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Post by broyager on Aug 5, 2023 0:54:40 GMT -5
Sanded the PGO head down, on a glass top set of scales.   Took a little too much off actually, only with a couple of goes on 240 grit, then 600 Edge to edge it's 46mm now, so a little bit small, although the actual bore measures 46.8, or there-abouts, and the piston is smaller than that. So there is a small amount of overhang, but it pretty much matches the piston size.. If only I could see it to get it dead centre when buttoning it up to line it up. Squish is around 1.3 now, so improved for sure. I get between the speed bumps, on the flat piece of road near my house, faster than I have ever before from 0... so improving so far. Pulls hard to 55km/h then the transmission changes or it starts reaching the powerband again and wants to go hard across 60 and beyond, which is the speed limit round here... Still would like to see what removing some mills of the base gasket would do, making the the top of the piston higher than the bottoms of the ports, where they are currently.. It seemed to run pretty urgently with ports and cylinder not quite at the bottom on BDC
Not running any head gasket or copper spray, no leaks or temp spikes. Might tighten the head nuts from the current 12.5 ft/lbs in a few days. I was able to swap the head on only removing the exhaust, so the base gasket never broke it's seal. |
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Post by broyager on Aug 17, 2023 0:50:09 GMT -5
I bought this KN Planning head from Webike in Japan, shipped to NZ at $37USD. www.webike.ph/products/25550695.html Hand sanded about 0.6mm or so off the face on some glass top scales. I had one side lower than the others... easy to do when you start pushing hard, but managed to bring it back. The mating surface is still very flat, but one side is maybe 0.1 or so deeper... Hard to measure...   This new head is pretty shallow, but was roughly the same cc as the Malossi head, comparing some rough fluid capacity measurements for both. The new head will increase compression after sanding it down, but I do want more compression, I think. It pulls hard at the moment, but pulls harder at higher rev's, so some more compression should give me more power on the way to higher rev's, though the result may be a tradeoff. The plug will need a couple of washers on it by my estimation, the thread depth is at least a mm or so less than the malossi, so I think it will protude too far into the cylinder without washers.
I haven't installed it yet, will try this head while I try to adjust the PGO head for a shallower squish band angle to match the malossi piston, which is actually quite flat. The naraku has a deeper curve. PGO head has a much wider squish band at this point, so will be nice being able to compare them. Still need to thin the base gasket by 0.3 or so. Will adjust that after testing what this new head does... if anything! |
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Post by broyager on Sept 1, 2023 0:53:50 GMT -5
I love that I can have the whole engine apart in 10 nuts or bolts and 4 or 5 tools or there abouts...   I found a pretty bad score on the exhaust side, I can feel it with my fingernail for sure, but just one lone scratch, and not on the sides where the ring ends are so... I think I won't worry about that for now. Obvious thing to do is to hone, and get the size up piston.... but the whole kit is already new - (1000km or less), so .... I've installed a 0.8mm gasket, which is cardboardy in consistency, so probably down to 0.6 or so after the head nuts are torqued. Squish is not measuring the same of each side of where the wrist pin sits, 1.14 vs 1.05, so I think I goosed that deck of the head. But scoot runs great, very urgent. I haven't tried the PGO head I decked yet, which has a wider squish band, but the KN Planning head feels fine, could do with 6g rollers, the way it surges at higher RPM. Unfortunately my piston slap noise is back, at the same time I get the most power from it..... I've seen some cutaway vids of chainsaw engines, which suggest the piston will be pushed toward the intake side on the down stroke (opposite side to the bottom of the rod) and the exhaust on the way up. I still have a lot of movement of the cylinder on the studs, I'm not sure how much difference any position makes to performance or noise.... I'll try positioning it so it hangs off the head studs, rather than trying to squeeze it up, which might bring the piston closer to the intake side, or top side, on the down-stroke. Ultimately it needs to be dead center though. With the regularity I'm pulling it apart though, I'm tempted to go with Alum, Nikasil, and single ring...... that newer Athena kit with the separate bolts for cylinder and head makes a lot of sense to me. The head looks slotted on that kit too. I haven't had a tach on it for a while, so install that again to see exactly where the power is coming in. |
