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Post by 90GTVert on Sept 18, 2011 8:45:44 GMT -5
Stock stroke is 41.4mm. The Hoca stroker crank Parts For Scooters sells is 44mm. Here, I made something for you... ;D 139QMB (GY6 50) Displacement ChartBore | Stock Stroke (41.4mm) | Hoca Stroker (44mm) | 39mm | 49.46cc | 52.56cc | 44mm | 62.95cc | 66.90cc | 47mm | 71.83cc | 76.34cc | 50mm | 81.29cc | 86.39cc | 51mm | 84.57cc | 89.88cc | 52mm | 87.92cc | 93.44cc |
Unfortunately, I don't know exactly what's involved to put the 44mm crank into the GY6 50. It may or may not require case cutting, depends how large the crank weights are and if there's room to spare inside the stock cases. It may require a spacer under the cylinder or piston mods to make it work. If the crank is more durable than the stock crank, I think it would be a worthwhile mod. I really haven't heard much about these yet, so I don't really know if it's any better or not. |
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Post by reveeen on Sept 18, 2011 10:59:42 GMT -5
Thread here: scootdawg.proboards.com/index.cgi?board=discussion&action=display&thread=43580I *think* cutting the top of the piston might be the ticket...... I am fairly sure a stock cam chain won't be long enough for a cylinder shim/plate, and a longer chain is going to mess with the timing too much (unless extra links are dividable by 2). Though, for all I know, maybe the rod is shorter (and you just have to trim the piston skirt). |
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Post by dude on Oct 8, 2011 12:33:18 GMT -5
I sent a Question to Parts For Scooters . I need some info on this crankshaft. What do I do to make it work? Does it need spacers under the cylinder if so does it need a longer timing chain? Or is it a shorter connecting rod. Does the case need any clearance? Thanks for any info. And this was the Responce Unfortunately we do not offer technical support since we do not repair or service scooters. We are only a parts distributor so we are not able to answer your questions. |
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Post by 90GTVert on Oct 8, 2011 12:40:24 GMT -5
That kinda sucks, but hey I'd rather hear that than to have them guess at an answer.
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Post by speedy1125 on Oct 11, 2011 20:50:47 GMT -5
there is no way a 52x44 motor is going to get turned by a stock starter. my starter barely turns my 50x41 motor with its lowered compression. anyone ever seen a high torque QMB starter? what do those euro race scoots use i wonder? maybe this would work? www.thescooterreviewshop.com/SPD/um-31200-4dm-00--80003892-1296505894.jspanyone know the starter specs like bolt spacing etc... |
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Post by speedy1125 on Oct 11, 2011 21:38:15 GMT -5
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Post by speedy1125 on Oct 11, 2011 21:42:31 GMT -5
also the solution to the deck height problem might be cylinder shimming/longer timing chain like the stroker GY6 (150) motors. I have found lots of stroker 150 parts like 92, 94 and 96 Link Taiwan made timing chains and +3mm and +8.2mm cranks...doesnt seem to be much in the stroker QMB area though.
I imagine that a shop could make a longer chain pretty easily out of two 82 tooth stock chains.
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Post by speedy1125 on Oct 11, 2011 22:41:22 GMT -5
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Post by 90GTVert on Oct 12, 2011 6:50:34 GMT -5
Upgrade your starter cables and keep your battery in good shape. That helps on my stroker 2Ts pushing double the displacement of stock. I also found that some stock starters work better than others. The only way to differentiate them though is to bolt them on and see if they work better though, unless I'm missing something.
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Post by reveeen on Oct 14, 2011 7:48:49 GMT -5
also the solution to the deck height problem might be cylinder shimming/longer timing chain
Cylinder shimming on an OHC engine presents it's own set of problems. You end up messing with your cam timing, which, on a "fixed sprocket" (welded) cam, is not a "happy place". Another place that is not "happy" is the extra sealing surfaces you are stirring into the mix and the added possibility of oil leaks.
I would *think* it would be better to top cut a piston (if one could be found with enough "meat" on it), or a combination of piston cutting/head machining.
I gotta question the value of 3.6mm of extra stroke
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Post by 90GTVert on Oct 14, 2011 8:23:51 GMT -5
I gotta question the value of 3.6mm of extra stroke I don't know that the extra stroke and displacement will do a whole lot, but if the crank holds up with the big bores it might be worth it for that alone. Of course there's that stock stroke crank around that is supposed to be better suited for that purpose too and it should just drop in. At any rate, I'm happy to hear that Speedy is planning to build it. I like seeing people try this kinda stuff. Keeps it interesting to me. As interesting as it is, it's kind of sad that no one offers a complete kit for this so it would be more of a bolt on. Maybe that would take some of the fun out of it though? |
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Post by speedy1125 on Oct 14, 2011 9:55:13 GMT -5
also the solution to the deck height problem might be cylinder shimming/longer timing chainCylinder shimming on an OHC engine presents it's own set of problems. You end up messing with your cam timing, which, on a "fixed sprocket" (welded) cam, is not a "happy place". Another place that is not "happy" is the extra sealing surfaces you are stirring into the mix and the added possibility of oil leaks. I would *think* it would be better to top cut a piston (if one could be found with enough "meat" on it), or a combination of piston cutting/head machining. I gotta question the value of 3.6mm of extra stroke the gy6 (150) boys over at total rukus bore and stroke theirs out to 205cc using cranks more than +8 with big ol spacers under the jugs and longer timing chains. seems to do well for them. i am currently running 2 thick hoca base gaskets under the jug of my 50mm motor because of valve/piston clearance because i had to replace the piston after 400 miles when i built it. it was a cheap chinese kit that should have had a thicker base gasket to begin with, couldnt get just the piston itself so had to use a hoca replacement which doesnt quite match this head. the 2 base gaskets have presented no problems for me. I tried 3 base gaskets just to see how this would affect the timing chain and it was too tight with 3. My friends over at www.thoff.com in Raleigh NC are going to assist me in the building of this motor. www.t-hoff.com/Machine%20Shop.htmlMODIFY: I posted a new thread at totalrukus.com asking how any cam timing problems are dealt with by them when using longer chains, this will hopefully give us some insight. |
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Post by reveeen on Oct 14, 2011 10:49:12 GMT -5
if the crank holds up with the big bores it might be worth it for that aloneI was under the impression that there is a bearing "problem", rather than a specific crank "problem", discounting high rpm usage. The 50cc GY6 engine uses a welded cam gear unlike the 150cc GY6. With a bolt on gear you can dial in the cam timing (slot the mounting holes), the welded gear can be cut off, but is otherwise is fixed, and really there is no room for a bolt on gear in the head. I'm *thinking* an E-Mail to Hoca might be in order (who knows, there might be a shorter piston to be used with that crank, and PFS didn't source them). www.hocacorp.com.tw/front/bin/ptdetail.phtml?Part=about
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Post by 90GTVert on Oct 14, 2011 12:31:38 GMT -5
I was under the impression that there is a bearing "problem", rather than a specific crank "problem", discounting high rpm usage. Most of us aren't gonna separate the crank to get to that bearing though. |
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Post by speedy1125 on Oct 14, 2011 22:43:11 GMT -5
the bearings are also an unknown, i intend to replace them with polini or stage 6. anyone have expierience with either?
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