cam timing after cylinder head replcement?

simonsGSA

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I now have my engine back together after my valve dropping incident (right hand side)... It turned over nice and easily by hand, then on the starter motor with no plugs in. However, once i put the plugs in and tried to start it, it seems as if either the battery is flat, possible but would be odd as its been OK up to now. Or the cam timing is out.

I didn't lock the engine at TDC when I replaced the head, I did set it to TDC on reassembly and could see the cam sprocket mark in the correct position but whilst the battery charges I wonder if the cylinder was at TDC on the exhaust stroke which would upset the timing somewhat! Is there a way I can check this?
 
Check the valves. One side should be on compression, so there should be a clearance under each valve lever. At the same time, the other side should be ending exhaust and starting intake, so both valves will be slightly open (on crossover).
 
Thanks. I though it was something like that but couldn't remember. I will leave the battery charging overnight and see if it starts then pop the rocker covers off again if it doesn't.
 
Batteries can self-discharge quickly if they get old and the plates get sulphated, my old battery lasted 5 years then lost charge rapidly if not used every few days, a motobatt replacement solved this problem cheaply and reliably.

If it is the battery (quite likely) then I doubt it is long for this world.
 
Battery. I rebuilt the front head on my Hardly Driveable and did exactly the same checks as you but still no start, a new battery installed and it started straight away. If it turns over by hand without issue I don't think you can do it any harm, but checking again while waiting for the battery won't harm either.
 
Battery. I rebuilt the front head on my Hardly Driveable and did exactly the same checks as you but still no start, a new battery installed and it started straight away. If it turns over by hand without issue I don't think you can do it any harm, but checking again while waiting for the battery won't harm either.


Exactly what i was going to say, but couldnt get the words right without it sounding all doom and gloom ;)
 
Think I have solved it, pretty sure its cam timing. Does the camshaft sprocket have a little lug to locate into the camshaft? Mine seems to have a shiny bit where a lug might have once lived.... Seems unlikely it would just rely on the friction to drive the camshaft?
 
Go to the OEM parts list and have a look.....Doesn't look like there's any lug. Find out, before you give yourself any more work. :thumby:
 
looks like there is a lug.... http://ebayapi.loc8apartltd.netdna-cdn.com/00/s/NzY4WDEwMjQ=/z/ncMAAMXQVT9SzY1F/$_1.JPG
 
If that is the case, you need to go deeper before you attmpt to run the engine.

that loose chunk could do a lot of damage :(
 
I was thinking that... Think I will drop the oil out and see if i can see any evidence of it.
 
My 2010 bike has nothing locating the camshaft sprockets on the camshaft, except the clamping force when the screw is tightened. Can't remember if tapered or not, think not.
 
Checked REPROM, Cam sprockets turn freely on the camshafts when the securing bolt is slackened.
 
Looking at Reprom,

it clearly shows there should be a lug on the sprocket (cant work out which though) which snaps into the crankshaft
 
My comments refer to twin-cam bike....maybe not correct choice. If single cam, you are of course correct, there is a lug.
 
My comments refer to twin-cam bike....maybe not correct choice. If single cam, you are of course correct, there is a lug.

It's odd, ive just had another look,

the sprocket is only fixed by a single bolt through the centre, the lug, would appear to be a crude alignment / semi locating feature.

My guess is when the valve has dropped the cam has locked, and the camchain has contunued to spin, and sheared the lug off,

(prehaps its a sacrifical feature, to prevent other damage?)

either way, if there was a lug it needs to be found

Unless it has dropped, it should be still in the female half of the camshaft - the op might be lucky and can recover it from there :)
 
That's exactly right, its a little pip on the back of the gear that locates in the camshaft. I drained the oil into a clean plastic pan and trawled it with a magnet... no luck... I peered into the cam chain tunnel with a torch, lo-and-behold there it sat! my trusty magnet on a stick extracted it and it seems to match with the missing part.

I did consider a blob of weld and some filing on the back of the old sprocket but that's a lot of faff for something that cost less than £10!

Whats odd is that i found it in the NEW cylinder... I wonder if it was lodged in the camshaft end, or was stuck to the chain and i didn't notice? Or maybe it had been weakened and fell off when I put it all back together? I am sure it was there on the cam gear when i put it back together but not sure enough to bet my house on it! Either way i think I have all the bits now. it all turns over by hand nice and easily. As soon as I get some nice new clean oil and a filter i will pop the plugs back in, cross everything and fire it up...
 
Simon, Pay £12 and join - we've just saved you that in help ;)


and we can send you pm's too ;)
 
It would have sheared off in the end of the camshaft and sat there probably held in under residual oil surface tension until disturbed.
 


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