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Post by Kenho21 on Jul 21, 2019 11:22:27 GMT -5
So I'm going to be getting more power out of my Jog one way or another coming up real soon here, but would like a little feedback or input as to which route makes more sense. I'm eventually going to end up with a 70cc Polini Corsa build with a new crank, carb and all that jazz over the winter, but until then would like to get a little more power from her as well. Here's the scenarios: Check my signature for '99 Jog setup, but here are the highlights... - Yasuni R exhaust - Polini clutch and bell - Performance variator - Stock everything else Scenario 1"Freshen" the motor with a new 50cc piston, rings, etc. and hone the cylinder/ports, then do BBK, Crank, etc. and overhaul over winter. Scenario 2Get a cheaper 70cc kit from PFS and just do the BBK for now, but can add carb and other mods leading up to winter, then do BBK and crank over winter. PFS kit: www.partsforscooters.com/47mm-2-stroke-Big-Bore-cylinder-set-169-57Scenario 2 has me spending a little more money, but may be more a pragmatic approach and scenario 1 is just a lot cheaper and probably carries a little less risk of unplanned downtime. Any thoughts?
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Post by 90GTVert on Jul 21, 2019 11:36:43 GMT -5
I'd probably just freshen it up for now. Winter isn't all that far away, so I wouldn't want to spend on a cylinder kit that isn't what I want for that amount of time. If you're comfortable with it, maybe check out the timings and perhaps do some porting or mods. If the cylinder is totally stock now, you might pick up some power/speed with the right adjustments for next to no money.
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Post by oldgeek on Jul 21, 2019 11:55:18 GMT -5
Since just freshing it up puts you through the same work, if not even more, I would slap that 70cc kit on, rejet the carb and enjoy.
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Post by Kenho21 on Jul 21, 2019 12:36:18 GMT -5
Since just freshing it up puts you through the same work, if not even more, I would slap that 70cc kit on, rejet the carb and enjoy. That’s my thought too, but then if I do another rebuild this winter, it’s kind of redundant mechanically and financially haha. I’d save at least $100 by just refreshing I think. I’m planning on a new crank, gears, and the rest this winter, so the actual workload is a bit more disproportionate when comparing the two imo. The speed freak in me just wants to get the short term 70cc though real bad haha. Aside from the kit I mentioned, a honing tool, gaskets/gasket maker/rtv, new wristpin bearing, and tools, are there any major supplies I’m missing to do it properly?
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Post by Kenho21 on Jul 21, 2019 12:36:54 GMT -5
To do the refresh, that is.
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Post by Kenho21 on Jul 21, 2019 12:37:56 GMT -5
I’ll probably mess with timing and stuff this winter as I’m not familiar with it and prefer to break things during downtime haha.
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Post by 90GTVert on Jul 21, 2019 14:01:04 GMT -5
Learning to check the durations and the basics to get a little more from it aren't awful. Pretty much all you will likely do is perhaps raise the roof of the exhaust port to get whatever timing you're after. Sometimes the duration of all ports can be raised with a base gasket thickness change and if it works out right the squish can be changed by just ditching the head gasket and using copper spray. Sometimes we file the piston crown a little to raise transfer durations. It is a daunting task if you have never done it, but in reality it's not that bad. The 50 sure would be good to learn on since it sounds like you have your heart set on a 70 before long regardless. It's all good stuff to know.
Another possibility would be to put the Charmo 70cc on and then mod it during the winter and add the other things you planned and see how you like it. It will probably never be a race engine, but it could pick up some power and not be all that bad compared to a Corsa. Also, any decent 70cc is gonna feel really good if you've been used to the 50s.
