Is this for real?

[James England]

I thought big bore kits were expensive??

http://www.ebay.co.uk/itm/80-81-Yama...item3cdb848b39

[jetmechmarty]

I thought big bore kits were expensive??

http://www.ebay.co.uk/itm/80-81-Yama...item3cdb848b39

Ships from Japan, but no information as to what it is. I believe I would avoid it. It could be a good deal if they said it was old stock, but I going to assume it's just cheap junk based on the lack of information.

[rdmcguy]

Big bore kit

I tried to gain more info on these kits with limited results.
I know that they are cast not forged which I believe are the same as our stock ones.
Nothing conclusive as to our 1100's however they also offer kits for misc. other machines .
The info I was able to glean was that they were slightly less tall (1 mm)
than a stock piston and there had been a small discrepancy in weight between one piston and the next.
These were exchanged by the supplier and were installed in the bike(kaw..h1/h2)and no problems had developed in a few hundred miles.
I have not attempted to discover further info .
I was hopeful that someone here might be brave enough to attempt their installation
kind of a pricey chancy proposition. Maybe we should do some kind of a group
thing where we take a tired old engine .fit it with these ...see what happens..
I would contribute some parts or money

[TopCatGr58]

Hey Marty/James,

Where you guys been?? This appears to be the same "inexpensive" kit that is sold on the USA ebay as well, and VIPER Ron already did this, he got it and installed it on his Standard, and rode it to XS Southeast and back home. He says it's been doing great, no real big improvement in POWER as we know that doing this is more for refreshing a worn out of spec engine, not so much for any real added boost of power!

T.C.

[James England]

Oops.... Didn't realise it was the same one.... It's definitely inexpensive though..well certainly for here, where a small bike single piston can cost $40. Even a head gasket is expensive...

[ViperRon]

Works great James it does deliver a little more power and definately I am glad I did it. The pistons in this kIt are the exact same as the original Yamaha except there is a slight relief in the top diameter of the piston. I think they did this to improve ring preasure. I have the jetting right now for the bike and gas milage is 41 at 75 mph running a little rich. Since I replaced the main bearing seals and can really guage things with oil there is no usage. I can measure. 2 things I do suggest is to get a good shop to do the cylinder bore. Make sure to leave at least a .0018 piston gap. Get a high amp AGM battery because when it is warm the compression is really high and you will not start it with a standard battery. Stone cold mine is in the 170psi range.

Because the rings are really tight I used a different method to instal pistons. I put pistons in cylinder assembly on bench. The inside wrist pin clip installed. Push the 2 and 3 pistons down till the wrist pin just has enough space to slide in and align with rod. Put in wrist pin and outside clips. Then follow the same procedure with pistons 1 and 4. Its much easier and less chance of snapping a ring.


Although this kit works great you can get a Weisco kit and spend 500 or more on it if you want the name and you are made of money.