Modern Vespa

Have a 1983 Vespa VBX1T, P150S Strada. 3 port. (This bike was made for the Indo. market) The new crankshaft I bought didn't fit. This orig. crank has 25mm shoulders on both the flywheel and clutch sides to fit into the bearings and some other maybe not so common, shoulders on it. Does anyone know of a replacement cranks with the same specs? Or something that would work? See photos. Thanks!

Before the crowd answers, Are you certain the old crank shaft doesn't have a bearing race still on the fly side?

Here is a photo of the flywheel side- on my old Crank. If the race is pressed on, it still totals 25mm round And fits well into the bearing. The New crank I bought (that doesn't fit), had a race pressed on and it was 28mm round. Obviously, not able to sit into the bearing that is installed in the case.

can we get some pics of the bearings & races, new & old as wells as the cranks?

I can't tell from the pic of the crank if the race is still on there because of the angle and shadow.

See below photos of the New Crank with the race pressed on making it 28mm on the flywheel side. ( the clutch side was 25mm and fit well). The bearing pressed into my case, and a photo of the old crank with the 25mm shoulder.

I am thinking, possibly trying to remove the pressed on race on the new Crank and with out it, it may fit. But I don't want to destroy a new crank that I can return if this is not an option. Thanks !

Why would you replace the crank but not the bearings !? In my opinion, start fresh with new bearings.
Order the right ones and go !

The bearings seem to be fine. There are 2 issues with the old crank:
1) the woodruff key slots are totally worn and the keys slip and keep getting sheered off causing the timing to be off.
2) The fly wheel side threads are stripped and a mess so the flywheel can not be properly tightened which again cause the timing to be off and the bike not to run.

I was advised to replace the crank and that would solve those 2 issues. The bearing size that fits this bike is the same for the clutch and fly side (25mm opening). I can not find a bearing that fits the case that has a 28mm opening to accommodate the new crank I bought( it has a race pressed on making it 28mm round), hence the issue...

New cranks must be fitted with two new seals and two new bearings. However, doesn't seem like you brought a new crank (eBay?). Those 28mm bearing rings are part of the PX bearing. They do come off but takes some skill.

For the cost of bearings why take the chance? And how much life is left in them, change them now and you've got a line in the sand.

Either a bodge job on the fly side or they used bigger bearings for that market. Check the overall dimensions. If they're 25x52x15mm then replace the one already in with a NU205 to make things easy. You'll also need to replace the race on the crank you bought. And as everyone said, new bearings, seals and I'd say a cruciform is a must since the engine's split...

The crank is new. I bought it from ScooterWorks.com (Mike there has also been very helpful trying to trouble shoot this issue, but we don't have a solution)

Here is a #NU205 bearing photo that fits my case. It is shown with the race not pressed in.

Here's the question: Is the race about 28mm on it's outside? If so, I am thinking I can press in the new bearing and then the 28mm size race that is pressed on the new crank will fit in?

Thanks!

NO!! Whatever you decide, you need to remove the race that's on the new crank. Crank is 25mm at the center. The race it has on it's from a split type bearing that's 25x38x15 mm and common on P/PX engines. Your case half is different. It was either bodged (enlarged) or it's common for that market. If the dimensions of the bearing currently in, match the NU205, replacing it with it will make future splitting easier...

Got it! Ok - What is the best way to go about removing the pressed on race - on the new crank? Appreciate the info and advice!

The crank with the 28.7mm ring on in your picture is not new. It actually looks fairly used.

That bearing is as a T5 if you are shopping.

I thought so too. Why would a new crank have a race installed. And the area where the fly seal works looks pretty worn...

What he said.

I have never seen a new crank with a race installed, race is coming with the new bearing ! Weird…

Or, maybe he wrote new as new to him but could be and probably is 2nd hand

FWIW.....

The key only indexes the crank to the flywheel for timing purposes and if the tapers of the crank and flywheel hub are properly matched and the nut is torqued to spec, there is, technically, no need for the key. If it shears, the issue is with the interference fit of the crank and the hub. On the other, straight end of the crank shaft the key is critical.

Also, as far as I know, bearings all come in whole numbered (Metric) increments.