Modern Vespa

Ahh...brilliant. I need to make one too.

Same money will get you the SC clutch (same, as all are based on the MMW design) with the CR plates and the 24. The 23 isn’t available for now...

https://www.scooter-center.com/en/clutch-bgm-pro-superstrong-2.0-cr80-ultralube-type-cosa2/fl-for-primary-gear-64/65-tooth-vespa-px200-rally200-22-tooth-bgm8322?number=BGM8322

I have the bgm one on my Stella. Wanted to try the sip one instead. Have seen fmp suggest the bgm gearing has wearing issues, which i had gickspeed cryogenically treat it for added strength. Hoping the sip one can skip that process. Also curious how different the sip and bgm cr80 plates are. Hoping interchangeable.

Swiss,
I was a bit surprised on how far I opened my exhaust port to clean it up and even it out. I was using various diameter sanding drums so nothing aggressive. Once you get it cleaned up, I wouldn't be surprised if you pickup some more overlap.

I had to laugh, Jack made fun of my exhaust port work the first time around. I thought it was pretty good, and better than what I started with. Needless to say I had to try again and redeem myself with the scooter gods.

I'm not familiar with those transfer ports, is the angle, the way there supposed to be or is it the rough casting? For some reason I'm thinking mine were angled also.

I'm jealous, looks like fun by the way, makes me want to buy one just to clean it up and see what I can get out of it. I have to work on heating my garage so I can get some tinkering time in.

Hibbert was asking me about the difference in sealing lip on clutch side of p200 crank compared to 150 crank, so his query got me out in the cold garage pulling the parts out to take pictures and post for him here. Mostly looks similar but slight differences i can see. If anyone knows more please share. I'll quote hibbert below with his original questions.


Lml on left, polini 60mm 200 middle, stock p200 right

Stock 200

Polini 200

Lml stock 150

p200 stock other side

Polini other side

lml other side

I'm easing back into this rebuild. One or two small things a day instead of trying to rush to do it all at once. Tonight I cleaned up some of the leftover oil and dust in cracks from the sand blasting on cases. Also took the cover off my Px125 bench seat that I'll use for this p200. Someone put a replacement seat cover over the original seat cover, and both were decaying and cracking. Gonna have to treat the rust on the seat frame and respray black to protect it for the next 40 yrs.

Regarding cases, I noticed some pitting next to the oil drain hole which are just on the inside surface of the case, no marks on the outside. Wondering if this is something I should worry about for structural issues or just ignore it? Also saw similar pitting on the sealing surface for the cylinder base. Should I deal with this pitting next to the right port? Finally, why do they have the side port indents on the case if there are no port openings on the cylinder skirts of these stock p200 barrels?


pitting near oil drain hole.

pitting on the mating surface at the top most port in this photo. Thinking I'll leave it alone.

why have these left and right indents in case when there aren't matching transfer port openings in the stock skirt?

no transfer port openings in skirts

bench seat frame from px125

rusty

Swiss - looking good.
That pitting is minor - and not a concern.
Even on a sealing surface - a thin layer of sealant under your gasket will ensure no leaks.
So nice to work on such clean cases.

Interesting point about the side transfers.
Looks to me like they were made for a cylinder with multi ports?
Will be interested to hear what others have to say about why and when they were added.
Perhaps it was to plan for the future...

Side transfers up inside the piston work well enough. When the base ports are opened up it makes no noticeable difference, without many more changes. Which then, is more work, than its worth. My PX200 is running a extremely modified (20bhp) stock cylinder. So much work I won't be doing another one anytime soon. Buying a kit (and tuning that) is way easier.

One of my lesser favorite tasks... getting the damn engine bushing mounts installed. One went on relatively fast. The other one is refusing to go on straight and keeps getting bunched. Heated case, lubed up the hole and plug with tons of soap. Still won't go in straight! Sounds like a personal problem

Save that one for another day.

BTW, I just swallowed hard on a damn expensive SIP order to get the rest of what I need for this engine rebuild. Closed my eyes and pressed purchase. ha!

How close are P200 cases to the earlier P150 cases? I've often wondered if the port locations were a hold over from them. But if that were the case why is the boost port in the correct spot?

