Modern Vespa

So the SprintV motor in my VBB has just developed a strange issue.

Under hard acceleration, and mostly in 3rd or especially 4th gear, the engine will surge and feel almost like it's jumping out of gear, but then jump back in, but without the full-on pucker-inducing (and possibly case cracking) slam. I can feel a little bit of pull on the shifter when this happens. I don't think it's ever done it in 1st or 2nd gear, but I don't spend a lot of time in those, so maybe I just haven't experienced it there.

It started doing it a couple days ago and did it consistently starting about a mile and a half into going out to grab lunch and then continuing for the entire two mile ride home.

I'm not sure if it's jumping out and back into gear, or it's something with the clutch. Any thoughts are appreciated before I tear into the motor, though.

Worn clutch plates or springs?

That'd be the best case. The suddenness of it going from "never happened" to "happens constantly" is a little strange, though. Easy enough to replace the plates, I guess.

It's the original six-spring clutch, too. so probably under-rated for what I've done to it.

Check the brass push rod and pressure plate as well. That will go from zero to 60 in no time as well. From too tight clutch cable.

I know that failure all too well. It used to happen to me about once per year when the road salt would cause the clutch arm to get stiff and not release fully. This isn't like that. It doesn't lurch into gear, it just jumps under power once it's in gear.

It could also be the gears and/or cruciform are worn, but I'd like to think that's not the case because the Sprint cases don't have a two piece fly side bearing, so a PITA to split and re-assemble.

My money on worn plates. Easy check.

Only way to know for sure is crack it open and see, I guess. That motor was mostly sitting for a couple years before it went in the VBB. I should make sure I have a spare cruciform for it if I'm going to be ordering stuff.

I'd jump into the clutch before cracking cases. maybe you get lucky in there with something wore the F out or wasted. that's were my money would be first.

especially with a 6er and what you got cooking? that's my first suspicion.

I expect a full autopsy after the fact!

I'll crack it open this evening after work. Once upon a time, I could do a clutch swap in 20 minutes with the motor in the frame. We'll see if I've still got it.

I went ahead and threw a cruciform in the cart along with a six spring clutch rebuild kit and a few other goodies I had on the shopping list, so Dave and Matt will be drinking on me tonight.

Well, I was gonna say it sounded kind of like a false neutral to me; checking the gear stack slop and getting a clean cross in there would have been my bet. But here's hoping I'm jumping the gears...er...gun on that! Have you checked the shifter cable tension to see if it's pulling a bit one way more? Might exacerbate the issue if its gearbox related

That'd be the issue with my P200, but I know what's going on there, I just never get around to fixing it because it's kind've just chillin' until I get ready to do the uber build on it.

This is different. I might try to get a little audio/video of it before I crack things open for posterity.

why not go 7 spring instead of rebuilding the insufficient 6 spring?

The gears are different diameters, so you're kind've stuck. I was going to put a 23t 7-tooth clutch I have on the shelf in it when I did the 8" conversion, but it was no bueno.

Unless someone knows some tricks in this department that I don't. Like could I just stuff the 6-spring center cog into a 7-spring clutch? Is that a thing?

you can, but it requires drilling and peening of rivets. but it is something that can be done.

for whats its worth, I put a Malossi 210 on my p200 and didn't upgrade the clutch and about 2 months later started having weird clutch issues, more like getting stuck going in the up direction, sometimes I had to force it into gear., When I took the clutch out it had been torn up pretty good from the tuned engine, the sides were blown out in some parts. Put in an sip ultrastrong (COSA 2 I think) and it works great

Yeah I've got a BGM Superstrong and love it - the pull is softer than stock but other than the corks it feels like it will outlive humanity

Yup. I have superstrongs in both my GL (BGM177) and SprintV (Malossi 210) motors.

The one in my GL is one of the original ones and the one in the 210 uses the CR plates. The GL clutch has seen things that no clutch should ever have to see, but I just throw in new plates and (and one time, a new woodruff key) and keep on rolling.

My money is on worn cruciform. I had similar symptoms on a long ride last year. It got progressively worse and eventually the bike wouldn't stay in fourth gear. New cruciform and gear shimming solved everything.

Putting a bet on a primary shaft/Christmas tree issue…

I think I owe sake and crackers to someone as well…

My money is on combo of clutch plates and thrust washer bending.
Have a look at the thrust washer for flatness.
Suspect its warped.
Not sure how that could bring on the issue - but Im throwing it out there blindly.
Clutch plates must be slipping - more likely to feel it in 3rd and 4th.

Cruciform worn. Maybe new cogs.
The gear change twitching is the clue. If it's been doing it a while the slide and selector will need attention too.

Whether worn or not, Clutch obviously is not up to the job. A banded Cosa would be the cheapest that would do. Ultrastrong the best option.
The 23 helical cog comes in two diameters. For 67/68 or 65 primary. Cosa, 6 or 7 spring all have these options.
If splitting anyway and you have a spare 65 ring gear, that might be a cheap way to use that 7 spring 23 you have.

