Ariel Owners Motorcycle Club

Hi All
More of a curious question: over time does the bearing mating face on the front sprocket become worn through fretting against the bearing inner? My front sprocket does appear to have had some significant fretting over time, and may have been worn down somewhat. There is clearance between the chain and engine casing, but it's pretty snug.....just checking before I throw things back together.

Cam

There will, inevitably, be some wear here in time as the sprocket rotates back and forth with the action of the shock absorber. Checking against a spare sprocket which has little wear on it, the face against the bearing appears to be 0.065" (65 thou) below the face of the sprocket teeth. You should be able to determine how much wear your sprocket has from this.

Thanks Paul
I'm bang on the .065", so good on that front. What I did also notice was the primary chain does tend to tighten up slightly, the loosen. Not to an alarming extent, but there. This is when the front sprocket and chain wheel are spinning freely. So, either an issue with the chain or sprockets. The You Tube wisdom tends to suggest sprockets not centred properly (usually referring to rear wheel sprockets not centred properly). If this was the case, it would suggest the chain wheel not riveted on at centre. Seems unlikely, maybe uneven wear on chain wheel ....Will need to try a few things to try and isolate the cause.

Cam

A primary chain which goes slack then tight when the engine is rotated on a Square Four is usually cause by a bent gearbox mainshaft. These are of course longer on the Square so prone to bending when someone does something silly like locking the chain to tighten the clutch nut by means of something between chain and sprocket. The GB gearboxes are more prone to bent shafts than the BA type though and I don't know which type you have.

Mine's a BA....I checked the runout on the shaft a while back and was within 0.005", and in any case I noticed the chain issue with both sprockets freewheeling, so the starts effectively out of play. Haven't had a chance to look at since but will investigate again tomorrow.
Cam

*starts = shafts