won't need it. A PK/Vrange clutch cover with a single spring clutch will be fine. Make sure the clutch is set up properly and use good corks like the Surflex ones and a good uprated spring like a Polini one.
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Post by amazombi on Feb 14, 2014 20:40:26 GMT
Raising it 5mm is a bit excessive, I guess. I usually use a 5mm packing plate, but machine around 3mm of the bottom of the barrel for a bit of extra meat around the transfers, so in effect it's 2mm raising more like. Measure port times first maybe.
Have you bought the 25mm carb already? If not you could go for something a bit larger. Would you be ok with a reverse barrel engine? If you leave the barrel as it is you'll have to chop some metal out of the frame if you want to upgrade to a decent pipe lateron. Reverse barrel setup doesn't need anything like that. I'm asking because I might still have a build kit for a reverse barrel pipe which you could have fairly cheap, you'd have to do the rolling and welding, but since you seem to know someone with welding skills that might be a possible option.
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Post by potatopl on Feb 15, 2014 11:47:52 GMT
A PK/Vrange clutch cover with a single spring clutch will be fine. Make sure the clutch is set up properly and use good corks like the Surflex ones and a good uprated spring like a Polini one. Got 3 Surflex plates and Malossi uprated spring in my DR75F1 engine. No slipping, but it does not disengage fully (the wheel is turning even with the clutch lever pressed). I've heard that the Malossi springs are a bit too long, and that causes this problem. Will try a Polini this time. Sorry Madmax, but I'll keep the XL2 cover, it might be useful in the future. 3 Surflex plates 'Sport' + original Piaggio plain plates + Polini uprated springHow many HP can this clutch setup hold? (I'm assuming my setup will be ~10HP) Raising it 5mm is a bit excessive, I guess. I usually use a 5mm packing plate, but machine around 3mm of the bottom of the barrel for a bit of extra meat around the transfers, so in effect it's 2mm raising more like. Measure port times first maybe. You might be right Amazombie, but the kit I've bought was already 'bearbeited' Polini 130I'll measure the transfers when I receive the package next week. Have you bought the 25mm carb already? If not you could go for something a bit larger. Would you be ok with a reverse barrel engine? If you leave the barrel as it is you'll have to chop some metal out of the frame if you want to upgrade to a decent pipe lateron. Reverse barrel setup doesn't need anything like that. I'm asking because I might still have a build kit for a reverse barrel pipe which you could have fairly cheap, you'd have to do the rolling and welding, but since you seem to know someone with welding skills that might be a possible option. I already have the 25mm carb (un)fortunately. 180deg setup sounds very tempting, but I think I'll stick to my plans for now. I've got plans for upgrade in the future, but you all know that it's not enough to upgrade just one piece. Bigger carb and good pipe will require better clutch, short 4th etc. I'll try to get to this point next year. And by the way, doesn't a reverse setup require cutting the frame for fixing the carb?
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Post by amazombi on Feb 15, 2014 11:53:59 GMT
So you did buy it in Germany? I guess I comes with a 5mm packer but machined at the base to raise it around 2mm, give or take a bit, that's pretty much common practise (or was before the new breed of kits took over).
You only have to cut the frame if you run a kit with the inlet port as part of the barrel (direct induction, or whatever you want to call it). If you go rotary or crank reed you simply turn the barrel 180°, no cutting required.
Your clutch should be good for 10 (and a bit more).
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Post by potatopl on Feb 15, 2014 12:23:48 GMT
Yes, I'm working in Netherlands at the moment, but staying in Germany.
I hope you are right Amazombi, the transfers look like they are opened, so the bottom of the barell might have been machined as well.
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Post by Juan on Feb 15, 2014 18:16:44 GMT
If that's the old style cylinderhead I'd take the chance to throw it away now and get the new style item.
Also you might want to contact Dayn about his multi spring widget that works with the single spring clutchs that's similar to the Pinasco item but I think it uses more springs. That should hold a bit more power than a single spring. Not sure if he's still doing them but it's worth asking anyway.
