Honda 20HP Cam Pulley Failure

[gerry11m]

Hi, a few days ago my Honda BF20D just stopped. Obvious that compression was not normal. Turned out that cambelt had jumped off and the cause of this was the cam pulley (hard plastic) had become loose on the metal hub part. Engine only 3 years old but 2nd hand so in truth don;t know how many hours run - but looks like new.
Anyone else had this problem? Other than replacing pulley, is there a more permanent fix so that it won't happen again. My faith in the reliability is seriously damaged!

[spartacus]

The only reason a belt should jump is through wear and tear. As suggested the pulley bearing could be shot, the belt itself was worn or it wasn't tensioned properly during installation. Not sure if there will be internal damage on the engine?

[Fenlander]

Isn't this a plastic pulley that wears away on the shaft until it comes loose or falls right off? I've heard of it before. Pulley about £50 I think.

[gerry11m]

Spartacus, pulley bearing is the camshaft bearing and is not worn. There is no provision for tensioning so lack of tension would have to be caused by a belt out of tolerance. Apparently there is no internal damage to engine (checked by Honda agent). Root cause as far as I can see was a faulty camshaft pulley with the plastic pulley becoming loose from the molded in metal hub part. Is this just a piece of crappy Honda design and/or manufacturing?

Also, I searched the net and came up with two identical failures on a Honda outboard forum.

Regards

[Turbodiesel]

I have seen loads of Honda's do this, the pulley breaks up and comes loose leaving the bolt in place. Cam belt comes off and most of the time the valves get bent. When i did a part number search the pulley is the same on there lawn mowers. We had 3 of these go last summer.

[spartacus]

Originally Posted by gerry11m

Apparently there is no internal damage to engine (checked by Honda agent). Root cause as far as I can see was a faulty camshaft pulley with the plastic pulley becoming loose from the molded in metal hub part. Is this just a piece of crappy Honda design and/or manufacturing?

Good news.

Looks like it's a design error then. Can the new pulley be modified (in any way) to reduce the likelihood of it coming off again? See Turbodiesel's comments regards the same engine. Might be worth bringing it up with Honda UK to see what they advise.

[gerry11m]

Hi Turbodiesel, so no point in beating myself up for any part of causing this failure.

I would like to replace the pulley with an all metal part: don't care if it is not OEM.

Regards

[Turbodiesel]

Honda told us the new pulley's we have fitted are different and upgraded. When they arrived they looked pretty much the same!. But who knows!?

[gerry11m]

Hi, the replacement pulley seemed to me to be exactly the same as the original.

One option to prevent a recurrence would be a flat metal washer that goes over the metal pully hub and the plastic pulley together with a longer bolt to attach to the camshaft.

I'll post a photo and sketch to explain. This would stop the plastic pulley moving upwards independently of the molded in metal hub (and hence throwing the belt). If I look at the witness marks that the belt makes on the pulley, the belt had been riding high by say 1/4" for some time. I would urge all Honda 20HP owners to check the belt tracking on the timing pulley, say every time the oil level is checked.

By the way, the only markings on the hub are "honda" and >PP-G< which I think referes to Polypropylene and the grade

[Andy C]

Hi gerry11m, could you post a short idiots guide on how to check the belt tracking please? Can the timing pulley be easily accessed to be checked for wear?