Cracked waterjacket

[Charles uk]

The majority of Seagull heads have Helicoils!

[headdownarseup]

Water return pipe:
Seeing as you've got a 102 cylinder mounted onto a set of silver century crankcases, why not do as the 102's did and have some of that water run inside the exhaust tube. You could drill one of the 2 holes already in the century exhaust tube a bit larger (i think the lower of the two holes) to allow the 102 pipe fitting to be bolted into this now enlarged hole. Fill up the now redundant second hole if you think it needs it and bob's your uncle

You will need to go a bit more carefully with your 102 cylinder as it probably hasn't been helicoiled like its square block cousins. A little smear of grease(don't go mad with it) on the spark plug threads will help a bit with keeping an airtight seal around the plug. Every little bit helps as they say.

For safety's sake i'd double check the main jet size in your mongrel carb just to make sure it's not going to be running a bit on the lean side. Bearing in mind a typical minimoto is normally (but not always) around 50cc displacement. Your "bitsa" is double this at 102cc so well worth a look just to play things safe. Don't want this running hot from having a weaker mixture.

I might have some bigger jets for this kind of carb kicking about somewhere if you need them or they're fairly easy to buy online. Plenty of guys selling them.

Jon

[Liam2k3]

Cheers jon will keep an eye on the carb and the plug and i use alu slip on my plug threads to keep them nice.
If the water pipe goes back into the exhaust how do you check that the water is still flowing nicely. If i couldnt see the steam coming from the engine because it was hidden i would have possibly siezed it.
Is there a clear pipe or sight glass that could connect the two. Or am i just thinking too much into it

[Liam2k3]

Aaaahh,answered my own question.
I need a union with a hole in

[headdownarseup]

Do you need one?

[Liam2k3]

I should have something i can bodge together. Its a bitsa afterall.
If not i will need one cheers

[Liam2k3]

Made an ally block for the water pipe. Gona weld it to the exhaust tube at the right level for the pipe.
What size should the tell tale hole be?

[Liam2k3]

102 cylinder is on and has good compression. Water pipe block welded on and connected. So its all looking good.

[Liam2k3]

Had a little play around with making a propeller aswell today something 3 blade with a little bit more pitch than the 4 blade prop on this wspc gearbox because of the lower ratio gears. Not finished yet but a work in progress.
240 mm diameter

[Keith.P]

Are you going to drill a small hole in the block for a let tail?
That prop looks heavy, it maybe too heavy for a seagull gearbox.

[Charles uk]

That looks like a lot of pitch Liam!
Can you measure the blade angle of attack at the 8" diameter point.

It's only doing 1000 revs if the motor can turn it, Keith.

[Keith.P]

I was thinking about the gearbox bushings and how well they would stand up to the weight.

[Liam2k3]

Drilled a 2 mm tell tale hole.

The steel prop does have a lot of pitch but being steel a can tweek it back if its too much. As for the weight its not as heavy as you think. I will weigh it when its finished once ive made the cup for the back and machined the front for the spring drive. Its 3mm steel blades.

[Liam2k3]

Has anyone on here ever cut and modified a seagull prop?
Whats it like to weld?

[Charles uk]

Tig welds ok, needs annealing before bending as brittle, like LM 25.