theo547
Scoot Enthusiast
Posts: 497
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Post by theo547 on Jun 13, 2011 23:15:25 GMT -5
Ok well scooter was acting funny today... then it started... stuttered and stopped... did not start up again. I was low on gas... so i thought maybe if i filled it up... that didnt work. Figured i would try and test for spark - it has spark. (for once...). tried putting some carb clean in the chamber... started for a sec then died. came back a few hours later and it still wouldnt start its at work so i cant do much to it right now, but here are my thoughts: Either a gasket totally gave and i have some sort of serious air leak or i just burned a hole in my piston or worse bent something up in the engine. hoping thats not the issue. The sad thing is that if it is the piston im not very upset... ive learned a ton playing around with this thing... and well... hey 100 bucks isnt that big a deal... still have the old cylinder. But, ill be going into work an hour early tomorrow and doing a compression test... then having a buddy haul it back to my house in his truck ;( Wish me luck!
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Post by reveeen on Jun 14, 2011 3:40:35 GMT -5
Bad luck.................
When you wail the crap out of them the weakest part let's go. You have to remember, at high RPM's, there is almost as much pressure below the piston, as there is above. This puts stress on the crank seals, the reed block gasket, and the cylinder base gasket. The last junker I bought had it's base gasket blown out...... there is no telling what you will find, just keep your eyes open while you take it apart, and try to figure out the "why?".
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Post by marshinman on Jun 14, 2011 5:09:41 GMT -5
The likely hood of it being a hole in a piston is going to be almost no way. I would check to see first of all if you are getting fuel, the fuel petcock is vacuum operated and if the diaphragm goes bad then no fuel will go to the carb. By spraying the carb cleaner and having it start shows that it has compression and has spark. Start with the fuel supply and verify that it is getting fuel. It could still be a gasket or seal but start with the easy thing before you decide to tear the motor apart. You could also have a clogged up main jet so it can not pull fuel from the bowl of the carb.
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theo547
Scoot Enthusiast
Posts: 497
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Post by theo547 on Jun 14, 2011 7:38:27 GMT -5
Have some better news... Compression checks out. About 135psi. When I tested it after I installed the bbk it was at 125... So in two weeks it went up. Hope that's a good thing.....
Guess I'm building a leak down tester at lunch. I have a spare base gasket so let's hope that's the problem.... Or better yet something in related
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Post by 2strokd on Jun 14, 2011 7:42:30 GMT -5
Getting fuel? Have you tried manually choking it by covering the carb with your hand while you crank it over? Sounds like a fuel delivery problem to me... Maybe even a busted reed?
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Post by jmkjr72 on Jun 14, 2011 8:31:25 GMT -5
im betting on a no fuel issue first eveb with a bad crank seal it should run just very lean
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theo547
Scoot Enthusiast
Posts: 497
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Post by theo547 on Jun 14, 2011 13:20:25 GMT -5
Ok updates....
This thing must have gremlins ... Installed a new plug... No start Disconnected the air filter ... No start... Reinstalled Disconnected all hoses from carb... No start... Reinstalled Disconnected the carb from the manifold....no start... Reinstalled
Now it starts... Going to clean the carb again tonight.... And I'd its still having issues I'm going to spike it.... I'll take video.
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Post by marshinman on Jun 14, 2011 17:40:08 GMT -5
Use a air compressor if you have one to blow out all the ports in the carb, if you dont have a air compressor buy some caned air. Carb cleaner does not always get everything. Remove the jets and blow air through them and then see if you can see light through them you will have to get them at just the right angle to see through them.
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theo547
Scoot Enthusiast
Posts: 497
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Post by theo547 on Jun 14, 2011 20:49:06 GMT -5
Carb has been totally cleaned out...
It had a real hell of a time starting after, but i have a new thought.
I pulled the vacuum line off the carb and no fuel came out. so i tried to suck some fuel through it. it is working or it appears to be. but..... it started about 3 kicks after i sucked on the vacuum line. Is it possible some gunk is causing the petcock vacuum seal to have trouble opening? is this something that has been a more common issue?. this things only 4 years old and 2k miles....
Also my idle seems odd to me... it starts at around 2k rpms... then ill take it for a ride and come to a stop and it will be at 3k if i sit for a extended period of time (30 secs or so) the idle drops down to 2k again... is this just my choke? or a sign that i have an air leak? maybe related to the possible petcock issue?
Air\fuel screw and Idle screw still not functioning the way i think they should...
And just something ive been thinking about: is it ok to run WOT for extended periods.. ive had so many issues im paranoid when im hitting 9k+ rpms that im going to blow the engine up or something crazy like that.....
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Post by reveeen on Jun 15, 2011 3:31:15 GMT -5
Is it possible some gunk is causing the petcock vacuum seal to have trouble opening?
Yes... they "gum" up too, just like a carb.
is this something that has been a more common issue?. this things only 4 years old and 2k miles....
I have no (0) luck with these things. One went bad on my Yamaha, and after 3 attempts at buying new ones to replace it, I went to a manual one. It, for me, is just "business as usual", to deep 6 the vacuum petcock, and install a manual one. Most dirt bike guys I know do away with them too. Your luck with a new one will likely be different, or try a little spray carb cleaner in there..... but not in the vacuum side, as it will "eat" the diaphragm. Keep in mind too: you NEED the most fuel at WOT, yet at WOT you have the least amount of vacuum to pull/hold the thing open, not an entirely sensible situation?
Electric chokes go bad, because I do not own anything with an electric choke and have no (0) experience with them you would do better getting advise from someone else. A choke "problem" could be the cause of you not being able to control your carb with the screws and cause an erratic idle, but so too could a vacuum leak, or a sticking throttle cable.
is it ok to run WOT for extended periods
Once the engine is broken in, your mixture @wot is not lean, and the oil delivery system you are using is ok, sure (as long as you don't over rev it).
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Post by 2strokd on Jun 15, 2011 9:11:23 GMT -5
I would richen the idle/air mix some. Just a tad at a time and go for a ride. About 1/4 turn. It could be a small air leak as well. You wont blow it up at 9,000+ if everything is tuned right and its getting good oil.
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