To cut a long story short my race engine has worn bores. The only possible cure is 1mm over sized pistons and a re-bore to cure the 8 to 10% loss on every cylinder which is costing me some much needed horsepower!

If anyone has a set collecting dust i would be very greatful if i could take them off your hands! Rings would also be good but not the end of the world.

I could also do with a spare crank to have lightend/balanced.

Fingers crossed!!!

if the crank is the same as the 3en1 then i think i have one!

Answers on a post card................

KIYOSHI wrote:Answers on a post card................

Hi Kiyoshi, Can you send me the same post card ?

No one has sent me it yet

Ok, I totally dont get this whole thread

Is there any where we can get a set of 1mm oversize pistons off the shelf !
Cant afford the $100000 to have them made special?

Buzzawak - do you need to rebore your engine ???

buzzawak wrote:Ok, I totally dont get this whole thread

Is there any where we can get a set of 1mm oversize pistons off the shelf !
Cant afford the $100000 to have them made special?

Yamaha still supply them for the 3TJ, I got a set last year. When I get home I will dig out the part number. I have a FZR400rrsp parts list and that gives the number for standard, +0.5 and +1mm pistons and rings.

Evilchicken0 wrote:Buzzawak - do you need to rebore your engine ???

Hi Evil,
Well Yes, but no but yes but maybe, I don’t know. I need to buy a compression gauge. Funny thing is I sold my German made gauge a few months back thinking I haven’t used it for years and wouldn't need it.

The bike is pulling ok and doesn't blow any smoke, but the top end is noisy. I think maybe most likely its coming from the cam chain or worn rings. I intend dropping the engine out in a month or so and figure I will do a top-end rebuild.

I have considered sticking in a 600 but our vehicle laws require a engineer certification for any modification of that type and it’s not cheap. It will also hike up the registration costs and insurance will be impossible.

I like the idea of the 560 modification which I am gathering information about.

The 1mm overbore is the most expensive way to do this as you'll need new pistons from Yamaha.
I was thinking the 560 mod would work well ... of course I won't tell anybody you've done it as long as you don't. You'll need the 3HE 600 engine (Yours is a 1WG 3en1 isn't it?) and you build the top end barrels and pistons onto the 400's gearbox crank and conrods. You'll need gaskets, it would be best to give the bores a hone and have a look at the rings.

It's more likely the cam chain ... or the tensioner's got stuck.