Manco Thunderbird build for granddaughters. Engine swap alignment issues

tried swapping my known good B&S intek 190 on this frame and both exhaust and clutch alignment are going to be an issue (by roughly 1.5”
Also have a great running old 3hp tecumseh off my tiller but that shaft is 2 different sizes to accommodate a small pulley at the end, & it seats against the larger base of the shaft.

should I scrap both and opt to go buy a predator 98cc or something or what will bolt straight up and work easily???
Thanks in advance


Well-Known Member
I see you are a new member, Welcome to the mighty OldMiniBikes!

Bolt up the Tecumseh to the bike plate and start engine, now use a hacksaw blade to slowly cut the small shaft near the housing. It will cut real nice and when that falls off now use a file to taper any rough edges. Use sandpaper after if you prefer.
Done it many times and it will allow you to use that engine.

P.S. Those Thunderbird motor plates are known to be weak and flexible. The 3hp shouldn't be an issue but a larger engine will be.
This can be fixed by welding supports on or by getting thicker plate.
Seat mounts into wood also give issues, drill a couple more holes in rear wide plate and use short wood screws to give better holding grip.
Had at least 5 of those bikes and they are fun, they just have some quirks.
Good luck and Enjoy!
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Well-Known Member
You might think about upgrading to better brakes, especially if you upgrade the engine. That little bike is little, and can be a lot to control with just a scrubber on the rear tire. Especially when wet.

Just my two cents, since you mentioned granddaughters.
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