G1 big bore kits??

[mikeasis]

I now wonder about carb modifications or replacement. And a plowmans exhaust would be awesome

[mikeasis]

I did it, I took the plunge...

[TheNewGuy]

How does this compare to Plowman's kit?

[mikeasis]

I think plowmans kits are stock bore while this kit uses a larger piston from another Yamaha 2 stroke, and the ports are cleaned up to. Here is the comments in the listing.

We Thrive on 2 cycle performance, Recently we found that G1 Yamaha only has .25 (010) & .50 (.020) oversize pistons available for G1. With lots of Cast Iron in Cylinder left for more bores. Two years ago, I did 2 kits ( Big Bore) for Customers and there feedback was "it's got a whole lot more power" yes 30cc's more . So I'm doing more and saving some of these cylinders . We use a Genuine Yamaha piston (70mm) over the 68mm std. from another Yamaha Sports Vehicle. This makes .080 over (2mm) bore. Cylinder is aligned bored, honed , all ports are chaffered and 70mm piston is fitted, comes with Yamaha rings , pin , clips and upper end Gaskets, All work done by person w/48 years experience . Fits Yamaha G1 (only) 78-81 and 83-89 models. Does not fit 82 year. With Larger piston , you get a lot more power ,see picture 4 . Check my other listing. Ships U.S.A. only. Any Questions Oh yes we Buy Cores...

[raydhd]

Originally Posted by mikeasis

I did it, I took the plunge...

We will be waiting for report on the power increase. There have been some modded G1's here but nothing I've seen has been that extensive. Hoping to hear a BIG WOW!

[mikeasis]

Not really a big bore kit but he offers .040 over Harley/Columbia cylinders with porting.

https://www.ebay.com/itm/Columbia-Go...c233%7Ciid%3A1

[slonomo]

Really you could do the same thing yourself if you knew what piston he's using. Just take the piston and jug to your machine shop and they will bore it for you. I'm guessing the piston is from a dirt bike. A good hard look on the internet will give you the specs on piston sizes and wrist pin sizes.

I'm not doubting that it will run better with more power. But I doubt it will be "a whole lot more power". Going from 215cc to 245cc isn't that huge of a difference. Just an overbore with more compression isn't all that's needed for bigger power. Now this coupled with a Plowman's muffler and a larger carb would get the job done even better.

[mikeasis]

you know at first I was thinking how great this could be for the G1 owners. I know the enticer top end is a bolt on but it changes the power band of the engine so much. And its around 250cc. I admit Im no 2 stroke guy and the theory behind getting power from them gets pretty technical. I posted this on the G1 facebook page and some people there brought up some good points. I didn't even notice the new piston doesn't have ports, it looks to be cut on the bottom of the skirt and the kit comes with a shim that looks to go under the jug. I would assume the jug is then cut to match to some degree the cut made in the piston. I would assume all of this is also going to change the power band of the engine. someone asked why not cut the windows in the piston to match the g1 piston then clean up the porting from there which I would assume would not change the power band but help make more power within the stock range. Again Io no 2 stroke guru. My excitement may turn to disappointment.

Either way when the kit arrives Ill take some photos and still plan on testing this bad boy out.

[Field6565]

Let us know how it looks when you get it Mike. I'm always looking for ways to increase power. I have an Enticer top end swap on mine now with a Mikuni slide carb conversion and it rips but I'm always tinkering with it looking to improve performance. It would be nice to know what piston is being used. A YZ 250 would probably be a good guess.

[mikeasis]

Originally Posted by slonomo

Really you could do the same thing yourself if you knew what piston he's using. Just take the piston and jug to your machine shop and they will bore it for you. I'm guessing the piston is from a dirt bike. A good hard look on the internet will give you the specs on piston sizes and wrist pin sizes.

I'm not doubting that it will run better with more power. But I doubt it will be "a whole lot more power". Going from 215cc to 245cc isn't that huge of a difference. Just an overbore with more compression isn't all that's needed for bigger power. Now this coupled with a Plowman's muffler and a larger carb would get the job done even better.

Slonomo any recommendations on a bigger carb that would fit the stock intake or carb and intake replacement.