Do my piston head look normal ?

[Betik]

I was doing end of the season maintenance today on 2015 MR1 ( non HO) engine that has 74 hours on it.
The spark plug gaps were 0.7 for all of the plugs and the compression was
Cylinder 1 at 120
Cylinder 2 at 120
Cylinder 3 at 115
Cylinder 4 at 120

So that I believe is all good, but when I decided to stick scope down the spark-plug hole, I started to get a bit concerned. It could all be poor image quality and wrong angle on the light, but I don't have much room there to wiggle around anyway.

Should I be worried ?

 

[Jgorm]

The compression seems really low. I see 190+ cold and 210+ warm. Is it a 2005 or 2015? The pistons are fine. You taking mm for the gap? I think these are around 0.030".

 

[Gym]

I'm a little confused also. Did the 2015 model year use the MR-1 motor? I thought they were using the 1.8 starting around 2010. If, as @Jgorm suggested, this is a 2005 I believe it would be an MR-1 HO motor. Can you clarify @Betik?

 

[jcyamaharider]

Pistons look good

 

[Scottintexas]

it's a 2015 Yamaha V1 sport jetski
it has a 1052 cc (not sure if it's HO or non-HO)
(edit to add - this a picture of the actual engine in question)

 

[Neutron]

Those pistons look almost too clean

 

[jcyamaharider]

it's a 2015 Yamaha V1 sport jetski
it has a 1052 cc (not sure if it's HO or non-HO)

Looks like the 110 horsepower motors out of the older 210 series boats, so yes an MR1. With the compression of each cylinder being so close in numbers I would say everything is fine.

 

[Betik]

I am 100% sure this not the HO version

 

[Betik]

I'm a little confused also. Did the 2015 model year use the MR-1 motor? I thought they were using the 1.8 starting around 2010. If, as @Jgorm suggested, this is a 2005 I believe it would be an MR-1 HO motor. Can you clarify @Betik?

@Scottintexas already clarified, this is a 2015 V1 ski. It it he last year that Yamaha used the MR1 before switching to the TR1 engines. I am also fairly postive this is the lowest output MR1 that yamaha has ever made LOL.

 

[Betik]

The compression seems really low. I see 190+ cold and 210+ warm. Is it a 2005 or 2015? The pistons are fine. You taking mm for the gap? I think these are around 0.030".

Yes I was taking on MM for the gap. I am fairly positive it is within specs.

The engine was ambient temperature. Around 90 degrees. I just started the engine and turned it off within a second or two. I did not apply any throttle at all.

 

[Jgorm]

Agreed it looks like the 110 hp version. Mine is 998cc and 95kw, 140hp. The ho version is around 1052cc.
You need to pull all plugs, remove lanyard, neutral full throttle and crank until it stabilizes.

 

[Betik]

You need to pull all plugs, remove lanyard, neutral full throttle and crank until it stabilizes.

let me make sure I understand correctly....

1. remove all spark plugs
2. put the meter in ( say cylinder 1)
3. remove lanyard ( so the engine does not start
3. put the throttle in neutral
4. crank until the pressure is no longer increasing with each compression

is that correct ? is so I can do that for the boat, but I don't think can do it for the ski. It wont fire without the lanyard

 

[Neutron]

You should have the throttle body's wide open.

 

[I_squared_r]

The carbon deposits aren't unusual and your engine has little hours. It's unlikely the piston rings have worn to 30% less then specification (157psi). Your low compression are a result of doing the compression test wrong or an inaccurate gauge. You can rent another tester from Autozone with only a deposit.

Other members have good suggestions. You also need to give the battery a good charge.

 

[Jgorm]

The ski shouldn't fire if you crank with full throttle. My fx140 works that way, as so most efi cars.

 

[Neutron]

The ski shouldn't fire if you crank with full throttle. My fx140 works that way, as so most efi cars.

Correct it cuts fuel i believe. Because i have diagnosed no starts on skis that had the tps open too much at idle