CB550/4K engine strip, Bore scratch

[Gary400/4]

Hello all, I have recently acquired a CB550/4 K project bike to sort out, I have owned these previously and enjoy them more than the CB400/4.
I have stripped the engine to check it over, the engine was literally seized together, it took a lot of effort to remove the cylinder head, the cylinder barrel had accumulation deposits around the front barrel studs. I ended up with a few chipped fins. On inspection of the cylinder bores, the piston ring end gaps were still in service, but not by a lot, so I have purchased a new set of standard rings. On inspection of one of the bores, I note that a scratch is evident about 1cm long by 1mm deep running horizontal in the cylinder wall. I will be honing the bores to help the new rings to bed in. But I am worried about a ring getting snagged on the scratch as it motions up and down at revs. Is this something to be alarmed about?

[taysidedragon]

It's difficult to judge without seeing it, but if the scratch is as deep as you say I would be looking at a rebore.
Even then it might be too deep and new barrels or liners may be required.

[Laverda Dave]

+1 with Gareth's response. 1mm is very deep and I doubt even a +1.00mm rebore will remove it. Considering you now also have chipped fins I would  personally be looking for another barrel but only once I'd got the whole engine apart and inspected especially if it has been sitting seized up.

[Johnwebley]

If the scratch is only 1cm long and  1mm wide it shouldn't be an issue,

OK, it's not perfect, but the rings are at least 2mm or 3mm wide,

So they shouldn't drop in,
On 2 strokes the ports are far bigger,



Sent from my SM-A546E using Tapatalk

[Bryanj]

Do you mean 1mm deep or wide? Wide probably ok but depp not.
If deep its too deep for a max honda size rebore but cruzin do a 3mm oversize kit taking it to 605 ish cc but dont expect a cheap rebore as that is a minimum of 6 passes per bore plus hone!

[McCabe-Thiele (Ted)]

As has been said if it's 1mm deep then it's a problem.

I would look for a replacement block, Bryan sourced one for me last year that was spot on. Plus as you know he does rebores as well. He might have a piston kit.

[SteveW]

Couldn’t you just replace the liner?

[Gary400/4]

Many thanks for the responses, I especially like the comment by JohnWebly, about 2 stroke rings not snagging on ports.the new rings placed in the bores have an end gap of 0.279mm which is between 0.15 - 0.35mm standard ring gap. This means the bores are well within service. Given the scratch dilemma, I would prefer the replacement liner option. Does anyone know where I could obtain a standard liner with a bore of 58.5 mm?

[Gary400/4]

Hi everyone I have posted a picture of the scratch in the bore, I am still in two minds about using the cylinder?

[Bryanj]

No pic seen here

[Johnny4428]

In the gallery Bryan.

[Johnny4428]

Hi everyone I have posted a picture of the scratch in the bore, I am still in two minds about using the cylinder?

Gary you need to post pictures as attachment to your post! Gallery is mainly for bike pics!

[Nurse Julie]

Just seen photo, that liner is as rough as a bears arse and is useless. You need to source another liner, check the others as well. That's water damage and the damage can easily go right through the liner. It's beyond re bore.

[Bryanj]

I agree, its scrap

[AshimotoK0]

Just seen photo, that liner is as rough as a bears arse and is useless.

Badger where I come from Julie 😁