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Scooters - 50cc => Super 9 => Topic started by: TheAmishSasquatch on June 14, 2015, 07:29:32 PM
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Has anyone here had any noticable gains by either shaving the cylinder head, shortening the piston skirt or porting the piston itself? I just knocked roughly .010 in or .25mm off the cylinder head. So far I cant really "feel" much of a power increase. Maybe a slight improvment in TQ but nothing to write home about. Todays test ride was under high heat and humidity and was made with a slightly out of tune carb. I seem to recall mention that the S9 head can have considerably more then .010 in removed safely. Any first hand experiance/ posted gains would be great. Thanks
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Hey, Squatch.
You HAVE to measure the squish band when you shave the head. It's the only safe way to know the clearance.
All the head shave does anyway is raise the compression ratio. That will do two things for you. One is a alight increase in torque, and two is to move you closer to pre-detonation. You need the highest octane you can find to prevent pre- det.
I would suggest reading the Two Stroke Tuners Handbook. It's on this site.
Portint the piston only works if you know how, and where. It's better to port the cylinder for many reasons.
Shaving the skirt(s) changes the port timings, and duration's. Again you have to know what you are doing or you might end up w/ a paper weight.
Find the book, and read it. It's the best zero dollars ever spent.
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Thanks zombie. I made sure to measure the amount above the cylinder that the piston crowns at TDC as well as the depth of the edge of the head deck mounting face. From the deck to the edge of the CC it varries from 1.07mm to 1.15mm. I knocked it down by .25mm giving .82mm edge/deck height. Im not sure what the new compression ratio is currently. Im glad you mention high octane gas. I found a place nearby that sells 100 + 110 octane racing fuel which I plan to run. I do not want to raise the compression so high that it requires 100 or more, nore do I want to move the powerband to high and have a peaky motor.
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Is it the OEM cylinder, and head?
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Yeah, Im working with stock parts currently.
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Look on Josh's sight, Scooter Invasion, and look for "port maps".
There are a ton of them all well defined, and you can choose anything that sounds like what you want.
As a shotgun approach on the OEM jug you can taper, and raise the intake ports by 5mm. Same for the boost port.
This will give you a higher power-band by about 1krpm, more intake charge per stroke, and about 5mph more top end.
From there you can maintain the height, and increase the width. The goal is getting more fuel in. You will need to open the pipe at some point but you can go pretty far w/ the porting before a performance pipe is a must have.
Even getting the angles cleaned up, and flowing faster is a bonus. I use one of those fluted steel cutting wheels on a dermel. It cuts better, and lasts longer than the cheap grinding wheels you get for dremels. about four of those cutting wheels will complete a through port job.
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Great info! I'll check that out. I have a pipe and PHBG 19 on the way. The bike has normal mods. Just thought it's time to mess with the engine without BBK ... yet
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You'll get about the same results, and it costs nothing but your time.
The only things I would do to the piston is sand, and polish the crown to prevent carbon from sticking, chamfer the skirt edges at a 60* bevel to force oil between the skirt, and cylinder wall, and drill two 1/8" oil holes in the wrist pin bosses.
When you look at the piston from the bottom you drill the holes in the bosses to allow oil to get onto the wrist pin to keep it floating smoothly. Between the skirt work, and the oiler holes, you can get a free'r reving engine.
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Thanks Zombie. I created an account and did some searching on port maps and even super 9 port maps, but didnt really have anything useful jump out and bite me, and some of those threads/builds are 30pgs long! Id like to give those mods a try very much. Maybe youtube has something?? Thanks again, Im enjoying that site.
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You can email Josh or PM him from the site. He'll give you the best maps for what you want.
His email is on his "The Scooter Garage" web site. Tell him I said hey.
http://www.tsgtuning.com/location.html (http://www.tsgtuning.com/location.html)
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Thanks, I'll give him a shout. I did find some good vids on youtube. I've done similar mods in the past, I just didn't know it was called port maps. Lol.
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Be careful of the Utube stuff. There is a LOT of misleading crap on there.
If you find something that sparks your interest, post it up here, and I can help to determine if it is worth pursuing.
I've just ordered another one of those JiangWayne 50mm cylinders, and I'm planning on copying the Polini Corsa porting into it.