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Post by broyager on Sept 10, 2023 1:46:14 GMT -5
Took the cylinder off again, and my rings are measuring > .40mm, top one was 0.45, and I can definitely smell bad rings slightly.. Something is wearing down the rings very quickly, they current ones have done maybe 200km's.. and I think this is causing the knocking noise, which I think is piston slap at this point. There were some very smooth sections inside the bore just below the exhaust port.. Did some porting on the cylinder skirts, which were covering the transfers on the way in, inside the crankcase. Shots are representative on the spare cases I have. Before  After  Also, knocked a whole bunch of rough castings out from the transfers, and some other minor casting "imperfections" out of the inlets to the tranfers and the boost ports. Chamferred all the port edges more aggressively, especially on the lower edge of exhaust port, honed the cylinder with 400 in a cross-hatch, re-chamfered all port edges, and rinsed thoroughly. Ground down where the restrictor washer weld was, just on the inside of the stock exhaust, there was a lump there which I smoothed down quite a bit. Still goes great, have 6g rollers in at the moment, I think I need the yellow torque spring in though, or need to investigate that, raises revs on WOT well enough, but revs drops down shortly after too aggressively. Raised the needle one notch to the middle position for peace of mind. Still running full synthetic Castrol Power 1 at 45:1. Plug looking dry, some carbon build up on the head nearest the exhaust port, and the top corners of the exhaust port have a build up of thick tacky carbon, which is a bit of worry. Graham Bell says this area lacks flow, eddies have formed and things accumulate. Not sure how to fix this yet. The changes I made seemed to have increased torque.. so I may raise the exhaust port slightly, as Zino has suggested he does on every Malossi Sport, which *might* bring that power back to higher RPM. I'm still not reaching peak RPM before hitting the road speed limit, so may try the 5.5g sliders I have along with a 10mm longer belt of which I have a couple. This stuff was off a Honda Giorno Crea (Today / Ruckus / related) which has some of the similar drive parts as this PGO. |
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Post by broyager on Oct 10, 2023 21:46:05 GMT -5
The yellow torque spring has changed things a fair bit, now I'm jumping right to 8500rpm or thereabouts, which holds until 60kmh.. at least. So puts me right in the middle of what I feel like is the powerband. Slightly higher temps because of this, but much more power, especially climbing hills, to where I live. I'll experiment using 5g sliders which I already have and changing the spring back to the white one next. Have a C spec piston (346172.c0) on order to try and counter the piston slap I have. Will measure the rings when installing that to see how much they've worn. Also have an 85m and 33p coming.... as well as this thing to help the torque spring slip (thanks Zino, your roughhouse thread is my bible)
torsion controller variator spring guide for piaggio - honda - kymco - peugeot - sym engines 50 cc Code: 2512828 I thought I was having some other sort of slip, from 10 - 25kmh. Clutch seems to engage ok, doesn't muck around, and I'd prefer not to change the clutch springs as I have urban traffic to deal with on a daily. My clutch bell does have a shiny spot on it, as though the bell is no longer completely round, maybe it's slipping on that section. I have a Honda Crea AF54 clutch bell which fits the spline, but doesn't go on deep enough, I'll try to trim the inside and test it out. Also sourced some Motul 710 for a higher flashpoint, currently getting quite thick carbon build up on the piston, not really any wash. |
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Post by Lucass2T on Oct 11, 2023 0:35:20 GMT -5
Motul 710 is great stuff. I use it in every two stroke i have/had.
