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Ticking & bad compression on 1 cylinder.

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adengtg
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PostPosted: 21:37 - 03 Jan 2019    Post subject: Ticking & bad compression on 1 cylinder. Reply with quote

First post of 2019, lets hope it will be the least serious of the year!

Cylinder 1 on my XJ600 has a loud ticking noise coming from the valve covers as well as pretty bad compression compared to the other cylinders. Theres also a lot of back pressure in the crank case, causing steam & oil to occasionally be ejected while the bike cools down. Theres also a few oil leaks causing moisture to get into the system in the rain but i'm working on it. The exhaust header on this cylinder is also significantly cooler than the others while the bike warms up.

Best guess for whats causing these issues? Something to do with valves, either timing or clearances i would think but ive not worked on valves before. Any guidance of what to check once i get the covers off or what the problem would be is very much appreciated.

Thanks a lot!

FYI, the bike is 8 valve DOHC with 4 Cylinders.
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Pigeon
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PostPosted: 23:43 - 03 Jan 2019    Post subject: Reply with quote

Surely the only way its pressurising the crank case is combustion content getting past the rings.

Low compression, pressurised crank case, cold exhaust.

Broken piston ring?
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adengtg
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PostPosted: 00:16 - 04 Jan 2019    Post subject: Reply with quote

Pigeon wrote:
Surely the only way its pressurising the crank case is combustion content getting past the rings.

Low compression, pressurised crank case, cold exhaust.

Broken piston ring?


That was my thought at the beginning but the ticking coming from the valves threw me off. Right, ill have a quick look for some new rings but i'm not hopeful that ill find any. Thanks very much!
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Pigeon
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PostPosted: 00:33 - 04 Jan 2019    Post subject: Reply with quote

adengtg wrote:


That was my thought at the beginning but the ticking coming from the valves threw me off. Right, ill have a quick look for some new rings but i'm not hopeful that ill find any. Thanks very much!


Sorry, just to clarify, I'm definitely no mechanic. But tend to throw my 2p around where it probably shouldn't be.

Ticking could also be the exhaust header leaking.

Also Cam chain. If its stretched a tiny bit, and the CCT isn't man enough, it can cause a little slack point in the chain (not enough to jump a tooth) and then get snapped back by the CCT.
This does sound like a very regular ticking noise.

But that wouldn't explain the pressurising the crank case, which I would presume to be from combustion mixture. But again, I'm only guessing.

Good luck though Thumbs Up
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adengtg
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PostPosted: 00:48 - 04 Jan 2019    Post subject: Reply with quote

Pigeon wrote:
adengtg wrote:


That was my thought at the beginning but the ticking coming from the valves threw me off. Right, ill have a quick look for some new rings but i'm not hopeful that ill find any. Thanks very much!


Sorry, just to clarify, I'm definitely no mechanic. But tend to throw my 2p around where it probably shouldn't be.

Ticking could also be the exhaust header leaking.

Also Cam chain. If its stretched a tiny bit, and the CCT isn't man enough, it can cause a little slack point in the chain (not enough to jump a tooth) and then get snapped back by the CCT.
This does sound like a very regular ticking noise.

But that wouldn't explain the pressurising the crank case, which I would presume to be from combustion mixture. But again, I'm only guessing.

Good luck though Thumbs Up


Right, i will check again tomorrow but i was sure it was from the valve covers at the top. Will let you know tomorrow
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Teflon-Mike
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PostPosted: 02:12 - 04 Jan 2019    Post subject: Reply with quote

A cracked piston ring will also 'tick'... there's no tension in it to hold it against the cylinder wall, you have two loose bits of iron flapping about, going from umpety mm per second half way up and half way down the bore, to a dead stop and back t'other way, each end.
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adengtg
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PostPosted: 02:21 - 04 Jan 2019    Post subject: Reply with quote

Teflon-Mike wrote:
A cracked piston ring will also 'tick'... there's no tension in it to hold it against the cylinder wall, you have two loose bits of iron flapping about, going from umpety mm per second half way up and half way down the bore, to a dead stop and back t'other way, each end.


Right, on Wednesday ill have a proper look and let a mechanic have a look at it and see what he thinks. Thanks
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andym
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PostPosted: 06:16 - 04 Jan 2019    Post subject: Reply with quote

Call round a couple of (bike) garages and ask how much it would cost for a leak down test, then go from there
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bikenut
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PostPosted: 11:52 - 04 Jan 2019    Post subject: engine Reply with quote

Valve clearance check and compression check. Feelers to check valve clearance, a bit of kit you should already have and know how to use.

A compression tester is also a good bit of kit but you have a thumb. You already know of a low compression so check valve clearances.

Crank case vent system "chuffing" .....

what year is the bike
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Robby
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PostPosted: 12:57 - 05 Jan 2019    Post subject: Reply with quote

I can see two separate problems. Crankcase pressure, and low compression on one cylinder.

Crankcase pressure first, because its easier. There should be a breather pipe going from the crankcases to the airbox. Find it, and check it for blockages. If you have trouble with emulsion in the oil (mayonnaise) then that can block up the breather pipe.

Low compression next. The cold header pipe points at low compression, because that cylinder isn't firing as often as it should. You have noise from the valve gear, so that's the place to look first. If you're lucky its just a loose valve adjuster clattering around, and setting the valve clearances will sort it out. If you're unlucky, it could be a broken rocker arm (if it uses them), a knackered camshaft lobe, or something like that.

Of course, it is possible that the problem is just a knackered exhaust gasket, but from the description this does sound like a valve train problem.
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redeem ouzzer
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PostPosted: 13:14 - 05 Jan 2019    Post subject: Reply with quote

If it is a mechanical issue then it’s not worth fixing. Chuck another engine in it, they are cheaper than the gasket set would cost on its own for splitting your old engine.
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