Modern Vespa

If the clutch and primary check out I would ride it carefully for a while. If something metal loose in there the gearbox might eat it.

I’m thinking of splitting the cases, waiting for gaskets and some other parts to arrive...

I’ll take out the base gasket and I’m thinking to extend the exhaust port to 195 deg

A decent number to aim for? Or something more conservative like 190?

I would set up the port timing you have first. Then decide what you want more or less of. If your going to put in a primary less than 65 it will limit your options.
182 is a little low for your Newline but the 130 is ok. Won't know until the carb is set and a few GSFdyno runs are done.

I do think 182 is a little pedestrian... I’ve pulled off the cylinder (preparing for splitting the cases) and seeing if I could see any problems with the primary... seems like there’s nothing too obvious...

So I’m thinking of grinding the exhaust port to 195

Had a bit of a fish around with the magnetic rod... couldn’t find anything

The clutch plates had some weird chips though... I can’t remember those being there when I installed the clutch... the CR80 plates are pretty tough... so must be something even tougher to put those marks there...

But I think I might have found a potential culprit to the problems... The helical teeth on the clutch seem pretty worn... 1-2 of the teeth seem pretty thin... slipped and jammed in the primary?











Last edited by 108 on Sun Apr 11, 2021 5:05 am; edited 2 times in total

Bgm super strong clutch? Fmp did a video on that thin tooth problem with their clutches last year.

When i ordered mine from Jonathan Gick, he had it freeze treated to add some strength to it. Haven't pulled out yet to see if that helped prevent wear.

No, it’s the SIP COSA 2 Race clutch basket... sold separately

It’s pretty old and it seems like one of the first reinforced clutch baskets available before all the new CNC clutches that have come out now...

It’s super tough but it’s the teeth which engages the primary which seem worn... but maybe not enough to slip and lock though...

The teeth on the metal clutch plates seem pretty worn too...

There’s quite a bit of play before the primary engages because of the gap worn into the plate, when I was testing the spinning of the clutch with the clutch tool.

Doubt it’s the cause of the lock up, but looks like I’ll be replacing them soon...

They look like different cogs is one a 23 and the other a 24?

Plain plate teeth wearing like that is the usual. CR 80 plates fix the outside tab wear but nothing new for the plain plates yet.

Both 23 teeth, but one is 40mm and the other 42mm just for comparison of similar sized teeth... (40mm for a 68 teeth primary...)

Yeah, seems like no new developments for the plain plates... had some BGM plates which seemed harder... but none of the 4 plates were flat... all had waves in them...

Good find on the clutch wear but with it out, spin the rear tire and shift through every gear. Do you hear anything grinding? Anything tighter than the others? Anything shiny in the gear oil? Any aha moments?

Yeah, went through the gears with the rear wheel in the air...

Found nothing... had a small mirror on a rod, down the primary area, still didn’t see any missing teeth...

But I’m still betting on something loose inside...

Something I did note I forgot to mention, is that the primary seemed to have a bit of play on its spindle... worn bearings I think... wonder if it’s enough for it to get jammed...?

Is your primary/ Cush drive spindle secured with a captive washer, a washer and then the nut? Is it currently tight?

Did you replace the primary gear bearing lately? Remember the circlip that holds it in?

Yeah, everything has been buttoned up to spec...

All parts present, tightened to the right torque value... maybe its just worn, its a used part... will take it off to inspect...

Picking this back up...

Parts arrived from SIP...

Opened the engine... couldn’t find anything inside... I was hoping to find missing teeth... but nothing...

The primary is a little swollen, the bearing has some play in it but no chunks missing, a bit disappointed to be honest... I’m going to take the output shaft apart and see if there’s anything there

But decided to go all out and get the KR automation gear selector and swap it out... it’s pretty robust, the dog teeth is a new laser cut part and the tolerances are tight... wonder how long it’ll last... not sure it’s worth the asking price at the moment... will see

Small update on the output shaft

Which had some pretty bad wear... the gears, horizontal and diagonal free play... circlip/shim gap definitely not to spec ( 0.5mm? Can’t remember if it’s that...)

not sure if it was enough to lock up the primary, but swapped it all out with a drt set from another engine...

Let’s see!