Engine Survivability?

[nuttyn01]

Hello 4 stroke yami gurus. I have an opportunity to buy a 14 yamaha viper xtx with light front end damage. The damage to the underside punched a dime size hole in the oil pan. My question is: does the yamaha ecm have a fail safe that shuts the motor down in the event of low oil pressure/low oil? Also, it sounds like the motor has been started a few times for a second or so to verify that it indeed runs. Any opinions on wether or not the bottom end survived?

Thanks in advance.

 

[thamax]

its has a arctic cat ecm and it should shutoff if u lose oil pressure. damage could have happened already hard to say its a gamble without a compression and leak down test. those are the 2 best things to check. the motor will most likely have to come out so u could verify damage when u replace the oil pan and pop the valve cover off and check top end for and signs of lack of lube.

 

[MTN_VIPER]

It might be ok depending on how long it was ran. Nytro/Viper motors run very tight rod/main bearing clearances, usually .001" to .0015" and the first thing to show oil starvation damage will be the rod bearings.
When you have the oil pan off I would go ahead and pull the rod bearing caps off and inspect the bearings/crank. Normally the PTO and center are the first to show damage.
If the rod bearings are not scored and the clearance is ok, then very likely the main bearings are ok as they receive oil before the rods. If the rod bearings are scored then you'll need the separate the crankcase halves and inspect the mains as well.
The bottom end is rebuildable and crankshafts/bearings are available from Yamaha.

Normally the cylinder head will be ok with the following exception.
When you inspect it and find that it has a spun rod bearing. Then you'll want to pull head and valves to check them for straightness. What can happen when a rod bearing spins is that the excessive clearance allows the piston to travel farther up the bore. When this happens the piston can contact the valves and bend them slightly. If this is not caught during the rebuild the bent valve stem may cause the valve to "hang open" and contact the piston bending it even more. Once this process starts it's only matter of time before the head of the valve breaks off and it's game over for your engine.

The main thing is to check the bottom end BEFORE you try and run it. If there is rod bearing damage and you try and run it, there is real risk of spinning a rod bearing and pitching a rod through the side of the block.
Nytro/Viper engines are very durable and usually will last a long time, however one thing that can kill them is oil starvation.

Bill

 

[nuttyn01]

thanks guys. Is there anywhere to download a service manual?

 

[stingray719]

It might be ok depending on how long it was ran. Nytro/Viper motors run very tight rod/main bearing clearances, usually .001" to .0015" and the first thing to show oil starvation damage will be the rod bearings.
When you have the oil pan off I would go ahead and pull the rod bearing caps off and inspect the bearings/crank. Normally the PTO and center are the first to show damage.
If the rod bearings are not scored and the clearance is ok, then very likely the main bearings are ok as they receive oil before the rods. If the rod bearings are scored then you'll need the separate the crankcase halves and inspect the mains as well.
The bottom end is rebuildable and crankshafts/bearings are available from Yamaha.

Normally the cylinder head will be ok with the following exception.
When you inspect it and find that it has a spun rod bearing. Then you'll want to pull head and valves to check them for straightness. What can happen when a rod bearing spins is that the excessive clearance allows the piston to travel farther up the bore. When this happens the piston can contact the valves and bend them slightly. If this is not caught during the rebuild the bent valve stem may cause the valve to "hang open" and contact the piston bending it even more. Once this process starts it's only matter of time before the head of the valve breaks off and it's game over for your engine.

The main thing is to check the bottom end BEFORE you try and run it. If there is rod bearing damage and you try and run it, there is real risk of spinning a rod bearing and pitching a rod through the side of the block.
Nytro/Viper engines are very durable and usually will last a long time, however one thing that can kill them is oil starvation.

Bill

Good information there. I bought an Apex years ago that was wrecked and assured it had not been ran out of oil. Engine blew 50 miles later.....

BUT, I rebuilt it and it ran great until I sank it like the Titanic in a powder snow bank and sold it...lol.

By all means CHECK THE bearings like suggested above. One other thing, the tolerances are so close a spun rod bearing will usually put a hole in the case, make sure the hole is not from the rod before you buy.

 

[kinger9]

I ran(idled) a RX motor with no oil 3 times for 20 seconds a time before I removed the engine to find the oil pump was disconnected (long story) Anyway head was toast and the rings looked good but it burned oil after that like 1 qt every 1000 miles.

More then likely the pressure switch kill helped save it but you need to carefully inspect everything.