03 Yamaha F115 broken timing belt

[tenmac3517]

Hi All,
I see allot of posts about timing belts. Has anyone ever had one break? I have a 03 F115 with 500 hours. Last week while at idle speed the motor shut down. After further investigation I found the Timing belt had a tear in it about 3/4 of way thru. I guess my next question is how do I assess the situation to see if any damage occurred? I hear this is a zero clearance motor. Im hoping because I was at idle speed and it shut right down I might be OK. Thanks

[pstephens46]

Other than the motor shutting down, did you hear any other unusual noise?
Metallic sounds?

I posed a similar question and this type of thing seems to be very rare.

What does this tear look like? Top to bottom as the belt is mounted or through the side of belt? Can you post a picture?

It possible it slipped a couple notches, enough to shut it down. Hoping maybe you did no damage...

[boscoe99]

Yes, although rare, some folks have had a cam shaft drive belt break. Unfortunately, some/all of those have had serious engine damage when a valve and a piston try and occupy the same space at the same time. On an interference engine that is.

I would first borescope the pistons to see if there are any indications of a valve strike. A really good borescope might allow you to inspect the valves. If anything looks amiss, I would then pull the head to further assess the damage.

Good luck.

[tenmac3517]

I cant get a pic right now because the boats in Florida, Im going back down to investigate. It looks like someone took a knife and cut it 3/4 thru in one spot. Heres the part I didnt explain in original post because I think I caused this. When I pulled the plastic cover off the flywheel I found the remains of a chewed up roll of black electrical tape right next to the belt. I havent had that cover off for 6mos so I think it was in there a long time. I remember taping up a wire that was chaffing in that area awhile back. Just dont know why it decided to jump up in the belt at idle speed in the canal. Yes someone else suggested using a little camera scope to inspect the piston/valves. Ill look into that.

[tenmac3517]

I didnt hear any weird noises when it shut down. But my first reaction was to try and restart it. I tried once for a few seconds. Probably not a good thing either.

[pstephens46]

I would imagine you would have heard some racket when trying to restart.
Good luck with this. In regard to tape, sht happens. Don't beat yourself too much. Just don't tell your wife....

[TownsendsFJR1300]

Removing the valve cover should show large valve to shim clearance if the valves are bent (and still attached to the stem)

A leak down test on each cylinder would definitely firm up ANY major issues.

I see at least a head coming off if any of the above show up...


I just asked last week about the in-line 4 belts breaking, NO ANSWER..

Good luck...

[boscoe99]

All too many years ago I worked part time at an aeroplane company turning a wrench. You would not believe the stuff that we found in the airplanes, usually on top of the engine. Screw drivers, pliers, wrenches, electrical tape, etc.

Now somewhere in Bandar Abbas, Iran there is a P3 airplane with a 7/16 combination wrench down in the belly, hopefully doing no harm. I was servicing an 02 pressure regulator and the wrench got away from me. I heard it slide down the side of the fuselage and I think it went to the bottom of the fuselage. I should have reported and then have done what was needed to find it. Leaving it there was a big no no.

As pstephens says, sh1t happens. We live and learn and hope nobody gets hurt in the process.

[pstephens46]

My brother was working on a DC-3. Apparently it was in good enough shape to convert over to turbine engines. Probably 15 years ago. In the belly they found hundreds of spent 30 cal casings. Seems the plane was one of feared "puff the magic dragon" gunships from Vietnam.

[panasonic]

So the timing belts have no life limit? supposed to last the life of the engine?

[rodbolt17]

the F115 is an interference motor.
if the cam becomes very far out of time with the crank bad things happen.
Yamaha recommends replacing the belt at 1000 hours OR every five years whichever occurs FIRST.

that being said it does not cover mechanical damage.

[boscoe99]

So the timing belts have no life limit? supposed to last the life of the engine?

The latest maintenance schedule for the F115 has the belt to be inspected (with replacement as necessary) every 100 hours or every year, which ever comes first. It is hard life'd at 1000 hours.

Necessary being in the eye of the beholder/inspector I suppose. 'It is only worn half way through at 500 hours so it should be good for a hundred more hours at least.'

Inspections? We don't need no stinkin' inspections.

Does the phrase "pencil whip it" come to mind?

[pstephens46]

What die Rodbolt say?

"Roll dem bones!"

[boscoe99]

Dem bones might come up "snake eyes".

When de snake bite you in the arse don't be surprised. That is what de snake do.

[TownsendsFJR1300]

Although I have low hours on the engine, it is still an 06 model. The belt looks absolutely brand new.