Frankenstein's Seagull

[StuartRB]

Hi

I'm after a bit of help.

Last year I bought a couple of cheap seagulls as something to footer with. The small one is a 1979 Forty Plus (GFP 778 BB9).

It was missing a piston, transom brackets, had the wrong fuel tap and had a broken block, but I decided to try and get it running anyway.

I bought the required second hand items and put it together.

Of course it won't start.

I'm getting a good spark, checked and cleaned the points. I've taken the carb off and cleaned it (even tried with a carb from another 40+ I borrowed) but still nothing.

As I'm amateur, I've a few questions about the attached images:

1. Have I put the piston in the right way up??
2. When the piston is fully retracted, it appears to still cover the fuel intake port. This seems like a problem to me!




Any ideas?
Thanks

[Keith.P]

Fuel inlet port from the carburettor is behind the piston, the transfer port that lets fuel from the crank case to the cylinder head is above the piston.
The piston is the right way up, you need a sealed crank case, so look for worn crank case bushes and piston compression, you have a spark, so must be something else.

[StuartRB]

Thanks for your reply, I think I understand how it works now

When everything was connected and I tried a few pulls, there was no sign of fuel at the spark plug.

[Keith.P]

Either a fuel problem at the carburettor, low crank case pressure from a worn or leaking crank case, or low compression, worn rings.
See if you have any sideways movement on the flywheel, that's normally a good indicator of worn bushes.
Anneal the head gasket if you are reusing.

[StuartRB]

I stripped everything down, as you suggested the bolts holding the crank case together seems loose and there were gaps.

I cleaned everything, softened the head gasket, replaces the gasket between the block and the crank case and put it all back together.

This time I am at least getting some smoke, but no start.

What I did notice is that it is a real struggle to pull the start cord. Even moving the flywheel by hand is a struggle at the point when the piston is moving back down the cylinder.

[Horsley-Anarak]

If the motor is still tight with the gearbox removed then it sounds like you may have a bent crank, have seen quite a few bent cranks on 40+ motors.
If you have access to a lathe, then stick the bare crank in the chuck and put a dial gauge on the flywheel end of the crank.
Rotate slowly by hand and you will see if it is running out of true.
A couple of donks with a mallet will get it true usually, I can get them true to within about a thou.
If then the crank is still tight in the crankcase with the bolts tightened up, then the crankcase may also be bent.
If that is the case replace the crankcase, or pop a long 5/8" reamer through the bearings.
Good luck.
H-A

[StuartRB]

OK Last throw of the dice.

I took only the block off the flywheel turns freely. Once the piston is back in the block and tightened up, the stiffness is back.

No sign of any marks inside the cylinder.

Would this suggest the crank is ok?

[Horsley-Anarak]

Would this suggest the crank is ok?

Yes if with the block removed the crank is free turning, it would suggest the issue is piston to bore fit.
Could be piston ring gap, with the rings off the piston and in the bore that should be a gap between the ends of the rings.
Or could be distorted bore, but I would think that would show as a mark in the bore.
I would look at the rings, also check the conrod is not bent.
H-A

[seagull101]

Pop off the rings and clean out the slots in the piston, there may be some grip stopping the rings from fully compressing.

Jacob