Adjusted camchain...locked motor

[Thunderdome74]

So I finally have this bike running very nicely.
One of the last things I wanted to do was adjust the cam chains as there was a slight chain type noise.

Went according to manual and adjusted the front with the engine on.
Went to do the rear and turned the bike off as it was a bit hot.
Loosened the bolt ( in my case it is just a domed nut?) About 100 degrees.
And went to start the engine with intention of snugging it up.

The starter clicked.

I have taken the rhs cover off and rotated on the crank and can get about 90 degrees turn back and forth on the spanner.
There areally definite chain noises coming from the engine.

Guys... what have I done?what are my next steps.
Any help would be apprecited.

I havnt even ridden this thing much.

[daves79x]

If the rear nut is still attached by some thread, then you didn't lose the tensioner bolt, but you really can't do that anyway even with the nut completely off. You should pull all of the plugs to be sure you don't have a cylinder full of fuel that's locking you up. Then you could try removing the starter and turning over by hand just to make sure something there isn't locking you up, but I doubt it. Then you are down to pulling the cam cover and trying to see what happened. If it has to do with the cam chains, something will be evident there. Sorry, can't remember from your other posts, but has this engine been apart recently?

Dave

[Thunderdome74]

Dave thank you so much for the reply.
Much appreciated.as fair as I know it hasnt been opened... but in 38 years...
Alk the bolts look new but it has 67000 km on the odo.
I can turn the engine 90 degrees via the crank before lock. And vise versa. There is a clicking noise down by the crank... similar to teeth jumping.(I am currenly pulling the tappet cover off to see) I will keep you updated

[Thunderdome74]

Right, so i have tilted the engine down and taken the tappet cover off.
Both Chains move when i turn the crank.
Cams look pristine (absolutly no scratches etc)
(in actual fact the whole thing looks amazing, )I will post a pic but i started getting dark so i packed up.

What i assume is the cam chain tesioner is sitting in the middle of the chains and clicks (rapid back and forth movement )when i turn the crank (still only 90 deg)

Is it possible that the dome nut could have sheared the bolt from the tensioner?

Any thoughts are very helpful as i will be giving it a more thorough going over tommorro.
Will pos a pic shortly

Thanks
Thor

[daves79x]

You need to study and understand what you are looking at. There are obviously 2 completely different tensioners. The horizontal one is for the cam-to-cam chain and adjusts with the front tensioner bolt. Loosen the front bolt again and push down on the tensioner. Does it move freely and come back easily to a tensioned position? Is the top rubbing block intact? Then move to the rear tensioner. It's the one with the acorn nut adjuster. All you can see is the end of the tensioner sticking straight up near the rear of the cam chain passage. Loosen the acorn nut and see if you can move the rear tensioner up and down when grasping the top end with a pair of pliers. It snaps down to tension the chain. Pulling up relaxes the tension. Shine a light into the chain tower when doing this and try to turn the engine over as well. It is hard to see anything down there, but look for at least loose parts floating around.

If that shows nothing to you, then drop the oil pan and see if there are chunks of chain tensioner in the sump. If there are, then the top end has to come off, at least.

You are sure you don't have a cylinder full of gas, since I see where that happened previously when you first got the bike?

Dave

[Thunderdome74]

Hi Dave , thanks for the help

Yeah, no gas.I switch off the tap religiously now, also i immediatly took the plugs out as an "in case" situation.

It is the rear tensioner.
Whilst going through the 90 deg turn availible to me the tensioner snaps/clicks.(rear)
I fear i might have sheared the bolt with the acorn (it might have been partway done for me) as it was extremely tight.

I will follow your advice tommorrow and report back.

Thanks very much
Thor

[daves79x]

The rear tensioner can be changed by just pulling the head. If a part broke off, it can very easily get lodged in the crank gear driving the cam chain. Are you up for pulling the head?

Dave

[Thunderdome74]

Thanks Dave

Not sure at all about the CBX's (done a sohc, but these bikes ... a different ballgame)
A mate of mine will help me (he has had bike shop,and has a soft spot for the old hondas) i just want to learn/do everything i can before tking it to him.

Tommorrow will tell more, but i am thinking new rear tensioner?
Front?
Valave stem seals
Head gasket

Then when its in his shop, measure bores (out of round/wear limit)
Possibly new pistons>?

Anything else i shoudl look at/renew while the head is off?

Thanks
Thor

[Thunderdome74]

So today i had the tappet cover off and checked it turns at the cran .

Yes it does both chains.

I will explain what i think has occured and perhaps you can tell me if it's possible?

The manual stated loosen locknut (with engine running).
I didn't do this as the engine was hot (burning my hand) so i loosened it with the engine off.
When i tried to start it the chain jumped off the lower crank and before firing it locked piston and valve?
(Due to the loosened tensioner)

Today when i turned the engine backward the tensioner seemed to "snap" (almost as if the chain was jumping causing the tensioner to vibrate)
I turned the engine back 3 "snaps" and retightened the locknut

Lo and beholed the engine now turns forewad 360 without locking at any point.

Is the above situation possible? A couple of mates think it's unikely even with a loose tensioner but i can't think of any other way the above could happen.

It has 67000, so i am taking the head off regardless(it has a weep anyhow).

I have bought an entire gasket set (David silver)
A new cruzin image set of rings

I am only taking the head off when the above parts arrive (hopefully in the next 3 months) i just thought i would ask about the possibility of the chain jumping?

Thor

[daves79x]

First - what did you find in the sump? Should tell you a lot and if anything let go. I suppose your scenario is possible, not sure what happened to the rear tensioner to do that. I'd just proceed and document every step and ask if anything seems incorrect.

Dave

[Thunderdome74]

Dave, thanks for all the help. i undoubtedly will ask some more questions when i get a bit further into the engine.

Thor