Welding and remachining rotary pad?
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Style Maven
74 50s x3 78 P200 x2 84 Cosa PK50XL2 58 AllState 68 Sprint 80 50special '66(?) Super125
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Mon Dec 15, 2014 1:24 pm quote
Anybody here done it? Please tell me how it's working for you and any suggestions you might have for best results.
I found a guy who has done the pad welding several times before. He does excellent work at a reasonable price and he can refer me to another guy who has done the close tolerance pad milling on Vespa cases.
Here's an example of his welding.




I'm thinking of trying it because I've got an otherwise good P200 motor except the top end and crank.
The wrist pin bearing disintegrated and ate the pad, so I'll be doing the bearings & seals as well.
Thank you.


chewed up good, nice deep grooves


these nasty bits probably did some of the chewing
they were hiding between the seal and the bearing so they must have passed through the seal

Mr. Clean
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Mon Dec 15, 2014 1:26 pm quote
I haven't but just wanted to give you props again for how titties your kickstart fix worked out.. real good T.. real good!
Hooked
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Mon Dec 15, 2014 2:25 pm quote
I believe Hot Rod Al offers this service!
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Mon Dec 15, 2014 2:31 pm quote
Yes, I've heard good things about his work, but only 3rd or 4th hand for this.
Wouldn't be too practical in this case, wrong continent.

And thank you Mr Vader, here's a link for the curious Cannot recommend...
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P200E
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Mon Dec 15, 2014 2:40 pm quote
I've not done it on a vespa but on a different project. IMHO the biggest concern is the heat on the cast metal when you weld. Because it is just a dramatic instant change cracks happen. You really need either a furnace or kiln to put the part into and heat it completely up and weld it hot.
Molto Verboso
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Mon Dec 15, 2014 2:45 pm quote
degrease, metalset scraped on with razor blade, allow to set for 72hrs, leak down test GTG
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Mon Dec 15, 2014 3:01 pm quote
Good point on preheating, also to minimize any warping of machined surfaces. I've mentioned this to my guy on the other job he did.

As far as cleaning and using Metalset or similar, I'm usually game for down & dirty but:
1. I'd be concerned about how it would last over time, lots of heat cycles and the Metalset is gonna have different expansion/contraction rates than aluminum - I might even sell the bike and feel I would have to disclose this.
2. The talent to do it right is available & looking for work.
3. Not much of a decent surface left to wipe the razor blade against and i doubt if it's true to the original surface.

If I don't do this, I'll consider a reed valve setup, but I like stock & this is cheaper.
Molto Verboso
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Mon Dec 15, 2014 3:26 pm quote
HRA fixed a totally screwed up rotary pad on a VBB motor for me...

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Mon Dec 15, 2014 6:18 pm quote
Al has done several sets of cases for me. I don't recall what he charges, but it wasn't too bad. He sends them out to a local machine shop to have the welding done and then he machines them.
Hooked
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Mon Dec 15, 2014 6:46 pm quote
Al has taken care or a rotary pad for me. I forget the price. But it was somewhere in the 150 to 175 range. He does a great job.
bodgemaster
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Mon Dec 15, 2014 7:40 pm quote
Right, but Voodoo's in Greece, HR Al's in California. I think what he needs are some tips he might be able to pass along to his welder or machinist there in Greece, or use himself, to make sure he gets the best results. Sorry Voo, never done it myself.
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Mon Dec 15, 2014 9:44 pm quote
Blast the surface with grit, coat with JB weld and hand sand... i.e. fix it like the locals would!
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Mon Dec 15, 2014 10:37 pm quote
If you ain't gonna fix it right...

I want to say machine off the damaged pad, build up with filler (preheat as was suggested before), and machine back to tolerance. You tried bringing it to someone yet? I bet a good welder or machinist would know right away how to fix that. Or a mechanic that does case repairs.
Hooked
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Mon Dec 15, 2014 11:32 pm quote
Pad
I agree with TR. I have jab welded a few cases over the years. One on a 210 malossi my friend is still blasting about on after five years. It's works ...
Hooked
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Mon Dec 15, 2014 11:37 pm quote
I've had this fixed (vacuum leak):






I sent the crank also (Polini longstroke), and they matched the pad to the crank.

