Tohatsu 50 mods

[Roflhat]

Planning some mods this summer, got Yamaha 70 carbs to go on, need to open up the reed block for them too. Got a Mikuni fuel pump to put on as well which is hopefully more reliable than the standard tohatsu one.
Was going to modify the exhaust tuner as well, open it up a bit and cut 25mm off the end. Has anyone else done this? How do you get to the exhaust tuner?

I read online that the flywheel ring gear can be removed so going to look into that. Or if not then maybe lighten the flywheel.

also if anyone knows roughly a big a job it is removing the crank, welding it and putting it back in? how many hours/days, just so I know what to expect.

Cheers

[Roflhat]

Apparently the easiest way to open the exhaust is just to buy a D1 tuner, anyone know the part no. for these? Can I get one new from a tohatsu dealer?

Also I've been told I can take the engine apart, weld the crank and get it back together in a day! sounds like a challenge...
Is this the only place I need to weld the crank? Like in these photos:
57287
57288

Is there anything else I should do while the engine is apart?

Thanks,
Seumas

[Roflhat]

Apparently taking 1mm off the head raises the compression by 30psi, so if I take 0.5mm does that mean it will raise by 15psi? Or is there more to it than that?

[Avalon]

Apparently taking 1mm off the head raises the compression by 30psi, so if I take 0.5mm does that mean it will raise by 15psi? Or is there more to it than that?

I’m a day late and a few dollars short but did you ever figure any of this info out? I am looking to modify my M40D2 with some similar mods. The next thing on the list is flywheel work and shaving the head to get 150 lbs out of it.

Best,
Avalon

[DeanFHobart]

Apparently taking 1mm off the head raises the compression by 30psi, so if I take 0.5mm does that mean it will raise by 15psi? Or is there more to it than that?

Ask on this site and on hydroracer.net…. Who is the guy that makes the racing tower house and gear case for racing. He lives in the eastern part of the US….I think he advertises in the APBA Propeller magazine. I’m sure he can help you.

[Roflhat]

Yeh I shaved 1mm from the head which gave 30psi more. Eventually put a TSR head on it which was slightly better again, along with the D1 exhaust. I've got the whole thing quite well documented here - https://www.rib.net/forum/f50/my-thundercat-61912-30.html