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Post by nelson on Feb 6, 2014 11:04:30 GMT -5
I picked up a case off of ebay. It is clean and bare. I already have a flywheel,clutch,cvt, and stock polaris cylinder. I think the cyliner is 52mm bore and 42mm stroke? Is that correct? My cylinder will need a hone and i will put some new rings but i think it is good to go. what would you guys recommend for a crank? Just go with autotech crank with bearings kit? Have to make sure flywheel and cvt fit. Will also have to have 12mm wrist pin. Will this make a good street motor? better than 70cc bbk? What if i use my LEo zx-r pipe on it? Will it still out perform my 70cc bbk? I plan to use 19mm delorto carb,v3 reeds
thanks for input
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Post by nelson on Feb 6, 2014 11:08:11 GMT -5
or should i get a 45mm stroke? then i have to mess with base gaskets andport timing and crap..
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Post by nelson on Feb 6, 2014 11:08:46 GMT -5
i would like about 15hp and gobs of torque @9000rpm
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Post by 90GTVert on Feb 6, 2014 12:07:02 GMT -5
Bore and stroke numbers sound right.
If you want more output I'd upgrade to a 45mm stroker crank. Autotech has good deals, PFS sells a Hoca 45mm.
45mm stroke, 52-54mm bore in a cylinder with appropriate timings for 9000RPM, Phongeer street exhaust, Hoca variator, 19-21mm DellOrto PHBG, stock airbox minus the snorkel. That's my favorite street setup that. The only real pain is getting the Phongeer pipe. I got mine from VT Cycle.
My last one was a Hoca 54mm short cylinder with mild port work (tall would prob be better for 45mm stroke, but they weren't selling those at the time). I rode that one 200-300 miles in a day a couple of times without issue. Even with me being heavy it would cruise upper 50MPH range all day. Good acceleration. This was a long case with 10.3:1 gears. My Venus was a stock stroke Polaris 90 engine with a generic 54mm kit with mild port work with the scooter's 11.08:1 gears. That one also took long trips reliably, topped around 60MPH, and did power wheelies.
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Post by moofus02 on Feb 6, 2014 12:18:58 GMT -5
I was wondering how you we'd doing on this lol. I would go with a 45mm crank(more cc and extra torque over the 42mm crank) the cylinders come in 2 Heights the exact measurements vary some but 77mm for the short and 79mm for the tall. Yours probably measures 77 something with mild timings. Raise the Cylinder to increase boost and transfer durations and port the exhaust to match the rpm range you want it to run in. Plus once you have the spacer built you have the option of using a short or tall replacement in the future. You can use a port map of your current Cylinder and a little figuring to determine what the timings would look like with both strokes with the Cylinder you have before you buy a crank
Sent from my SPH-L720 using proboards
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Post by nelson on Feb 6, 2014 13:19:55 GMT -5
i would much rather just slap a crank in there and put my stck cylinder on. How do i know how thick the spacer needs to be? And port timings?? Surley there is a link?
thanks guys
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Post by nelson on Feb 6, 2014 13:24:05 GMT -5
so i need to measure the height of my cylinder i have now. If it is 77 i will need a 2mm spacer to get it to 79mm? I assume i can just order a spacer because that is very thin to have to cut. Or will 2 base gaskets take care of it? So i have the cases...next step is order a 45mm crank?
Would it be a total dog with the leo zx-r pipe?
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Post by 90GTVert on Feb 6, 2014 13:40:08 GMT -5
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Post by nelson on Feb 6, 2014 14:22:12 GMT -5
thank you for all the links!!!
right now with mild 70 set up I have hit 53 fairly easy. I dont want to go over 55mph. I just want to get to 55 faster!
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Post by 90GTVert on Feb 6, 2014 14:27:49 GMT -5
Larger displacement can give a nice torque output at lower revs with the right setup. It's quite nice to hardly need to rev to get going and to keep revs down with a somewhat quiet pipe so no one even pays attention or suspects what you're riding is anything more than stock if you don't choose to show off.
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Post by ryan on Feb 6, 2014 15:28:00 GMT -5
get a diff pipe 90cc dont do very well with 50cc pipes at all really. get a pipe with the right dimensions. its more then slapping in parts
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Post by nelson on Feb 6, 2014 17:20:06 GMT -5
they slap factory 90 cc engines togetherI really don't want to spend a lot of time porting measuring etc ceterathe other member of this form is building the secret 90 didn't he just use the stock crank and stock cylinder? are you just saying its not worth the time to build a 90 if you're not going to do it correctly get the most power out of it?
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Post by ryan on Feb 6, 2014 19:20:23 GMT -5
all im saying is if its not right it will go wrong in no time.
if you use a stock pipe it should matter being a stock 90. once you get a 54mm bbk and stroker then a new pipe is kinda needed to not only get the power you upgraded for but to maintain reliability. most 70 pipes wont really "work" but they can manage. the c30 i believe will work with a 90cc the dimensions are really good from what i know and 190mech makes good pipes i hear.
i personally bought alot of my high end stuff from web bike japan and picked up a windjammer replica and a actual 600 dollar windjammer with a 23.9mm stinger ID and is a monster in size volume over the 50-70 pipes. i havent used it yet but i will once i have time to build another engine.
a stock 90 will do good with stock pipe and componets but as soon as you upgrade cylinder and crank cc's go up and so does the cost of parts to help it "breath" and not over heat and detonate. i will say if you get a 90 all stock and only replace the pipe with a 70cc and carb jetted right you should be pleased and not have to worry much of the problems mentioned. ive built alot of 90cc plus engines and can tell you personally if you wanna go bigger make sure you have the parts to make it work or it wont be up to your expectations
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Post by nelson on Feb 11, 2014 16:50:16 GMT -5
i am here to report, the new cases have been delivered and are perfect. It was packed bomb proof! seller was great.
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Post by nelson on Feb 12, 2014 21:17:13 GMT -5
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