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Post by sevenninesandtens on Feb 9, 2020 18:42:23 GMT -5
sevenninesandtens When you say a "tar leak" was there a drippy black substance leaking outside of the cylinder? If so that's a problem. It could be that the stud wasn't seated into the block enough, and caused an air leak at that corner. The rings should move somewhat freely, but there is usually pins in the ring lands to clock the rings. They get clocked so the ring gaps do not line up with each other, allowing a compression leak. I'd try to clean things up, reassemble, and do a compression test. Then a leak down test. If you do t have a leak tester, there are quite a few different ways to build one all listed here on the forum. Brent, 90GTVert, has many videos which show you how to use one as well. Any tiny air leak, even an exhaust gasket leak, can wreak havoc with a two stroke engine. They are "simple" engines, with complicated taste.... The only thing simple about these engines is their construction. The operation is convoluted in that the tiniest thing off, will cause hell, or can possibly cause your cylinder to eat itself. Check the bore for any gouges, scratches, or marks that your finger nail can feel. Use new circlips to put things back together. A $.79 piece can cause your $300 top end to turn into a paper weight, stupid fast.....
Yeah it looked like a thinner tar type substance. not as thick as tar, more viscous though. Once I got the head off and the cylinder I noticed there was a spot on the bottom right (as you look at the installed cylinder) where the stud that came out was that was tar/oily. I assumed that would probably be where the issue was then. Should I copper seal the gasket? As it turned out I had 2 gaskets on that part, one was the original paper one and the second was a metal one that came with the BBK. I dunno why I left the paper one on there honestly, I don't even remember seeing one there. Must have looked past it in my excitement. So I'm gonna remove the paper one and put it back together. Locktite on the loose stud and I think copper spray sealer on the metal gasket. Then put her back together and do the leak test and compression one too. From what I could tell the cylinder and piston are still smoother than my 1 year olds buns. So I'm feeling okay there. The rings worried me though. I guess I could get new rings? They slide around like there's no stopping them at all.
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Post by ThaiGyro on Feb 10, 2020 4:06:35 GMT -5
In addition to the great advice above, ensure that your cylinder and head mating surfaces are flat when cold. If you do not have a gauge, either buy one or find a local machinist who like bikes. It is not hard, but requires some learning.
Of note: The black tar is partially burned two stroke oil. It is common, but should be an integrated part of your tuning knowledge and cleaning/maintenance regime. It happens when you are too rich, it happens when you cannot control the oil injection well... and it happens when your engine is cold. We see exhaust ports with carbon and black goo, all of the time. If it is there, it is inside the pipe. You can likely double your power, just by freshening up and cleaning everything.
Since it is apart...best time to do it! If you are a freak like me, or desire to become one...I measure expansion chamber volumes. Two reasons. First is tuning. If you know what is was at birth or now, (baseline) then you know what you are tuning to; which secondly, also shows that your chamber has accumulated too much poo! We now coat every chamber we build or buy with Cerakote. Tastes great, less filling. (Haha, many will not understand that joke. Miller beer commercial)
Do not be afraid to measure before cleaning! Then clean using a safe and reliable method. (I do not bake in the fire. Some use caustics, I do not. I use diesel or gasoline or warm mineral oil circulation with air removed) You can re-measure AFTER your initial reading. Plugged minus unplugged gives you the same data as unplugged minus plugged. (Give or take a +/- sign)
Many methods available here. Choose one that preserves your welds or weld seams. Oh, nearly forgot...I have a boroscope too. It has Bluetooth wifi to my phone. I can see! Not recommended for goo-poo envirionments. Clean first until you think you are golden, before you put your endo or boro scope into the butt. Ask you father...GOOGLE
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Post by Zino on Feb 10, 2020 9:16:53 GMT -5
You only need one gasket or no gaskets with copper spray only to get a good seal .
I always use copper seal on the gaskets .
If you have Dark Goo Your Carb jetting is on the rich side Which probably happened from you trying to richen up the idle and jetting to make up for your air leak .
Another way to clean your pipe is take it to a radiator shop and have them dip it in a solvent tank.
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mattyslimz
Scoot Enthusiast
Posts: 222
Location: Northern Virginia
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Post by mattyslimz on Feb 13, 2020 19:57:46 GMT -5
Hopefully just the extra base gasket was your main issue. Once you have everything back together and have your idle squared away, go ahead and get yourself a cylinder head temp gauge. TrailTech makes a 14mm version that sits in place of your spark plug gasket (that will be removed prior to install, No doubles).
