is this a possible loose cam chain on My GN250 single cyl?

[Paul]

This is the bike cold (needed a little choke) I'm thinking this rattling / tinkling is my cam chin, but don't know?

http://www.youtube.com/watch?v=-PzEjs_BuH4

should I just pull off the cam chain adjuster inspect it and fit it back on...are there any things to look out for on a worn/broken adjuster?

Cheers

 

[Steve]

Kind of hard to tell, as most phones have pretty good noise cancelling abilities.

Three likely areas that might cause similar noises:
1. Loose valves
2. Loose cam chain
3. Loose clutch basket

For the valves, check the clearances. I have not worked on a GN, but I think they are similar to the GS.

For the chain tensioner, again, it's probably similar to the GS, one of the biggest problems is that somebody installed it incorrectly. Before removing it, loosen the locknut, tighten the set screw, back the set screw out 1/4 turn, lock it in that position with the locknut. See if the noise is gone.

For the clutch, you will have to pull the cluch cover (requires a gasket for re-assembly) and the pressure plate, along with all the disks. Keep the disks in the same order and orientation, so they go back in exactly the same way. Tighten the nut that holds the basket to the shaft, put everything back together.

If the engine still makes noise, it might be "normal".

.

 

[Agemax]

Paul, did you recently check your valve adjustment? i think i recall you posting a thread up about it. did it rattle like that before you did the adjustments?
if not i suggest you recheck your valve clearances again

 

[Paul]

Paul, did you recently check your valve adjustment? i think i recall you posting a thread up about it. did it rattle like that before you did the adjustments?
if not i suggest you recheck your valve clearances again

Yes I have been trying to master valve adjustments and perhaps they are a little tight still... I just had a look now, and the weathers so cold the oil doesn't want to show me the TDC mark, so I'll order a filter, change the oil and have another go in couple of days. Not sure if it rattled so bad before, but the chain tensioner doesnt look like it been touched in years

I'll report back when I've had another go at it
Thanks guys,

 

[Agemax]

Yes I have been trying to master valve adjustments and perhaps they are a little tight still... I just had a look now, and the weathers so cold the oil doesn't want to show me the TDC mark, so I'll order a filter, change the oil and have another go in couple of days. Not sure if it rattled so bad before, but the chain tensioner doesnt look like it been touched in years

I'll report back when I've had another go at it
Thanks guys,

i dont understand how your oil wont show you TDC? am i missimg something here???????

 

[Steve]

i dont understand how your oil wont show you TDC? am i missimg something here???????

I was wondering that, too, besides the fact that tight valves won't make noise. :-k

If the valves are making noise, it's because they are too LOOSE, not tight.

.

 

[hampshirehog]

i dont understand how your oil wont show you TDC? am i missimg something here???????

The TDC mark is on the LH side of the engine on the outside of the rotor. You remove a small bolt to look through a hole so it can be a bit tricky. Because it's bathed in oil the oil, when it's cold, can stick on the outside and mask the TDC mark.

 

[Agemax]

The TDC mark is on the LH side of the engine on the outside of the rotor. You remove a small bolt to look through a hole so it can be a bit tricky. Because it's bathed in oil the oil, when it's cold, can stick on the outside and mask the TDC mark.

ah, now i understand. thanks Wally......

 

[hampshirehog]

That engine design is really reliable (unburstable even) but they do have a few weakpoints and you have probably copped for one of them. The camchain tensioner can stop working with a build up of gunk, get worn etc. It is worth, like you thought, pulling the thing off and cleaning it up. There are aftermarket tensioners that you set manually - they sort the problem and are lot cheaper than a new OEM.

Valve clearances need sorting regularly. As we know they are so often just ignored. No biggy as they are conventional screw and locknut type and easy to get at.

And change the oil and filter a lot. That little engine has to work hard and the oil capacity is only a little more than a thimbleful to start with.

And of course finish. Some / most of them (all of them?) were put together under licence in China and the build quality is a bit iffy. The exhausts and mudguards will rust before your eyes. Fortunately replacement parts are dirt cheap.

 

[Paul]

That engine design is really reliable (unburstable even) but they do have a few weakpoints and you have probably copped for one of them. The camchain tensioner can stop working with a build up of gunk, get worn etc. It is worth, like you thought, pulling the thing off and cleaning it up. There are aftermarket tensioners that you set manually - they sort the problem and are lot cheaper than a new OEM.

Valve clearances need sorting regularly. As we know they are so often just ignored. No biggy as they are conventional screw and locknut type and easy to get at.

And change the oil and filter a lot. That little engine has to work hard and the oil capacity is only a little more than a thimbleful to start with.

And of course finish. Some / most of them (all of them?) were put together under licence in China and the build quality is a bit iffy. The exhausts and mudguards will rust before your eyes. Fortunately replacement parts are dirt cheap.

Well, I feel a bit silly, but I changed the oil/filter, fitted a new cush drive, and some second hand shocks as the centre eye on one of the shocks was missing from the previous owner, so thats all good, pulled out the chain tentioner and rechecked the valves and seemed ok, this time I happened to be wearing my hearing aid and as the engine was cold I was able to touch the engine and narrowed it down the a loose heat shield that was rattling on the down pipe so alls good!