Clinician
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Post by 95civicsi on Jun 24, 2012 18:06:22 GMT -6
Hello all. Let me start by thanking the many members who have helped my knowledge on small engine repair and GY6 specifics explode rapidly over the past couple of week. I've done a significant amount of reading and there is a wealth of knowledge to be found here. Now an explanation of my problem. I recently purchased, second hand, a Sportiva scooter with a 157QMJ. This is my first motorized two wheel anything and I did not have a lot of knowledge on their workings or what to expect. When making the decision to purchase this scooter, my research turned up that I should be able to expect about 50mph and 70 mpg. I had several complications during my first ride. Lighting did not work when the engine was running, starter solenoid had to be bypassed to start the engine. When I rode home the first day, the total ride from pickup to my house was about 25 miles. 20 of that is no stop back country. At best I was able to get 40mph. I spent most of the ride home driving WOT (to which I am now aware I should not have done). After about 15 miles, the engine started to smoke severely both from the exhaust and from an oil leak under the engine. When I got home, I let it cool down. The oil leak was from the section where the piston cylinder meets with the engine block on the bottom side of the engine. I thought that most of my problems were from bad wiring. The stator was not wired to the voltage regulator at all. There were a number of other problems. I spent a whole day learning the wiring for the scooter and fixing the problems I found. After getting my scooter back together I decided to ride it to work, another 25 mile drive. I forgot to check the oil and spent the majority of that ride fighting to keep any speed. It died and will not crank. Sooo, with that said, I feel that I have a compression issue (which I understand is my mistake) and after tearing down the head and piston cylinder, the head gasket did not appear to be damaged. My next guess is the piston rings. I'm sure there is spark and fuel. The spark plug is firing when trying to crank and there was gas in the carb and intake port when I took the carb off. I also checked the front variator and discovered that the rollers are damaged. The glide keys are missing. Is there anything else I should look into while I'm replacing parts? Also, the plastic shroud around the casing is damaged. Is it important to replace it?
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Doc's Anything Goes
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Post by tvnacman on Jun 24, 2012 19:51:30 GMT -6
The black plastic goes around the engine ? Yes you will kill the rebuilt engine very very fast . That is for cooling .
John
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Scooter Doc
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Post by justbuggin on Jun 25, 2012 0:52:48 GMT -6
with the number of problems with the motor you might want to look into getting a new motor with it leaking oil and being run for a long time with out oil the bearings in the bottom end could be damaged with that said best of luck with your rebiuld
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Scooter Doc
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Post by rob63 on Jun 25, 2012 9:04:40 GMT -6
If it died and didn`t crank then you probably had a seizure of some kind due to the lack of oil. There`s a very strong possibility that you`ve damaged the crank bearings to some extent which means a full strip down and replacement of probably the crank, bearings and seals, maybe the oil pump as well and possibly the camshaft and bearings have some damage. If smoke was coming out of the exhaust then also a barrel and piston/rings along with associated gaskets. Then there is the rollers and probably a new variator assembly and a belt. I can only echo what people have said above, if I was in your shoes I`d start looking for another engine, although depending on what you paid for the bike and the condition you describe it as, I`d be tempted to right it off as maybe spares and look for something which has had a bit more care and attention given to it.
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Clinician
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Post by hunter on Jun 25, 2012 14:20:04 GMT -6
I agree with rob63. You said you were a novice so put this in your oops file,save it for parts and look for a better scoot. At least you'll know a little more about what to look for before buying. Good luck
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Clinician
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Post by 95civicsi on Jun 26, 2012 11:59:25 GMT -6
Sorry for my poor choice in wording. The engine would turn over but not start. When trying to start the engine, the engine would turn over but would not run. When trying to start the engine, if you opened the throttle up, you could hear the engine try to move faster. I've already removed all the gaskets and ordered replacement rings, gaskets, and the rollers. The plastic around the engine was something I was unsure about because it looked like it was directing the air from the fan around the casing but I wasn't sure. Once I get things back together, I'll post how it's turned out. I spent most of today cleaning the engine. More pics to come.
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Post by Bashan on Jun 26, 2012 15:13:07 GMT -6
If it was turning rapidly when you were cranking it that's low compression. That could be roasted rings, a seized valve, or both. Make sure when your putting everything back together the valves are operating normally. If the gap is too tight you'll lose compression also. The engine will crank slightly faster with the throttle open, it releases the vacuum on the piston, nothing to worry about. So compression will keep it from running but of course electricals will also so who knows. If you need help assembling and doing the rings here's a thread. Rich
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Clinician
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Post by 95civicsi on Jun 27, 2012 10:38:31 GMT -6
Thanks for the link. That is one of the threads I looked at that helped me pull the piston and variator. Tomorrow I'll put things back together. Got the parts I need today and the day off tomorrow. I appreciate all the feedback and I'll post as I go.
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Clinician
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Post by 95civicsi on Jun 28, 2012 13:21:38 GMT -6
So after what appears to be a successful rebuild, my cdi decided to give out. Great compression now, but no fire.
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Scooter Doc
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Post by sprocket on Jun 28, 2012 16:25:17 GMT -6
Could be the pick-up coil on the stator, unless you jumped the battery off running vehicle that cooks the CDI Check your voltage between the stator and CDI on the red and black wire, also you should get a pulse voltage on the blue and white or blue and yellow. All AC volts
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Clinician
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Post by 95civicsi on Jun 29, 2012 22:40:09 GMT -6
So I put in a new cdi. Didn't fix the problem. Checked the wiring, the ground on the ac output of the cdi was tied to chassis ground. I believe it's only supposed be connected to one pole of the ignition coil, so I changed it. The positive output was connected to the other pole of the coil. The boot on the coil had intermitent connection, replaced the coil. I'm getting fire now. The black/red output on the stator showing 34-40vac and 5vac from the timing pickup. CDI is outputting 25-28vac. Engine still won't start. I'm rechecking the wiring to see if I made any other mistakes. The only thing left that makes since to me is that the fuel isn't actually getting in the engine. Inline fuel filter pulled gas through it when I first tried to crank it. Would the electric choke cause a problem starting?
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Post by Alleyoop on Jun 29, 2012 23:51:29 GMT -6
To find out if it is fuel delivery, take the Vacuum hose off the INTAKE MANIFOLD and squirt a little bit of gas straight down the intake through the intake connector and out the vacuum hose back on and try to start it. If the Spark Plug is fireing it will attempt to fire and it might start and die. Alleyoop
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Clinician
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Post by 95civicsi on Jul 6, 2012 10:05:18 GMT -6
Should there be any back pressure on the intake side?
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Clinician
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Post by 95civicsi on Jul 6, 2012 10:14:32 GMT -6
Should there be any back pressure on the intake side?
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Doc's Anything Goes
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Post by tvnacman on Jul 6, 2012 14:37:13 GMT -6
No back pressure on intake side. Recheck your timing. Be sure that you line up to your marks at TDC .
John
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