OP
UTC

Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 362
Location: St. Catharines, Ontario
 
Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 362
Location: St. Catharines, Ontario
UTC quote
Hi all,

Can I perform a leak down test with the carb installed? Or do I need to remove it and mount a manifold?

Any tips on how to complete the leak down test with a stock engine?

Thank you.

N
@charlieman22 avatar
UTC

Nedminder
62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4096
Location: california
 
Nedminder
@charlieman22 avatar
62 VBB1T Round Tail W/ leaner sidecar
Joined: UTC
Posts: 4096
Location: california
UTC quote
Here are a few.
1. Cut a piece of inner tube or flat rubber - pull your carb (it has to come off) and air box. Then put the rubber down with holes for the carb studs - and use the air box back on top of it and tighten down sealing off the inlet. save that piece of rubber with the holes - it will be a tool for the future.

Get a tapered rubber stopper from hardware store Dia. under size of exhaust port on one end and over sized at the other. Drop exhaust pipe or box and stuff the rubber stopper in the exhaust flange.

Either modify a spark plug or get a cheap leak down tester form harbor freight. You won't be using it other than for the part that screws into the spark plug hole. Get a blood pressure gauge from drug store. That will have a gauge and a bulb to pump pressure. Pull it apart and plug it into the part from the leak down kit that screws into the spark plug hole.

Look up how to convert the numbers on the BP gauge to pounds - and pump it to about 260mmHg (5 pounds). Use a spray bottle with soapy water and mist it on the motor to find any leaks - start by checking the inlet sealed off and the plug into the exhaust...

https://www.amazon.com/Sphygmomanometer-LotFancy-Pediatric-Pressure-Approved/dp/B01HEKQNVI/ref=zg_bs_8404650011_4?_encoding=UTF8&psc=1&refRID=VER9HFRYG4VTWBS4XFXP
@pdxjim avatar
UTC

Molto Verboso
2005 PX150 In a Part-time Relationship with a 2-Stroke Vespa Since 2007
Joined: UTC
Posts: 1867
 
Molto Verboso
@pdxjim avatar
2005 PX150 In a Part-time Relationship with a 2-Stroke Vespa Since 2007
Joined: UTC
Posts: 1867
UTC quote
You might want to take a look at my somewhat neurotic post of several years ago on this subject.

Serious About Air Leaks

And no, I don't believe it's feasible to do a leak test with the carb in place, unless you're just using the carb to hold a blocking gasket in place. It would take too many plugs and stoppers to close off all the openings on a carb. (Hint: I tried it and couldn't get a reliable air seal.)
OP
UTC

Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 362
Location: St. Catharines, Ontario
 
Hooked
'81 Vespa P200e, '85 Vespa PX125e, 1985 T5
Joined: UTC
Posts: 362
Location: St. Catharines, Ontario
UTC quote
Great starting points. Thanks gents!
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9838
Location: Nashville

46 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9838
Location: Nashville

46 Days Since Last Explosion
UTC quote
I built mine and pump it up with a bike pump. It uses the same hose as my compression tester. Cost me less than $15 in parts and works great.
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@dsmith181 avatar
UTC

Hooked
1965 Allstate, 1979 Rally 200
Joined: UTC
Posts: 144
Location: Philadelphia, Pa
 
Hooked
@dsmith181 avatar
1965 Allstate, 1979 Rally 200
Joined: UTC
Posts: 144
Location: Philadelphia, Pa
UTC quote
chandlerman wrote:
I built mine and pump it up with a bike pump. It uses the same hose as my compression tester. Cost me less than $15 in parts and works great.
Where did you get all those parts for less then $15?
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9838
Location: Nashville

46 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9838
Location: Nashville

46 Days Since Last Explosion
UTC quote
dsmith181 wrote:
Where did you get all those parts for less then $15?
Amazon, but it was a few years ago now. I think I already had the air tool fitting, so call it $16.
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