DieselTech Posted August 26, 2008 Report Share Posted August 26, 2008 Hello all, I have question regarding leak down testing. I fabricated my own tester out of rubber plugs, a tire valve, and a small air pressure gauge. The plug with the tire valve was installed in the left side cylinder exhaust port, and the plug with the gauge was installed in the intake air boot on the same cylinder. I blocked the crossover tube port on the air boot as well. I used a small air compressor (12v electric type) to try to perform the leak test, but the gauge would not move - the compressor apparently couldn't move enough volume of air to build pressure. So, I used my tire chuck to put air to it - I made sure not to go past 5 psi - but the pressure leaks down almost immediately. I sprayed windex on all my connections (the 2 plugs, all fittings/tire valve stem, plug in the air boot crossover, reed cages, etc.) and retested, checking for bubbles - there were none. I repeated the test numerous times, listening for air, and I discovered air entering the right side cylinder (I put my finger into the reed cage and pushed a reed petal open and heard the air escape). I'm not familiar with a Banshee motor - I've never had one apart. I looked at the parts diagram on BikeBandit, but I don't see any type of seal on the crank that seals between the two sides of the case - what seals the crank between the two sides? I see that there is a left and a right side crank seal - but they are at the ends of the crank. I'm assuming that there needs to be a seal between the two sides, otherwise wouldn't you get a fuel mix into the opposite cylinder? Any advice on this would be appreciated - and if I'm doing something wrong, please educate me! Thanks Quote Link to comment Share on other sites More sharing options...
peak-j Posted August 26, 2008 Report Share Posted August 26, 2008 I plugged both exhaust ports, one intake port, and put the a valve stem in the other one. Do you have the right side open? If so I believe you need to plug all holes up. Quote Link to comment Share on other sites More sharing options...
bansheejoel Posted August 26, 2008 Report Share Posted August 26, 2008 (edited) wait a minute......you only blocked one intake boot and one cylinders exhaust? The bottom end doesnt have any seals seperating one another. You have to block off both exhausts and both intakes or you it will NOT work at all. As for the seals there is only one on each side of the crank. Both of the cylinders share the fuel/air mixture. My dad make up some aluminum plugs at work, one was tapped for the air valve and one was tapped for the air guage. Those were put in the intakes and clamped down. He made two rubber plugs up with a bolt and one washer on each side of the rubber so the rubber would expand when the bolt was tightened. Those were put in the cylinders where the exhaust comes out and tightened down....worked amazing. :beer: Edited August 26, 2008 by bansheejoel Quote Link to comment Share on other sites More sharing options...
DieselTech Posted August 26, 2008 Author Report Share Posted August 26, 2008 I plugged both exhaust ports, one intake port, and put the a valve stem in the other one. Do you have the right side open? If so I believe you need to plug all holes up. I will purchase 2 more plugs so that I can plug both intake ports and move my pressure gauge over to the other exhaust port. I was under the impression that the cylinders were isolated from each other, but now I'm realizing that this must not be the case, as I see no seal at the center of the crank/case. I was checking for air leaks due to having one cylinder "skipping", but now I'm thinking that this may be related to something electrical. I checked compression and both cylinders were equal (both just over 100 psi if I remember correctly) - which may be low - I'm not sure what the "normal" compression is supposed to be - I do know that if they are both equal then it's not a problem with the piston/rings/cylinder causing a misfire in just one cylinder. Quote Link to comment Share on other sites More sharing options...
bansheejoel Posted August 26, 2008 Report Share Posted August 26, 2008 stock is 130 psi...give or take. Quote Link to comment Share on other sites More sharing options...
DieselTech Posted August 26, 2008 Author Report Share Posted August 26, 2008 Thanks for the spec. I will re-check after I finish the leak down test and compare to that. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted August 26, 2008 Report Share Posted August 26, 2008 I wouldn't use an air compressor to air it up, you could damage the seals. Just a hand or foot operated pump will be plenty. The tester I bought comes with a bulb identical to that on a blood pressure monitor. It doesn't take much to get it up to 6 psi. Quote Link to comment Share on other sites More sharing options...