A video would be great - it's hard to picture but sure sounds like the cross and correct gear seat are losing track of one another in the heat of the moment (esp since it happens more in 3rd)! I was able to compensate for that on my p for a while with selector box adjustment but eventually had to do the cross

Ohh, ohh (as I put my hand up passionately) ... it could be that you Clutch is slipping, it happened to me once...l

So a new cruciform is on the way from Mercato. I'm already assuming I'll need to do that swap.

* Mental Note: make sure I have case gaskets for a Sprint motor... *

If I need gear cogs, I'll have to order those, but I'm also pretty interested in doing the primary drive swap if that will let me run the 7-spring 23t clutch I have on the shelf.

If I need gear shims, that'll be a(nother) parts order.

Should I put a band on the clutch basket while I'm at it? This motor isn't super-hot, but it's a respectable 17 or 18 HP, IIRC. That's kind've in the maybe-maybe not range for a banded clutch, right?

I have at least one 68t primary I could liberate from a ruined Stella xmas tree. I have a second one, but not sure how many teeth off the top of my head. It might be a 65t.

I have a cush drive rebuild kit, I think. Is it just rebuilding the tree with the larger primary?

* Mental Note 2: Make sure it's all there or I've figured out what I need BEFORE I order... *

I didn't open up the clutch last night. Instead, I did a "two steps forward, one step back" worth of work on the GL. Back when I welded up the blown out transfer, I raised the port timings with a .5mm based gasket to see if that would be a better fit with the PM Tuning pipe. It was not. I shifted the power band up, but didn't gain, maybe even lost a little, peak power.

So last night, I pulled that base gasket out and put the head spacer back in. Then, since I had the pipe off, I replaced the strap-on (heh-heh heh-heh...I said "strap on"...) EGT sensor with the broken wires by welding on a bung for it so I can now screw a sensor on. Ray8, I know you'll sleep better tonight knowing this .

Then, I set out to replace my center stand, which has been on the verge of collapse for a couple months and had gotten to the point it was more like training wheels than a proper center stand. Naturally, the new center stand was fouled by the exhaust, so I threw my side stand on in the interim, which I don't like but is more trustworthy than a center stand that the bike rocks side to side on.

So now I also have to either fabricate a center stand bracket to move it forward or modify the new stand. I'm leaning toward the former, but still have to actually do it.

In the meantime, the bike just gets to look super-fierce when parked, even if it's a complete pain to do little things like buy gas with it that way.

Sooo...winning?

well since you are "having" to go in to swap primaries, I guess you know that you need VR1 cases, right? your hand is being forced here

Even *I* have my limits, John! It may not seem like it, but if you try hard enough, you'll eventually find them.

Also look closer at selector box...especially the arm with the roller and pin and spring...the arm has a hole in it that is prone to wear and often over looked...press and wiggle said arm with your thumb to check for play. Should be none

Bat wing notches can also get worn and wont "hold" in gear...or .......move in and out a bit and you blame the clutch springs /plates for slipping

You can get a kit of replacement bits with spring, pin arm/awl etc.....or a new box entirely

If you need a new selector box do the research. One Brand is 1mm shorter and needs a spacer.

It was "game changer" on a scoot that initially I blamed a random lurch like yours as clutch related

"Not Even Ow"..twas heavily worn selector box ( and I changed cogs, cables , clutches covers , cruciform prior..as you do only to find the heavily worn box weeks after

Easy check

I have a new, spare selector box. I don't think it's EFL, but that'd be an easy fix if it was the cause.

I'm still intrigued about swapping the primary drive gear so I could run a seven spring clutch, though.

I remember well... "This guy could REALLY use a welder."

Last year:
"Honey, what's that?"
"Ray8 said I could really use a welder."
Later this year:
"Honey, what's that?"
"Ray8 said I could really use a bigger compressor."

I posted how to make a bracket to move the stand forward a while back. Very happy with it, though a pre-made one isn't a lot of $.

More stable than before, btw. Like bigger triangulation with the tire or something -- at least on the VNA.

And add this guy to your cart:
https://www.amazon.com/gp/product/B008RA5JEW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I knew you'd approve!

I have a can of anti-spatter spray. I just didn't realize it was for spraying on the work area, and not just the torch itself. Makes a lot of sense now that I know...

And, yes, welding up a bracket to move the center stand forward is 100% on my list for the weekend, probably this evening since I think I have all the metal stock I need on hand.

I think I should be able to get away with just doing it with just 1" strips extending it forward since I'm using the 1/8" steel.

I don't think a single engine ever left hodgespeed after a rebuild with a 6 spring clutch in it, except maybe a handlebar bike or some of the tricky VNA/VBA engines that use some one-off clutch bits. They just do not hold up to even modern stock builds and the way people ride nowadays. Stock 7-spring clutches are plenty durable for most people as well; some people insist that you need at minimum a banded clutch (or even some exotic re-engineered cosa clutch that costs $500), but to be honest when I raced MASS just about all of the racers running vespas ran unbanded stock 7-spring P clutches, even eschewing cosa clutches. To be honest I don't think I've ever had a banded clutch in any of my personal bikes.

