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Post by gdoug12 on Jul 31, 2013 20:23:46 GMT -6
Hi There, I have a YY250T-2 that I have been trying to resurrect for quite some time. Keep in mind this puppy only has 120 mile on it. The original owner had no idea of what he was doing and never performed the checks recommended by JR, i.e. coolant flush, oil change, vacuum lines. Anyway this resulted in clogged coolant hose, burned rings, damaged head, severe blow-by, you name it. Tore it down and replaced the rings, head, piston, long story short after getting it back together, confirming timing is correct, it has always started right up and idled. Also runs while the enricher is working, but once it would really warm up and the enricher circuit closed it would become a real dog and eventually stall. Replaced the intake boot, no change. After playing around with it for a long time, today I had it out, let it warm up and when it started getting bad I happened to squeeze the u-shaped vacuum line going from the air cut-off valve to the side of the carb. When I did this the idle came right back and again it had throttle response. Let it go and it would die. I cut the line and installed golf tees and now it runs much better but more importantly it isn't trying to die. Does anyone know how that valve works, and why the drastic change in behavior when I close it off?
Also noticed that the helix CN250 connects the ACV to the manifold. Mine has it connected to a "T" which goes to the manifold and the fuel pump. Did the Helix have an electric fuel pump?
Thanks
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Post by gdoug12 on Dec 12, 2012 19:12:24 GMT -6
Understood, nothing I can do about that now. do you know anything about the flywheel marks?
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Post by gdoug12 on Dec 12, 2012 17:36:41 GMT -6
Thanks, but I should have been more specific. It is not real CN250 but rather the clone Jonway/Roketa/JMStar (take your pick it has all of them on it). I have the Helix shop manual it it tells you to line up the "punch mark" on the cam shaft and also tells you there is a "T" mark on the flywheel. This does not have any punch marks on the cam shaft that you can see through the inpspection hole (doesn't exist) and the flywheel has a " " on it and then if you keep turning it a little there is some other strange looking marking. I'm sure that I am not 180 degrees off as I didn't rotate the flywheel or chaing during the piston/ring replacement. But what I do know is that the cam sprocket has the holes you line up with the head when it is at TDC. The question is, what marks am I using on the flywheel? I did google this and found that someone said that the second " mark as you are turning the engine clockwise is the one you want to use. Any idea if this is correct? If it is, then my sprocket is a tooth or two off and this is why I can idle great but bog down severely when giving it the throttle. My original problem was solved "Oil in the airbox" by replacing the piston and rings. But this new problem didn't exist before so I assume it is something really silly like this that has me pulling my hair out. I hope this makes more sense JR, if it were a real Honda I'm sure it would be much easier.
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Post by gdoug12 on Dec 11, 2012 20:56:37 GMT -6
I am trying to verify if I have the position of the cam sprocket vs. the flywheel set correctly. The cam doesn't have any marks in it, so I am relying on the two holes in the sprocket being parallel with the top of the head when cam lobes are downward. If that is the correct position of the cam when at TDC, can anyone tell me what marks on the flywheel should be lined up with the index mark? As the flywheel rotates, I come upon a set of marks that look like " ". After those there is another strange mark and then after that what looks like a flat mark. After reassembling I'm wondering if my timing is off due to me aligning with the wrong marks.
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Post by gdoug12 on Nov 23, 2012 16:48:19 GMT -6
I did stagger the rings and honed the jug. The piston and rings are new. There is no oil in the airbox and since replacing the piston and rings it no longer blows oil. The compression is 165 lbs. I also just finished looking at it some more and I double checked the timing and all is good. Starts right up but again bogs with just the airbox adapter attached even when the filter is not in place. Crack it from the carb and it will accelerate. So just the screens inside that are enough. BUT....I held that back in place and sprayed carb cleaner around the intake manifold and the idle actually lowered for a moment. I then tried to accelerate while spraying and it revved higher without bogging. So I will check the intake manifold for leaks. Any other insight of course is appreciated.
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Post by gdoug12 on Nov 21, 2012 20:40:09 GMT -6
Well I cleaned the carb and tried the mixture screw but no change. I then rechecked my cam chain position and it was off. Moved it one tooth after putting at TDC and aligning holes in the sprocket with the head. It did improve a bit but still cuts out when starting to rev. I will check once again to see if it may still be off a tooth. Also any idea of what the compression should be on the CN250 motor? I don't think it is measuring much higher than before when the top rings were dead and I question if the piston and rings installed were correct.
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Post by gdoug12 on Nov 21, 2012 20:33:24 GMT -6
Well I cleaned the carb and tried the mixture screw but no change. I then rechecked my cam chain position and it was off. Moved it one tooth after putting at TDC and aligning holes in the sprocket with the head. It did improve a bit but still cuts out when starting to rev. I will check once again to see if it may still be off a tooth. Also any idea of what the compression should be on the CN250 motor? I don't think it is measuring much higher than before when the top rings were dead and I question if the piston and rings installed were correct.