I should see the jug in a week or two so if you like I can post the Corsa numbers/map up here. It will work great w/ a 8.5-9.5k pipe in OEM porting. I opened mine to run 10.5 - 12k, and love it. It's just too much for a daily driver so I'm building another engine for daily, and keeping the race engine on the shelf.
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That would be be great Zombie! Probably alot more reliable and safer then blindly shaving 5mm out of my ports. Im glad I read this when I did. I literally have the 9 apart and the rotary rasp ready (unintentional tougne twister there). I did knock the head down a couple thousanths more. Not sure what my squish or CR is but the piston crown potrudes 1.05mm above the jug iircc and the head deck height to CC is in the upper .80s not including a .25mm head gasket. I didnt notice any pingging on 93 octane so I guess Im okay. Anyway thanks for offering up the corsa port maps. Keep me posted when the new kit arrives. Thanks
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https://www.rbracing-rsr.com/compstaticcalc.html (https://www.rbracing-rsr.com/compstaticcalc.html)
http://www.wiseco.com/Calculators.aspx (http://www.wiseco.com/Calculators.aspx)
https://www.lunatipower.com/Tech/Pistons/HelpfulCalculations.aspx (https://www.lunatipower.com/Tech/Pistons/HelpfulCalculations.aspx)
To measure the squish use a piece of solder. Insert it into the sparkplug hole all the way to the edge of the piston, against the cylinder wall.
Kick the engine thru one stroke, and measure the thickness of the solder.
You want as close to one mm as you can get. 0.5 is the smallest, and 1.5mm is the largest. It's best to adjust this number with head gaskets, and you can find all sorts of materials to make them.
These guys are the best. Go with either the softest aluminium or copper, and anneal it before installing it. Generally these will flatten out 0.0001 - 0.0002" when installed
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Just performed a compression test on the 9. Results shown 120psi on electric start and 135 on kick-start. How do I set about calculating my compression ratio ? Is 135 a little low for a decked head? Seems like 150 would be more of an expectation, no?
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You have to figure in ring sealing, and bore wear for compression. 135 sounds about right to me.
Use this Calc, and fudge the dome numbers until you get the right CC's. When your cc's are right your Ratio will be right.
Then once you have your total cc's use this site, https://www.cbperformance.com/v/enginecalc.html (https://www.cbperformance.com/v/enginecalc.html) to figure the displacement. Those numbers will allow you to subtract, and find your combined combustion chamber cc's at TDC.
Then with the head off you can measure the Combustion chamber volume w/ water (you tube for the process).
The difference in those numbers is the Piston dome area in cc's.
Sounds like a bunch of work but it's not. It's all easy breasy stuff.
Post it up. I'd like to see.
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I'll try to bang this out tonight if possible. I have a concern over the numbers though. My cyl head (though square and seals) does not have even depth in the dech height. I measure from the edge (where deck meets CC) just as you would for squish but the numbers varry. The lowest point is in the low .8's with 90% of the rest in the .9mm range. Is this pretty common to be off a little, and how badly will it affect my calculations?
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What is the bore and stroke of a stock AC super 9? I measured 4.9 ml/cc in the combustion chamber with tbe plug installed.
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All mass produced, cast aluminium, machined parts are "off" somewhere.
For your squish, you have to set it using the lowest point so it will throw the effect off some but nothing that you would ever see on a dyno.
It's getting more theoretical than real.
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Great to know. I was worried there would be an unbslanced burn from either a mistake I made during milling or that the head was warpped or something. Today I might remove the poston an weigh it against a Koso replacment I have. Maybe polish it as well. Going to check the service manual for bore and stroke specs and post up compression figures. Thanks Zombie
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So I sanded a little more off the cyl head and have a more accurate CC volume of 4mL. With a bore of 34mm and 41.41.4mm stroke and deck height of .91mm gives me a compression ratio of 8.8
I will probably chamfer the cylinder skirts and possibly piston skirts today. Ive also read that a slight grinding of around 1-2mm off of the edge of the piston crown side which passes the exhaust port (usually has a cast arrow) will slightly open the timing of the exhaust pulse without changing tbe stock port timing, and allows for higher rpm.
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I call that Kerfing the piston. If you take the exact center, and taper a "pie wedge" to the port(s) it does change the timing, allows in more fuel sooner, and more exhaust out sooner.
