Rebuilt engine seized

[GregMcN]

Engine is back together now but currently showing a reluctance to start, essentially this has been a 2nd full rebuild and I also took the opportunity to rebuild the carbs so plenty of things to check. Not helped by failure of the electric start... (luckily? - some may question my sanity given my experiences so far) I had bought another cb77 project which has now donated its starter.

Greg

[Merz64cb77]

Did changing the starter fix your electric start problem?

I had a similar issues but turned out to be a bad starter solenoid.

[GregMcN]

Yes the ‘spare’ starter does work. I am now thinking that the starter failure is another legacy of the engine seizure because it is also seized and when the starter cog seized I assume the starter would have been turning at engine speed?

[DJM]

When the starter sprocket seized onto the crank the starter would have been turning, or at least trying to turn, at least twice as fast as the engine given the difference in sprocket sizes.

Hardly surprising that the starter is feeling a bit sorry for itself so glad the 'new' one is OK.

Hopefully you'll get the starting problem sorted out and then think of the fun you'll have restoring your new 'project bike' too.

Good Luck,

Dennis

[G-Man]

Greg

Nice to see the crank end and bearing put to good use! Had a visit from Dave to return the spare wheel and check out what I was doing. He gave me some tips for the SL175 crank I need to build up.

It's funny how retirement seems to throw up plenty of jobs you didn't know you had and project possibilities that you have been putting off for years......

I now have my new milling machine installed so the fun can begin.





G

I have now had my crank rebuilt.
Many thanks to Graham for providing the necessary repair parts.
It turned out that it is actually a cb72 crank but this does not appear to be of much concern. There was good news in that the rest of the crank was undamaged.
However the builder found that both the centre section was too wide (by about 1mm) and that it was not exactly at 180 degrees. His view was that the seizure was likely due to this causing the bearing to rub and overheat. I am not totally sure, as the bearing position is pegged I assume if the crank was wide there would be pressure on the cage/bearing but if too wide then the pin would not engage in the bearing and you could not fit the cases together?







Greg

[GregMcN]

Graham

I was going to check whether Dave had returned the spare crank part, pleased that he has. Milling machine looks great.

I have got the bike running after going back to the original air screws rather than the new ones that came with the carb kits. As far as I can tell everything is working as it should............ but it has an oil leak. Unfortunately it is leaking quite badly from the '9th hole' at the base gasket, very frustrating that I will have to strip down again. It seems a bit like I am going round in circles and this probably relates to why that brass tube was in the engine when I got it.

Greg

[G-Man]

Greg

You'll be getting quite good at this but you're almost there. I have a couple of suggestions.

1) You could put some silocone around that area - probably won't last.
2) Strip the engine.
Test that area with a straight edge - looking for burrs or hollows.
Bring top crankcase & barrel to me and we'll get my miller set up and take a skim off
crankcase / barrel or both to get a better seal.


Can you post a picture of that area on both barrel and crankcase, please?

G

Graham

I was going to check whether Dave had returned the spare crank part, pleased that he has. Milling machine looks great.

I have got the bike running after going back to the original air screws rather than the new ones that came with the carb kits. As far as I can tell everything is working as it should............ but it has an oil leak. Unfortunately it is leaking quite badly from the '9th hole' at the base gasket, very frustrating that I will have to strip down again. It seems a bit like I am going round in circles and this probably relates to why that brass tube was in the engine when I got it.

Greg