New head gasket blowing and lumpy as hell ...

[madoc]

Ok.

I done the strip enough to get a good look inside:

http://www.sohc.co.uk/index.php/topic,4615.15.html

I could not find where that piece has come from. It's conceivable that the damage was already fixed as it looks like some bits have been apart before.
I changed the camchain, re-ringed (the rings were about .4/.45mm) and honed the bores as they were ok.
All the valves came out for grinding and non-bent ones went back where required.
I found an OEM gasket kit at an autoumble for a tenner. In it's original sealed bag.

Took a while to fire up but immediately the head gasket was blowing everywhere and then settled down to a very small blow at the front only (and I mean tiny). I torqued it all down in the order, and to the numbers, in the book and even waited 48 hours and did it again. I am thinking a 20 year old head gaskets might not have been the best idea.
More worrying is that the engine however sounds sick. Really sick. I guess the blow is upsetting compression but I can check that with my tester at some point.
It has the original exhaust (4-1) and it's now leaking badly where it joins the silencer, in one rusty lump, which isn't helping. Not sure this fixable as it's tough to get in there with sealant or the welder.
It will hold an idle but it won't rev at all.
On the plus side, I cannot hear the camchain now 

I am thinking that I could lift the rocker and re-torque or am I kidding myself and I need to take it all apart AGAIN and do the whole top end AGAIN.
I am also thinking that it could be a misfire or carb synch causing the lumpy running  ...

For the amount of time and money, so far, I could have completely built three old british bikes from scratch.

[hairygit]

It's possible that the cam timing could be out by a tooth, that would let it idle but not rev properly, also the head gasket may well have been damaged by even a short period of running whilst blowing. Did you make absolutely certain that all the studs and dowels were clean and had no sign of binding? and the gasket face of the head was not damaged/warped?  Sadly, if the gasket is still blowing, no amount of tightening is going to stop it, all that will happen is things will distort, or may even rip a stud out of the crankcases ( to be avoided at all costs!) In your position, I would take the top end off again after checking the cam timing, but it looks like a new head gasket will be needed (I don't think age of the gasket has any bearing on this problem) I know it's disheartening, but I really cant see any other satisfactory solution Look on the bright side, at least you can leave the engine in the frame unlike those of us with 750s

[madoc]

I thought I was 100% certain on the cam timing.
I lined it all up and drew a little picture before taking it off and matched the manual and picture on putting it back together.
I also thought I had removed all dirt as there were no gasket traces and I was almost polishing with meths ..

everything went together fairly cleanly although the barrels were an utter faff, even with three of us.

I'll do a compression check, balance the carbs, check for a misfire, try and seal the exhaust and then I'll curse and dismantle it all again.

[Bryanj]

Did all the head nuts spin freely and did you have the proper thick washers under the nuts?

Also are you sure it's the head gasket leaking and not one of the exhaust port gaskets

[kendo57]

Could the silencer have blocked causing back pressure and blowing the head gasket.
Just seems strange the head gasket and exhaust have both blown.

[madoc]

Here is the camshaft alignment vs points alignment.

There are two lines against the F mark.
I am matched against the first one.
Moving the engine a few degrees brings up the second ..

Is this correct ?

I cannot seem to be able to release any tension on the camchain to walk a link around the sprocket to see what effect that has.... no amount of fiddling on the adjuster does anything. The chain is really tight.
It took me hours to get the sprocket off/on the other week.

[mickwinf]

 as above cam is in correct position but you should have the T mark aligned so you are probably a tooth out.to get some slack back off the adjuster, if it is a new chain you may have to unbolt the cam sprocket to get the slack.

[madoc]

You cannot see the F marks, in my original picture, they are  out of sight to the right.

I found a picture on t'internet (to save me going back out and trying to get all the marks in)

Just to clarify, are you saying that of these two "T" marks, the one I am lined to is NOT the one I need and the one (you can see in the picture just to the left) is the actual TDC mark ?

[Bryanj]

You need the mark that the arrow IS NOT pointing at (Marks in order turning clockwise are 2 advance marks then the Firing F then the TDC T) and to release the tensioner loosen the locknut then carefully insert finger or screwdriver to push the blade to the back and whilst holding there re-tighten locknut.

Even when in this position you will not be able to walk the chain without unbolting the sprocket from the cam and letting it off the register it sits on

[madoc]

Ok
Finally had a few hours today.
Re-torqued the head, re-aligned the camshaft as instructed (and triple-checked it), helicoiled a stripped thread, refitted rockercover, carbs back on correctly (I bought some more hoseclippy things as they had cable -ties between carb and airbox).

Started bike and it sounds even worse. Much worse. Won't even idle now.

To be fair, the bloody ignition switch seems to let me take the key out and stay on.
It had a flat battery and I may have cooked a coil. I'll check the resistance across them.

I had a search for a youtube clip of a honda SOHC four, running on two, but couldn't find one.
Having only british singles and russian twins then I don't know what a jap four sounds like on two ....

[matthewmosse]

In a word the sound of a sohc 550 running on 2 is rough. I didn't video it but I did g
et several miles home with a snapped camshaft once with a sidecar and passenger. It was hesitant to rev under load and spat and backfired a lot.

[Bryanj]

If you have used ordinary jubilee clips there will be an air leak! The honda ones are narow and are the only type that seal properly

[madoc]

If you have used ordinary jubilee clips there will be an air leak! The honda ones are narow and are the only type that seal properly

Oh bum
Are these the £4 each parts from David Silver ...
A couple of rubbers are not great (and not cheap) - is there another source ...

An update is that I have the bike revving but its still not quite right.
I'll own up to not tightening an exhaust rocker adjuster nut and was effectively running on three... I also had the breather jamming the carbs ...opps

I can see u are in Gloucester. I am in Lea (between gloucester and Ross). Small world.

[Bryanj]

I thought thr carb to head rubbers were quite a reasonable price and yes the clips you need are the £4 each fron DS or possibly i have seen stainless ones from specialists but not sure where

[madoc]

it's the carb to airbox rubbers, where they are not the best, and now fastened with jubilee clips.