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Post by stancejontland on Feb 10, 2018 22:47:20 GMT -5
I do use them just have been working on it and took it off but yeah i have it. Ok im gunna go rent a compression tester and get back to you. What psi am i looking for like above 130? And say it is bad then what should i do new motor??
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Post by ThomasTPFL on Feb 11, 2018 0:33:53 GMT -5
Get the piston to BDC, take off the carb, put your hand over the exhaust, blow cigarette smoke down the intake. You're looking for bad seals.
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Post by 'O'Verse on Feb 11, 2018 0:43:18 GMT -5
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Post by stancejontland on Feb 11, 2018 1:58:40 GMT -5
So put my hand over exhaust pipe or should i take it back off? The exhaust i mean.
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Post by stancejontland on Feb 11, 2018 2:06:08 GMT -5
Ok lets look at best case scenario. Say i have good compression. Then what should i try? I have gone through 5 carbs and that didn't solve the issue so i went with a new exhaust pipe. Got the new pipe on and it's not working. Should i try one of the other carbs? They are all brand new other than trying to get my bike running.
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Post by ThomasTPFL on Feb 11, 2018 10:12:20 GMT -5
If you have a case leak you will still have good compression, just air won't flow the way it should.
Minor leak you can hose down every possibly leaking area, cylinder base, case seam, reed block, both crank seal areas, with carb cleaner and the bike will start and run until it's sucked that through. Bigger leak that won't work.
I just located the bad crank seal on my Derbi by pulling the carb, taping over the intake, getting he piston to BDC, holding my hand over the end of the exhaust to cap it, pulled the vacuum line off the petcock and used it to blow cigarette smoke, i smoke anyway, into the case through the vacuum line. It was very obvious when the puff of smoke came out behind the variator.
You can also pressurize the case with a mighty vac or something and spray I wih soapy water but you want very low psi as some of the seals will easily blow out.
Someone posted a nice homemade rig for checking case pressure in the hints section here.
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Post by stancejontland on Feb 11, 2018 17:13:23 GMT -5
so if i have good pressue.. start looking for leaks?? so i should leave the vacuum line on carb just pull it off the petcock, then blow smoke through the intake tube while holding exhaust pipe/covered and look for where the smoke comes out?? i vape so i can get alot more smoke through.. but im going to do a compression test first.
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Post by pinkscoot on Feb 11, 2018 20:44:50 GMT -5
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Post by ThomasTPFL on Feb 11, 2018 22:10:46 GMT -5
so if i have good pressue.. start looking for leaks?? so i should leave the vacuum line on carb just pull it off the petcock, then blow smoke through the intake tube while holding exhaust pipe/covered and look for where the smoke comes out?? i vape so i can get alot more smoke through.. but im going to do a compression test first. Yeah, pretty much. And an engnr can have good cylinder compression with an awful crankcase leak, as I learned.
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Post by stancejontland on Feb 12, 2018 1:09:27 GMT -5
Should i take carb off or leave it on when i blow smoke through?
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Post by ThomasTPFL on Feb 12, 2018 8:30:10 GMT -5
It's easier if you take the carb off. Then only one hole to seal.
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Post by stancejontland on Feb 12, 2018 12:14:35 GMT -5
Ans just blow smoke through the intake side of the carb. Or well where the air would go lol. Oh and ive noticed every time i try to get my bike running this black gassy smelling liquid comes out of my exhaust somewhere. Could that be a sign of something?
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Post by ryan_ott on Feb 12, 2018 13:59:49 GMT -5
Have you checked for spark? That black fluid is unburnt fuel washing off your piston and pipe - flooded. I’m starting to think your idle mixture is rich or your idle screw isn’t in far enough to start or weak spark. If you pull the carb off you should be able to see some light between the carb slide and carb body 1.5-2mm should be ok. Have you opening the throttle while cranking it? You’ll probably need to pull the plug and crank it some to rid some of that unburnt fuel from the crankcase.
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Post by stancejontland on Feb 12, 2018 14:21:04 GMT -5
The carb i have on it is kinda jenky and im going to put one of my other ones on it today and try that. And ok ill take plug out and crank it over to get fuel out. Plus ill try my spark. What would make me have weak spark? What could i replace to get better spark?
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Post by ryan_ott on Feb 12, 2018 14:41:41 GMT -5
Weak spark can be a bad spark plug (I’ve seen new ones bad out of the box) spark plug cap, the part that screws into the plug wire, ignition coil or other components as he cdi box or stator or poor wiring.
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