Cb400f project #2

[David01]

Hi Guys,

Getting near to the end of stripping the current project.

Electrics are shot so I haven’t been able to start the motor, however I have managed to get the starter motor to turn the engine over.  Compression test are low ~60psi across all cylinders. The pressure goes up to ~125psi when oil is added to the cylinder.

Low values could be due to motor still idle for years, cold test and cheap compression tester.

Also the cam chain tensioner set bolt is broken. I have no history about the bike so I’m assuming the worst engine wise.

Next step:

1. Fix cam chain tension set bolt - do nothing else and get the engine running
2. Do a top end rebuild, possibly with a 466 kit and install new cam chain
3. Do a complete engine rebuild

I’m taking the approach of test, research and repeat before splitting the engine for my first rebuild. I welcome your thoughts on what would be next step that is sensible.

The rolling stock is solid but rough. But the front end has been changed to a cb250n. I have sourced hubs and forks from the USA and will return to stock wheels.

So while deciding on the engine component I have much to do on the rolling stock.

Thank you in advance

David

[Bryanj]

I have posted a link on here somewhere to a very nice looking stainless repair kit BUT it all depends if the horseshoe is free. You may be able to check that if you remove cam cover but not always.
Just a top end is possible in frame so as long as horseshoe moves ok i would repair lockbolt, fit engine and try and get it running, fitting as little as possible

[K2-K6]

For compression testing,  this may shed some light on the reading;-

http://www.sohc.co.uk/index.php/topic,17461.345.html

You're working with such small volume of cylinders,  with any error magnified in terms of absolute psi measurements.

[David01]

Hi both,

Thank you.

You have confirmed my thoughts - if  it isn’t broke don’t fix it.

However, before trying to start the engine I will clean the carbs and rebuild. Visual inspection, two bowls are missing one screw and on inspecting the bowls have significant residue in them. I don’t want to run the rubbish into the engine.

I will get a the cam chain bolt repair kit. However, I will need to extract the broken bolt first.

David