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Post by 90GTVert on Apr 25, 2016 7:37:09 GMT -5
There's also the option of cutting valve reliefs in the piston if that's an issue. Even a valve relief drops compression a good bit if you have to cut it deep, but you will keep compression higher that using a huge base gasket. You only need about 0.080" P2V clearance on the exhaust side to be safe, maybe a little less if you are willing to push it, 0.050" on the intake side. Using a huge base gasket could really kill compression and totally ruins squish clearance. Wide squish is better than too narrow, but a closer squish, around 0.035" minimum, may help to avoid detonation and move the majority of the mixture toward the center of the bore to help it burn. If you have interest in that stuff, check out the last few pages of my Roketa 150 build in the builds section because I went over all of this with my 150 and it's the same process as well as figuring out the static and dynamic compression ratios.
Opening a box and expecting it to be great happens all the time. Many times it works, sometimes you end up killing the engine or part of it and sometimes you just don't get the performance you're after. It takes a bit of effort to really dial it in.
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Post by Clank on Apr 25, 2016 19:58:12 GMT -5
I'm still breaking in my fourth engine before I go balls out on this one. But I will say it's definitely got some serious low end torque and HP. I bent a valve bad on one head. I also had to cut reliefs even with the thicker gasket. I'll post pics and videos soon.
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Post by Kick start on May 1, 2016 11:56:50 GMT -5
I have the same piston but with the stroker crankshaft and im hearing the valve hit the piston at only higher rpms not at low rpms. My thoughts on this is that its valve float and needs titanium valve springs.
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Post by Kick start on May 16, 2016 9:10:30 GMT -5
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Post by Kick start on May 16, 2016 9:13:44 GMT -5
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Post by Kick start on May 16, 2016 9:16:16 GMT -5
As i was saying ^^^^
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Post by niz76 on May 16, 2016 11:26:16 GMT -5
OUCH!
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Post by Silar on May 16, 2016 21:22:51 GMT -5
Holy Bejeezus!
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Post by kagetenshi on May 16, 2016 21:58:46 GMT -5
I guess an oil change is in order after that gore fest.
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Post by humanshield on May 22, 2016 11:13:19 GMT -5
Yup. I've barely even touched the CVT at all and it hit 51 on GPS yesterday. Pretty slow for a 50cc according to some. I was talking to a couple guys at the local hardware store the other day and they were telling me about their "friends" scooters. "Completely stock 49cc scoots hitting 60-70 "easy", GPS verified, all the time." They swear this was not only GPS verified, but car odometer verified riding behind their cars on the expressway. And they bought them that way. No mods at all. (Man, I'm doing something wrong) You can't argue with that "proof". Or,.... you "shouldn't"
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Post by humanshield on May 22, 2016 11:27:21 GMT -5
I have the same piston but with the stroker crankshaft and im hearing the valve hit the piston at only higher rpms not at low rpms. My thoughts on this is that its valve float and needs titanium valve springs. Man, sorry to see that. What RPM's are you running when that occurs? How was the power and torque SANS the valve problem?
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Post by arkie on May 22, 2016 12:48:16 GMT -5
Im hoping to get the same piston next payday. I've got the big valve head and compression is less than stellar. Hopefuly that piston will be the answer.
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Post by humanshield on May 22, 2016 16:00:10 GMT -5
From what I've read here so far, it won't clear the valves without some work. That's manageable. Getting it to clear the valves and still have proper compression is the trick.
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Post by arkie on May 28, 2016 14:55:58 GMT -5
It's here, arrived today and it's beautiful. So pretty in fact it seems a shame to install it. I got this on their ebay listing. www.ebay.com/itm/172185323416?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT It came well packaged with rings, wrist pin and circlips just as in the photos on ebay. Reading the listing you will find that a base and head gasket are also included. These came also, but with a bonus item not in the listing. A much thicker spacer/gasket with fire ring was also included. Now for the backstory and what I plan to do with this thread. A few months ago I installed 50mm bbk with big valve head from 02starrider in truth it worked fine and there was a noticeable improvement. However I felt there was always a lack of compression. The blame points to the much larger volume of the big valve head. Not wanting to give up on my better flowing head I searched out this piston. I plan to update this thread to give you my impressions after the install. I'm not an overly technical guy as is I don't have a compression guage or even a speedo on my scoot atm. I will however give you my honest opinion of how this little jewel does. As in is it worth it.
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Post by 2shaynez on May 30, 2016 2:27:07 GMT -5
Well I bought a bbk from stg and the airsal piston... This has me worried it will hit the valves after reading this forum.
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