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Post by gdoug12 on Oct 26, 2012 19:39:11 GMT -6
It's been a long time since the last posting but I had to put the project on hold and in storage for quite a while. But about a month ago I took your advice and finally it led me to the rings. There it was, the top ring was somewhat functional but the second was totally stuck and there were scorch marks and smearing on one side of the piston. Bingo! I assume it was caused by the person who first purchased the scooter and put teh first 26 miles on it since when I got it the coolant lines were clogged and the shipping oil never drained. So now it is back together and not blowing oil......but there is another issue. I first started with the airbox connected and a new filter. It idles fine but when you give it the throttle it initially revs but then bogs down really bad the more you give it. So I loosened the airbox from the carb and allowed a little air and then she revved up nicely with no bogging. But then when it decelerates there is a popping from the exhaust. I did adjust the valves before starting it but it was the cold method finding TDC and then moving the adjusters out and back in a half increment. I feel like am almost there and just in time for Winter  Any ideas to get me over the final hurdle? Just to refresh you, it is the CN250 clone (Helix) YY250T-2 thanks |
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Post by gdoug12 on Sept 19, 2011 6:34:20 GMT -6
I thought about that but if it were rings I'd think compression would be an issue and also smoke in the exhaust, but I don't have any smoke and it only has 100 miles on it.
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Post by gdoug12 on Sept 16, 2011 14:27:22 GMT -6
Hi JR,
I took it outside and started it up and wow did I ever see a problem. As I mentioned above the valve cover vents down to a small reservoir which then is vented up to the airbox and it also has a large clear drain tube and plug. I stared it up with airbox connected to the carb and right away that tube filled with oil. I removed the connection from carb to airbox so there is no air intake and it still filled. I then removed the plug and drained the oil out of the tube and left the plug off. I started the engine and oil was blowing out of the tube like spray paint. So there is positive pressure doing this. Could it be one of the valves doing this? Possibly not closing and creating blow by the valve? I'd assume the exhaust valve? Any insight anyone can provide would be great. Thanks.
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Post by gdoug12 on Sept 13, 2011 13:30:02 GMT -6
Thanks, I assume you check it with the front wheel touching the ground? If it touches the ground I don't read anything, if I pivot on the stand so the tires are equally off the ground I do measure the correct level.
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Post by gdoug12 on Sept 12, 2011 11:21:06 GMT -6
I'm back at this again after cleaning the oil out of everything, and I found that the vent from the valve cover goes into a little reservoir below the air inlet tube, then the reservoir connects to the air inlet tube with a short tube. I haven't found anything kinked that would prevent the air from sucking through the filter which was new, however would this happen if the oil level was too high? I did notice when I first got this that the oil level seemed high but forgot to go back to it to confirm. Now I have a silly question, do I check the oil level on the center stand or with wheels on the ground? If on the ground the dipstick doesn't measure any, if I am on the center stand and make the bike level it does show. So at this point I don't know if I really have a problem or if the oil had been over filled from the factory. Any ideas?
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Post by gdoug12 on Aug 18, 2011 11:37:34 GMT -6
Thanks JR, I took a few minutes and removed the air box cover and much to my surprise I had a waterfall of oil come gushing out. It had to be 1/3 full at least and the filter of course is soaked. After cleaning up the mess I had to quit for the day so I will start looking for the lines connecting to this tomorrow. The scooter only had 27 mile once I got it working so it probably has 200 now. Hard to say for sure because the speedometer seems to lie : )
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Post by gdoug12 on Aug 18, 2011 10:57:13 GMT -6
Hi Gatekeeper, I ran into a similar situation with a 2008 model that the PO couldn't get to run. I brought to life but the thing would overheat right away. I found the entry to the water pump totally clogged so the lower end of the radiator where the sensor is would not get hot at all and so the fan never kicked on. Once cleaned and flushed it all worked except now my fan stopped working (another issue). Regarding the fan, it needs to pull air through the radiator and blow back toward the engine.
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Post by gdoug12 on Aug 16, 2011 11:31:08 GMT -6
Hi There! After taking care of my YY250T-2 Jonway overheating and running the scoot for a few trips before selling my house and losing my work area  , I was able to run it to work a few times and it ran great at lower speeds. On the highway it was a bit scary because at full throttle it would buck like it wasn't getting enough fuel. Plus my speedometer lies so I was probably getting 55 mph max. I will look into this but more importantly I was noticing leaking from my airbox! There is what looks to be a rubber bleeder on the bottom and oil leaks out of this when it is sitting. It's the CFMoto 244cc, any ideas of why this would happen? I assume there is a breather tube to the engine. I was able to trailer it to my work so I will start tearing into it tomorrow. Thanks! |
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