Wasn't cheap, and took ages, though: 150 euros

had it done at Karl Schweisstecknik in Germany, where they can turn this:


into:


and also fix:






http://www.schweisstechnik-karl.de/
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P200E
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Tue Dec 16, 2014 1:52 am quote
also guys this isn't a quick and dirty thing you are wanting done. it does take a while. you have to grind/machine/clean up the affected area. build it back up above what was previously there, then machine it back to specs. mr10 commented it wasn't cheap and took ages. you gotta realize this is not slapping a little bondo on and going with it.

not trying to be negative towards anyone just pointing out that it is more work than most realize to do it correctly.
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Tue Dec 16, 2014 9:03 am quote
That's some nice work there Mr10, those guys look like they know what they're doing.

I get that one could do a repair w/ JB Weld or similar and have used it to fill & level motor surfaces in the past. I'm not knocking it, perfect to fix a pad on a beater 125 or 150 motor. But I gave my reasons for wanting to try doing it 'right' on this 'valuable' P200 case when I have a great opportunity to try it.



I repeat:
1. I'd be concerned about how it would last over time, lots of heat cycles and the Metalset is gonna have different expansion/contraction rates than aluminum - I might even sell the bike and feel I would have to disclose this.
2. The talent to do it right is available & looking for work.
3. Not much of a decent surface left to wipe the razor blade against and i doubt if it's true to the original surface.

I even think I'll spend less than others have and it'll take a couple of days at most - I do all the legwork & humping the part around between shops, I deal directly with the shop owner that's doing the work and usually I get to watch. He gets to keep all the money and it usually just goes straight into his pocket.

Back to my concerns - I don't think it's necessary to premachine before welding. It would probably be ground down a bit and scrubbed sterile by me per the welder's wishes. Bad idea? Any reason premachining would be required?
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Tue Dec 16, 2014 12:23 pm quote
Too bad about the geography. Hotrod Al would do a fine job on this project. He's always come through for me!
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Tue Dec 16, 2014 12:31 pm quote
the reason i put machined/grind/cleaned all in one was because IMHO to get the build up of new material laid down correctly you need to get all the bad material out plus look for possible small cracks that go into it. sometimes it is easier to machine it down than it is to use a grinder on it was what i was going for. Another concern is get something you can get some magnification on the problem area and look around it for spidering cracks. there may be none which is a good thing, however i've seen them go out like a broken winshield and that will cause problems as well.


gl with the project
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Wed Dec 17, 2014 8:10 am quote
Step one done
and as it turned out, that was the easy part. It was much harder than I thought to find a shop with the right equipment that could do the machining. After asking at 4 or 5 shops I found a little two man shop where the two guys immediately started discussing what would be the best way to approach it.

We thought about mounting the case half in a rotary table and milling the pad by rotating the table, but finally they agreed on setting up an adjustable boring bar in the spindle of the mill and boring it. It'll be easier to mount the case to the mill table, dial it in so the spindle is on center w/ the bearing bore, then sneak up on the correct diameter by adjusting the boring tool. I think that'll give a better result, we'll see. Stay tuned.


some welding action


all done
I left the bearing in place to help prevent distortion in the bearing bore


close up, this guy welds like a surgeon putting little beads of molten aluminum exactly where he wants them
the aluminum foil was to keep any spatter out of the threaded holes but wasn't needed

Addicted
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Wed Dec 17, 2014 11:29 am quote
~ lookin good
Nice one Voodoo !
you remind me of mighty mouse !!! Here he comes to save the Veeesssppppaaaaaa!!!!



look forwards to seeing how the rest of it goes - seems like you have a great start. Good luck and enjoy your scoots over there . BTW - whats up with the one with all the stickers ? Running good ?

Cheers ~
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Wed Dec 17, 2014 12:57 pm quote
The 1965 service manual has the specs for rotary repair. It calls for epoxy to fill and build up the pad but welding it is fine if done well.

