Detonation is a bad thing. A very bad thing. That pinging that you are hearing is preignition/detonation. It is a sawtooth oscillation that causes pressure spikes hundreds of times higher than normal in your cylinder. AVOID IT at all costs. Your either too lean or or too low octane or too much timing. My guess would be your too lean and causing detonation. Raising the ocatne would help but you would be treatign the symptom rather than the problem. Octane is a numerical rating that indiacates its ability to resist detonation. Different octane rated gasolines do not burn hotter, colder, faster or slower than each other. It is simply its rated ability to resist detonation.

 

I will try higher octane i am running 87 right now. my jetting is 146/144 i think, and the clips are in the 4th ring from top on needle valves. air fuel mixture screws 3 turns out.this was dyno jets recomendations below 3000 feet. should i open the air fuel mixture screws another 1/4 turn or what is best way to richin it up a little. Or will the higher octane take care of it? i know my headpipe is not glowing or anything and it is running good but i don't know the exact temperature it is running at.

 

I've had the same problem with my Raptor since it was new. It did it before and after the valves were adjusted. Stock everything but axle. I just don't lug it around and I avoid the problem. I guess I should try 93 octane some day rather than my usual 87 just to see if the problem goes away.

Just for reference - from the owner's manual: "Your Yamaha engine has been designed to use regular unleaded gasoline with a pump octane number ([R+M]/2) of 86 or higher, or research octane number of 91 or higher. If knocking or pinging ocurs, use a different brand of gasoline or premium unleaded fuel."

Hmmm... A different brand of gasoline, eh? Maybe I'll try that one as well.

 

mine is bone stock and it does this. it's about 5 months old and it has done it since it was new. i only run 92 or 93 octane depending on where i get it. it does it when there is a slight load on the motor. i also know another guy who bought his right after mine and his does it to.

 

My money is on your valve lash. Did it do it BEFORE you made the adjustment?? It takes some touch to get them right. Also, make sure you are at TDC (top dead center). Sometimes you have turn the engine past the locator mark twice before it's on TDC. That's what happened to me. I turned the engine to the mark and everything was WAY off. I rotated around one more time and there it was.

I have always ran Premium gas in mine and I haven't had any problems. You should probably try that first, but before you go buy some expensive race fuel, go back and check your valves one more time. I really think that's what you problem is.

 

GregV,

Yes, the noise was identical in mine both before and after I adjusted the valves. When I adjusted the valves, I made sure all the valves were closed (it was on the compression stroke) before I took the measurements and made the adjustments. I also made sure to hold the tappet when tightening the lock nut and re-measured the clearance when everything was done just to be sure nothing moved.

Raptor58, from what you are saying, it sounds like higher octane fuel doesn't help.

So what's next?

 

The key is to find TDC on the compression stroke, there is no guessing that way. How do you know your are on the compression stroke, good question. As you rotate the crank you will see the intake valves rise & then fall, the intake stroke is when the intake valves open(you'll see them rise) while the piston is falling. As the piston approaches bottom the intake valves close(you'll see them fall) & then the piston begins to rise, this is the compression stroke. As you continue to turn the crank during this stroke you'll see the "I" mark approach(or is it the "H" mark, I forget, refer to your manual or ask someone who remembers). This mark indicates when the piston reaches TDC on the compression stroke with the intake valves closed. This is where you can safely & properly adjust both your intake & exhaust valves. The manual is a little sketchy if you've never done it before, hope this helps, have fun!

 

<< The key is to find TDC on the compression stroke, there is no guessing that way. How do you know your are on the compression stroke, good question. As you rotate the crank you will see the intake valves rise &amp; then fall, the intake stroke is when the intake valves open(you'll see them rise) while the piston is falling. As the piston approaches bottom the intake valves close(you'll see them fall) &amp; then the piston begins to rise, this is the compression stroke. As you continue to turn the crank during this stroke you'll see the &quot;I&quot; mark approach(or is it the &quot;H&quot; mark, I forget, refer to your manual or ask someone who remembers). This mark indicates when the piston reaches TDC on the compression stroke with the intake valves closed. This is where you can safely &amp; properly adjust both your intake &amp; exhaust valves. The manual is a little sketchy if you've never done it before, hope this helps, have fun! >>



That is a very good method for finding TDC on the compression stroke, I use it. Another very simple way to tell if it is on the compression stroke is to pull the spark plug and put your finger over the hole while you rotate the engine. You will feel air begin to push out of the cylinder when the piston starts up the compression stroke.

 

Chimmer,
Yeah, that's what I was talking about when I said I was on the compression stroke. Good, detailed description.

I think the point that we're missing here is that the problem occurred for more than one person when the quad was new, when we should be able to assume that the valves were pretty close to correct. The problem got no better or worse when the valves were adjusted after break-in. And it appears that 93 octane doesn't help. People are using 93 octane with the Trinity 686 kit with 11:1 compression with no problems, and we can't seem to get rid of the problem with the stock 9.2:1 compression. Hmmm...

 

Very good points! Compression isn't the only thing that can cause detonation. A bad lean condition will need more than 93 octane to help. Id pursue that path first, especially since if it occurs at a particular throttle position. Other things that influence detonation but probably have no relevance here is timing, combustion chamber design, and hot spots like the spark plug in the combustion chamber.