Engine locking then unlocking, then locking...etc...

[MG#43]

Hi all, hope everyone is all good and looking forward to spring!

Got a weird one...weird to me anyways...

My engine and cams are out of my bike.

On turning the crank by hand it locks up after about 20 secs of sitting still. I then need apply alot more pressure using a wrench and it turns happily for as long as i wish to sit and turn it for. But if i stop it locks up again but oddly only after about 20 secs... After 1-20 secs it seems ok, but after this it's locked. It's like something is slowly returning to a position after these seconds where it gets stuck.

It did the same thing with the transmission removed so to me seems clear bottom end is damaged somehow but i can't explain why it will free up then lock again... As mentioned cams removed so timing and valves are not at fault in terms of the engine turning (my view).

Anyone dealt with something similar...?

Thanks!!

[Polarbear]

So all you are turning is the crank and pistons? Everything else is disconnected?
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Triumph Trophy Launch Edition

[Weisse Schlange]

Just sounds like overcoming the friction on the rings to me.
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Hing Oan

[MG#43]

[Nobby the Bastard]

Is the timing for the cams correct?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[stinkwheel]

And it's nothing to do with the oil pump?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MG#43]

[steve the grease]

Was this bike running , or is it a project. It sounds to me like you need to do a bit more stripping down , the barrels off at least, if its not just going tight because of ' sticktion' you need to find out exactly what is causing the problem , maybe the bore needs a quick hone, maybe one of the rings is gummed , maybe one of the bearings is jamming . Without a more thorough stripdown you will never know.
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All the above is my personal opinion, you can see my lips move, but I'm talking out of my arse.
I've been riding, and fixing , bikes for 50 years, in that time the more I learn, the less I am absolutely sure of.....

[MG#43]

[MarJay]

Sounds like it could be hydraulic lock. Maybe there is liquid petrol building up on the inlet valves, and turning the crank allows the petrol in, and then it seeps past the rings allowing you to turn it again? That's my first thought, could be nonsense, but it was nevertheless what popped into my head.

Sounds bad to me anyway.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[MG#43]

[sickpup]

If the cams are out what have you done with the cam chain?

What engine is it?

[MG#43]

[sickpup]

Have you removed the plugs?

[MG#43]

[A100man]

with no tension on the cam chain it 'could' be getting snagged up

I'd have that out too.. they're cheap enough to replace, then the head off.. then the barrels.. process of elimination it has to be right?
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[MG#43]

[steve the grease]

About the worst it could be is a roller bearing where one of the rollers has a flat on it and jams rather than turning, once turning it will carry on turning , yeah , it's unlikely , but it does happen.
You mention that it's pretty ' shagged', I think its likely that once the top end is off you will have a free running bottom end , if you don't and it's still stiff you've got problems.

My best bet is a plantpot shaped bore ( the classic wear pattern) and a jammed, broken or gummed ring(s). If that's the case don't use caustic ( oven cleaner aerosol) on aluminium it eats it. Boil the piston in a pan to free the rings off , then scrape all the crap off with scrapers , scissors, scrubber dubber pads, sharpened electrical screwdriver etc etc. Let us know how you get on.
____________________
All the above is my personal opinion, you can see my lips move, but I'm talking out of my arse.
I've been riding, and fixing , bikes for 50 years, in that time the more I learn, the less I am absolutely sure of.....

[Lone-Wolf]

Wotcha.

Yep - roller bearings can have individual rollers fail.

https://www.moonshiners.org.uk/LWMEimages/weekend2014/2014week25.jpg
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Cheers.
^..^
L.W. - www.moonshiners.org.uk

[A100man]

An interesting investigative workshop thread - how refreshing.
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[stinkwheel]

[steve the grease]

I believe this ' bearing surface failing' thing is called 'spalling, it generates lots of tiny flakes of metal, not what you want really. Hopefully its a bore problem....
____________________
All the above is my personal opinion, you can see my lips move, but I'm talking out of my arse.
I've been riding, and fixing , bikes for 50 years, in that time the more I learn, the less I am absolutely sure of.....

[pepperami]

[mentalboy]

[MG#43]