180cc Big Bore Kit By heruk (Read 2,881 times)

[heruk]

Looking at this Big bore kit and have a couple of questions about it

1 What is bottom end boring?

and 2 how will i know if i need it done?

[cyborg]

In a nutshell it means the bore is bigger than the hole in the crankcase so the engine needs to be disassembled and cut to the correct size so the new cylinder will slip in

[Alleyoop]

Just an F.Y.I it is a 61mm BBK so the displacement is 169ccs NOT 180ccs. They love to round things up a lot to make them look really good.
Alleyoop

[heruk]

gosh!
So my 157qmb will need to be bored if i get this?

[jct842]

Most of the big bore engines do not last long so you know. Alley has one of the few done right, and professionally that has lasted. That gy6 engine in your scooter was designed as a 110cc as I recall so punching it up to 169cc's puts a whole lot of extra stress on the lower end of engine and makes a lot more heat that you need to get rid of if your engine is going to survive. If the chinese could be assured of some sort of reliability you know they would be selling big bore factory engines in all their scooters. They could bump up the size for very little extra cost but they keep selling the 150's because they are a lot more trouble free.

[fugaziiv]

Just for reference, a no bore 180 (63mm) kit usually looks more like this. Also, these tend to be more reliable than the kits that require you to bore the bottom end, as many of the parts are beefed up. The cost of the kit reflects this, and its Taiwanese quality as well. We use this kit in our GY6 drag racing scooter.


Matt

[cyborg]

You know I'm gonna have to build one of those don't you?

[kevinharrell]

Here is a 61mm kit that does not need boring.

www.uniquegy6.ecrater.com/p/20240666/ncy-bolt-on-61mm-cylinder-kitlink

[fugaziiv]

Sept 8, 2014 14:12:05 GMT -6 cyborg said:

You know I'm gonna have to build one of those don't you?

Well, that's kind of the idea.


Matt

[rapidjim]

Sept 8, 2014 9:32:26 GMT -6 fugaziiv said:

Just for reference, a no bore 180 (63mm) kit usually looks more like this. Also, these tend to be more reliable than the kits that require you to bore the bottom end, as many of the parts are beefed up. The cost of the kit reflects this, and its Taiwanese quality as well. We use this kit in our GY6 drag racing scooter.


Matt

Nice kit indeed. What crank did you use?

When I did Alleys motor he had elected to go with a stroker crank and bore the cases. I have an excellent machinist here in town that matched bored the case to the jug and made sure it was a tight perfect fit. That is the key. I have seen where folks use a dremel tool to open the case size, OMG that is not smart and that is where they have issues. I have also seen the hand tool to bore the cases, I have not ordered one yet to see just how good a job it does.

The kit you sell is the way to go if you don't have a good machinist to do the bore work.

[fugaziiv]

Jim,

Actually, for the drag bike we decided to use a stock crank for our most recent build. It worked very well and held up nicely to the N02 that we were pushing all day. In a previous build we ran a +2.5mm stroker that works nicely with this kit in a NA application; It brings the kit up to 187cc. We found that the smaller lighter stock crank is a bit faster in the NO2 powered drag bike, whereas in a street bike the added tq from the stroker is pretty awesome.

The other nice thing about this kit is that it is a true GY6 "big block" kit, and therefore it moves everything out a bit, and there is quite a bit of locked up power still in it for someone with the skills to bore it our further and to make use of it.


Matt

[dmartin95]

Sept 10, 2014 9:03:44 GMT -6 fugaziiv said:

Jim,

Actually, for the drag bike we decided to use a stock crank for our most recent build. It worked very well and held up nicely to the N02 that we were pushing all day. In a previous build we ran a +2.5mm stroker that works nicely with this kit in a NA application; It brings the kit up to 187cc. We found that the smaller lighter stock crank is a bit faster in the NO2 powered drag bike, whereas in a street bike the added tq from the stroker is pretty awesome.

The other nice thing about this kit is that it is a true GY6 "big block" kit, and therefore it moves everything out a bit, and there is quite a bit of locked up power still in it for someone with the skills to bore it our further and to make use of it.


Matt

What size carb did you use with build?

Also, what other upgrades did you do? CVT / GEARS / Clutch? 

[cyborg]

Who is doing the balancing?,,,, and what kind of numbers are you getting out of the mill?? 30-35? And are you running 1/8th or 1/4 mile?

[cyborg]

Sorry to pepper you with questions Matt,,, you runnin a 2 valve head or 4?,,what kind of piston are you runnin?forged or cast?,,,i got a million more but i don't want to completely swamp you,,,lol

[tvnacman]

Sept 7, 2014 22:12:09 GMT -6 heruk said:

Looking at this Big bore kit and have a couple of questions about it

1 What is bottom end boring?

and 2 how will i know if i need it done?

the link above does not work , but will start to work later when the kits get here and pass QC . When I sold 3pcs local last week I ordered more . When the item is at zero it takes it off line .

John