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Post by kekoaquiroz420 on Nov 1, 2014 20:33:45 GMT -5
Aloha everyone!,
So yesterday I got my chinese qmb139 with a 83cc bbk and stroker to start after sitting for 6 months and thats when bad things started to happen. It fired up and I was throttling it a bit while i adjusted the idle and all of a sudden I heard a strange sound folled by the bike dying. I pulled the cvt case and found out that my variator nut had become loose and almost screwed completly off! I reimpacted it on and then I decided to drain the fuel from the tanks, fuel lines and carb, so I did and took out the carb opened the float bowl drained out the old fuel and inspected for gunk, saw none. I reconnected the carb and fuel lines and put in fresh fuel and now when I kickstart the engine it turns but doesnt feel like it has very much compression or resistence. I can just kick it and kick it where as before there was quite some resistence on the compression stroke and it used to occasionally kickback. now it just doesnt sound like its firing, though I know im getting gas to the spark plug(when i pull it out it is wet and smells like gas.) and im getting spark,(when I ground it to my frame I get a strong spark). Im getting a compression tester today so thats my next thing, i got a feeling something busted when the variator nut came off. Any ideas or help from anyone would be appreciated thanks!
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Post by 90GTVert on Nov 2, 2014 16:20:25 GMT -5
 What does the compression test read? You want to see at least 100psi for it to start reliably, but more like 150psi for a strong runner usually. Have you flooded it? Try holding the throttle wide open when you attempt to start it. |
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Post by kekoaquiroz420 on Nov 2, 2014 19:24:00 GMT -5
So I rented a compression tester from oreillys and it was way too big to fit in the spark plug hole and I don't think they even have the adapter so I can't do that. I plugged the spark plug back in and sprayed starter fluid in the intake manifold and still it didn't really feel or sound like it would start. So I know I'm getting spark when I'm grounding my spark plug to the frame and I'm pretty sure sure I'm getting fuel so the only thing I can think is its has to be a compression problem, so I think I'm gunna strip down the top end and see if there is any damage, I know I have an airsal piston I used to have installed that I could put in anyways it will probably be worth it! I miss the old days of cruisin down the road at a steady 50 mph I have GPS confirmed it at 63 mph on a slight hill and that wasn't pushing it. And my bike is a heavy beast. But ill update when I get the rebuild done
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Post by stevec on Nov 2, 2014 19:54:37 GMT -5
compression, timing, fuel and spark, if you have all 4 the engine will start, you have fuel and spark,if your timing marks are lined up and valves are properly adjusted it is a compression issue.
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Post by kekoaquiroz420 on Nov 2, 2014 20:12:23 GMT -5
Ya its gotta be the compression I mean everything else seems right on. So I'm gunna break it down and see of I can get a diagnosis and ill update honestly I kinda hope I find something broken so I'm not left questioning why
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Post by kekoaquiroz420 on Nov 2, 2014 21:17:50 GMT -5
Alright so I broke it down and everything looks fine my worst fear.... So I guees ill just put it all back together and maybe ill get a miracle or something lol
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Post by kekoaquiroz420 on Nov 3, 2014 0:51:41 GMT -5
EUREKA!!!!
After taking my top end apart, multimetering all my wires and checking all the voltages I found a bunch of problems ended up changing the cdi, disconnecting the kill switch and rewiring all my grounds and sure enough when connected everything and fired it up it started on two kicks and was idling nice. But when I tried to throttle it up I heard some knocking.... It kinda sounded like it got worse the more I throttled so I returned it to idle and killed the bike. Could this be caused from the starter fluid? I'll probably readjust my valves tomorrow but I did it again brought her back from the grave and I am a strong believer to the fact that any bike is repairable with patience and wit anyone can do it in their garage. Thanks everyone for the suggestions I'm excited to be apart of the forum now!!
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Post by 90GTVert on Nov 3, 2014 8:20:41 GMT -5
If there was a lot of starting fluid in there I could perhaps imagine it knocking when it first fired up if it were under load because ether is low octane, but after running for a minute it should clear out and not be causing anything.
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Post by kekoaquiroz420 on Nov 3, 2014 15:14:40 GMT -5
Hmm well today I'm gunna readjust the valve lash quadruple check both and make sure they are good I'm gunna set the intake to .004 and the exhaust to .006. I may have not done it right in my confusion,daze and frustration yesterday, even though ive done it like a hundred times. Hopefully today ill finally get to drive it down the road today woooot!!!
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Post by kekoaquiroz420 on Nov 3, 2014 21:23:40 GMT -5
Ok so readjusted the valves and the knock is gone! So now she is running. Let it idle for 5 minutes and then rode it down the road and by the time I got home like after 2 minutes it died I think cause of a loose wire but I felt the head and it was rather warm. I remember before it was quite a while before the valve cover got warm. Maybe I didn't do my piston rings right? I set the ring gaps at 120 degrees from eachother although that probably changed a bit after I installed it back into the cylinder. I hate doing that part. Anyways I won't be able to find out til I get a new gasket kit. Anyone know the easiest way to install the piston into the cylinder? Anyone got ideas on preventing overheating? I have an oil cooler but it takees a while to do anything, and I feel only cools on long rides
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Post by 90GTVert on Nov 4, 2014 5:46:50 GMT -5
Best ways to prevent overeating are usually to keep the shrouds and fan on and in good condition and to make sure the carb is in tune and err slightly on the rich side.
If you aren't losing compression or burning oil I wouldn't take it apart to check the rings just yet.
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Post by kekoaquiroz420 on Nov 4, 2014 16:07:15 GMT -5
Ya the engine is pretty new(less then 300 miles) before it originally broke down in march(I was driving it and it just died which we.def up being cause of electrical problems and had to push it home 4 miles from the beach to 1500ft) it never overheated even driving 20 miles wot it wouldnt be as hot as it is now after 20 minutes of driving. That day in march I had my temp gauge installed and the oil never got above 195 degrees F so I think my tuning and fan and shroud are good the fan and shroud are in nice condition and I have a 95 jet installed. It definitely smells like burning oil though, and eventually starts smoking so I think its the cylinder or head gasket leaking extra air into the cylinder, making it run super lean and overheat quick and the oil is leaking into my shroud so I can't see it leaking then when it heats up it burns and starts smoking. Haha I'm a retard and reused the cylinder and head gasket which I know is a big no-no, so I'm gunna order a new gasket kit and do it right and I think it will solve my problem
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Post by birdman on Nov 4, 2014 17:15:39 GMT -5
Welcome. This is a great place to be and read/ lurk.
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