Are you going to do some o tuning and put in case ports? If you've got another cylinder you want to put on later now would be the time to cut them in.

The cases are much the same from crank centerline down, but much different for the top half. I think.

For your messy motor, you're on the right track IMO and looks like there might have been a deelux upholstery kit included when you clicked BUY?


Good!

Not sure how your trying to install your bushings. I used this method when I did my polyurethane bushings and it worked great. I bought the hardware at my local home supply store. I've seen it at hardware stores also.

https://youtu.be/2Qjk_TuMEKs

I used perforated square tubing for the square tubing. Instead of trying to find a pile of washers for the end I cut a piece off and turned it sideways to make a T shape.

https://www.homedepot.com/p/Everbilt-1-in-x-36-in-Zinc-Plated-Punched-Square-Tube-803037/206939549

I do basically the same but using a sip bearing puller tool on one side and washers on the other side. But the bushing is not going in straight and one edge keeps getting hung up. If you try to push it through it's just gonna rip the bushing apart.

V oodoo, i didn't buy anything for the seat. I need to figure out a new cushion for the bench seat cause the original way rotted away and stiff. Don't see anyone selling the cushion, only covers.

Out of curiosity are you using rubber or polyurethane? Wondering if the stiffer urethane material slides in easier?

The piaggio original rubber.

Here's my installer and puller. And you can see the problem where this one edge of the rubber gets hung up and won't go in. I'm thinking I'm gonna have to sand the rubber down just slightly around that inner edge of bushing to get it to start off correctly seating as it gets pulled in.

Parts on way include SIP fast flow fuel tap, same exact 24/24 carb I got on my stella (cause the bike came with a 20/20), VAPE DC Variable ignition, SIP Cosa 2 Ultrastrong with 23T cog and CR80 plates, and I went with the SIP Road 3 exhaust cause it was cheaper than the polini and everything I found online seems to suggest they are very similar in performance. Also got tubeless rims and Heidenau K62 tires which I'll throw on the stella and use the current tubeless on this p200 to start. Did not go with 11" tires/rims cause going with them just seemed a random decision until I hear more about their benefits.

I also just realized I did not get everything I need to complete this engine as I believe I need a new primary gear for the christmas tree cause the existing one has a slight gouge going around the whole gear down the middle of all the teeth faces.. and I should probably rebuild the christmas tree with new springs anyways. Might even need a whole new Christmas tree cause i can see more indents on the face of some of the gear teeth pictured below. Or maybe it's so minor that it didn't matter.

So I guess I'll have another order coming this month to get this engine built.







Last edited by swiss1939 on Sat Nov 21, 2020 12:00 pm; edited 1 time in total

Nothing wrong with your primary. Those gauges are normal and they’re there to carry oil...

Perfect. One less thing to purchase! Actually i vaguely remember mentioning them in the past and think you said the same thing. It's been a while since i looked at this engine.

That’s a great list of SIP parts!

For the engine mounts, maybe put them in a pot of boiling water for 5 minutes? It will soften them up quite a bit. Also get the case hot enough that you don’t want to touch it with your bare hands, put some grease on everything, then use a mallet to hammer them in.

Ha yeah maybe too brand specific. Good tip on warming the rubber mounts. I'll try that as well. I've been heating the cases pretty hot but that didn't work.

Greasing them up and twisting in by hand normally gets them in half way. They're not that tight.

Tried that as well. My cases must be tighter tolerances cause these things aren't easy to get in or out.

Can you take out whatever that spacer is between the rubber bushing and the big flat washer? Looks like it’s allowing the rubber bushing to turn sideways.

thats not a spacer, thats the metal tube the rubber bushing is attached to. Photo is of the puller tool loose after I backed off from trying to get it in, so everything is just sitting freely and the bushing was still stuck in.

Hmm, I put the urethane bushings, then slid the tube in after I had the bushings in place.

as far as i know these original bushings the metal tube doesn't come out of the rubber, they are attached so you gotta put them both in together. Its similar with the lml original bushings. I tore one of those up last year and they have some metal ring on the outside of the tube which the rubber is molded over, which helps hold the rubber to the metal tube. I'm assuming from the way this rubber is molded over the tube it is the same basic construction on the piaggio original bushings.

