Has anyone checked ZXR400 valve dimensions,Very similar motor

No but will get on to it - does anyone have a service manual to save some leg work????

is there a way to work out from a part number what bike it was used on. I have a Kwak and its very easy to do from the "KIC" system. It would help a lot if its possible.

You can only really go by the model codes 3TJ, 3HE 3GM etc but once you have a part number you can do a websearch and see what comes up.

I think Yam part numbers tend to work like this-

XXX-YYYYY-ZZ(-ZZ)

XXX= the model code
YYYYY= what the part is (ie inlet valve, rear wheel, top yoke, whatever)
ZZ- issue number (ie 00 is usually the first version of that particular part, 01 might be a revised version of it or a differently handed version of it)

eg

The 3TJ chain slider/seal guard is 3TJ-22151-00 and the FZR1000 EXUP part is 3GM-22151-00. It's the same type of part (a chain slider) but is actually a completely different shape (because the model codes are different).

The 3TJ parts list suggests that the inlet and exhaust valves are unique to the 3TJ but Yam sometimes supersede old model codes with ones from newer bikes that use the same part- are the 1WG valves the same?

Better still - if it's the same part used on a different bike they can use the model code from the other bike - you get 3TJ part numbers coming up on different bikes like the FZR600R.
Adds a bit spice to a part search

Mang,the inlet valve;
3TJ-12111-00 has been superceded by;
3TJ-12111-01 and seems to be model specific.

A good comparison site (part number applications) may be found here;
http://www.boats.net/parts/detail/yamah ... 10-00.html

In this example it lists the valve guide which has numerous applications but there is no listing for the valve itself.(uncommon model in USA)

The best I can find is ;
http://www.cmsnl.com/products/3tj-12111 ... tj1211100/
and carraige from Holland will add considerably.
It does mean however that the part would be available from any UK Yamaha dealer (you would have to wait for the order to be processed from Yamaha Europe (Holland again) but without shipping charges.)

You will have to decide if new (known to be good) valves plus existing head reconditionining is preferrable to sourcing a good used head or engine.

It is more than probable that the previous owned faced this dilemma and attempted to modify existing valves or alternatives.

Hope this is of some small help.

Here are 4 new valves,if you have experience of Yahoo Japan;
http://yahoo.aleado.com/lot?auctionID=g121263619

So here is where I am at as of this evening.

Top end is fully dismantled - pistons, rings and bores are all in good order. Decoked pistons and cleaned up rings And checked they were in tolerance and reassembled. I think Evil suggested replacing the Gudgeon pins as a matter of course with a head rebuild. Does anyone have a way of defining if the Gudgeon pins are out of spec? If its best practice then I will of course replace them but I am interested to know.

Regarding the valves my local machine shop is working on them so I hope I don't need to buy the 8 I originally thought.

Thanks for your help every one.

I mean the retaining clips not the actual pins - sorry