Big Bore 62mm With 3mm Stroker Reliable?
 

Hi,

I am new here. I want to get the most performance while not eliminating reliability. Have a 150cc GY6 buggy. I found that the 63mm is no a good idea, so now considering 62mm.

1.) Do you suggest the 62mm big bore? If not what is suggested?

2.) Do you suggest stroker crank? 2.2mm, 3mm or stock?

3.) For all around performance, what cam, clutch and variator springs, carb and manifold?

4.) I am at 2200elevation. What jetting to start with?

Thank you,
Charles

I personally don't like the 62mm bore and there's plenty of other people who have had problems with them. Do a search on Google or yahoo. The 61mm bore is the absolute max I would go if you want reliability. With the 61mm bore you will be fine with a 3.3 stroker but I would get the piston shaved down so you don't have to use a spacer for clearance of the stroke. Camshaft there's tons of options, it all depends on your terrain , weight of buggy, and weight of riders. For clutch you will get some people like stock, some people like dr. Pulley, and some people like the ebay performance ones. Stock carb is plenty for stock motor, I bet it will be efficient enough also with the big bore and stroker just rejet and tune carb. Welcome to the sight post some pics of you ride.

Thanks for the welcome.

I was seeing that too just a bit ago where people have been having issues with the big bores blowing up.

I am considering the 59cc bolt on although I hear there is no performance gain. With this would it still be beneficial to stroke?

The other is as you mentioned the 61mm. I know there are some that bolt right on, I think Taiwanese kit. Either way, do you think this would be a noticeable improvement over the 59cc to make it worth the total engine tear down and boring?

I had called Scooterdomain and the guy mentioned a 1500 spring on clutch and a 2000 setup on variator. Any thoughts on that?

The rollers I had considered 12g.

Our riding area is some hills with wide open. So plenty of both terrains. Our typical rider weight is about 380 pounds (2 people).

You have to be careful with the 61mm bore there's 2 kinds. The first one will have a super thin piston skirt wall. The 2nd one will be a thicker skirt wall but the case has to be bored. Company name is taida that makes it. The 59mm kit your talking about is actually 58.5 piston. Guys who have it say they don't see any gain. I've seen kits that say high compression that is suppose to raise the compression 1 point. 12 gram roller would be a start so you get an idea. I always liked a A11 cam with 10 gram rollers in the yerf dog. But that was with a big valve ported head, and 31 tooth sprocket with 22 rear tires.

I found this one that I was considering: http://www.ebay.com/itm/191962551007...torefresh=true

That's a really good price, I've bought stuff from them with no problems before. Actually there head and camshaft are on my hammerhead. You would have to ask them about that 61 mm bore, I would go with the one that needs the case bored.

Thanks for the feedback on them. I agree the prices are good.

So you had mentioned going with the 3mm stroker but needing to shave the piston. Are you meaning cuts for valves or?

I really like the hammerheads now Polaris. The only thing I don't like about the new ones is the wheel width. Most trails are 54" max and theirs is much over that.

Do you have any ideas on exhaust? I keep seeing the shorties for like $85.

My build is in my sig below.

It's been quite reliable and we've flogged the Hell out of it

My Yerban assault vehicle: 2.2mm stroker crank, 62mm Nikasil cyl, Taida large vavle head, American made valve springs, ported intake manifold, TM 28mm carb, stock CDI, Bando coil, TK exhaust, stock CVT except for the 14g sliders, 13/40 internal gears, 16T drive, 31T axle sprocket, 22" rear tires, and ONE BIG POTATO CANNON mounted on top..........

Do you have a picture?

I see you have a 62mm cyl. You had mentioned you did not like that mil, is that a better one or do you wish you had not done it?

Do you feel the 28mm carb is adequate or does it need a bigger?

Just found this NCY kit that says no boring. NCY suppose to be a good brand. Do you think this one would be a good choice? http://www.ebay.com/itm/GY6-150cc-Hi...-/182242234685

Excatly like I was telling u before they mention the size of the cylinder skirt compared to the standard size one that has to be bored. It's ur call on which you choose but you said you wanted a stroker crank so at that point the case has to be split anyway so why not get the case bored for the correct 61mm. It says the ncy kit has a cut down piston I would ask how much it's cut down because that will determine also what crank it is for. As for xlint with the 62mm bore he's the only one I know of that it is still running strong lol.

The trick with any big bore kit is to get one with a steel sleeve and not the recycled cast iron. They are getting hard to come by. Most stuff today is made with recycled materials since China buy's up all the worlds scrap metal. Recycled metals aren't necessarily a bad thing if the minerals lost in smelting are replaced, but China does not do this. I bought some 2" steel tubing for my trailer project a few months back from Memphis steel. This stuff was horrible for when I used the chop saw to cut, one minute it cut like butter then halfway through the cut I had to apply weight for the wheel to cut it. It was also a bear to weld 3/16" thick tubing. It would start out good then all of a sudden you blow a hole through the tubing. Being I was building a bench I went ahead and used it. I just purchased some more to redo my side door and it was 3 times the cost but it was US steel. As far as shaving the piston, I would not suggest doing this to a Chinese cast piston cause they won't last especially if the cylinder is heated from detonation or overheating. It can be done but you have to have good metal to start with and preferably forged aluminum billet. I know people who do it but it is a crap shoot on weather it will last .