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Post by broyager on Oct 21, 2023 18:45:27 GMT -5
Motul 710 is great stuff. I use it in every two stroke i have/had. Interestingly running the Motul at just below 50:1 and with only this change, from Castrol Power1(tts) it's running a fair bit richer. Maybe I was on the edge before hand but had to adjust idle air for quite a bit more air, and need to raise the idle too. |
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Post by broyager on Oct 28, 2023 1:26:34 GMT -5
So my rings have worn down again to out of spec, in about 4 tanks of gas.. top is 0.55mm and bottom 0.5mm, went in at 0.12mm Piston slap noticeably worse. What's happening here? The ends of the rings are butting together right? Wearing them down? All port edges are heavily chamfered and those edges filed down to smooth. I'm running it on the edge of being too rich afaik, with the stock pipe, and it never overheats. Is there too much back pressure from the stock pipe? Has the cylinder warped, is there a high spot somewhere, somehow? Do I need to get a bore dial gauge? I am using 12ft lbs for the head bolts, possibly I have used a bit more in the past. Has this altered the shape of the cylinder? I might as well get a new alum nikasil single ring kit the way I'm going through rings... Both iron kits I have had have gone this way, ie rings going out of spec causing piston slap. Is it the way I'm riding it? I am shaking the tank before each ride and letting it warm up for a couple of minutes, and not doing anything WOT until a way after that. I have downhill to work for 2km, all 60k limit, with 2 or 3 WOT pulls possible during the 5.2km trip there. Way back is flat city traffic then a pretty steep climb for the last 2km. Doesn't get above 270F. Aside from this, running great.. My stock variator was looking pretty worn, at 12000km, so I ordered the gold one from NCY along with the torque driver. I have a Malossi clutch bell, along with the C spec piston on it's way too. 
I've swapped the rings over in the meantime, and raised the exhaust port 1mm or so. I put a heavy chamfer the rooves of the transfers, and smoothed the boost ports further, and cutaway more of the skirt on the intake sides. Also opened the exhaust outlet a touch.
Sealant curing tonight, will see what I have in the morning.... Swapped the 86 main back in as well.
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Post by 190mech on Oct 28, 2023 6:08:30 GMT -5
Is the air filter element in good shape? Appears to be a lot of abrasive scratching in the bore,, The feeler gauge method between the piston and bore is a sound way to measure, must keep the gauge thickness to .002" and stack them so they follow the curve ..
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Post by broyager on Oct 28, 2023 21:49:55 GMT -5
Thanks for the tip, I will need to check the new piston.
Air filter is new, or same age as the new crankshaft.
Some fod definitely got in there at some point, but probably introduced on one of the many times I've had the cylinder off.
It's going pretty much perfectly otherwise aside from the ring wear issue.. so I'm happy with it, just wish I knew what was causing it.
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Post by broyager on Nov 21, 2023 1:22:55 GMT -5
Installed the NCY torque driver and variator, which haven't made that much difference to be honest. I'm back to the white torque spring from the yellow, and have it currently right in the power band with the above installed - 8800 ish. Acceleration is improved possibly, new clutch bell is still wearing in, has a slightly different angle to stock, so only half the pad is gripping at the moment. Stock clutch bell, variator and torque driver had significant wear @ 12000km so am happy to refresh them in any case. Good news is my piston ring wear has slowed, and can be attributed to one of the following; *Head bolts only tightened to 10lbs - that's at the lower end of the torque wrenches capability, possibly I was actually squashing the cylinder a bit. *The extreme chamfers I've added to the transfer ports - in an attempt to raise those without a right angle porting tool, and all other ports last time I had it apart. *Motul 710 at 40:1 rather than 50:1 with Castrol TTS, which I ran for the beginning life of the current ring set, but also didn't have the extreme chamfers *Only running the Malossi head with 1.3mm of squish, and supposedly dead uniform chamber shape, as opposed to my other modified ones. Lower compression than the other heads too On my last breakdown I'd measured the ring gaps, and swapped the bottom at 0.5mm to the top postion. The top ring was 0.55mm. I have the cylinder off now - was making some bad noises when I got home today, wet misty day, possibly I'm too lean.... The top ring is not more than 0.55, after 4 or 5 tanks of gas. Piston slap is getting more present, not as extreme as when I've taken apart previously Question about piston clearance, as far as I can learn and read, 0.05mm (0.002 americans) is minimum for 70cc? Below is the C0 spec Malossi piston in the current Malossi Sport bore, is this enough? I should probably clean the oil off the cylinder wall first though.... Feeler gauge is 0.002" / 0.05mm C spec in Malossi Sport bore Naraku in Malossi Sport bore
Interestingly the old knackered Naraku piston I have, measures identically to the brand new pricey Malossi piston. The Naraku also is taller from the wrist pin than the Malossi by 0.8mm, which would mean a tighter squish....
