Oil pressure

[johnmc]

Hi everyone. I finally got to dismantle the engine this morning. The big end bearing on the conrod's seem to have a burnt colour. The crank will have to be sent away and fixed as there are groves on the jernals .

[johnmc]

Hi everyone. On Futher inspection of the engine crankshaft and conrod's I found that I had installed the conrod's back to front. On the conrod's there is a small hole that must face forward and stupid me had put them facing backwards.
The conrod's have been heated to a point that they have changed colour slightly. Will try to post pictures soon for all to see . John ( not the best engine builder) .

[Grimly]

Is this hole an oil squirter for the underside of the piston or for the bore walls? If the crankshaft was still being supplied with the right amount of oil, the bearing should have survived, but the pistons wouldn't have got any cooling.
It's a bit peculiar.
Check, double check and check again that oil supply from the pump is unobstructed.

[johnmc]

Finally figured out the picture thing .

[Nessism]

Is this hole an oil squirter for the underside of the piston or for the bore walls? If the crankshaft was still being supplied with the right amount of oil, the bearing should have survived, but the pistons wouldn't have got any cooling.
It's a bit peculiar.
Check, double check and check again that oil supply from the pump is unobstructed.

Agree. A misaligned hole won't wipe out the bearings like that. If anything, there will be more oil for the rod bearings because less will exit upward at the cylinder walls.

[Cipher]

Agree. A misaligned hole won't wipe out the bearings like that. If anything, there will be more oil for the rod bearings because less will exit upward at the cylinder walls.

Deadheaded oil pump?

[KiwiAlfa156]

It looks like those shell bearings have worn through the top 'white metal' layer to the copper layer underneath. This means the crankpins haven't been supplied with enough oil at sufficient pressure to create a cushion of oil between the pin and the shell and metal to metal contact has occurred. Given all the end big bearings appear damaged, its likely that low oil pressure/no oil flow has caused the all that damage. What caused the low oil pressure isn't obvious and whether it was caused by a bad bearing, a bad pump, or a blockage is a bit chicken and egg.

What condition were the crankshaft/main bearings in? Generally the main oil gallery feeds the crankshaft bearings that then feed the big ends. Where the damage begins and ends might help troubleshoot where the problem lies.

Have you inspected the oil pump? There is a specified rotor lobe to star clearance and side clearance. Any wear or scoring will lower oil pressure especially at idle/low rpm. The pic below is from the 750 manual, so specs might be different. Did it knock? Big-end failure is generally noisy.

Screenshot 2022-09-02 140718.jpg

[GregT]

Sadly, those shells are pretty typical of a GSX400/4 of thsi age. Earlier on this thread there is mention of the 2nd gen 750/4 and it's plain bearing troubles. The 400/4 I think hit the Jap home market fractionally earlier than the 750. Same design team, same problems.
If the crank is marked, it's very possibly cracked too. If you take it to a reconditioner, before anything else, get it crack tested.
Grimly's mention of inserting a bigger engine is one possibility - if Aussie regs allow it.

[johnmc]

Hi everyone
sorry for the late update on my engine. There must of been some glass media from the hydra blasting that I had done on the engine case's. I had used a gerni to flush out all remaining media from all the oil passage ways , but unfortunately this was not the case . If any else is going to have this done to there engine please please be very careful and be 100% sure that all passage ways are clean.
☹️

[GregT]

I had a set of Honda CBR600 cases aquablasted. They sat on the shelf for a month waiting for parts. Slowly but surely a small pile of white dust accumulated in and under them.
And yes, they had been pressure washed several times. That stuff is very very hard to get completely out.

[Grimly]

Hi everyone
sorry for the late update on my engine. There must of been some glass media from the hydra blasting that I had done on the engine case's. I had used a gerni to flush out all remaining media from all the oil passage ways , but unfortunately this was not the case . If any else is going to have this done to there engine please please be very careful and be 100% sure that all passage ways are clean.
☹️

Wow, rough luck.
You're certainly not the only one to have been caught out by that. First I came across it was a UK bike mag ran a series about a rebuild of a classic (750-4, iirc) and all was shining bright and glorious until it shat the blanket one sunny day. Turned out the chap doing the rebuild hadn't totally cleared the cases of blasting media, with exactly the same result.
I must admit I've been leary of any blasting media near my cases ever since. I prefer to just get in with plenty of degreaser and elbow grease.

[KiwiAlfa156]

The only media I've ever blasted cases with is blasting soda for this very reason. Soda is water soluble...

[johnmc]

I will not be going down the same road with my next project. 1978 gs550e . Once again thanks to everyone on this forum.