It also has the specs for the radius to machine it back to as well as the diameter of the crank and clearance.
Mr. Clean
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Wed Dec 17, 2014 1:13 pm quote
oopsclunkthud wrote:
The 1965 service manual has the specs for rotary repair. It calls for epoxy to fill and build up the pad but welding it is fine if done well.

It also has the specs for the radius to machine it back to as well as the diameter of the crank and clearance.
sorry Patrick but do you have this manual? in PDF? or is it in any 65 vespa manual?
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Wed Dec 17, 2014 1:57 pm quote
http://oopsclunkthud.com/Vespa_service_manual/index.html

The page scans are really large making it hard to find what you are looking for, but the detail is there when you do. I know it was posted in another thread and someone put together a pdf and reposted it
Mr. Clean
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Wed Dec 17, 2014 2:00 pm quote
Thank you.
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Wed Dec 17, 2014 2:03 pm quote
Here's the page

http://oopsclunkthud.com/Vespa_service_manual/Pages/209.html

The specs are on adgasent pages
Mr. Clean
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Wed Dec 17, 2014 2:48 pm quote
Vader19 wrote:
Thank you.
again
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Wed Dec 17, 2014 3:13 pm quote
Thank you Patrick for the info, you can find a link to the PDF file here, on page one of the 'Tip & tricks' thread. But I've got a hella slow connection & can't seem to load it. Could you or anybody w/ a fast connection please tell me what the specified bore diameter(or radius) and the clearance between the crank and the pad is?

Interesting that even the manual suggests filling w/ epoxy. This pad was chewed so bad that I think if I had tried it, the new pad surface would be nearly all epoxy. Would you buy a bike w/ such a motor over one weld repaired like HRA does? Not me. Hoping we get results as good as many have reported getting from him.

Should get the machining done within a few days and with some photos of the work being done, but it's my first time dealing with these guys and regular customer work will usually take priority. Best to wait for the phone call when they're ready & I'll go watch it happening. My years working in a foundry/machine shop sometimes pay off when I'm trying to get hooked up with these little shops.

Mr Falcon, re ratty smallie w/ ancient decals - Maybe you missed it on the smallframe page? This post and the one 4 or 5 posts further down. It's still running strong many kilometers later and has become my current ride of choice. Details on the porting work to match the Primmy top end are in the 'Cannot Recommend' thread.
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Wed Dec 17, 2014 7:05 pm quote
looking good so far cant wait to see the finished product.
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Thu Dec 18, 2014 8:58 am quote
V oodoo wrote:
...
But I've got a hella slow connection & can't seem to load it. Could you or anybody w/ a fast connection please tell me what the specified bore diameter(or radius) and the cle...
arance between the crank and the pad is?

...
Anybody? It would be much appreciated. TIA.
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Thu Dec 18, 2014 9:18 am quote
The radius of the pad is listed as R 49 -0 +0.04

Can't find the crank diameter but you can measure it and infer the clearance.
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Thu Dec 18, 2014 9:38 am quote
Thank you Patrick, that helps a lot - now I can give the machinist a number to shoot for. We will measure the crank diameter and work out the clearance, trying to keep it to a minimum. Hope to know more tomorrow.
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Thu Dec 18, 2014 9:57 am quote
Re: Welding and remachining rotary pad?
In your 2nd image, it looks as though the carb inlet has been drilled to extend it the opening.
Is this so?
And if so, whats the benefit?
Does it need a reed valve to run as there's not much of the rotary pad left where the drilling has taken part of it away?



The reason i'm asking is that i've got a set of P2 casings that look just like that & was wondering of they're useable with a standard 24 carb without installing a reed valve.

Cheers.
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Thu Dec 18, 2014 10:15 am quote
^^^ I think that was done at the factory, seems I've seen it before on 200 motors. There's still plenty of pad to seal against and bear in mind that the crank is relatively 'dry' going past the long end of the pad, but has a fresh load of fuel & oil by the time it gets to the shorter end. I think you should be able to use the normal 24 carb w/ no problems.

