Pressure Test

[ski4]

thinking i would love to do a leak down test on my motor before i install and run
anyone have any plans to make a rig in a fasion macguyver would be proud of

 

[Matt_E]

Fab up an aluminum plate that you will bolt to the cylinder in place of the exhaust manifold. The goal is to seal the exhaust ports.

Fab up another plate to take the place of the carburetor(s) on the intake manifold. Again, the goal is to seal the intake manifold. Except here you leave the manifold on, where with the exhaust you take it off.

This is easiest with two pulse fittings: Hook up a pressure gauge to one fitting, and an airpump to the other. Pump the case up to 10-15 psi, and let it sit for 10 minutes.
Ideally, you don't want to see more than 10% pressure drop, I believe.

 

[ski4]

if just one pulse fitting is there i guess just tap into the aluminum plate and pump in there

 

[Matt_E]

That would work - just make sure that your plates and connections to pump and gauge are not leaking. You're trying to find leaks in the motor, so a good test setup is paramount.

 

[ski4]

sounds good
i dont have access to sheets of aluminum
could prbably get by with a couple nice pices of some kind of hard wood?? after running trhough a joiner or something to ensure they are flat??

 

[Matt_E]

Go to home depot and buy sheet aluminum or steel. Either Lowe's or Home Depot should have it. Wood could work, I suppose, but either way - seal with silicone or similar.

 

[crammit442]

Fab up an aluminum plate that you will bolt to the cylinder in place of the exhaust manifold. The goal is to seal the exhaust ports.

Fab up another plate to take the place of the carburetor(s) on the intake manifold. Again, the goal is to seal the intake manifold. Except here you leave the manifold on, where with the exhaust you take it off.

This is easiest with two pulse fittings: Hook up a pressure gauge to one fitting, and an airpump to the other. Pump the case up to 10-15 psi, and let it sit for 10 minutes.
Ideally, you don't want to see more than 10% pressure drop, I believe.

Leave the exhaust manifold on. That way you only have to make a small plate and you can also see if the manifold is leaking.:wink: I actually use a plug instead of a plate, but it doesn't matter. Most people also only recommend pressurizing to 6-8 psi. 15 psi is a LOT. I don't quit until it doesn't leak at all.

Charles

 

[ski4]

a plug

good thought:woot:

 

[crammit442]

a plug

good thought:woot:

I use rubber plumbing test plugs. They have a bolt through them with a wingnut that makes them expand like a drain plug in a boat. Works and you don't have to cut a bunch of metal plates for the manifolds. You can make them with a rubber plug. Just drill the plug and use fender washers either side with a 1/4" carriage bolt and a wingnut. Lowe's sells everything you'll need.

Charles

 

[hangtime]

Got any pics of what the hell you guys are talking about :biggrin:

 

[Matt_E]

Ha! Thanks, that'll make it a bit easier next time.

 

[ski4]

holy macguyver

that is the plan then

simplicity in it's ultimate form and still completely great

now for guages ,, what are you using there? i have a hand vacuum pump but that won't help, i suppose like a pop off guage or something could work
??

 

[Matt_E]

Use a pump for inflating soccer balls and such.

For a gauge, get some cheap gauge intended for irrigation. You're not looking for accuracy, but consistency.

 

[SUPERJET-113]

I use rubber freeze plugs for auto engines which are like what Crammit describes. You can get them at a auto parts store. I use a new high tech hand pump Bell bike tire pump and put a inline gauge in the hose. I attach the hose to the pulse fitting. Also I keep on the intake manifold and exhaust manifold. I usually go for 7-8 PSI for 10 minutes. No need for 15 psi that might blow a seal out of whack or something. This bike pump doenst leak at all, which i find amazing. I should install a valve after the gauge and before the pump just for no worries of it leaking. I have used this many times and it works great for me. Got the pump at Walmart.
If you have a leak use "leak detect" or soapy water in a spray bottle to find it.

 

[ski4]

nice
i have to get my shopping list togehter
you guys rock :biggrin:

 

[Yamah0]

Cool didnt know i could do a leak down test with a home made rig.
Does anyone have pics of a motor hooked up for the test?

So if u find out that its leaking somewhere.. what do u do then?
Is it only gaskets and seals that will causing the leak?

Zane..

 

[ski4]

no

the yo yo i bought my ski from had ported the cases a little too radically and went through the intake area causing a leak into the flywheel housing and there was a leak under the cases , i am guessing a rod blew through once and he tried to fix it with epoxy and silicone

 

[sflsurfrider]

ive used the expanding plugs before, but the easiest method i have found is rubber gasket material. cut 2 pieces. one goes between the carb and manifold and the other goes between the headpipe and manifold. only cut the bolt holes and not the bores and bolt your carb(s) and pipe. dont go past 8 lbs psi.

if you only have one pulse fitting, just put the guage on a tee between the air pump and pulse fitting.

you shouldnt see ANY droppage in pressure. if you do, pour some soapy water onto the engine and look for the bubbles.

make sure to do the test w/ the flywheel cover off.

 

[SuperJETT]

One thing to think about is, if you're pumping into the pulse fitting, and your reeds actually seal well, you're going to be putting that pressure on them and they could be damaged. I like to leave the reed cages out when I do it just to be safe.

 

[Yamah0]

Great info guys!

So when i plug the carb and exhust intake where do i plug the pump to pump the air in the motor?
Errr and i take it.. u pour the soapy water ON the engine not IN the engine.. right lol.

Im gonna pressure test my motor when i pull it out to put it in the new XFT hull:woot:

Zane...