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Post by pinkflames420 on Mar 9, 2017 11:51:38 GMT -5
I think squish would be a good topic too since we're at it. I recall reading a few build threads which call on squish as a baseline for getting close to a good compression range. I do know those 2 measures are different. Please correct me if i'm wrong at any point though. To measure ones squish, you use basic lead solder wire in 1.5-2mm diameter, clip a section roughly 5-7 inches and give it a nice angle bend. The idea is to get the wire into the cylinder through the spark plug hole in the head and to the side of the cylinder, then "squish" the solder wire between the head and piston by rotating the crank. You then remove the wire and check how flattened the wire got with a micrometer. Its also good to take this reading for all 4 corners around the cylinder (12, 3, 6, and 9 o clock if you prefer.) Heres where i'm fuzzy though, what we should have for a good squish and how quickly outside this range does it go bad? I know too thick, it runs poorly (lack of compression) and too thin and you need race gas octane, detonation happens, and extreme wear on starting components also becomes an issue. If i recall, the range should be 0.8 to 1.2 mm? Thanks for that tip! Noting: check squish at 12,3,6,9 o'clock. In Brent's squish clearance video, he states .6-.8, quoted from the book "2stroke performance tuning". Can someone identify where the squish may be too wide or thin. I watched a video claiming thinner squish/more compression/smaller port timings are/is better? |
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Post by AtariGuy on Mar 9, 2017 12:05:52 GMT -5
Thanks for that tip! Noting: check squish at 12,3,6,9 o'clock. In Brent's squish clearance video, he states .6-.8, quoted from the book "2stroke performance tuning". Can someone identify where the squish may be too wide or thin. I watched a video claiming thinner squish/more compression/smaller port timings are/is better? Port timing and squish are set differently. Port timing is adjusted with base gaskets under the cylinder to set where the bottom of the piston stroke lines up with the ports. Thats then measured like so. 49ccscoot.proboards.com/thread/353Once you got that set where you want it (we can discuss port durations after this) then you check the squish on the head and add or remove head gaskets from there. 49ccscoot.proboards.com/thread/2355Halfway down this post... 49ccscoot.proboards.com/thread/345 |
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Post by pinkflames420 on Mar 9, 2017 12:08:02 GMT -5
Thank you thank you!! I've been skipping out on homework I see....  bad bad bad So port adjustments made on the cyl base , and squish on cyl head of course. Sorry that makes COMPLETE sense when I picture it lol sometimes I feel those types of things are common sense , but why don't I get them right away! |
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Post by pinkscoot on Mar 9, 2017 12:54:30 GMT -5
Something something Brent taught me to do when I install my base gaskets and head gaskets is give them a coating of copper spray. It helps compensate for any imperfections. If you need to leave one out to get squish or good port timings it can be used in place of a gasket.
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Post by AtariGuy on Mar 9, 2017 13:07:30 GMT -5
Sometimes I feel those types of things are common sense, but why don't I get them right away! Don't beat yourself up, this is your first build. I used to lurk a lot before i bought my venice just reading everything. Once i bought it, i've read even more. I am a serious learn-aholic. Whether i knew it or not, i read it and i would find stuff i didn't consider, learned even more, and researched more. I've dug deep into my engine, disassembled and reassembled components multiple times to feel comfortable opening up anything i would need to work on or upgrade. I spent hours cleaning parts, mostly to detail in my mind what i'm looking at. At this point, i could take a lump of clay and carve out every detail of my QJ1E40QMB and each of its parts. That still don't mean my engine runs, i still have a cylinder to install and all those details i have to consider. I still read and read. I have stock (semi-junk) cylinders i would like to practice porting on before i would even consider touching my new 47. Even then, i think i would pick up another 47 cylinder, preferably used, to port. I still have a lot to read on port shapes, durations, and then some. At this point, nothing is common sense if there is still so much more to learn from it. I havent even discussed exhausts, but i have already done a couple hundred hours worth of reading and research there too. Still more yet before i'd feel comfortable opening my yap to insert foot lol - point is, we're never truly done with our homework, theres always more. It just depends how far down the rabbit hole we want to go... |
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Post by eclark5483 on Mar 9, 2017 14:05:49 GMT -5
36-38 is Huge on a typical Chinarelli carb. All of mine use 17.5-22.5 stock. I've been able to keep stock pilots, but I don't use open filters. I always have a big selection of main jets around. At least 70-100. As long as you buy in kits, they aren't terribly expensive. That's odd, according to scrappydogscooter's site, the stock pilot is a #35. It's always been my understanding as well that a pilot is usually a #34 or #35 stock.  |
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Post by AtariGuy on Mar 9, 2017 14:32:57 GMT -5
36-38 is Huge on a typical Chinarelli carb. All of mine use 17.5-22.5 stock. I've been able to keep stock pilots, but I don't use open filters. I always have a big selection of main jets around. At least 70-100. As long as you buy in kits, they aren't terribly expensive. That's odd, according to scrappydogscooter's site, the stock pilot is a #35. It's always been my understanding as well that a pilot is usually a #34 or #35 stock. having tore mine apart (genuine mikuni) it came stock with a 22.5 pilot. I plan on grabbing a... (update pinkflames)... 27.5 pilot for mine. I suggested earlier a 26, but it would appear they come in 2.5 increments lol |
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Post by AtariGuy on Mar 9, 2017 15:11:15 GMT -5
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Post by eclark5483 on Mar 9, 2017 15:49:40 GMT -5
Maybe it just depends on the carb. My Spree for instance, also uses a 34 pilot. The performance carbs I bought for the TaoTaos I own, each came with 38's.
