Author Topic: Help! What's caused this?  (Read 2727 times)

Offline Bristolbadger

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Help! What's caused this?
« on: March 25, 2022, 03:15:32 PM »
Hi folks, I'm properly gutted after I finally finished my k3 750 sohc, got her MOT'd and finally on the road and driving sweet. After 30 or so fairly gentle shakedown miles I decided to pop the cover and check valve clearances and re-torque all the bolts... only to discover the cam seemed off centre on the right side holder...
Low and behold the horror in the pics! I'm mortified to say the least after 2yrs of ground up build.

What could have caused this? Only a bent camshaft that I can think of as I did a full bench check to check oil circulation to the head and all metering jets were clear and oil was getting up to the journals and everywhere nicely. Was getting good running pressure with a gauge attached to the pressure sender initially and also no oil light warning (yes the pressure switch is working) when I was riding it with that back in.

The left side cam holder/journals and camshaft are fine and unmarked as was everything up there when I assembled the engine.

I can't vouch for the straightness of the camshaft when I got the bike so I guess its possible the cam had been dropped or bent and I just had a dodgy one to start with.

Not sure my best course of action now?
 I'll strip all the parts off and take the cam fully off and investigate for any further damage I guess but then best case scenario is me left looking for a second hand camshaft and right side holder and journals. F**k f**k f**k!



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Offline Bryanj

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Re: Help! What's caused this?
« Reply #1 on: March 25, 2022, 03:39:38 PM »
That was caused by crap blocking the oil jets, did you use silicone goo on the crankcase?

Online K2-K6

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Re: Help! What's caused this?
« Reply #2 on: March 25, 2022, 03:42:23 PM »
As above, classic head feed oil passage impeded (there's one for each side of the head) and consequently oil starvation.

You can see the heat range on the rockers as they've over heated too without oil.

Offline sye

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Re: Help! What's caused this?
« Reply #3 on: March 25, 2022, 03:43:10 PM »
I have no idea what caused it but it's bone dry. There should be oil everywhere.

Online K2-K6

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Re: Help! What's caused this?
« Reply #4 on: March 25, 2022, 03:47:03 PM »
Certainly feel for you, it's horrible putting in all the time and effort to then get a failure like this.

It won't show on the pressure guage or oil light as even with this route completely blocked they will look ok.

Offline Nurse Julie

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Re: Help! What's caused this?
« Reply #5 on: March 25, 2022, 04:18:50 PM »
With the oil pressure switch being situated in the top crank case, all it shows it that you have pressure to the bottom end of the engine. It's definitely oil starvation that's caused that. That's a great shame, I bet you are totally gutted. I'm assuming you could get the rocker cover off without removing the engine with the frame being slightly modified, which is a major result.
« Last Edit: March 25, 2022, 04:21:45 PM by Nurse Julie »
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline haynes66

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Re: Help! What's caused this?
« Reply #6 on: March 25, 2022, 04:36:29 PM »
i was told by an old honda guy to turn the engine over with the rocker cover caps off to see if oil arrives at the head. i assume that's a good idea?
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Offline Nurse Julie

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Re: Help! What's caused this?
« Reply #7 on: March 25, 2022, 04:50:53 PM »
i was told by an old honda guy to turn the engine over with the rocker cover caps off to see if oil arrives at the head. i assume that's a good idea?
Yes, it is. Always take the 2 end tappet caps off and make sure the oil is getting up there on both sides before riding the bike and putting the engine under load.
Im a Nurse, trust me, this won't hurt.....much !!!

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http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Online K2-K6

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Re: Help! What's caused this?
« Reply #8 on: March 25, 2022, 05:11:48 PM »
i was told by an old honda guy to turn the engine over with the rocker cover caps off to see if oil arrives at the head. i assume that's a good idea?
sensible containment definitely.

Core cause, absolute, paranoia over making sure there's nothing in the oil distribution system to travel  up that route and get caught by the restrictor coming into the head.

It's there to preserve pressure at the crankshaft,  the head being effectively open bath type distribution,  the restricors set the boundary between the two.

Offline Bryanj

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Re: Help! What's caused this?
« Reply #9 on: March 25, 2022, 05:13:38 PM »
I have even seen bits of old scraped off base gasket block a jet

Offline Nurse Julie

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Re: Help! What's caused this?
« Reply #10 on: March 25, 2022, 05:22:32 PM »
I suppose in theory, even though oil is observed getting up to the cam on a newly rebuilt engine at initial start up, it could take a few miles of riding to dislodge any debris that is in the bottom end, such as the dreaded silicone sealer, blobs of glass bead etc, etc.
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Bristolbadger

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Re: Help! What's caused this?
« Reply #11 on: March 25, 2022, 05:27:57 PM »
That was caused by crap blocking the oil jets, did you use silicone goo on the crankcase?

Oh man I'm still reeling from this discovery and blocked jets weren't really a fear as I was meticulous on the engine build, especially after the 2nd engine lift out where I had to go into the gearbox... and followed Hackaweeks channel and was careful with the jets and their surround rubbers, the dowels, the rubber pucks etc as I knew the implications after his explanation and Hondaman's and all was spotless putting bottom and top end back together. I used the Permatex ultra grey on the cases and was super sparing with it so minimal chance of any squidge out coming off and blocking the jets.. already if at all.

I bench tested the oil circ and it was squirting up to all the right places on the rockers - I took a video off it and will upload and link to it here.

Starting to lose faith with this now, not sure I've the time, space or money to get this repaired even if I could find the parts. Gutted :(

Offline Nurse Julie

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Re: Help! What's caused this?
« Reply #12 on: March 25, 2022, 05:43:33 PM »
Don't give up, it's all sortable. Be positive, at least you haven't had oil starvation to the bottom end.
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Laverdaroo

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Re: Help! What's caused this?
« Reply #13 on: March 25, 2022, 05:55:23 PM »
Just had a quick chat with Nick, (Bristol Badger) and I'm gonna bob over for a moan n a brew tomorrow and see if we can form a plan and a list. There's gonna be a bunch of questions coming and some desperate;y seeking requests me thinks. ;) :)
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Offline Nurse Julie

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Re: Help! What's caused this?
« Reply #14 on: March 25, 2022, 06:01:25 PM »
Just had a quick chat with Nick, (Bristol Badger) and I'm gonna bob over for a moan n a brew tomorrow and see if we can form a plan and a list. There's gonna be a bunch of questions coming and some desperate;y seeking requests me thinks. ;) :)
Well done Roo
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

 

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