Valve check?

[edc]

If i did my math right the exhaust spec is .21 mm - .25mm so it looks like all exhaust valves are are with in lower spec except one and it may be in spec because my feeler gauge sizes jumped from .20mm to .22mm so my .20 reading could be .21

 

[cannondale27]

If i did my math right the exhaust spec is .21 mm - .25mm so it looks like all exhaust valves are are with in lower spec except one and it may be in spec because my feeler gauge sizes jumped from .20mm to .22mm so my .20 reading could be .21

That’s good news! Thanks

 

[FrozenTows4]

I could only image how tight the valves are at -15F.
Could this be one piece of the puzzle for cold start difficulty's at -15f/-23c? And possibly the after fire through the muffler?
Since it's apart, I don't see any harm adjusting to the Looser side of spec. They're only going to get tighter.

 

[Allan]

If i did my math right the exhaust spec is .21 mm - .25mm so it looks like all exhaust valves are are with in lower spec except one and it may be in spec because my feeler gauge sizes jumped from .20mm to .22mm so my .20 reading could be .21

Do you have the problems described here?

 

[cannondale27]

If in spec I would leave them alone.

 

[edc]

Do you have the problems described here?

My sled sits in a heated garage so the cold cold starts are maybe 30 or so. It starts consistently to -30c any colder and who knows. When started cold it will start and die right away, then start on second attempt, idle rough for 30 seconds but stay running.
The latter part of this winter i have had several back fires out the exhaust( shot gun ) on startups after parked for about an hour for lunch.

all starter gears are good right now no chips from these back fires .

Kind of ironic i bought this sled for the reliable yamaha motor and it the only part that has given trouble and had it apart more than any 2 stroke I have owned.

It's funny the problems we put up with in this sport , if any of my vehicles ran and started like this i wouldn't have it!! LOL

 

[Allan]

My machine is in the shop now because I have all what is described with the hard staring and ideal drop. They checked the valves and there inspect. so there going to check some other things. he said it could be a injector problem?

Edit , found out later my valves were not checked

 

[cobrajet ltx dx]

I’m still with the belief that the ECU
logic/mapping was subpar at best with the 14-15 model years.Yamaha made it worse with there flash updates hence backfires, 2key attempt starts, hunting idles ect.
They published my 19 models with new ecu so maybe they changed a lot.
If that ecu works well in real world conditions for the 19 season then all pre 19 viper owners should DEMAND a 19 ecu.
At this point I think people are chasing there tales with mechanical checks, part replacements ect because of the horrible ecu design and mapping.

 

[Mike P]

I’m still with the belief that the ECU
logic/mapping was subpar at best with the 14-15 model years.Yamaha made it worse with there flash updates hence backfires, 2key attempt starts, hunting idles ect.
They published my 19 models with new ecu so maybe they changed a lot.
If that ecu works well in real world conditions for the 19 season then all pre 19 viper owners should DEMAND a 19 ecu.
At this point I think people are chasing there tales with mechanical checks, part replacements ect because of the horrible ecu design and mapping.

I really don't seem to have a lot of the issues that some people have. It might be as simple as an ECU and Map issue however I would think that the number of people with issues would be much higher and a lot more consistent. Are there some bad ECUs out there? Could there be some engines that are not responding well to the Maps? Yes. An ECU change may fix one, two, or even all of your problems. You could get lucky and solve all of your issues with the ECU change.
If in fact the ECUs are bad and the Maps are wrong, we should all be having issues. I would agree that the ECUs should be considered and the Maps looked at, I'm just not sure it is the smoking gun some people are looking for.

 

[cannondale27]

There is also other very good possible culprits including the Web based map downloads and sloppy stub shafts which is where pickup is located. All just educated guesses at this point.

The REAL problem is YAMAHA they are not talking about it at any level.

 

[cobrajet ltx dx]

The smoking gun is YAMAHA!!!!!
Well said cannondal 27!!!!!.
I’m not on here stirring the pot,
Or bashing Yamaha sleds or there owners for being loyal.
My past and present comments are strictly directed to the Na vipers that Yamaha basically said.... Deal with it and go away.

 

[Allan]

Have my machine in getting the valves checked because my machine is doing what is described here. Just herd from dealer and 3 valves are tight.
Machine as 18600 km

 

[cannondale27]

Have my machine in getting the valves checked because my machine is doing what is described here. Just herd from dealer and 3 valves are tight.
Machine as 18600 km

Crap. Been avoiding looking myself. Can you get more specifics from them? How tight. Which ones?

 

[Allan]

Crap. Been avoiding looking myself. Can you get more specifics from them? How tight. Which ones?

I well try once i get it fixed and go pick up machine.

 

[cobrajet ltx dx]

Yamaha’s valve clearance specs are basically indentical to what Subaru valve specs are.
So for the people checking there own clearances,You must use a TRUE METRIC feeler gauge.
Not a standard/ metric set.
Believe it or not.... there is a difference.
Subaru tells us to get as close to the middle of the spec as possible.
Most of the time the exhaust valves get tight, and if you find that they are way out then most likely the valve face is deteriorating and sucking up into the head seat limiting the clearance.
Hopefully Yamaha doesn’t use sodium filled valves.