Yamaha VX - Compression - Valves

[jsmob]

Hope all are well.
Got the 2010 VX out of storage this year and had a bit of an issue with starting/idle. Tried the normal things and have ignition and fuel. Replaced plugs, resistance checked coils, removed and tested/cleaned injectors, among others, you know the normal things. Realized I was dealing with a little deeper issue I moved to compression testing. Happy camper when I see 190 psi on the first three. When I get to the last and final cylinder - 0 psi!!
From here, I know I at least have one or more open stuck valves, and possibly some dreaded valve damage.
If anyone has some guidance from here on these engines, I would be much obliged.
I studied the forums and see where at least one advised that it's not quite time to pull the engine, instead one suggested that removing the valve cover, some had used an undivulged method of unsticking valves.
Have a good knowledge base on rebuilds and have removed some heads for rebuild, no problem. Just looking to see what guidance y'all might offer first on these OHC motors with this issue. I have access to the shop manual. Thank you!

[jsmob]

Re: Yamaha VX - Compression - Valves


Here's a pic of what I think it is from the topside (valve cover off). This is one of the intake valves that once the lobe is off of it from the camshaft, it is still down! Stuck. Any thoughts? In the picture the adjacent "valve pad" demonstrates the approx. location it should be - it's the other intake valve for the same cylinder.
Very pleased at how clean everything looks and nice oil coat in here.

[jsmob]

Re: Yamaha VX - Compression - Valves

Sorry these are the exhaust valves!

[Mxzx]

Re: Yamaha VX - Compression - Valves

Just posted this on the 2008 Compression thread:

I had this issue on my '08, no compression on one cylinder. This was after I started it on trailer once a week and ran it for about 20 seconds.

I think mine was a stuck intake valve. With almost 600 hours on the clock (former rentals), I just went ahead and pulled motor. Unless your oil tank bolt has been modified, you have to pull the engine to get head off. Not a very hard job with right equipment. I found light corrosion on all of the valve stems. I re-used everything except the seals and head gasket. I just wire wheeled the valves and the looked like new. I have a soda blasting cab, so I did the head with that just to clean it all up.

[jsmob]

Re: Yamaha VX - Compression - Valves

Thanks mxzx. I ended up doing the same. Pulled the engine and head off. The rest was easy. One exhaust valve really stuck but I polished all of them. All you need out of the ordinary is a proper spring compressor with the right size spacer. Anyone attempting this, just make sure you keep track of the valve buckets and get them back right. My valve clearances were spot on and didn’t need any adjustments/spacer changes.

[Mxzx]

Re: Yamaha VX - Compression - Valves

Oh yeah, I forgot the part about the buckets! I ended dumping mine and mixing them all up. Guessed at how they went back and all were in spec, luckily!

Did you find the mod on the oil tank bolt so you can pull head again without pulling engine?