Help! I may lose it.

[Slimted]

Fitted new barrel. pistons and head. Triple checked timing.
Put the rest of it together. Can I get it to start? Can I f#ck!
What is most common mistake a hobby spanner monkey like me gets wrong?

[Skippernick]

did you take the tank off?
did yo turn it off or kink the fuel pipe putting back on?

[Gnasher]

Fitted new barrel. pistons and head. Triple checked timing.
Put the rest of it together. Can I get it to start? Can I f#ck!
What is most common mistake a hobby spanner monkey like me gets wrong?

What bike/engine and what was the problem in the first place ect?

[Major Rant]

What is most common mistake a hobby spanner monkey like me gets wrong?

 
They don't go through the logical fault-finding steps that help to identify problems.   
 
The simple ones are:
Does it turn over?
Is there compression?
Is there fuel?
Is there air?
Does it spark?
Are the plug leads on the right plugs?
 
Then theres :
Is it sparking at the right time?
Is the fuel very old?
Does it fire at all ?
 
If there's good fuel, air and its sparking at the right time then its got to at least attempt to run, surely!

[sjdfzs]

if its the fzs you might have the timing 180* out. you can check swapping the wires over between the coils
so the wires that power the left hand coil put on the right hand coil and same from right to left

[sjdfzs]

the timing will look spot on if it is 180 out

[limax2]

What is most common mistake a hobby spanner monkey like me gets wrong?

Accidentally having knocked the kill switch into the off position  .
Or is that just wishfull thinking on my part.

[Slimted]

Thanks all, a few things to look for. Not gonna get a chance to check till Saturday. I am feeling more positive though, thanks!

[scottyboy2203]

i refitted my head and cam chain etc recently, checked everything over as per the 'book' but when pressing the starter nothing would happen. Turns out the timing was off by a couple of teeth making the whole thing impossible to turn over! moral? check the cam timing is spot on

[Slimted]

Checked timing again.... I am sure I am right ( I think), if it was 180 out the dots would'nt line up when crank is at tdc, would they?
 
I may have to give up and let the pros do it. Cant be with out the bike much longer!
 
 

[Deefer666]

Slimted, where in Berkshire are you? I will be in Newbury at some point over xmas to visit the family

Is it turning over but not firing or is it not turning? I will happily take a look at it as not wanting to blow my own trumpet but I have probably rebuilt more FZS engines than anyone on this board.

Deefer

[sjdfzs]

theres 4 strokes 2 up and 2 down if the timing is 180 out the marks could line up but the cam would be on say 1 of the down strokes but the crank on the other down stroke, so the valves clear the pistons as the timing between them is right but the ignition is wrong
http://minhazchhiboo.blogspot.com/2011/04/how-four-stroke-engine-works.html
either try swapping the wires over, just to test
to correct it you would need to disconnect the cam chain from the cam and turn the cranks 360 and line up the timing marks again and try again

it sounds a lot harder than it is

[Slimted]

I gave up in the end..... I have taken bike into Slocombes in Neasden, London. No news yet. Thanks to all advice and offers of help. I have been on a steep learning curve with the 4 cylinder Yamaha. The last bike I rebuilt was a xr250 honda (the first was a 2 stroke Garreli 50 many moons ago!)it was much simpler in those days. Tool collection and knowledge has grown a bit......for the next time! I will report diagnosis from Steve at Slocombes.

[Slimted]

ARRRRHHHH Feck! Turns out some of the shims had become unseated and valves were not closing properly.
No compression, no start, loads of grief! Thanks to Steve Slocombes!!