On mine I'll be blending the passage between the carb & pad, and opening up the carb end a bit to better match the 24 carb but I don't know if it matters much - just seems like a 'good idea' and so easy to do now.

Reed valve? What's that?
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Thu Dec 18, 2014 11:57 am quote
Re: Welding and remachining rotary pad?
nebulae wrote:
In your 2nd image, it looks as though the carb inlet has been drilled to extend it the opening.
Is this so?
And if so, whats the benefit?
Does it need a reed valve to run as there's not much of the rotary pad left where the drilling has taken part of it away?
That is a factory thing. Not sure when it started, but always noticed on the P-series, but never on the vintage-looking scooters' engines. I think it was purely to extend the intake duration. It is always so sloppy. I usually clean it up a bunch with a grinder.
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Thu Dec 18, 2014 1:20 pm quote
On early motor (vnb, vbb ,gl ,early super, early Sprint), on later Supers, Sprints, and P125/150 they open the rear of the rotary pad and on P200 the front of the pad is opened.
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Thu Dec 18, 2014 2:07 pm quote
Cheers for that.
I checked a couple of casings at my mates tonight.
Its certainly a Piaggio factory bodge.
I'll also be cleaning mine a bit with a dremmel before building the engine.

Sorry to hijack yer thread Voodoo.
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Sun Feb 01, 2015 12:45 pm quote
No hijack problem, I wanted to know for sure too.

I got the P200 motor almost completely assembled after bringing it home with me in my luggage in pieces. When I went to put the piston on I discovered I must have a P150 crank as the wrist pin bearing for the 200 piston is bigger & won't fit. Everything else works so smooth & silky too- shitshitshit. Oh well, all I gotta do is find a good used p200 crank & put that in and it should be good. The rotary pad looks real good & seals nicely against the crank. Never even thought to check the crank further when I saw it was for P style bearings. It was with other P200 parts and it's in really good shape too.



You can see that there were some gas bubbles in the weld that got uncovered in machining. It was easy enough tp JBWeld them up & sand smooth. I also cleaned up the edges more with the Fordham & smoothed the inlet after this pic. Passed leakdown test OK, not great - the oil did seep out after a while.

So, in conclusion, not as nice as HRA's work and it should work but in hindsight I'd pay the extra for the better job Al does. The welder preheated the casting with a torch, but if I was gonna try it again I'd want to bake it in an oven for a couple hours to get more gas out before welding. Total cost was 15 euro for welding and 50 for machining or a little less than $75. If anybody in Greece wants contact info for the 2 shops, PM me.

Please let me know if anybody has a usable stock P200 crank laying around I can trade for goods or cash. Even if it might be bent, I could try to straighten it.
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Mon Mar 02, 2015 7:10 pm quote
Sprint 200
I got a good stock P200 crankshaft from Skotieono's motor build and put it in the motor. Thank you Skot, your crank still lives! I had to relieve along the edge of the pad for the small lip on the side of the P200 crank that the P150 crank didn't have. The crank had about .004" runout and I was able to get it down to about .001".



It's stock for now except for a PX flywheel lightened by removing the ring gear. Next I'll probably get the cylinder honed & put in new rings as I can see the compression isn't all that great. After testing in the stand, I installed it in this old Sprint that I rebuilt the floor on(look here).

Still lots of little details to finish up, but I took it for a short first ride today & all seems well - easy start, lots of power & good idle. Clutch & transmission both work well too. Now to put some miles on it and see how all these recycled parts and rescued case are gonna hold up.


I replaced the kick start quadrant with an older one so I could use the older style curved lever to match the scoot.


I like the old paint and the giant Euro headlite plus now 200 cc's, 12V & CDI

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Mon Mar 02, 2015 10:49 pm quote
I can't understand how this motor - it's a 200 right? - had a 150 crank in it, how did that work? Unless it had a 200 rod fitted to it to the 150 crank, otherwise the rod would be too short. And did you releive for the crank lip because it had weld in it from the repair?
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