Help im stuck :(

[quinny-fzr4003tj]

Founddd it :) went past it like 6 bloody time really need to print this out haha :)

[MarkT]

Yes get the manual ! But generally you start from the centre and go around like a clock loosening bit by bit until they can be removed by hand.

If you warp the head not my fault lol...

[Hogdigerdy Dog]

shite copy i know
but if you full screen it you can see the order to undo the head bolts

[quinny-fzr4003tj]

Cheers guys! All cleaned up now no real problems gasket set on order valves re lapped everything de coked only thing i fancy doing is replacing the rings does anyone know where i can get standard ones? Can only find oversized sets.... one thing to mention though all the conrods move easy but n#4 is just that little bit stiffer should i look into this?

[MarkT]

This confuses me (easy done!!!) I still don't get why you would only get 25 compression across all four and it was running ok the night before? I would have expected one or two exhaust valves burnt out and possible blown parts through the head gasket?
If the valves are now ok just with grinding them in then this only leaves rings pistons and bores? Is there a ridge in the top of the bores and are the pistons showing scorch marks town their skirts?

I would imagine that rings only are available from Japan if still made!

I don't know what you want from the bike in the future? Whether to keep it or sell it?

Personally I would be keeping and getting the bores done with new pistons and rings as you have done so much now. As for the con rods they should all move freely and have no play in the vertical plane. Yes I would look at it and check big end shells. This again depends on what you want to do with it.

In my past days working on engines I have never come across a bike with compressions like yours, even Kawasaki gt 550 that was over 100,000 miles!! With compressions as low as yours it should have been obvious when the head come off.

Sorry if I seem negative as I don't want to be and believe me if I could wave a magic wand and have it all fixed for you!! But something is not making sense here?

You did check the valve timing when you were taking it apart didn't you as the compression figures across all four cylinders really don't make sense?

I won't bore you with what I would do next as I have made this post long enough already but I really want to help you get it on the road!!!
Regards
Mark

[quinny-fzr4003tj]

i was expecting exactly the same! i was shocked when it all looked ok, even the gasket wasnt to bad the paint had worn slightly but there were no burn marks or blow outs the barrels and side skirts are all free from any scorch marks / scratches i even checked for cracks in the ehad as best i could seems solid, gona measure it tonight to see if its warped atall, im as baffeled as you ... that doesnt take much either though :D

there is a complete sp head on ebay, but i cant justify buying it if i cant find a problem haha :) might wait for another engine to come up aswell kinda fancying the tcat lump though

the bike wont be sold fixed or not, its winter anyway so i'm enjoying tinkering around. even if i'm not the greatest at it :]

i can get more compression blowing through a straw probably

I found these, I havent checked if they are the same size as the tj yet though

http://www.cmsnl.com/yamaha-fzr400a-199 ... /A-10.html

[Evilchicken0]

You probably lost compression through the inlet valves - I think I'm right in thinking they're smaller than the exhaust's and they're lighter construction causes them to stretch, that's why the tollerances get smaller at the cams. They also dish so the contact point between the head and valve changes slightly and that maybe what happened here.

If you had problems starting before especially when the engines cold that can be a symptom but it can be the will start then not rev. Once the head warms up it expands sealing the vales better and the engine feels normal. Because this happens over a period of time you get usde to it, until one day it becomes more noticable.

You should be able to keep the rings if they're not worn (otherwise try a main dealer), just hone the barrels to take the shine off them. I'd look to get the head skimmed flat. I'm not sure but you should be able to get the big end open and have a look at the shell. but after that you should be good.
Changing the pistons is dubious it will hard to find a set unless you go for something like a big bore kit and then your looking at big dosh.

[quinny-fzr4003tj]

one of our local lads races for wilock consultants in metzler superstock & he did mentioned the possibility of valve stretch and you are correct with the inlet valves being smaller than the exhaust.......not supprised haha

the rings arent perished i just fancied changing them to help out i'll take the intake valves out again and i'll measure them i've borrowed my friends verniar calipers so i should know then :)

it was a bad starter in some respects it always started with no throttle either with or without choke but the button had to be help for a few more seconds than i felt it should...& it definately was alot better at starting warm like you said

thanks again for all your help so far guys i dont fancy missing anything bolting it back together and still no joy cause thats a full gasket set down the pan haha

[quinny-fzr4003tj]

engine will be back in the frame next week i hope :) just a case of timing now :) any tips? hope she fires

[Evilchicken0]

Should be fine.
Turn the engine over on the starter without the plugs in until the oil pressure light goes off, then start it up