You can follow along with my long story here. http://buggymasters.com/forum/showthread.php?t=2601


I have no problem with my 62mm cyl thus far. It is a NCY Nakasil plated cylinder. Cyl walls aren't real thick, but I don't seem to have the problem others have had? I'm not gentle on the engine at all either. I've broken the top end from over revving twice now. Good valve springs are a MUST if you're going to be revving pretty hi IMO. Tom Syc got me a set of American made valve springs for my last build and are holding up quite well. (thanks again Tom)

The 28mm is supposd to be too big already, so larger is prob not needed. My 28mm does just fine for meeting my needs.

Sycarms, good explanation. I can fully understand that weaker metals can overheat or prematurely fail.

I think I am likely to go with a 60-61mm kit. I hated to have to take it to a machinest locally who is the only one in town so is about $50. So I was considering the bolt in 60mm or the bolt in NCY 61mm.

Xlint89 I have 13/40 internal gears too. How is the performance after all the parts upgrade with those gears?

Xlint89, you did not feel the need to go with the 30mm carb set with big bore and stroke?

Xlint89

Where did you buy the NCY Nakasil plated cylinder? I have looked all over and did not find it.

I've got the same kit on mine. The 59 bolt on kit. I went with the A12 cam. Say it's good for both top end and torque. Just make sure you check everything out of the box. First Cam I got from them the bearings was locked up. So had to send me a new one. Also the free spark plug that came with the kit, was shot. So if do go with them, Check out everything, right out of the box.

With the kit, not huge change. I think I got some more torque out of it. Biggest notice for me, was changing the Rollers. And upgrading the intake. Think Exhaust helped also. Not sure if gave more power, but sounded a hell of a lot better. ;)

tkeagle

I can see it would not add too much power increase on the 59 but probably added some extra compression.

Where or who did you get your kit from?

I believe it was Jmansrocket who stated not to go with the 60-61mm drop in.Now I'll reinforce that statement today. Do not go with a drop in any larger than 58.5mm. The 58.5 is nothing but a bored out 57.4 stock cylinder. Any larger than 58.5 the case needs to be bored out to fit the larger OD diameter cylinder sleeve. I know a dealer who once sold the 61mm drop in cylinders. Everyone he had sold failed. The reason is simple. A stock cylinder can be bored safely to 58.5mm any more and the sleeve is too thin. To achieve a 61mm or larger cylinder the sleeve needs to be a larger diameter OD in order to have enough metal to handle the constant forces of piston to wall. What the Chinese have done is to take a 61mm cylinder and to make it a drop in machine material off the bottom of sleeve that protrudes the cylinder. This leave too thin of material at the critical point where the piston transitions from down to up. It is this point that the piston creates sidewall pressure against the bottom of the sleeve. It will eventually crack the sleeve and most times at high rpm's forcing the piston up sideways destroying crank, cylinder, case and head. A big bore kit alone will not give you any more power. Your power 90% will be made from the head and camshaft. A Quality performance head properly ported along with a performance camshaft will give you the most bang for your buck. Only after your head and cam have been upgraded will a big bore kit make any difference. The good quality performance parts for these buggies cost a fraction of what it would cost for any of the popular Jap brands. If your on a budget than save until you have the funds to do it correctly otherwise you will have wasted money on a short lived project leaving you disappointed and with no ride to enjoy. There are only 2 ways to do something, the correct way or the cheap way.

1. Performance is good. Accelerates quite nice with a top speed around 40 MPH with my sprocket choice and tires.

2. No need for the larger carb. 28mm Mikuni is plenty for my liking.

3. PM sent. (out of respect for the vendors/donors to the site, I don't advertise other businesses that don't support it)

SYCARMS

Wow! Great feedback.

What is considered to be a PERFORMANCE camshaft? I see alot of them out there but have no idea how to distinguish.

Do you have any links to some good info on porting and polishing a gy6? I looked and did not find much.

Do you think I should still consider the stroker 2.2-3mm?
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xlint89

Thank you for the info.

same place Ebay. If you got stock heads on it, you can notice the difference in the port sizes, from the stock, to the higher performance. As stated, what torque I think I might have got, could have been the better cam.

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Give me a call sometime 662-301-1563 or e-mail me your # with a good time to call.

Moving to the next step with buggy. I bought a 62mm NCY ceramic coated cylinder.
I know I can not have it all but want all around performance. Need to climb some hills and still have good top end as I drive the buggy on the street and long back roads.

I found I have 13/40 internal gears. Any suggestions or is this good?

I am leaning to do the 3mm stroker, good idea?

30mm carb with ncy 30mm intake, what do you think?

Definitely considering an oil cooler now.

Was thinking of 11rollers. Is this good for my needs? Slider better? What size?

Clutch springs.... Was told to use 1500 on the big spring and 2000 on the small springs. Whatcha think?

Thanks guys.