SOHC.co.uk Forums > CB500/550

Engine seize after complete engine rebuild

(1/3) > >>

RBoss:
Hi all,

So I have rebuilt my engine completely to replace the primary chain. Put the freshly painted engine in a freshly powdercoated frame, but after riding two trips of a total of 100km, my engine seized on the motorway. After getting to a stand still the electric start could not turn over the engine anymore and the kickstart was seized up as well. I feared for the worst.

However after being towed to the first gas station the kickstarter was free again and I could start the engine with the electric starter. The engine didn't sound as nice and quiet as right after the rebuild though. I am quite lost what the problem could be...

I'm thinking of the engine running too hot and seizing up the pistons, especially as it freed up again. I am also afraid that this is because I might have used too much liquid gasket when putting the two engine cases together.

Some context info: I have ridden the bike two times after the rebuild and before the breakdown. 1st time was on the motorway at a normal pace, second time was on countryroads quite easily. The breakdown ride was a little faster at around 130km/h for 15 min on the motorway before it seized. I started on the motorway almost straight after starting up the bike.

Anybody that has some advice or might know what this would be, as well as how to solve it, or diagnose the bike? All the help is welcome!

attached some pictures of the engines liquid gasket, and my breakdown... :-\
[ Guests cannot view attachments ]
[ Guests cannot view attachments ]
[ Guests cannot view attachments ]

K2-K6:
Ooooh that doesn't sound good :o

The gasket cement I would guess could be the prime suspect here. If any oil supply routes have been compromised by excess squeezing into them, then that can easily lead to problems.

Not easy to assess without looking inside,  at least the cam cover to start with.

K2-K6:
To add, I'd not run it like it is until understanding quite what is happening inside.

Oddjob:
What exactly was done on the rebuild?

Did it have a rebore for example?

First thing I'd do is pop the camcover off, I suspect the cam may have seized, it freed off when the engine cooled as the metal would contract when colder allowing it to start to spin again, however it's probably toasted the head and most likely the cam. You may get away with the rockers as the mileage was still low.

Did the oil light come on before it seized up?

RBoss:

--- Quote from: Oddjob on March 16, 2022, 08:49:05 PM ---What exactly was done on the rebuild?

Did it have a rebore for example?

First thing I'd do is pop the camcover off, I suspect the cam may have seized, it freed off when the engine cooled as the metal would contract when colder allowing it to start to spin again, however it's probably toasted the head and most likely the cam. You may get away with the rockers as the mileage was still low.

The oil light didn’t show so I guess oil pressure was OK.

Did the oil light come on before it seized up?

--- End quote ---

I replaced the primary and cam chain, and lapped the valves and replaced the valve seals. I didn’t do anything else to the head and cilinder as the pistons + rings and cilinder bores looked good.

I’ll start pulling the top off soon to start diagnosing.

Navigation

[0] Message Index

[#] Next page