Oil in the Air Box By gdoug12 (Read 8,106 times)

[gdoug12]

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!

[JR]

The airbox along with the breather system off the engine are all connected together, first thing is to open it up and make sure the filter is clean and check the breather vent hose from the valve cover to make sure it is open not pinched anywhere and all is well on this part.

If the filter is real dirty the engine will suck oil from the valve cover hose because it's trying to pull more air and can't through a dirty filter.

Another thing that can cause this is the airbox is cracked and it's pulling way too much air which can suck oil out through this hose also so we need to check out the entire air filter housing and the filter.

Either one of these things could cause the engine to act like you described at higher speeds.

Keep us informed and we're here to help.

JR

[gdoug12]

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 : )

[gdoug12]

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?

[JR]

If it's overfilled for sure it's going to blow or get sucked out. Yes I put my scooter on the center stand and try to do it on a flat surface to get an accurate reading. FYI the 250A and B with the linhai holds about 1-1/4 quart and that's it.

I fill mine to where it reads about half way up the marked part of the oil stick with just it sitting in the hole not screwed in again a little over a quart.

JR

[gdoug12]

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.

[gdoug12]

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.

[problemchild]

i would say rings

[gdoug12]

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.

[JR]

You did mention the valves and if they are very badly off then it could cause this problem but it probably would run very badly if they were off that bad? For sure it isn't going to hurt to adjust them and yes if the vavles are not off you certainly have either positive pressure blowing the oil out.

Adjust the valves, fill her back up to the proper level of oil and then leave the vent hose off and see if it still blows oil after you start it up, if so then the rings may be a concern and it could be just the oil ring? If the compression rings are good then compression will be fine even if the oil ring has collapsed.

JR

[gdoug12]

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

[alleyoop]

Different sounds a motor makes tells you what it needs, so listen for any sounds the motor makes.

Popping while accelerating is a RICH condition.
Popping while de-celerating is a LEAN condition.
Burp Sounds accelerating is a LEAN condition
Backfires are a Lean condition.

First check if your idle is to LOW it should be anywhere from 1800-2000 rpms and your rear wheel NOT spinning.

If the idle is good and not low THEN give the Fuel Ratio Mixture Screw a 1/4-1/2 turn COUNTER CLOCKWISE to richen it up some. It is getting colder and that means the MOTORS need more fuel.
Alleyoop

[gdoug12]

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.

[gdoug12]

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.

[tvnacman]

Did you stager the rings , hone the jug . Was there a wear spot on the pistion ? Is there oil left in the air box ? Have you done a compression test ?

John