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Post by potatopl on Feb 22, 2014 8:36:37 GMT
I got the kit yesterday. You were right amazombie, it was milled both from the top and the bottom, that’s why it comes with 5mm packer. I’ve managed to do the rough port timimg measurements: Exhaust: opens 88° after tdc closes 88° before tdc = 184° Transfers: opens 115° after tdc closes 115° before tdc = 130° Blowdown: (184°-130°)/2= 27° Intake: opens 110° before tdc closes 50° after tdc = 160° The sealing pad has 42mm but is not opened yet. It was damaged by previous owner (looks like piston rings broke and got into the crankcase). I will first repair/fill it with JB Weld (actually, I’ll use Belzona 1111), and then open as much as possible. Hopefully, I’ll gain a few more degrees on intake, however only after TDC. What do you think about my timings?
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Post by jonnysnatchsniffer on Feb 28, 2014 18:55:13 GMT
you can cut the crank for more inlet duration and it will open earlier than btdc as the limiter for after is the big end, aim for around 200. not sure the pipe is going to do you any favours tbh as to get things in tune you are gonna need closer to 190 degrees exhaust
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Post by potatopl on Feb 28, 2014 22:37:09 GMT
Thank you all for the responses! I am at work in Germany right now, but tooke some of my parts and tools with me. Unfortunately I don't have a proper camera with me, so I have to use a shite phone one. Sorry for the photos quality. I've made an engine stand, much bettet than the wooden one I had before. A friend of mine made for me a few pairs of dummy bearings, which helped a lot with port timing calculations. I've repaired the sealing pad with liquid metal. The black line is what I'm planning to leave of it. I've prepared too much of that liquid metal, so I decided to ass some on the outer side of the casings. It wasn't neccessary, but it didn't hurt either I've started to open the transfers on the casings to match the Polini kit. I didn't go very deep, rather tried to maintain the original tapered shape of the transfers and make them a bit wider. You can see the comparison with the original size. Is that enough, or should I take out more material and remove the tapered bit? I have beared in mind what you've said to db971 in this thread, not to make the transfers too steep. Now about the port timing... I know that sometimes more does not mean better. Please remember, that I'm using a 25mm carb and a snail pipe (Proma), not a proper tuning exhaust. Will this low-end tuning components benefit with quite high timing values you gave me, JSS? Or high exhaust timing will only make the kit rev very high but without torque and power comming with it, because of poor resonance of my snail?
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Post by potatopl on Mar 2, 2014 18:13:18 GMT
I've done some more porting to the cases. The transfers are matched with the barrel. Eventhough, I tried not to go to deep, I broke through the cases on flywheel side. Luckily, I've added some liquid metal on the outside first I took out quite a lot of material on the intake port. Also broke through the cases (darker spot). I've left about 1,5-2mm of the sealing pad, just to stay on the safe side. The intake timing changed from 110 oBTDC->60 oATDC=170 o to 112 oBTDC->71 oATDC=183 o. Some progress, but I'll think about cutting the crank to get a bit more intake BTDC.
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Post by briggsy on Mar 2, 2014 21:39:59 GMT
Looking good - nice to see other forum members handy work.
