OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 223
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 223
Location: Nebraska USA
UTC quote
Backstory -- my '74 Primavera was mostly parked for 14 years and I started this summer getting it going again. I cleaned out the tank and rebuilt the carb and put in a new spark plug, and it started right up, nice tat tat tat sound like before. Rode circles in my driveway, tested the brakes, started adjusting the cables and doing all the little maintenance things so I can get it registered.

By this time, I've started it a good handful of times, and it sounds great each time, but this time I go to start it, and it won't keep running unless I keep on the throttle and keep the choke open. I see that the exhaust is leaking, so that's when I decided to replace the exhaust with that whole saga. While I had that out, I cleaned out the carburetor again, and upjetted.

So, it still sounds the same. When it's dying, it doesn't sound lean, it sort of glubs glubs and then stalls.

I was going to clean the carb again and try new fuel, but the inlet sleeve just popped off while I was taking the carb off. I need a new clip for that and to access it I have to lower the engine, which is an incredible PITA with the new Polini pipe, and I'm wondering if that's a wild goose chase and it's something more serious like seals.

So what are the chances it's bad fuel or too big a jet (bearing in mind it had this symptom before the new exhaust and upjetting) and not an internal seal leaking?

What would you do next to diagnose this?

(the VAPE kit and rewire will have to wait)
@greasy125 avatar
UTC

Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
Joined: UTC
Posts: 14763
Location: The state of insanity, SoCal
 
Sergeant at Arms
@greasy125 avatar
Weird 80's Vespas & Cool Vintage Lambrettas
Joined: UTC
Posts: 14763
Location: The state of insanity, SoCal
UTC quote
if I had to roll the dice, I'd say it's clutch side seal.

check your gearbox oil. if it smells gassy then there's your answer!
OP
@spacecat avatar
UTC

Hooked
Vespa Primavera 1974
Joined: UTC
Posts: 223
Location: Nebraska USA
 
Hooked
@spacecat avatar
Vespa Primavera 1974
Joined: UTC
Posts: 223
Location: Nebraska USA
UTC quote
Finally got a chance to drain the oil and smell it -- maybe it smells gassy? I had just refilled it a couple weeks ago and only started it a few times so it may not have had a chance to build that up.

But it was a bit discolored.

That said, I don't know what else it could be, so I'm proceeding as if it were the clutch side seal.

A weird thing -- a couple months ago when I took of the rear wheel for the first time in years, there was a noticeable chemical smell. But there was no oil or grease oozing so I didn't think anything of it.
@garncarz avatar
UTC

Addicted
1964 Allstate Cruisaire, 1966 Allstate Blue Badge Small Frame, 2022 Husqvarna Vitpilen 401, 1980 Honda NC50
Joined: UTC
Posts: 988
Location: York, PA (the intellectual center of the universe)
 
Addicted
@garncarz avatar
1964 Allstate Cruisaire, 1966 Allstate Blue Badge Small Frame, 2022 Husqvarna Vitpilen 401, 1980 Honda NC50
Joined: UTC
Posts: 988
Location: York, PA (the intellectual center of the universe)
UTC quote
Unscrew the clutch breather. With your (or an assistant's) finger over the breather hole, turn the engine over. Pressure? If yes, most likely the seal.
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