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Post by 190mech on Feb 15, 2014 19:16:46 GMT -5
Robert,The skirt cut is good for its application,may want it longer for a high mile street build..Gotta figure where the piston pin is in relation to piston skirt support,these tall topped scoot pistons need all the help they can get!OH,if only these motors had a long rod,then the piston pin to dome could be decreased..(dont want to get on my rant again!!) Doc,Real tuners study their parts,educate themselves through reading tech info and make the best out of what they have!There is no black magic with this stuff,the 'web' has all the answers,just gotta find it and ask!!  |
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Post by usmcdoc on Feb 15, 2014 19:33:27 GMT -5
Robert,The skirt cut is good for its application,may want it longer for a high mile street build..Gotta figure where the piston pin is in relation to piston skirt support,these tall topped scoot pistons need all the help they can get!OH,if only these motors had a long rod,then the piston pin to dome could be decreased..(dont want to get on my rant again!!) Doc,Real tuners study their parts,educate themselves through reading tech info and make the best out of what they have!There is no black magic with this stuff,the 'web' has all the answers,just gotta find it and ask!! Agreed..there is no 'Black magic' and so far I have done some pretty good 2T builds. I am leery of info from the 'web' as I have been in forums that were shockingly incorrect. One of them is a Zuma forum where there is more fighting than a good Hockey game. You gotta read through 200 posts to get past that stuff and find the real Tech stuff. That is why this forum rocks. People put the info out there..with vids..pics..explanations and all the stuff a person needs to be able to learn..  |
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Post by 190mech on Feb 15, 2014 20:28:53 GMT -5
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Post by 2strokd on Feb 16, 2014 10:32:13 GMT -5
Bells book is great for opening up your mind to the 2T world. Most
all of the info can be translated to use. Its done me wonders over the years.
I still refer and or just open the book for input or inspiration even.
Doc, going to a bigger 47mm bore with a set of cases tuned for a 39mm bore would just open
another can of worms. The cases would then need cut, shaved and port matched to the bigger cylinder. Then the exhaust, etc, etc...
Same theory when going to a 50+mm bore from 39 or 47mm. To install a 50+mm bore cylinder on a set of cases without at the very least port matching the trans tunnels would be a waste of time IMO. The cases would be very restricted with huge eddy,s in the trans tunnels etc. Like steps were a slide should be.
I am working on getting some "before and after" dyno results from case tuning.
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Post by 2strokd on Feb 16, 2014 10:42:42 GMT -5
This pic shows a set of cases tuned for a 54mm cylinder. Notice how much material was removed to get a good transfer match? Before  After  |
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Post by oldgeek on Feb 18, 2014 20:45:24 GMT -5
I picked up a new 50cc cylinder kit to replace the stock YAMAHA one on the VINO. The porting on the new cylinder is very similar to the stock cylinder. However, the new piston does not have any ports in the skirt. Did they forget to put them in? I would think that since the cylinders are so similar, that the pistons would also match up.  Hey man..stop holding out on us..will ya?? lol. How did that piston work out for you? Been very curious to find out as I am sure most others are... Your new piston is a good example of what we have all been talking about here.. So give us the scoop on it..  Glenn LoL! One thing about me is I am painfully slow! For various reasons, mostly work, and bad weather at the moment. I have not had a chance to work on the vino project. I am on 24 hour call for work every other week, so my scooter time is limited! I have had the new crank installed for some time now, but that's it. I have been slowly moving all the vino stuff to the warehouse and I think I have just about everything I need to finish this project, so hopefully I will soon have some time to work on the engine assembly, and then get the rest of this basket case scooter together. I will most likely just throw the new piston and cylinder on just as they are, since they are nearly identical to the stock Yamaha set (with the exception of the piston ports, and the exhaust flange angle) Not looking forward to fighting the stock exhaust pipe to make it to fit THIS cylinder though. I just want to get the vino back together so I can get started on the next project.  Your input has helped this thread become loaded with awesome info, it will be my "go to" thread for porting/trenching examples. Thanks, Scott |
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Post by oldgeek on Feb 19, 2014 21:23:12 GMT -5
By chance I had a little time to spend over at the warehouse this evening so I took a few pictures of the cylinders side by side. I did the best I could, but I don't think the pictures tell much. I checked the end gap on the rings and they measure around .22 - .23 I calculated using a formula from one of Brent's posts. For a 40 mm cylinder they should be around .17 so I need to order some rings, or just install them as they are. I also ran into another problem. The small end bearing that came with the crank is too wide to fit inside the piston. The bearing is 14.7 mm wide (12 mm pin) I would say it is about 1/2mm to 1mm too wide to fit all the way in. Should I order a smaller bearing, or can I file the inside of the piston just a bit. While we are talking about small end bearings, are the bearings that adapt a 12mm piston to a 10mm crank reliable?    ] |
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Post by 2strokd on Feb 20, 2014 9:44:06 GMT -5
I will trade you even up for a new bearing that will fit your piston like a glove!
Or you should at least know that bearing is for a 47mm piston with a wider gap to fill.
I would say taking off what you need would be no biggie?.
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Post by 2strokd on Feb 20, 2014 9:45:26 GMT -5
As far as the rings go, ide use em.
Those reducer bearings only tend to work on Stage6 cranks. If you are speaking of the S6 one?
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