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any engine with a rubber timing belt will have that tendency when the belt has stretched far enough. And given the 4514 is a 3813 block, crank etc, that one's a no brainer. But the 4518 timing belt is no more durable or stretch resistant than the 3813. Remember - it gives honda something to sell you on a planned basis. Gratefully, on the honda's there enough clearance between the piston crowns and the valves that you can slip in a deck of cards between the valves and pistons, regardless of timing belt position.

heckuva, even metal timing chains will stretch. Back when i mechanic'd at a dealership, Nissan (then Datsun) went from a double timing chain to a single timing chain (late 60s/early 7s), and 6-7 years later we saw the occasional engine job from chains jumping one or two teeth on the timing sprocket and helping valves meet pistons. That's when timing chain replacements became a standard service item on the recommended maintenance schedule. Before that, the chain's tensioner was the only maintenance item.

Nissan wasn't alone, don't think the other mfgrs didn't see that move as a good way to increase future parts & svc work sales - they all followed suit.
 

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I don't own a 4518 so I don't have direct knowledge that the parts schematic below is correct and that #9 in the schematic is actually a springed moveable belt tensioner.

http://www.boats.net/parts/search/H... MZAT-4099999/TIMING BELT (H4518H)/parts.html

However, if #9 is a springed tensioner, IMO the 4518 is less likely to jump timing since the tensioner keeps the belt tight as it wears/stretches - minimizing belt slack,friction and belt wear.

The 3813/4213,4518 models do not have a belt tensioner so tension is static set with the water pump pulley by adjusting belt slack and then tightening the bolts to a fixed position. Obviously as the belt wears and stretches it becomes looser and looser compounded by the fact that as it gets looser the more it wears on the cogs on the belt and the timing gears creating even more friction promoting more wear.

However, even with a belt tensioner, overtime any belt might deteriorate to the point where it will eventually break.

Since all of these models are now over 15 years old, the best preventive maintenance, IMO, is to bite the bullet and replace the timing belt whether you own a 3813/4213/4514 or a 4518 or inspect and just retighten if the belt if in good still in good condition
 
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