I should have taken a picture of it when I pulled it apart.

Shouldn't be that hard, I've had to file or Dremel a chamfer in the edge of the hole and use lube and a big hammer to swat it in to start, then draw it all the way in like you are. Maybe some luck was/is involved. Therefore... Good Luck.

The Clauss mounts the center metal parts are separate, you put the bushing in then the metal tube.
https://www.claussstudios.com/store/p765/Vespa_PX125_PX150_Polyurethane_Engine_Mounts.html

Working on this engine in my living room cause it's damn cold out! Doing all the mockups inside and anything dirty out in the garage.

Got those bushings installed finally. The one I was struggling with was warped and not gonna go in. New one installed with much less effort and a combination of all your suggestions.

Got the plastic bearing dummies and set up the crankshaft with piston to do measurements of the rotary timings.

Rotary opens at: 42.78mm
Rotary closes at: 26.77mm

I measured these by shining light into the case up through the rotary valve and spinning the crankshaft until it either cut the light out or let the light through the valve.

Trying to understand what the goal of tuning the rotary inlet is. I understand it in regards to the same concept as a camera shutter speed, so by widening the rotary inlet, I am letting more air in which will still have to compress to the same end volume at max compression.. which means more power. But I'm still trying to decipher what are good targets in terms of amount of time open and when it opens or closes in relation to the cylinder timings.

Just watched a few FMP videos and it seems he targets 200 degrees for admission timing, and through grinding the rotary pad on the open side wider, and the crank cheek on the closing side, he expands the inlet open and close and admission to suit his targets. From what I'm watching it seems the important targets at least for his tuned engines are concerned.. 200-210 degrees admission is a goal.. and 8 degrees of overlap between transfer and inlet opening. Now I'm not entirely sure how a 200 degrees admission and an 8 degree overlap equates to rpm or torque similarly to how I get the exhaust, transfer and blowdown relate to the same in cylinder timings. Does it relate similarly? Or is tuning the rotary timing purely a process of ideal intake volume or instead ideal open/close in relation to cylinder timings?

If I were to try to target 200-210 admission and 8 degree overlap on my current numbers, this means I would need to grind out the intake opening 10mm earlier than current on the rotary pad, and leave the crankshaft closing cheek on the crankshaft where it is currently at. This would give me a 206 degree admission with 8 degrees overlap of the rotary opening to the transfer port times.

EDIT: Tuning Vespas The Norrie Kerr Way. Just came across mention of this book in searching about inlet tuning and it seems like a good book to get through. Gonna try to get my hands on it soon. And also getting through this discussion 6 months ago from chandlerman on the same topic, where it seems for my desired touring slightly optimized stock setup I should be closer to 180-190 admission which is not far off from where it stands as is, but still begs the question of how much overlap helps or detracts from torque.. and if it benefits a touring setup to shoot for more overlap...
http://modernvespa.com/forum/post2419515#2419515

Also realized my calculator numbers were off from most recent cylinder measurements. updated images to correct measurements.

Here's the calculator attached below with no base packer so the negative PBT is where it sits by default.


Measured as stock.

0.59mm base to get 1.2mm squish. Grind rotary inlet 5mm wider to get 190 degrees admission.


Last edited by swiss1939 on Sun Dec 13, 2020 7:37 am; edited 1 time in total

Trying to understand what you are talking about here.. are you saying 28 degrees in terms of 128 transfer? or 28 degrees for blowdown? To get the transfer ports to 128 degrees would mean a 1.32mm base gasket.... which would throw the squish off as it would be up at 1.93mm.

Or are you suggesting just increasing the squish to 28. Cause that would involve grinding exhaust up 4mm making it 180/124 28. Is it really that much of a difference for the effort to modifying the barrel? I'm still leaning against modifying the barrel aside from cleaning it up slightly. Not gonna widen the exhaust as its too close for comfort to the stud holes. I will drop the exhaust port to PBTD though.

Your new crank is cut for higher rpm. 75 degrees ATDC is quite a bit. Some would say the max. The longer ATDC the more blowback. Not ideal for torque. Obviously you will use this Polini crank. To give enough torque the power will need to be increased a bit more. Go for under 200 degrees total inlet. Approx 195 will do it. If slightly more is ok but keeping under 200 should be the plan.

