2004 50 hp T50TLRC starting problems

[Fishhauler]

I will check fuel to the bowls when I get out of work. I believe I checked that before and I was getting fuel to the bowl.

[Fishhauler]

Yes I am getting fuel when I pump the fuel bulb to all carbs. I also pulled the fly wheel, stator and pulse r coil so I can verify the timing. Might be off one tooth. Mosquitos drove me out at that point. Where to next???????

[Fishhauler]

Do you think 1 tooth would keep it from running?

[TownsendsFJR1300]

It'd probably still run but re-set it properly. I'd replace it if it jumped or if you have a tensioner, address it.

I've seen (I think it was a 50HP Yam) run two belt notches off (non-interference engine).

On the above mentioned engine, it was about 12 years old (looked brand new-original belt) but the belt had a bunch of slop in it and there was NO physical tensioner (the belt itself only). There was enough slop to pull it up off the cam and re-set it (single cam) till he got it replaced with a new one.

[Fishhauler]

Yea I planned on resetting it. I see where a mud wasp built a nest up under the fly wheel. Looks like the damn thing went around between the belt and the sprocket. I got to clean the mud out from under there. I also got to figure how it (the wasp) got in there.

I will reset the timing and check the valve clearance again after that and then try to start the motor again.

[zenoahphobic]

It'd probably still run but re-set it properly. I'd replace it if it jumped or if you have a tensioner, address it.

I've seen (I think it was a 50HP Yam) run two belt notches off (non-interference engine).

On the above mentioned engine, it was about 12 years old (looked brand new-original belt) but the belt had a bunch of slop in it and there was NO physical tensioner (the belt itself only). There was enough slop to pull it up off the cam and re-set it (single cam) till he got it replaced with a new one.

All belts and chains should have tensioners on them. I know drive belts and chains on motorcycle generally don't (or have what I call as dampeners). And how many issues has this caused? I betcha everybody knows of chains coming off sprockets.

The old in line 6 Mercury O/Bs with an actual distributor was driven with a toothed belt untensionered and had issues jumping the odd notch. Excuses were given that an outboard would not decelerate as suddenly (less backlash) as a land born vehicle dropping down gears would.

[TownsendsFJR1300]

All belts and chains should have tensioners on them. I know drive belts and chains on motorcycle generally don't (or have what I call as dampeners). And how many issues has this caused? I betcha everybody knows of chains coming off sprockets.

Ang... Wrong answer....

This Yam I worked on kept belt tension between the single OHV cam and the crank stictly with the belt itself. There was NO tensioner, nor any place to put one. It was on one of the members boats here (not active anymore).

My Snapper, self propeller mower does NOT have a tensioner to the drive unit either(from the verticle crank to the rear drive transmission..

As for bike belts, they DO HAVE adjusters for the belts. All Harley's with belt drives have adjusters.

As long as the chains are adjusted properly, their very reliable. Yamaha, on the earlier version of my FZ6 had a re-call for the front sprocket coming loose(not good and very dangerous). Unless you don't maintain the chain nor adjust, its very rare for it to come off. Most times, it'll break and literally get thrown thru the engine case(engine is toast)

As for Motorcycle "dampener's", many, mine included, do have rubber dampener's in between the rear sprocket and wheel (to make shifting a little softer).

[zenoahphobic]

It is funny how things change over decades.
I rarely knew of a chain breaking- almost a myth decades ago. But they used to jump sprockets thru whipping action. I suspect those that actually "broke" most were due to link falling off, or they were of such dilapidated state that they should have been replaced long ago.

When I referred to dampeners they are the ones on a spring sliding on the chain. You might call them tensioners but I believe they stop the chain from building up shaking energy (resonance).

I believe unless a substantial amount of sprocket is covered by the belt then a proper design would incorporate a tensioner.

It takes very little wobble of the belt for it to engage the next notch in a belt drive, given that it has some stretching ability and the many more "teeth" than the chain equivalent.

[rodbolt17]

the cam timing on that motor is to stupidly easy to check.
run the flywheel to TDC #1 compression stroke, look at the frigging cam marks.
its right or not.
never seen a non tensioner motor jump a tooth.
don't hunt that wabbit.

[zenoahphobic]

The problem with belt drives occurs when the belt becomes too supple from continuous flexing. A chain however is completely flexible from new.
Remember belt drives were introduced for cam drives because of cheaper cost. Not necessarily because they are quieter and can absorb shock better.
They however have added to fuel consumption because of their greater friction

[Fishhauler]

Got a question. What exactly are you referring to when you say interference or non-interference motor. The timing looks to be a basic line up the marks and put the belt back on. It's got a tensioner and looks to be easy enough to set.

I don't believe this (timing) is the reason my motor won't start. I will adjust and go back together with it. I'll check the valve clearance. Then try and start. Going to check compression again. Carbs are squeaky clean. Got good spark. Should run. Will let you know after that. Thanks again for your help.

[boscoe99]

Got a question. What exactly are you referring to when you say interference or non-interference motor. The timing looks to be a basic line up the marks and put the belt back on. It's got a tensioner and looks to be easy enough to set.

I don't believe this (timing) is the reason my motor won't start. I will adjust and go back together with it. I'll check the valve clearance. Then try and start. Going to check compression again. Carbs are squeaky clean. Got good spark. Should run. Will let you know after that. Thanks again for your help.

What is meant by interference or non-interference relates to the possibility of the valves colliding with the pistons if the cam shaft gets out of time with the crank shaft. In an interference motor if a timing belt/timing chain/timing gear breaks the valves and the piston can contact each other and cause some major damage. In a non-interference motor the valves and the piston will not strike each other if a timing belt, chain or gear breaks.

[zenoahphobic]

What is meant by interference or non-interference relates to the possibility of the valves colliding with the pistons if the cam shaft gets out of time with the crank shaft. In an interference motor if a timing belt/timing chain/timing gear breaks the valves and the piston can contact each other and cause some major damage. In a non-interference motor the valves and the piston will not strike each other if a timing belt, chain or gear breaks.

And you would pretty much assume all modern engines are "interference" because of reasonable compression ratio and ample valve opening for performance. The possibility that the piston won't hit the valves in the event that the timing belt breaks will be religated to the past.

[TownsendsFJR1300]

Just a side note, the engine I referred to earlier.

The crank was set to TDC, the cam mark two notches off.

Once the belt was lifted up off the cam, the cam literally "jumped" to the correct position on its own with the cam marks NOW lined up. Slipped the belt back over, done..

I doubt the belt timing is an issue for you but its easily checked W/O pulling the flywheel. Access to the marks (flywheel and cam(s) is all you need to have at compression TDC... Replacement, yes, the flywheel, etc need to go..

[boscoe99]

And you would pretty much assume all modern engines are "interference" because of reasonable compression ratio and ample valve opening for performance. The possibility that the piston won't hit the valves in the event that the timing belt breaks will be religated to the past.

Remember what they say about the word "assume".

Not all Yamaha four stroke motors are interference motors. I suppose that if they are not one could "assume" they are not modern.