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Junior Mint
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 Post subject: 2-Stroke Pressure Testing
PostPosted: Wed Oct 07, 2009 5:37 am 
Hi guys,

This isn't put together for the best how-to really, but I figured I'd post it up regardless.

Doing a pressure test on a 2-stroke is a good idea, especially one that's been freshely built. The reason, is because a proper pressure test is the only reliable way to detect leaks in your engine. It's different from a compression test in that it is not testing cylinder compression, but rather it tests the ability of your engine to take and hold pressure for a set amount of time. If your engine ends up having a leak, it can cause the engine to run lean as there is extra air that is not 'metered' by the carburetor. Lean running can destroy an engine.

Here are some photos of the "shopping spree" I went on when getting the parts. I got the medical bulb and the "Y" connector from Rick at Macdizzy.com. The rest of the parts came from Lowe's.

I realize that this is largely irrelevant to most Ruckus owners, but to those who have (or are thinking of) doing the 2t swap, this could come in handy. There's also a video at the end.

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When heading off to Lowe's, I grabbed my inlet manifold, and a few other odds and ends. The medical bulb and the brass fitting I got from Rick. You can find the bulbs on eBay for around $5 shipped. There are many other alternatives to the brass fitting, but for it's ease of use I decided to go with it.

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First, I had to find something that would fit my manifold.

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This PVC adapter looks like it'll do the trick!

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I then found this piece that I could thread into my manifold adapter.

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I picked up 3 feet of clear vinyl tubing. Cheap enough...

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Then I found an adapter to go from 1/8 NPT to 1/4 NPT. This adapter will go between my brass "Y" connector and my pressure gauge.

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Standard pressure gauge. I'm sure I could have found it cheaper than $8 elsewhere, but I didn't really care.

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My collection of parts to build the pressure tester. I also have some expansion plugs, but I will have to post those later when I get into the garage.

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I found a 60psi gauge, which is better than 120 I guess. I'll upgrade to a better gauge sometime soon.

Here's the latest:

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An ATV low pressure tire gauge would work better, but I didn't have access to one on short notice. After looking at a few links, I also found this: ATV Low Pressure Tire Gauge

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I removed the fitting that come on the gauge.

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1/8 NPT female adapter.

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Gauge, adapter, and "Y" connector.

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Using teflon tape on the threads of the gauge.

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Gauge mounted to adapter.

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"Y" connector mounted. (Thread tape is used at all connections).

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These are the parts that will hook into the manifold. The more I think about it, the more I want to go with some kind of quick-change coupler so that I can easily change between manifold adapters. My next adapter that I make will be for Minarelli Horizontal engines.

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Threads are taped, and parts are together.

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There it is! I ended up putting small zip-ties on the tubing at the "Y" connector because it was leaking air from there. Also, to get the tubing to become flexible so that I could fit it to the large nipple on the manifold adapter, I heated it up just a bit with a lighter. You can also dip it in really hot water for a little bit and it will easily go on.

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I make more adapters as I need them. Here's the kit to date.

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Testing a Kymco Mongoose 50 ATV.

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Testing a Yamaha QT50 Scooter.



http://www.youtube.com/watch?v=ySu2NC1X7s4 ~ The Video.
To directly download the video: http://www.scooterinvasion.net/techdata ... stroke.wmv

Hope this helps someone out there. :)

~Josh

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 Post subject: Re: 2-Stroke Pressure Testing
PostPosted: Wed Oct 07, 2009 9:44 am 
Yo Josh, hurry up and make a kit for sale. I'd be down for one in a heartbeat. :D

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Junior Mint
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 Post subject: Re: 2-Stroke Pressure Testing
PostPosted: Thu Oct 08, 2009 7:34 am 
I thought about it honestly, but it's too easy to just make your own. My thinking was that a kit that covers a broad range of scooters would work really well (kymco, yamaha/Minarelli, Piaggio, etc). Who knows, perhaps someday if someone doesn't beat me to the punch.

I have been making some neat stuff in machine shop class though! Gotta hone those mad skill before spending the 'mad dollars' on expensive machinery for the shop. :|

If you guys have any questions on the pressure testing, lemme know. :)

Ciao!

~Josh

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Junior Mint
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 Post subject: Re: 2-Stroke Pressure Testing
PostPosted: Sun Oct 11, 2009 1:00 am 
a stupid question, but

this can be done when the engine is already mounted on the bike... correct? :)

which means do I just plug a hole on the exhaust? or I have to take it off and plug it from the cylinder? (the exhaust tube might be too big to hold pressure to perform this test....)?!? :?

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Junior Mint
Junior Mint
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 Post subject: Re: 2-Stroke Pressure Testing
PostPosted: Wed Oct 14, 2009 5:31 am 
Yes, this can be done easily with the engine still in the bike. You'll need to remove the exhaust to plug the exhaust port though. You can also do it the other way around, by plugging the inlet and pressurizing through the exhaust port! It's easier in most cases though, to block the exhaust.

:)

~Josh

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Junior Mint
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 Post subject: Re: 2-Stroke Pressure Testing
PostPosted: Thu Oct 15, 2009 8:16 pm 
Great write up Josh! I ended up making one of these during my rebuild and it worked like a charm!

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Junior Mint
Junior Mint
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Years on TRYears on TRYears on TRYears on TR

Posts: 124
Location: Mebane, NC United States of America
Gender: Dude

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 Post subject: Re: 2-Stroke Pressure Testing
PostPosted: Sat Oct 17, 2009 7:39 pm 
Glad to hear! It's always a good idea to pressure test any 2t engine when rebuilding. Do you have any photos of the one you made? What kind of gauge did you use? The one I'm using is actually not the best type. A lower pressure gauge (0-15 lbs) would work much better for a pressure test, since we're only using around 6 PSI for the test.

All the best,

~Josh

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