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Post by sprocket on Jan 22, 2012 11:30:56 GMT -6
At 12k miles the engine is approaching it's final stages on average... so compression check would be advised..however.. the low RPM bogging is much more likely a fuel problem as Alley mentioned.
I would just replace the carb...
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2008 Roketa MC-74-150cc & 82' Honda CM 250 Custom
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Post by bcgreatness on Jan 22, 2012 13:17:52 GMT -6
dont spend money on a carb when yours is fine. just get your hands on one of these! you dont have to get this exact one but you can pick one up from any tool store, and maybe for cheaper. if your bike has been sitting for a very long time, it is gummed up for sure. just a simple soak and spray will NOT completely clean it out. you need a carb cleaning tool set. scooterdoc.proboards.com/index.cgi?board=150cc&action=display&thread=270&page=16 |
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Post by sprocket on Jan 22, 2012 13:29:31 GMT -6
You don't have to buy a tool set.. just get a B string for a steel strung guitar they are the right size.. cost about a buck at any music store
Also if you do want a jet cleaning tool set get a welder's tip cleaner set, many more wire sizes and much cheaper...
I often use the wire out of a plastic twist tie...works well
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Post by runningslow on Jan 22, 2012 14:56:00 GMT -6
At 12k miles the engine is approaching it's final stages on average... so compression check would be advised..however.. the low RPM bogging is much more likely a fuel problem as Alley mentioned. I would just replace the carb... Sprocket, the engine in question only has about 3-4,000 miles on it. It replaced my original motor that lost a main bearing at about 9,000 miles. I'm not so worried about it being compression... ...however, that being said, I just replaced the head on the new engine with that of the old engine. If any of you may recall, the head on the new engine decided to crack at one the exhaust studs. I had to use my old used head, because both of these engines are QMK (QML) engines with a slightly oversized head bolt spacing. During that replacement, I had to resuse a head gasket, because I could not NOT find a suitable replacement. I cleaned it best I could and coated it with Permatex copper. Scrappy lists a QMK gasket set, but the head gasket was not correct. SO, its very possible I have a leaking cylinder, but I haven't seen any oil leaks yet. We'll see if it holds. I hope it just turns out to be a fuel issue and I'll get a new carb. |
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Post by sprocket on Jan 22, 2012 15:02:59 GMT -6
You could be out a link on the cam sprocket...the engine will idle but won't rev.. the timing is out... If you used the flywheel T mark.. then this is probably the case... if you used the TDC of the piston then the cam chain is likely OK, but I have seen engines where the mechanic replaced the head and the cam chain slipped off the crank sprocket and is sitting to one side of it...you can see if that is your problem by looking doen the cam chain well with a very bright light... Is the cam chain tensioner working? It is all coming back to me now...I want the rights to the movie  |
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Post by runningslow on Jan 22, 2012 16:12:21 GMT -6
You could be out a link on the cam sprocket...the engine will idle but won't rev.. the timing is out... If you used the flywheel T mark.. then this is probably the case... if you used the TDC of the piston then the cam chain is likely OK, but I have seen engines where the mechanic replaced the head and the cam chain slipped off the crank sprocket and is sitting to one side of it...you can see if that is your problem by looking doen the cam chain well with a very bright light... Is the cam chain tensioner working? It is all coming back to me now...I want the rights to the movie There are so many things that I know now that I wish I knew before pulling the head. Most prominently would be marking the chain and sprocket. I tried my best to determine TDC with a wire down the spark plug hole. I found it little hard to find that precise moment at the top of the stroke, so its possible I have it a link or two past TDC. Without pulling the head, are there any better ways to check for TDC? I want to avoid pulling the head for the reasons mentioned in the previous post  If the cam chain slipped off the crank sprocket, would the bike even idle?? How can I tell if the tensioner is working? Movie rights? Ha. Only if you get George Clooney to play me. ;D |
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Post by sprocket on Jan 22, 2012 16:26:10 GMT -6
I have never had any luck on a GY6 with a wire or straw in the plug hole.. it is really easy to overshoot the TDC. The cam chain links are very small and it sure doesn't take much to be out a link
Yes I have seen engines idle with the cam chain off the bottom crank sprocket...there is enough friction to keep thing going but when you rev the cam chain slips and the timing goes south...
The tensioner... is the cam chain good and taught on both sides of the cam sprocket?
Sure... will get George, I will contact his agent...