DieselTech Posted August 26, 2008 Author Report Share Posted August 26, 2008 I wouldn't use an air compressor to air it up, you could damage the seals. Just a hand or foot operated pump will be plenty. The tester I bought comes with a bulb identical to that on a blood pressure monitor. It doesn't take much to get it up to 6 psi. Yes, I realize that - this is why I used a small battery-powered air compressor to begin with. Of course, since I didn't have both exhausts and intakes plugged, I had a gross leak and hence no pressure build-up. Chalk one up to stupidity........ Hopefully today I can get to the hardware store and get 2 more plugs so I can do it right this time. Quote Link to comment Share on other sites More sharing options...
LiftdT4R Posted August 26, 2008 Report Share Posted August 26, 2008 I might grab some electrical tape or something too. On my leakdown tester I can never get the plugs to stay in the bike, even with 6 lbs, it always blows them out unless I rig them up somehow. Quote Link to comment Share on other sites More sharing options...
DieselTech Posted August 28, 2008 Author Report Share Posted August 28, 2008 Well, I got some more rubber plugs and retested.....found air leaks at the intake boots where the crossover tube goes in (I have a WB boost bottle in place of the crossover tube). I couldn't get them to seal with the stock spring clamps, so I used 2 small hose clamps. It seemed like the right side was leaking worse than the left. I'm not sure if it's the boots or the tubes on the boost bottle causing the leaks - I may try to "polish" the tubes (they are a little rough). I also performed a compression test, and got 112psi on the left cylinder and 105 on the right - which is apparently low (I'm not much above sea level). I haven't had any issues with my plugs popping out - I'm using tapered rubber plugs from Home Depot that are made for the bottoms of furniture legs or round posts. They are 1 1/8" in diameter, and I twist them in, so they fit pretty good that way. Quote Link to comment Share on other sites More sharing options...
bronco91shee Posted August 28, 2008 Report Share Posted August 28, 2008 (edited) THE issue is the boost bottle. it did the same thing to me and many other guys on here. the bottle weighs to much or is just to big and causes the boots to work to much until they rip. toss that piece of shit in the trash and get a stock tube. i just made one out of sum copper tubing from plumbing that i had laying around. dont try pvc....it just gets eaten by the gas...lol. boost bottles are nothing more than a headace. tehy add nothing to power or antyhing. just run intakes. period! it did make mine run goofy on one cylinder. after that, it ran great. ur bike does sound a bit low on psi...how old is the motor? mabye you could skate by with just sum new rings for another season or two, before you have to rebuild. i know my dads is a 98 and he threw a new set of rings in last year. still running the stock OE pistons 10 years later...he gets bout a good 15 tanks thru every year, so not alot, but it does get ridden. write back when you find the cure for others to knwo as well..... Edited August 28, 2008 by bronco91shee Quote Link to comment Share on other sites More sharing options...
DieselTech Posted September 3, 2008 Author Report Share Posted September 3, 2008 Ok, I got it all back together and fired it up. Once I got fuel into the carbs it fired right up. Warmed it for a few minutes, then rode it - seems low on power for sure - free revs fine, but just doesn't pull when loaded. I brought it back to the shop to check it out and noticed fuel dripping from the right side carb vent hose. Looks like I gotta tear the carbs apart for a once-over. Just a quick question about stators though. What are the symptoms of a stator that is going bad? I've heard alot about the stock stators going bad all of a sudden. I have all the lights removed from my bike so there are no electrical loads besides the ignition (so I can't run it and look at the brightness of the lights as an indication). I also noticed that the bike fires right up on the first kick when warm - which makes me think that the engine is in good shape, as far as rings/pistons/cylinders go - even though the compression seems low. I gotta get the carbs off and go thru 'em first before I go any further though. Quote Link to comment Share on other sites More sharing options...
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