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Post by Kenho21 on Jul 21, 2019 17:29:19 GMT -5
Learning to check the durations and the basics to get a little more from it aren't awful. Pretty much all you will likely do is perhaps raise the roof of the exhaust port to get whatever timing you're after. Sometimes the duration of all ports can be raised with a base gasket thickness change and if it works out right the squish can be changed by just ditching the head gasket and using copper spray. Sometimes we file the piston crown a little to raise transfer durations. It is a daunting task if you have never done it, but in reality it's not that bad. The 50 sure would be good to learn on since it sounds like you have your heart set on a 70 before long regardless. It's all good stuff to know. Another possibility would be to put the Charmo 70cc on and then mod it during the winter and add the other things you planned and see how you like it. It will probably never be a race engine, but it could pick up some power and not be all that bad compared to a Corsa. Also, any decent 70cc is gonna feel really good if you've been used to the 50s. Well, I was doing this work on a time crunch and I just found out I have an extra day to play with, so I might as well try my hand at some porting. What will I need to find and adjust port durations aside from normal hand tools? Timing wheel and what else? (Need to place an order tonight to have by wed or Thursday)
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Post by 90GTVert on Jul 21, 2019 18:01:31 GMT -5
Aside from the wheel, there isn't a lot to it. Not really stuff you'd have to order. You'll need a piston stop, which could just be a piece of flat steel or aluminum with holes drilled for 2 studs to pass through. You need some kind of spacers to put under the cylinder nuts since the head will be off so the cylinder can be tightened. You need a timing pointer, which is often just a bent paperclip or piece of wire. You may need some sort of adapter for the degree wheel or washers. Depends on the wheel and the crank. Most likely something you could work out in a hardware store. If you port a steel cylinder, these work well... and they are good to have around for a lot of projects. amzn.to/2y3q1GdYou'll need to drive those with something like a Dremel or Foredom etc... It's easiest with a flex shaft and hand piece, but plenty of porting has been done with a regular Dremel and comparable tools. These are good for finishing. amzn.to/2Yhp2kdThere is other stuff that could come up, but you should be able to source it locally. Stuff like copper spray, files, sandpaper...
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Post by Kenho21 on Jul 21, 2019 18:21:20 GMT -5
Aside from the wheel, there isn't a lot to it. Not really stuff you'd have to order. You'll need a piston stop, which could just be a piece of flat steel or aluminum with holes drilled for 2 studs to pass through. You need some kind of spacers to put under the cylinder nuts since the head will be off so the cylinder can be tightened. You need a timing pointer, which is often just a bent paperclip or piece of wire. You may need some sort of adapter for the degree wheel or washers. Depends on the wheel and the crank. Most likely something you could work out in a hardware store. If you port a steel cylinder, these work well... and they are good to have around for a lot of projects. amzn.to/2y3q1GdYou'll need to drive those with something like a Dremel or Foredom etc... It's easiest with a flex shaft and hand piece, but plenty of porting has been done with a regular Dremel and comparable tools. These are good for finishing. amzn.to/2Yhp2kdThere is other stuff that could come up, but you should be able to source it locally. Stuff like copper spray, files, sandpaper... Okay then. I'm gonna order some stuff and get ready to give this a go come Wednesday night through Friday afternoon. I'd appreciate if you all could show this thread a little love over the course to help with snafus. I'd be forever grateful!
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Post by 190mech on Jul 21, 2019 18:30:24 GMT -5
If you like 2 strokes,port duration checks are a primary measurement to take in order to know what you have and what to do to make it better!Many times Ive checked the durations and the cylinder design was so poor,it would be more work than what the part is worth to make it better...Once they are calculated and an adjustment is made,the combustion chamber squish must be addressed,Its all pretty simple once you study the process and get your hands greasy!Find A.Graham Bell's Two Stroke Tuning book,tons of info there,a bit dated,but still works for our scooters!!
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Post by Kenho21 on Jul 22, 2019 11:00:25 GMT -5
If you like 2 strokes,port duration checks are a primary measurement to take in order to know what you have and what to do to make it better!Many times Ive checked the durations and the cylinder design was so poor,it would be more work than what the part is worth to make it better...Once they are calculated and an adjustment is made,the combustion chamber squish must be addressed,Its all pretty simple once you study the process and get your hands greasy!Find A.Graham Bell's Two Stroke Tuning book,tons of info there,a bit dated,but still works for our scooters!! Definitely going to search out that book, thanks. I guess the only part that I don’t really understand about the process is how to find or know what my goal durations should be and exactly how to calculate final powerband and such. I’ll read that book, but in the meantime, I’ll probably be asking a couple questions come wed or thurs haha.
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Post by Kenho21 on Jul 22, 2019 11:01:57 GMT -5
Got everything ordered and on the way, by the way.
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Post by 90GTVert on Jul 22, 2019 14:57:08 GMT -5
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Post by Kenho21 on Jul 23, 2019 9:51:36 GMT -5
Thank you. I've already looked through and am reading through a lot of that stuff again, but you listed a couple new resources to me as well. Started reading through that 2 stroke tuning book and it's not the most well written book I've read, but tons of good info in there! Yeah, I want the cylinder to make peak power right around or just below 9,000 rpm. Seems like that's a sweet spot for my pipe.
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