The piston windows on the Naraku are dual with a bridge, so I might need to widen the Malossi cylinder skirt window more to compensate. Just ideas at this point... new Naraku pistons are very cheap though....
Below is a collection of info on what the clearance should be
I've given a really good hone with 240, just by hand, concentrated on the areas which were shiny, and the cross hatching had worn off, basically below the exhaust port, and the opposite side. I can't feel any of the scores anymore, which I could feel before.
The 0.05mm feeler slips out more easily now, so I think I'm going to just run it in
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Post by broyager on Nov 21, 2023 2:09:30 GMT -5
Actually scrap that about the Naraku piston fitting, the ring ends would be too close to the B transfers.
The rings gap on the set which came with the Malossi C piston measure 0.3mm....
Also.. the noise I heard to make me want to tear it down turned out to be a loose flywheel.....
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Post by broyager on Dec 10, 2023 19:03:44 GMT -5
C spec piston is in, working fine, and no more rattle and slap... I did unfortunately discover some end to end play in the crankshaft, with a very small amount of radial play... Caved and bought the Tecnigas Silent Pro from Scootertuning during Black Friday. NZD to CAD rate is pretty good at the mo, by far the cheapest place to get things shipped to NZ currently. Took quite a bit of effort to get the inlet restriction out... The 2x big mounting spacers supplied were quite a bit too wide, for the Malossi Sport at least, the restrictor from the exhaust tip almost worked... but I ended up piling some washers together, and used a large nut for the other mount, between exhaust and crankcase. In the end 10.5mm spacers were required top and bottom. The buddy case is different to the 12" roughhouse case, where the top exhaust mount protrudes a bit further. Installation confirmed what I suspected, that the stock exhaust I have was not holding the engine back. I am not experiencing any or much additional power, but the Silent Pro does seem to make the engine better behaved. Idle is more consistent, it's actually quieter than my stock exhaust, and just feels overall more focused / refined. Need stiffer clutch springs now though... Also bought some new crank bearings, and a china crankshaft puller for that coming adventure..  |
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Post by broyager on Dec 13, 2023 19:49:54 GMT -5
Just need to walk back that "silent pro hasn't made any difference" comment... it definitely has more high end pull, like it has an actual power band, does struggle down low though, so will be getting stiffer clutch springs. Feels like performance matches all the dyno charts and comments I've seen for this pipe. The clincher was this graph for it on the Sport Pro MkII. www.pedparts.co.uk/c/asset/sports-pipe-blog/Stage6-MKII-Sport.pngGranted it looks poor compared with the Yasuni R, but it peaks at 10k, so will react to a higher reving port map etc.. Performance is the same with both 85 and 86 main, so going with the 86 for now. Needs to be a little bit more lean at idle I think. |
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Post by Zino on Dec 14, 2023 0:48:44 GMT -5
Nice work
With a similar set up silent pro and malossi sport on a yamaha zuma .
the yellow malossi clutch springs gave me real spunky take off .
I was pushing mid to high 9000s rpms with that combo .
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