They can be had for fairly cheap $50 shipped on EBay or the like and this will confirm you’re leak issue for sure because even if your idle is sounding right, it can always just be an UNDER idle setting making it seem like the issue is gone. As mentioned, even a small air leak can fry a top end, with the gauge you’ll always know if your getting too hot. You may need an extension because the gauge isn’t long enough for MOST scooters footrest and tree length, but a smaller Vino it may reach, 24 inch extensions are available.
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Post by sevenninesandtens on Mar 5, 2020 14:20:33 GMT -5
Hopefully just the extra base gasket was your main issue. Once you have everything back together and have your idle squared away, go ahead and get yourself a cylinder head temp gauge. TrailTech makes a 14mm version that sits in place of your spark plug gasket (that will be removed prior to install, No doubles). They can be had for fairly cheap $50 shipped on EBay or the like and this will confirm you’re leak issue for sure because even if your idle is sounding right, it can always just be an UNDER idle setting making it seem like the issue is gone. As mentioned, even a small air leak can fry a top end, with the gauge you’ll always know if your getting too hot. You may need an extension because the gauge isn’t long enough for MOST scooters footrest and tree length, but a smaller Vino it may reach, 24 inch extensions are available. Extra gasket was not the issue. Now it's worse and when I turn the engine over after putting everything back on and torquing to the specs it now revs up to 7500 rpm right off the bat which it did originally before upping the idle jet to 52. Going to hopefully have time to get the leak down stuff this weekend. Frustrating now that it's already in the 60's here and I "could" be riding it. |
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Post by geoffh on Mar 5, 2020 15:56:33 GMT -5
Just so its clear,can you tell us what the set up is now.I would try going back to the basics of new 70 cyl old carb and air box but upjet the old carb by 10% just to find a base line that you can improve on.
Geoff
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Post by ThaiGyro on Mar 6, 2020 7:41:24 GMT -5
Hey One thirty-three...(that is 7 nines and seven tens) How did your repairs and tuning end up? What did you find? Some of us have no life, so we circle back and look...for food.
Hope you have some good news! If not...put it on here! Too cold and wet where you live?
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Post by sevenninesandtens on Jun 20, 2020 18:16:42 GMT -5
Finally got back around to the scooter today. My wife took the kids camping for father's day, which I'm not entirely sure why. But, that gave me free time so I hooked up my air leak test. After spraying and pumping and spraying and pumping and the air not holding at all, I started to take things off. Was fearing that the crankcase was leaking since it wasn't holding any pressure at all. Took the variator off and everything behind that and sprayed and nothing. So I went back and started again and it appears as if the intake manifold is leaky. I did some fast pumps to get some pressure and got lots of little bubbles under there. FINALLY!
Now I just gotta figure out how to put the stuff behind the variator back on properly and try to seal the intake. It's brand new along with a brand new gasket and the hex bolts were torqued correctly so I'm gonna try some copper seal and see if that works. Fingers crossed. Had this thing almost a year now and haven't been able to ride it yet!
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Post by sevenninesandtens on Jun 20, 2020 19:28:31 GMT -5
Oh boy what an adventure this is. Now I got everything back together and put the variator back on closed up the CVT cover and it won't hold any pressure again. Sigh.
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Post by 190mech on Jun 20, 2020 20:11:22 GMT -5
Make sure your tester isnt leaking...
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Post by sevenninesandtens on Jun 21, 2020 7:30:46 GMT -5
That for sure isn't..... BUT I just went back to 90GTVert's leakdown page and completely forgot the exhaust! that's still hooked up so I'm sure the air is just going right out the exhaust! Will do that today. Hoping that's the fix cause I could get some air into it later after I put copper gasket maker on the intake. Sprayed with soapy water and there were no bubbles there. Fingers crossed it's because the exhaust pipe is still on!
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Post by sevenninesandtens on Jun 21, 2020 12:28:32 GMT -5
Good news!
Took off the exhaust pipe and plugged it. Holding air! WOOHOO!
Full 30 min test and the gauge didn't move at all.
Happy Father's Day to me!
I think the issue is the exhaust design makes it REALLY hard to get to the bolts to attach it to the cylinder. I finally found a 10mm crescent wrench that is short enough to use. However the gasket looks to be toast. Can I just use copper seal there too?
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Post by matlock on Jun 23, 2020 10:42:37 GMT -5
also check ur throttle cable it might be jammed
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Post by sevenninesandtens on Jun 23, 2020 21:24:19 GMT -5
also check ur throttle cable it might be jammed just to be safe I loosed it so the slide sits all the way down, I think it was definitely too tight before. |
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Post by matlock on Jun 24, 2020 0:21:50 GMT -5
did it solve ur issue?
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