Billy Golightly
08-02-2007, 09:53 AM
If you search around on the old Mac Dizzy site (use Google) you can make a pretty cheap one. I opted to use a radiator cap tester as a base of the tool because it was just much better quality and the dial is not tiny. If you go to an auto parts store and buy a radiator cap tester, have them make a custom hydraulic hose to fit on the end of it that is 1/8th male pipe thread WITH A SWIVEL! If you don't get the swivel you will be cussing yourself trying to get the thing into place and trying to read the gauge. I then turned a piece of solid round aluminum stock on the lathe to fit in my intake boot (I turned mine about 40mm OD if I remember correct. BUT, I've already stretched the boot for a 39mm carb so you might want to go with like 36 or 37mm if you have a smaller regular size carb) drill a hole all the way through it big enough to tap and thread the 1/8th male pipe thread fitting from the new hose onto one end of it. Its a good idea to put a good chamfer or bevel on the end going in the boot, makes it easier. Use a little bit of thread tape or some thread sealer like loctite to ensure theres no leaks there. You'll need to take your pipe off and then remove the ehxaust flange. Make a plate to bolt flat against the cylinder in its place. You'll probably have to add silicone to the back of the plate everytime to put it on to do a test.
Now, for the actual testing. The "Common" test point and procedure is 7lbs of pressure for 7 minutes. Take note though, this does NOT mean it can bleed off 7lbs in 7 minutes. It has to hold the 7lbs entirely without dropping any for the 7 minutes. In my opinion 95% of the machines that complete the 7lbs for 7 minutes test will fail it. I went through a great deal of trouble on the motor in my flat tracker now (The stock one) to make it seal 12lbs over night. This is borderline eccentric, but, its actually a pretty decent power boost once you get the crankcase and the motor COMPLETELY sealed off. It makes jetting infinitely easier to do also.
When :D you do find a leak, the best way if its still in the bike is to use some soapy water to spray around the base gasket, the reed cage/boot area, the plate over the exhaust. The next place if you don't get anything there is to put the transmission vent hose close to your ear and listen to it, or try the soap water there. If anything comes out then you gotta go in deep. Probably a right side crankcase seal, possible a center case gasket (which is what I've been fighting with on another motor because the surface was warped. ) The head gaskets will definitely leak also, but they are pretty much impossible to tell from the outside. I just go by the process of elimination. The intake area don't leak, the exhaust don't leak, the base gasket don't leak, the crank seals and center case gaskets dont leak, then its probably the head gasket and I replace it.
I've got about $90 in the radiator cap tester, a couple bucks in the custom hose, and then just some time machining the round stock. I've used it so much in diagnosing and finding problems. I'd reccomend EVERY 2 stroke owner to build one of these and run the test. If it doesn't meet the standard test, plug the leaks and I GUARANTEE that you will feel a substantial increase in seat of the pants power.
Now, for the actual testing. The "Common" test point and procedure is 7lbs of pressure for 7 minutes. Take note though, this does NOT mean it can bleed off 7lbs in 7 minutes. It has to hold the 7lbs entirely without dropping any for the 7 minutes. In my opinion 95% of the machines that complete the 7lbs for 7 minutes test will fail it. I went through a great deal of trouble on the motor in my flat tracker now (The stock one) to make it seal 12lbs over night. This is borderline eccentric, but, its actually a pretty decent power boost once you get the crankcase and the motor COMPLETELY sealed off. It makes jetting infinitely easier to do also.
When :D you do find a leak, the best way if its still in the bike is to use some soapy water to spray around the base gasket, the reed cage/boot area, the plate over the exhaust. The next place if you don't get anything there is to put the transmission vent hose close to your ear and listen to it, or try the soap water there. If anything comes out then you gotta go in deep. Probably a right side crankcase seal, possible a center case gasket (which is what I've been fighting with on another motor because the surface was warped. ) The head gaskets will definitely leak also, but they are pretty much impossible to tell from the outside. I just go by the process of elimination. The intake area don't leak, the exhaust don't leak, the base gasket don't leak, the crank seals and center case gaskets dont leak, then its probably the head gasket and I replace it.
I've got about $90 in the radiator cap tester, a couple bucks in the custom hose, and then just some time machining the round stock. I've used it so much in diagnosing and finding problems. I'd reccomend EVERY 2 stroke owner to build one of these and run the test. If it doesn't meet the standard test, plug the leaks and I GUARANTEE that you will feel a substantial increase in seat of the pants power.