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Post by buzzbug on Nov 10, 2013 16:14:32 GMT -5
Hi,Im new to the forum ,but I've been messing about with the gy6 motors for a couple of years now.
We use them in racing grasskarts,the CVT trans is perfect for it and have found them very reliable.
1 kart has a GY6 with 58.5 NCY kit,NCY cam,ignition ,30mm Keihin pumper [slide, not CV carb],custom supertrapp exhaust and Koso variator kit,it goes great,but lacks top end.
2nd Kart has a factory GY6-180 163Qmi,with NCY ignition,NCY variator kit and 30mm Keihin pumper,its a bit of a slug compared to the 160,but I think its due to std cam ? [NCY cam wont fit 180 head]
Problem is the rules have changed to allow up to 200cc engines now,so we need more power.
So I need to build up a hot GY6 under 200cc,I have a few parts ie 4 valve head,NCY inner rotor kit,Oko 32mm flat slide,but not sure if I should use the 150 or the 180 as a base [4 valve wont fit 180].
Is the 180 a "B" case ? ,also why do some parts sellers say the bbks wont fit ona 1P57QMI,I've compared them for cyl spacing etc and they seem the same.
a lot of questions,sorry but i live in New Zealand,not much knowledge here about GY6's
Heres a video of my Daughters kart [skip first min] enjoy lol
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Post by wilds on Nov 11, 2013 0:55:44 GMT -5
Hi, and welcome. Looks like great fun with the grasscarts. Too bad Charlotte spun... If you want to get up just under 200cc you could take a 175cc cylinder and a 8,2mm stroker crank. That would give you 199,16 cc. Personally I do not like 4 valve heads. You can't adjust the valves individually and it seems unnecessary with two small valves and ports. I rather have one bigger port which is lot easier to do a proper port job on. I have this cylinder head and I'm really happy with it. Tuning headThe head comes with a new camshaft (which is a must since original cams want fit the head), new rockers, new longer cylinder bolts and a longer timing chain. A Fuel injection is also the way to go! |
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Post by alleyoop on Nov 11, 2013 1:17:06 GMT -5
Just remember you need more displacement so you have to go bigger than 58.5 but to do that the case has to be bored to except the bigger jug. Here is my 157QMJ setup: The B motor has wider spacing Studs and a taller head along with a longer chain. There are not many performance parts for the B motor so I would work on the 157QMJ motor that one you can build it up to 232ccs if you wanted to.
Alleyoop
Here is what my PST150H Ice Bear Trike currently has it was a 157QMJ 149.6cc Motor now it is 182cc motor:
62mm BBK
60mm Stroker Crank
16/37 Hoca Tranny Gears – Original were 13/40
Reduction gear is 43 teeth
K&N Air Filter with a Short Stack
SuperTrapp Muffler
1 1/4 Header Pipe
24mm Carb
#122.5 Main Jet
#38 Pilot Jet
Peformance Coil/CDI
Manual Choke
Iridium Plug
115mm KOSO Variator
12g Dr. Pulley Sliders
205/65-10 Kenda Load Tires-3"s taller than OEM
29 tooth Drive Sprocket-came with 24 tooth.
DID 428 Pro V Series O-Ring Chain
Givia 29" tall Windshield
All Led bulbs Except the Headlights-I do not drive at night
4 way Flasher
Turn Signal Beeper
Relay for the Beeper connected to the Brakes
VIP Trunk with Led lights
Flasher on Vip Trunk lights
Radio with SD card,MP3 connections
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Post by buzzbug on Nov 11, 2013 4:31:10 GMT -5
Thanks guys,good ideas to think over,I was finding little in the way of performance parts for the "B" case,so prob will go the 157 route ,although most crank/piston kits seem to make the motor close to square [bore/stroke],isnt the optimum ratio approx 60% bore to 40% stroke?I'd thought maybe just a 66mm piston kit on the "B" case motor would be heading in the right direction,or do we need the torque of a longer stroke to optimise the CVT ?
.Has anyone used one of the inner rotor flywheel kits ...good or bad ?,i dont need much in the way of charging.
Also seems not many are using the 4 valve heads,any reason ?,4 valves seem to work better on motorcycle and car engines.
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Post by wilds on Nov 11, 2013 5:49:50 GMT -5
A oversquare engine (short stroke bigger bore) has it's torque at high rpm's
A undersquare engine (long stroke smaller bore) has it's torque at low rpm's
So a square engine should have a little bit of both... mid-range rpm's.
I always optimise the CVT after what i've done to the engine by trial and error...
Why people doesn't use the 4-valve head on these engines could be because it doesn't have much more to offer that a good 2-valve head...
As I understand, 4-valve heads is more used with twin cams...
I haven't tried the inner rotor kit, I need the lights on my scooter.
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Post by buzzbug on Jun 8, 2014 0:14:00 GMT -5
Hi again,we finally got the 4 valve head to work on the GY6,it seems the cam supplied is quite a way out and caused a lot of headaches,we ended up making one and used a yoshimura grind for a 4 cyl race bike and it works great.So this has a 63mm bore and 6mm stroked crank for 196cc,seems a good size and under our 200cc limit for racing.
So now next question,Im trying to find a supplier with good quality parts[cranks 6mm] who also sells BBK spacer and gaskets for "B" case engines,I cant find anyone online who does and as freight to New Zealand isnt cheap,I dont want to go shopping at several suppliers.
Hope someone can help,as we are building another engine,same specs but with a big 2 valve head,just so we can compare them.
Thanks
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Post by bvance554 on Jun 8, 2014 1:30:34 GMT -5
Post us a video when she races with the new set up. I enjoyed that  |
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Post by buzzbug on Jun 8, 2014 15:39:23 GMT -5
Will do....most of the other karts are powered by Lifan 200 dirtbike motors [5 spd] Her new kart pulls away from them down the straights whereas the old one [in the video] used to loose ground and catch up in the corners.I,ll mount the camera on her helmet next time [lol].
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Post by craisin on Jun 9, 2014 6:19:32 GMT -5
There is maybe was a place on Bruce Maclaren Road in Henderson that i have got to make copper plate cylinder base gaskets for a bike engine i had. They also made me handmade gaskets for a racecar i had many years ago.
I will go by and see if they are still in business and get back to you.
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..BAD TO THE BONE..
