Timing Marks CN250 By gdoug12 (Read 8,938 times)

[gdoug12]

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.

[JR]

Timing the CN250 doesn't require marks on the cam? Look at the Helix shop manual on page 29 on how to time this engine;

thescooterprofessor.proboards.com/index.cgi?board=ncmanuals&action=display&thread=415

Now on the linhai it's a different story, use the Yamaha YP250 manual here page 103:

thescooterprofessor.proboards.com/index.cgi?board=250ee&action=display&thread=278

JR

[damin69]

Dec 11, 2012 20:56:37 GMT -6 gdoug12 said:

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.

Yes that is what you line up with. I believe there are 3 holes in that sprocket the two should line up parallel to the top edge of the head. If it runs rough you are 180 degrees off on the cam. I had that happen when I rebuilt mine the first time.

[gdoug12]

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.

[alleyoop]

That is the reason it is ALWAYS good to bring it up to TDC THEN mark the Chain link and CAM Sprocket as well as a mark on the FLYWHEEL where the pointer is pointing to. That way you will always be right on.
Alleyoop

[gdoug12]

Understood, nothing I can do about that now. do you know anything about the flywheel marks?

[alleyoop]

There are usually two marks looking at the marks the one to the left is The "T" top dead center mark the next one going clockwise is the "F" fireing range. Don't forget it does not FIRE right on the TDC it fires just before TDC. So as the flywheel rotates CLOCKWISE it fires around the "F" mark then the "T" follows.
Alleyoop