Head rebuild problem

[Andy novice]

Hi,
I am a novice in the middle of putting the head back together after replacing the head gaskets.
Everything appears fine - when the engin is turned manually the pistons travel up and down in the cylinders until I attempt to Torq the head nuts.
When I apply ANY Torq more than finger tight to the nuts the engine will only turn a quarter turn and then is solid!
Can anyone tell me what I am doing wrong?

 

[dirtdigger]

Do you have the cams in the head?

 

[Andy novice]

No,
The pistons are in the cylinders and move fine until I start to Torq the head nuts.
I have tried to Torq them all to 15 ft/lbs, 20 and 26 ft/lbs but the same thing happens every time, I can turn the engine 1/4 turn but no more.
I can not understand why it is fine until I bolt it down as I can not think what changes by doing this.

 

[dirtdigger]

I guess I cant say for sure, without being able to see it in person its going to be hard to see what is happening. Maybe wrong head gasket? what else did you have apart?

 

[Andy novice]

just the head to replace the gaskets as I had a oil leak.
The bike had been stood for over 14 years and the previous owner had done enough it make it a runner and I have done about 200 miles on it before stripping it down.
When it jams it is like it is hitting something.

 

[dirtdigger]

is it possible the timing chain is getting bound up when you are trying to turn it over? Unless you have a wrong head gasket of a valve hung up or something in the chamber there is no reason for it to bind up tightening the studs. I would take the head back off and take a serious look at things again. Post some good pictures of everything if you want maybe can see something?

 

[Andy novice]

Thanks I will be taking it off again tonight. Not the timing chain,
I will take pics.

 

[Andy novice]

Hello again,
Took the head off last night. Gave it a good looking at. used an airline at 6 bar to blow out all the insides. Found nothing wrong that I could see so put it back together again. Once again it turned fine until I applied pressure to the head nuts. Even when I snug them down the engine locks solid. It is as if it is hitting something.
Next step, unless you can see an obvious mistake from the pics,

I am going to remove the rings and see if that makes any difference.

 

[Old_Crow]

The only thing I can think of that might do this is a valve that was open when it wasn't supposed to be. Maybe the cam chain jumped a tooth on the bottom sprocket during re-assembly?

 

[Bo82CB]

Agree with above, I can think of two reasons, one is wrong timing or piston to valve clearance is wrong (not enough).
Was the head sent to machine shop for any reason, if yes was it milled, what is thickness of the head gasket you are using now?

 

[Andy novice]

Thanks for the replies. As far as I know the head has not been machined but it may have been in the past.
I do not have the cams in place so correct me if I am wrong but it can not be to do with the valves?
I have gone though my bin and dug out the old gaskets. They are in bits from when I removed them but it may be that there were 2 on the top joint - one material and one metal, is this possible and would it make a difference? If so can you get different thickness or double up?

 

[Bo82CB]

My question was did you send head to machined shop? Sorry for not being clear about this. If in past head was at machined shop and bike ran before you took it apart, obviouslythat would not create new issue you are experiencing.
I don't know are different thicknes head gaskets available now, maybe long time ago when these bikes were raced, DO NOT double up head gasket or any gasket for that matter.
Double triple check your timing...

 

[Andy novice]

Thanks,
All I have done is strip the head and replace the gaskets and O ring seals, no machining

 

[Old_Crow]

Thanks for the replies. As far as I know the head has not been machined but it may have been in the past.
I do not have the cams in place so correct me if I am wrong but it can not be to do with the valves?
I have gone though my bin and dug out the old gaskets. They are in bits from when I removed them but it may be that there were 2 on the top joint - one material and one metal, is this possible and would it make a difference? If so can you get different thickness or double up?

Okay, I was assuming that you had the heads completely assembled. Without the cams, all valves should be closed, thus out of the way of the pistons. Not sure how much compression you'd build rolling the engine over with all the valves shut, but maybe you're hitting that compression and just thinking the motor is stuck? It's a head-scratcher for sure.

 

[Bo82CB]

I also assumed your head was complete when you installed it on the block.
Since you don't have cams in, are your spark plugs out of the head, reason for this question is due to all valves being close, compression has nowhere to go if plugs are in.

 

[dirtdigger]

Lets see some pics of bottom of cylinder head, new head gasket, base gasket and some of the good pieces of the old head gasket. There has to be an issue with gasket thickness or something like that. There is no way you are making the pistons tight in the bores just by tightening head bolts, cant happen. There has to be piston to head clearance issue of piston to valve issue.

 

[Bo82CB]

Good point, I am thinking ahead of myself, he is having issue just tightening the head down...SORRY!

 

[Andy novice]

Sorry for not posting I have been tied up working.
Pics of the old gaskets the green one looks as though it could be 2 gaskets stuck together with gasket sealant?
Any ideas?

 

[dirtdigger]

Do youhave a good caliper to accurately measure the old gasket thickness and the new gaskets?

 

[Andy novice]

Do youhave a good caliper to accurately measure the old gasket thickness and the new gaskets?

I have measured the base gaskets, old and new - new gasket 0.4mm but the old is 1.8mm