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Post by 190mech on Mar 9, 2017 17:45:07 GMT -5
Checking the squish at TDC and if the piston top is even with the bottom of the transfers at BDC is an easy task without the rings installed,just slide the cylinder on with 1 base gasket and give a look down the bore at BDC,if it looks good,great,if not add or subtract base gaskets till it does..lots of folks run with no base gaskets,just a sealant..Once thats good,check the squish and adjust as needed...
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Post by pinkflames420 on Mar 9, 2017 18:20:39 GMT -5
Yup same as mine! Jets r us has a good selection, but I don't get why they don't ship international 😕 And of course, my luck. Anytime I wanna do anything on my scooter this happens! No riding in snow for me guys! Well not to tune my bike anyways.Usually these ones only last over night. If your kit arrives tmr , you'll be ahead in the game  Might even install same day.  |
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Post by AtariGuy on Mar 9, 2017 18:43:31 GMT -5
I work tomorrow and saturday, my fun wouldn't be until sunday. Sounds like my wife is ordering a 100cc kit for her 4T tomorrow, so i get to dismember her scooter when that arrives lol
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Post by pinkflames420 on Mar 9, 2017 20:42:03 GMT -5
Checking the squish at TDC and if the piston top is even with the bottom of the transfers at BDC is an easy task without the rings installed,just slide the cylinder on with 1 base gasket and give a look down the bore at BDC,if it looks good,great,if not add or subtract base gaskets till it does..lots of folks run with no base gaskets,just a sealant..Once thats good,check the squish and adjust as needed... So basically our goal is to open the transfer ports up all the way, but no more? Correct? Edit: I meant at BDC.my apologies. Thanks for the tip aswell! Heheee I have a collection now.That'll definitely save Me(us(Atari)) the hassle of going back and forth with those damn piston rings!!  AtariGuy , I would like to walk the plank! Thanks for the kind words. I am willing to learn, and I know this is the place, but being in a place so full of knowledge and experience , it can be overwhelming. I'm learning to take things slow aswell lol. pinkscoot , appreciated. I managed to actually find some copper gasket maker, no spray. Medium threadlocker, anti sieze and a fresh bottle of 2 stroke oil  |
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Post by niz76 on Mar 9, 2017 21:00:59 GMT -5
I very rarely have ever had to change the idle jet from stock (unless you install a pod filter or something, even then stock idle jet usually still usually worked fine) even when installing a 70cc kit...
I wouldn't be too worried about port timing with your 1st BBK install, especially considering it's a mild sport kit...
Your squish might end up wider than optimal just because manufacturers like to make the parts with lots of room for error- they try to make the parts 'foolproof!' haha. (Which is why I often just eliminate the base gasket to try to get a better squish gap and a little more compression). Without getting into machining parts for high performance build, sometimes just have to accept it for what it is...
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Post by pinkflames420 on Mar 10, 2017 0:37:33 GMT -5
I very rarely have ever had to change the idle jet from stock (unless you install a pod filter or something, even then stock idle jet usually still usually worked fine) even when installing a 70cc kit... I wouldn't be too worried about port timing with your 1st BBK install, especially considering it's a mild sport kit... Your squish might end up wider than optimal just because manufacturers like to make the parts with lots of room for error- they try to make the parts 'foolproof!' haha. (Which is why I often just eliminate the base gasket to try to get a better squish gap and a little more compression). Without getting into machining parts for high performance build, sometimes just have to accept it for what it is... Yes, I do remember you and Brent mentioning that on my other thread. We will see how this one goes. (I'm hoping I can still adjust my air screw,remember I ground the housing) After you said you don't even use gaskets and hearing others don't either, I'm considering doing this aswell for my head gasket. I didn't grab any silicone gasket , as I assumed the paper would be fine, but I can get some. I don't have copper "spray", just high temp copper gasket material. Crossing fingers for tomorrowww  |
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bad bad bad
Might even install same day.