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Post by potatopl on Mar 13, 2014 21:46:30 GMT
Note to myself: Read more before starting the work! Principally because it is so free of blow-back problems, the proper time-area of a rotary intake valve is much higher than for the piston-controlled port. This does not mean that one may indiscriminately whack away at the valve disc without getting into trouble, especially on the port-closing side of the disc cutaway. The valve's opening point has an influence on power output, but in general it is relatively insignificant as compared with port-closing. Curiously, the best port-closing timing for a very wide variety of disc-valve engines is about 65-degrees after top center, but before deciding to apply that timing you should consider that any appreciable delay in closing the port, after the piston has started down from top center, will cause some low-speed blowback. At higher engine speeds inertia effects in the intake tract will overcome the slight blowback caused by the delayed intake closing, but there will be a loss of low-speed power. All things taken into account, the best approach here is to increase the valve-closing delay in very small stages, not more than 2-degrees at a time, until the desired result is obtained. Remember that retarding the intake-closing point moves the engine's power peak higher, while reducing power at the lower end of the range. Remember, too, that changes in the length or diameter of the overall intake tract, such as would occur in substituting a carburetor of some different size, will alter the point at which port-closing delay reaches its optimum. I hope my inlet closing at 70° ATDC won't cause serious spitback. Right now I'm working on the crank, to lengthen the intake BTCD so it's around 200°. I've changed my setup plans a bit, since I got a Zirri Silent pipe at a bargain price oc 45EUR (incl. shipping ) I've found information that this pipe works well with 125°-185°(blowdown 30°) timings. Mine, roughly mesured are 130°-184° (blowdown 27°). These particular values have proved over time effective: Exhaust port between 176° and 188° Transfer port between 120° and 128° Blow-down-timing between 28° and 32° My transfer timing seems a bit high, to obtain optimal blowdown of 30° I'd have to rise the exhaust port more than recommended for this pipe. I've read, that long blowdown period is needed to clear the cylinder at high rpm's. Can anyone explain the pros and cons of rising the ex port compared to leaving it as it is (mind, that ex. port timing is already like suggested for Zirri). What would you suggest?
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Post by amazombi on Mar 13, 2014 21:54:53 GMT
I don't think you've changed that much on your inlet in terms of closing time. It's not going to be a problem, the position of the big end pin and the size of the rotary pad limits timing so that it is impossible to run into trouble there.
Do the crankcase and the inlet, and then fit your kit. Check squish gap. If it is over 1.3 or so use the chance to lower your barrel. This will reduce transfer timing and raise blowdown at the same time. If I where you I'd run it first though. Taking the barrel of again to modify it later isn't that much trouble, but it will give you a chance to get some first hand experience of what happens if you do something.
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Post by potatopl on Mar 13, 2014 22:36:30 GMT
I've got the kit honed at the workshop right now. I'll measure the squish when I get it back. Should I use additional gaskets between the casings/5mm packer/cylinder, or sealing compound is enough there? Check squish gap. If it is over 1.3 or so use the chance to lower your barrel. This will reduce transfer timing and raise blowdown at the same time. Not really, it will reduce both transfer and exhaust timing, so the blowdown will stay the same unless I alter the exhaust port. I understand, that my goal should be a squish of 1.3 mm ? If it's more I'll mill the packer (it seems the most reasonable and least intrusive way of lowering the cylinder). And another question that came to my mind, wahts the proper way of determining the port "opening". Should I use a feeler gauge that I put between the piston and the port window, or do you do it just with your eyes?
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Post by jeanshorts on Mar 14, 2014 4:17:34 GMT
If you have room to lower the barrel and therefore transfers, you can the raise the exhaust port with the dremmel tool
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Post by amazombi on Mar 14, 2014 5:30:37 GMT
No, blowdown will increase when lowering the barrel. Both transfer and exhaust port timing goes down, but transfers loose more duration, so blowdown does actually increase. Depending on how much you drop it that does make a difference. Remember the piston's journey is a sinus curve, so it doesn't travel the same distance per degree crankshaft revolution everywhere.
Compound will work, as will gaskets, so use whatever helps best with your target timing.
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Post by potatopl on Mar 14, 2014 7:00:46 GMT
Remember the piston's journey is a sinus curve, so it doesn't travel the same distance per degree crankshaft revolution everywhere. Forgot about this detail
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Post by potatopl on Mar 15, 2014 22:16:05 GMT
Worked on the crank today. What to cut: Work done (the edge is not that steep, that's just a shade): From side: And a finishing, custom touch: The outcome is around 203° intake timing. I think I'll work on it a bit more, and make a bigger angle towards the middle of the crank.
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Post by briggsy on Mar 16, 2014 17:39:40 GMT
Looking good!
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