Bravo rebuild at standstill

I stopped my engine rebuild because I'm stumped. I reassembled the crank halves by the book. Let it cool, placed seal,etc. And it states to turning the crankshaft for tight spots. It turns, no grinding or hitting, but I got it in pieces and I have no reference as to how freely it should move. Should it spin like a top? Or stop in place when I twist ? It feels stiff to me. I'm not going any further so I don't do damage , and hear from the pros.

Re: Bravo rebuild at standstill

DrGeorgeTompson (Alan) /

I almost never get vespa case bearings to seat perfectly after torquing the case halves. It find that it helps to heat the outside of the bearing seats and tapping case with a metal hammer to try and coax it to a good resting place where it doesn't bind. you are just shocking the case to try and get the bearings to settle and de-stress the crank.

I do this before i put the seal in. The seal will add some resistance but before the seal, it should spin freely. I guess you could heat it with the seal in, just don't cook the seal.

Re: Bravo rebuild at standstill

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Ok, I did that with the large case bearings went in easy. Warmed the small case on the per instructions, went together good tightened bolts, set the seal when cooled. But I’m stuck to as how freely it should move. I got this in pieces, so I have no reference point , go to by .

Re: Bravo rebuild at standstill

> Les B. Wrote:

> -------------------------------------------------------

> Ok, I did that with the large case bearings went in easy. Warmed the

> small case on the per instructions, went together good tightened bolts,

> set the seal when cooled. But I’m stuck to as how freely it should move.

> I got this in pieces, so I have no reference point , go to by .

Brand new crank, brand new bearings, you should be able to turn it by hand but it won't spin like a top. New cranks/bearings feel a little bit tight before you actually run them

Re: Bravo rebuild at standstill

Thanks guys, it’s moving easier all afternoon I shot it with a little 2 cycle

Re: Bravo rebuild at standstill

Finish the build.

Re: Bravo rebuild at standstill

yeah they are always a little snug when you first build them. it helps to get them all ready to fire and turn them over with a drill while holding the decomp for a good minute or two. They'll loosen up nicely then they usually start when you pedal them.

Re: Bravo rebuild at standstill

Did you put the shims between the bearings and the crankshaft on both sides?

Re: Bravo rebuild at standstill

Yes sir, Stephen! Everything is moving a lot easier this morning. But I'm having a fuck of a time getting the cylinder over the piston rings. I just walked away to cool down. Any tips? (edited)

Re: Bravo rebuild at standstill

Getting a cylinder on over the rings can be a pain sometimes. Just take it slow and don't try to force anything. A second set of hands to compress the rings can be a huge help

Re: Bravo rebuild at standstill

Yesser! Checked out Fred's Guide.. suggest taking piston off the road, insert into cylinder, then hook up piston again... after I cool off I'll look at that option.

Re: Bravo rebuild at standstill

Dirty30 Dillon /

I typically do the heat and beat method after assembly is complete.

Heat complete setup, torqued down, to a couple hundred degrees, pull it out and give the bearing journals a tap, and the crank ends a tap (with nut) back and forth. Usuall has them spinning with much less binding.

Re: Bravo rebuild at standstill

Watched a Dutch mopeder do a similar method online. Used a rubber mallet on the case.

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