Problem is unless your pipe is matched it will lower your red line rpms, and give no advantage in torque or hp. This is usually done in high compression engines to eliminate ping.
A better option would be to continue shaving the head, and raise the jug. You will get higher compression (more torque), and lessor timings that will allow for regular pump gas to run without pinging.
What pipe do you have?
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I currently have a tecnigas RS? RSII ?. Im concerned its too late on the cylinder skirt. I wanted to simply grind off some casting marks and not change the profile, but it seems just that was enough to throw things off. I also ported the stock intake manifold from a 14mm opening on the carb side to 20mm and opened the exhaust port on the cyl (just the part that attaches to the muffler, and the muffler opening itself) needless to say, everything is outta whack. It only runs for 2 seconds and dies. I think I f***ed up :( Might just have to get the Malossi setup while they last
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I currently have a tecnigas RS? RSII ?. Im concerned its too late on the cylinder skirt. I wanted to simply grind off some casting marks and not change the profile, but it seems just that was enough to throw things off. I also ported the stock intake manifold from a 14mm opening on the carb side to 20mm and opened the exhaust port on the cyl (just the part that attaches to the muffler, and the muffler opening itself) needless to say, everything is outta whack. It only runs for 2 seconds and dies. I think I f***ed up :( Might just have to get the Malossi setup while they last
Too much grinding and porting :'(
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Too much grinding and porting :'(
My thoughts exactly. The skirt I literally just cleaned up and smoothed but I have a feeling that I inadvertantly changed the profile. The exhaust port is another concern. Even though I didnt grind into the port map area, I think I did too much. Im more concerned about my pipe then the jug to be honest. I did use a stepped bit an routed out some material at the inlet. I dont figure tbat has much effect though.
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You didn't read the book did you...
That sucks but it is a learning experience. I have a shed full of wacked up parts that oddly all seem to work in combinations that I did not intend. Like a Malossi that's running a piston meant for a 12k rpm yamaha 80 but it runs better on an 8k rpm Technigas pipe.
Porting is an exact science. No mysteries... one mm in the wrong direction...
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How the crap do I post resize pics to post em here? I found a couple 70 & 75cc kits Im interested in as I obviously missed the Malossi stuff posted in the other thread. Im unable to post links or do any real picture editing because I dont have a computer. The kits are not S9 specific but fit AF18, ZX50 and Dio. I seem to recall that the cylinders fit but other non cylinder/head related parts wont work. Is this correct or am I misinformed?
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Honestly I don't know if the parts swap. I really don't think they do.
I THINK it is the like, and the people 2t's that share the same engine/parts.
Posting from a phone? I can't help w/ that either. I don't own one. Sorry sir!
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Yeah using phone and tablet. Mostly tablet. I would really like to get the Malossi kit, but cant justify $200+ currently. If I were able to find the kit tbat was on sale I would have bought it as Malossi seems that its a dirrect swap and I need not worry about gasket spacing for tuning port maps and such. Ill just have to keep looking. Until then Im hoofing it :(
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Just ordered a Malossi 70cc kit. I really wanted an Airsal kit but too much $$ considering the kits I seen require you have to buy the head seperatly. I really liked the all aluminum construction. Great for even thermal expansion and cooling properties, not to mention weight savings.. (Especially nice for a squatch like me) Oh and my PHBG arrived yesterday :)
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Glad to hear bro.
I just ordered another of those Taiwan 50mm kits for the ZX too. You'll hopefully be riding long before my kit arrives.
One thing... Do all the prep on the kit. Chamfer ALL the sharp edges in the ports, skirts, and polish the piston dome.
The difference between that, and an aluminium kit is almost nothing. I Very much prefer the cast iron kits for long life.
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Lol I dont know if I want to get anywhere near this new kit with a dremmel. Everything you suggested to do to it is what I was doing to the original with the exception of porting out the exhaust- inlet manifold. Im still not clear if/how that could have ruined the jug. I never broke through to the port map, and I cant belive the cylinder skirt is that sensitive to the slightest change do to deburing. It is what it is though... I wanted the mods to work, but secretly hoped they wouldnt so I could go BBK without a divorce being involved ;)
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I think you just had an air leak when you assembled it. Any leaking gasket will act like yours did.
https://www.youtube.com/watch?v=rVeQPOHKrJk (https://www.youtube.com/watch?v=rVeQPOHKrJk)