Clutch swaps aren't as tricky as you are making them.

Only the 200's came with a 23/65 tooth primary; otherwise early P125 and 150 and everything before them came with 22/67 primary. Later PX setups had 21/68 setups. (mostly EFL, though there is a transitional non EFL setup in like 1983 or so that also came with 21/68)

Any of these setups can be swapped to a 7-spring from a 6-spring with some clearancing modifications to the case and cover, if used with an appropriate gear cog.

125's and 150's typically used 6 springs; 180's, 200's and PX 125/150's used 7-spring.

65 tooth primaries can be used with stock 20/21/22/23 gears.(T5's had a 20 tooth clutch).

67 and 68 primaries are so close in gearing as to be pretty much interchangeable. They also work with any stock 20,21 or 22 tooth gears. However, they do NOT work with a stock 23 tooth p200 clutch gear.

However, DRT makes a 23 tooth gear cog for both the 6 spring and 7 spring clutches that will drop in and work unmodified on a 67 or 68 tooth Christmas tree gear if you want to upgear.

These days, unless you are after a specific gearing or have a very high performance setup it usually isn't worth swapping the Christmas tree cog. All of these 20-23 tooth gears (including the DRT 23) are available on backplates to fit both the 6 and 7 spring clutches, and even in equivalent parts to fit Cosa clutches. Usually, on non PX 10" model gearboxes a 23/67-68 (using the DRT cog) works really well with a kit + 24/24 + exhaust setup, though if you go more exotic or esoteric (like the polini 208 I built on 8's once....) higher gearing is sometimes justified.

So glad to see Hodge back in the house!

Thanks, Rob!

I have a spare 22t Stella/P clutch (as well as a 21t or two) on the shelf that I can use if they'll fit. I was under the impression based on the 23t that there was a fundamental difference in the cog diameter between the 6-spring and 7-spring clutches.

If that's the case, it becomes an easy swap, plus probably the cruciform, which is probably in bad shape now, even if it wasn't before, and whatever else I might find.

The difference is in the outer diameter of the clutches, and therefore the backplates on the cogs.

the 23 doesn't fit the 67/68 because you only have so much distance between the Christmas tree shaft and the crankshaft centers, and the larger 23 an the larger 67-68 gears are too big combined to mesh. the DRT 23 is made slightly smaller in diameter than the stock 23 and that's why it works with the 67-68 gears. Stella is a 21 tooth stock; a 22 tooth 7 spring used to be a rare bird, only used stock in the rally 180; however due to use in some Bajaj models and the aftermarket stepping up to make them they are easily obtainable and a nice upgear for a Stella.

you will also need to grind down the rib in the clutch cover at 12o'clock, as well as trim back a coresponding bit at 12o'clock on the case; the case bit is easiest done by grabbing it with vice grips and breaking it off.

Hodge, it goes without saying: you are an asset to the community and it is very nice to see you back around these parts. Your knowledge and understanding of these machines is renowned and appreciated with the utmost respect.

all I can say is thank you.

and if you find yourself in LA beers and carne asada tacos are on me dude.

And if you're ever in Nashville, beers and BBQ or something are on me.


That tidbit about DRT making a 23t that fits the 67/68 primary makes sense. I'm sure I saw that on SIP's site or somewhere and mis-filed it in my brain, then didn't think to work through the other options when it didn't fit as expected.

I was fully expecting to modify the case. That's the least interesting bit of the
modification.

Well, thanks for that-

Don't know how much I will be around on here; I've got a workshop space and am getting my bikes back on the road after having them in storage for a few years.

I'm working on a 193cc ELJR conversion for my Stella in the original cases to get it back on the road. I'd have it done this week, but these newfangled cranks are only setup for the later, non-castle style clutch nuts.

I'm also gonna be out at band camp (but bikeless), if any of you are going. Should be a hellova lot of fun.

Hey if you are ever in Sonoma County the wine tasting / Farm to table pairing is on me. Just let me know as I will have to book extra work $$ lol.. I learn so much from all of youse, thanks.

I modified the shit out of my clutch cover when the new one wouldn't fit only to discover the weird washer on the primary drive gear was in the way of the clutch cover fully closing! oh well live and learn, luckily I had a spare less modified.....

Warm beer, p ie and mash in London.

I mentioned the different 23 cogs half way up the page! I often wonder who reads what. So much on here.
Plenty of gear options for the case split. I would still do the 65 ring gear.

I read it!
And you're right. So many options now.

Upgeared 2 bikes with the "younger brother" of the BGM Superstrong(at that time half the $). Rated up to 15hp

Installing SIP Cosa2 cr80 plates.
New and old(old can't have more than 2k miles):