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Post by runningslow on Jan 22, 2012 17:56:30 GMT -6
I have never had any luck on a GY6 with a wire or straw in the plug hole.. it is really easy to overshoot the TDC. The cam chain links are very small and it sure doesn't take much to be out a link Yes I have seen engines idle with the cam chain off the bottom crank sprocket...there is enough friction to keep thing going but when you rev the cam chain slips and the timing goes south... The tensioner... is the cam chain good and taught on both sides of the cam sprocket? Sure... will get George, I will contact his agent... I don't think the chain is off the sprocket, because it reliably restarts after each attempt. So the timing stays consistent, even if its not correct. Also the tension on the chain seems good. Looks like I may need to start marking the chain and adjusting it link by link. I want to rule out fuel issues first though. Sent from my MoPho using the ProBoards App |
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Post by bcgreatness on Jan 22, 2012 21:07:28 GMT -6
im positive you got the tdc on point if not within a link away from true tdc. i set it on mine using a feeler and it works just fine, im sure your throttle issue is something else.
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Post by runningslow on Jan 23, 2012 7:51:48 GMT -6
im positive you got the tdc on point if not within a link away from true tdc. i set it on mine using a feeler and it works just fine, im sure your throttle issue is something else. You're probably right. The symptoms really look like a fuel issue. I'm going to adjust the valves tonight. If that doesn't help, I'll pull the carb again for another cleaning and I'll look into a compression tester. Looks like I can get one from Harbor Freight for about $20. If compression is good and another good carb cleaning doesn't help, I'll just order a new carb. If the timing is off, it has to be only a link, maybe two. If that's the case, shouldn't it at least start to rev and then just run rough? EDIT: If I can get it to idle, does that at least mean the Pilot Jet is clear? |
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Post by bcgreatness on Jan 23, 2012 16:15:11 GMT -6
the carb cleaning tool set has small pins designed to clear out the jets. BUT like sprocket mentioned, you dont have to buy one! he said you can use a B string ( which is the string before the last string ) or a wire tie. you could use a wire tie from a loaf of bread but i would go with the longer ones that come in some packs of garbage bags. dont forget to strip the plastic coating off lol. theres some good instructional vids in the tech section that bashan posted that how how to clean the carb using the tools ( or b strings or wire ties ) hope that helps, hate to see somebody spend money they could have saved. if the timing was off i dont think it would idle good. it would have equal effect on the idle as it does giving it throttle. it might not be the same but ive gotten timing on vehicles a link off and they wouldnt even start, they had to be dead on. but again on vehicles theres alot more systems that rely on the timing being spot on.
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Post by Alleyoop on Jan 23, 2012 16:47:23 GMT -6
Test out the PILOT JET PASSAGE, Start the Scoot and let it warm up at least 5 minutes until the ENRICHER cuts off the extra fuel. Then Turn the Fuel Ratio Screw 1/4 of a turn Clockwise waiting about 10 seconds in between each 1/4 turn. The IDLE should go down and at some point it should kill the motor. Then just turn it until it stops and turn it out 2 1/2 turns and start the motor back up. Now turn it COUNTER CLOCKWISE like 1/4 turns and wait 10 seconds and let the motor catch up with the new setting. IF the Idle goes up or down the Pilot is Clear. *** IF WHEN TURNING IT IT DOES NOTHING then you know Part of the PILOT JET passage is Clogged. It could be the Tiny holes by the Butterfly and you can get a small needle to clear then out. Spray into the Pilot jet and Spray should squirt out of the tiny holes by the BUTTERFLY. Alleyoop  |
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Post by runningslow on Jan 27, 2012 13:47:45 GMT -6
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Post by sprocket on Jan 27, 2012 15:41:41 GMT -6
Run a fine wire through all the passages too, carb cleaner is fairly useless in those tight spaces...
That is not a standard carb... if it gives more problems spend the $30 and just replace it...
Is there a name on it anywhere?
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Post by runningslow on Jan 27, 2012 17:13:27 GMT -6
Run a fine wire through all the passages too, carb cleaner is fairly useless in those tight spaces... That is not a standard carb... if it gives more problems spend the $30 and just replace it... Is there a name on it anywhere? Its a Keihin carb. Its been on the Matrix since the day I bought it.  The latest cleaning did not help. I also change spark plugs, since I had a spare laying around. Same exact symptom. Idles rough and dies the moment you give it gas. I'm not convinced its the carb, yet. I think the timing may still be off. Thoughts? |
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..BAD TO THE BONE..
