Can I use a vacuum pump instead of pressure to leak check?

[Edddyjoe]

Hi all,
I picked up a used blaster that was supposedly rebuilt but po said was running lean and was tired of messing with it. It has some kind of pipe on it, bigger than stock carb, and po said minor porting. When I got it running it was lean as he said. I made an adapter to hook up the airbox, raised the jet needle 1 notch from the bottom. Put a new plug in and made a few zips up and down the drive(1/4 mile) in 4th gear which was the fastest I could get it as drive is ice covered here in MI. Pulled the plug and was totally grey/silver which I know is a bad sign. Looked the same color as a piston which I am sure the color came from. From reading here the last few days I realize that I need to do a leak test before I even start trying to re-jet. My question is can I use a vacuum pump as I used to do refrigeration and have all that stuff. I realize that it wont tell me where the leak is but if it is leaking. How much vacuum do you take it down to. Sorry to be so long winded just wanted you to know where I am at.
Thanks

 

[Edddyjoe]

I will be honest, I picked this up with the idea of flipping it. It is only a 200cc after all but after zipping around on it I might just keep it. This little thing is a blast. I traded a old but well running ice auger that I paid $60 for and about $50 worth of ice fishing gear. Who would have thought that 200cc could be so much fun

 

[Awk08]

you can use vacuum, you'll need that gauge, but i'm not sure of the inches of mercury required to do it with vacuum

 

[Awk08]

Who would have thought that 200cc could be so much fun

wait till you get it properly tuned !

32.5 pilot jet
airscrew @ 1.5 turns out to start
needle clip in middle slot, possibly 1 down for colder temps.
unknown pipe ? start with a 300 main jet and plug chop to adjust main jetting.....
http://www.blasterforum.com/threads/how-to-plug-chop.53237/
do not ride it besides the plug chops till you get it jetted correctly

 

[harley1-5]

I just sold a bone stock 1 still very peppy

 

[Edddyjoe]

I have the gauges used for refrigeration that shows vacuum. I used to go down to 30 in of mg vacuum in a system. Any clues if needed to go that far for this? I just want to know if leak free before I mess around trying to re-jet a leaky motor. Po said pipe was off a 250 like that means it should go faster LOL. Carb is not stock either, is bigger. I just don't want to chase my tail trying to jet with a leaky motor. Have everything to do a vacuum test just don't want to draw too much vacuum and maybe damage something.

 

[Awk08]

for a leakdown test using pressure, it is recommended to not exceed 7 psi. or risk blowing the seals out.
it's not possible to suck them in, as they are pressed in from the outside ?

I do see the reeds possibly being a problem if trying to apply vacuum at the intake as we normally do with a pressurized test ?
maybe have to apply vacuum at the spark plug hole and block off intake and exhaust ?


what pipe, carb make and size for jetting starting point ???

 

[Edddyjoe]

Awk, didn't think about sucking through the reeds Duhhhh. Pipe is a abortion, which is leaking a little at the joint where the silencer hooks to. carb is a mikuni but have not measured, but a 1 1/2" plumbing boot fit to rehook up the airbox. I should be able to suck through the exhaust tho correct? Piss on it am gonna rig up a real leak test rig. Thanks all.

 

[Awk08]

Awk, didn't think about sucking through the reeds Duhhhh. Pipe is a abortion, which is leaking a little at the joint where the silencer hooks to. carb is a mikuni but have not measured, but a 1 1/2" plumbing boot fit to rehook up the airbox. I should be able to suck through the exhaust tho correct? Piss on it am gonna rig up a real leak test rig. Thanks all.

a proper leakdown tester is best.
just for reference.... my 34mm carb takes a 2.25" I.D. fitting on the backside

 

[Edddyjoe]

Awk are you the one that sells the tester? I am 1 1/2 hour away from a home depot ect. buying the stuff at the local hardware will be quite high.

 

[Awk08]

yes sir i am.......
http://www.blasterforum.com/threads/leakdown-testers.55015/

we'll need to know what size carb or intake is on there though to get you the correct size ?

I have enuf parts for one more before I place another bulk order.
I'll message you with paypal info if you decide to go this route

 

[Edddyjoe]

Ok will measure tomorrow. How do you do the payment thing? Ok just seen the paypal stuff. Works for me wil get the measurements and paypal you. Thanks again.

 

[Awk08]

How do you do the payment thing?

PAYPAL
or send me a usps money order, but thats gonna take a while

 

[Edddyjoe]

You just need the size of the carb boot correct?

 

[speedyslyder]

got pics?
just get awks tester it will save all the guessing,and wonder if i did it right
do you have digital caliper? you can measure it

 

[Awk08]

You just need the size of the carb boot correct?

I.D. of intake or O.D. of front side of carb

 

[Edddyjoe]

Ok will check tomorrow. The bike is in Dads garage (heated).

 

[Edddyjoe]

Pretty bad am 47 years old and still use Dads garage LOL. We do excavating and I put alot of work into that garage so should be able to use it right? LOL. Am still amazed how much fun this little blaster is. I have a 4x4 quad and have always had motorcycles from a xl75 Honda to a M2 Buell. My current bike is a 83 Yamaha XT550.

 

[Awk08]

Ok will check tomorrow. The bike is in Dads garage (heated).

lemme know
but read the message i sent ya,
i'll just send ya both fittings, the 34-36's aren't that popular, and I have both laying here

Pretty bad am 47 years old and still use Dads garage LOL. We do excavating and I put alot of work into that garage so should be able to use it right? LOL. Am still amazed how much fun this little blaster is. I have a 4x4 quad and have always had motorcycles from a xl75 Honda to a M2 Buell. My current bike is a 83 Yamaha XT550.

i'm older than you and still use moms garage to store my quads
same story, i'm the only one out of 3 who have ever done chit around the homestead.
but have moved my fabbing, and 79 cx500 bobber build i'm doing to our new construction garage.

 

[Edddyjoe]

Working on getting a tester from Awk and started monkeying with it today. Float was stuck or set too high and filled the crankcase with gas. Noticed gas dripping from the stator cover. Removed the cover and the stator and sure enough gas was running out around the crank seal as fast as I could wipe it off. Have a new seal ordered. Will replace that and leak test. Hopefully holds then. Did pull the head and the piston and cyl look pretty good. His porting leaves a little to be desired. Looks like he took a dremel and just knocked off the edges LOL.