28 degrees blowdown. 126 duration is a good amount of transfer for this cylinder. Still has the slanted transfers so this isn't like normal 126 degrees. Will be like 126 for blowdown as the reversion will still happen but will be more like 122 or so for performance. No point aiming for really high power as the transfers are just too high velocity and it will just run flat. In summary 126 transfer duration plus 28 blowdown means exhaust should be 182.

Ahh damn. So the crankshaft choice requires doing some exhaust grinding to make it useful and not run like crap. Sounds like i have to do a little more than desired in order to have the parts chosen result in a useable engine. The result of mismatched parts ordered for intended purposes!

Minimal dremel work needed to make these parts useful:

-Widen the rotary inlet pad to achieve 195 degree admission (approx 7mm)
-grind exhaust up to 182 and down to pbtd (approx 4mm)
-chamfer

Time to get the dremel out again.

Wondering if something like this crank would have been better choice regarding the blowback mentioned. Mine is 138/6. This one is 125/-5. Guessing the earlier timing on the crank translates to lower rotary times with the same admission?
https://www.sip-scootershop.com/en/product/long-stroke-crankshaft-sip-premium_45021510

Also I'm gathering from what you say about ATDC rotary timing being more for higher RPM.. that the position of the rotary timing in relation to the cycle does matter for desired torque or rpm targets. This was something I was wondering and I guess the way I'm trying to understand it is using the graph from that calculator.. the top crescent depicting the rotary timing.. if kept same duration, but rotated more towards ATDC shifts the engine performance towards the RPM end of the spectrum, and conversely, rotating that crescent on the graph backwards towards BTDC shifts the engine performance towards the torque end of the spectrum.

Mocked this idea up below:


shift the rotary timing further past ATDC == RPM

shift the rotary timing earlier before BTDC == TORQUE

minimum to make the parts work well together.

Rotary inlet duration needs to be in tune with the cylinder and exhaust. And even this is not one size fits all.

Generally though the longer the duration the higher the torque but if you go over what the cylinder and exhaust are aiming for, the torque starts to go down again.
The one thing you can be sure of is the stock inlet is sized and timed for maximum economy and lower rpm max power delivery.
What you're planning only makes yours better.

Last looks before the dremel comes out. Just about to get out the dremel and work on this. Just to recap.. not raising the exhaust top at all.. grinding bottom down to PBDC, not really widening the exhaust either due to studs. Currently exhaust width is around 61% of bore. Could go to 68% but Im not risking that.

Exhaust shape.. should i make it more boxy like the example below?

Also will grind the rotary inlet to 7mm wider than stock.


p200 stock exhaust profile

p200 modified boxy profile.

I up and moved my p200 rebuild operation to Florida for a month or so to take advantage of warmer weather and current ability to work from "home". Home being my parents house in port st lucie.

Couldn't wait to get the dremel out on first day down here! Rotary inlet opened up 7mm to achieve the desired 195 degree admission. Just barely broke through the stud hole. I've not had good luck using jb weld putty especially for filling small holes like this stud opening. I'm curious if anyone has used this permatex liquid metal filler? I'm thinking i might try using this to fill the opening between rotary pad and stud hole.

https://www.amazon.com/dp/B000ALDYJI/ref=cm_sw_r_cp_apa_fabc_9Zm9Fb315F4F5

What's the split on the 195 degrees? Looks like not a lot off at the back.

Did you do the cylinder? What ring thickness you using?

Not sure what you mean? I didn't touch the rotary close side.


Didn't start on the cylinder yet. That's next. Gs piston with 1.5mm rings.

I believe Jack is asking about timing BTDC and ATDC opening and closing times. Looks like you are modifying the opening section of the rotary pad. Per Jennings, "The valve's opening point has an influence on power output, but in general it is relatively insignificant as compared with port-closing. "

I believe that is why most (instructions on Polini cylinder also say) cut the disc on the crank to alter the closing timing as there isn't much room on the closing side of the pad.

Hope this helps.

Ah ok.

121 open (after grinding) and 74 close. Based on the calculator with my target numbers.

I'll physically confirm that when i get a chance.