Okay guys, I went to my dealer and they got the spark arrestor out for me, it required heating up with a torch.

First let me say that while I was there, Yamaha had called to talk with the mechanic about the replacement of my A-arm and to ask that it be sent back in to inspect. Also, they claim that only 2 A-arms have been replaced, so even if they are off by a small amount, there is NO huge problem with the A-arms as some would like for you to believe. They did ask if it looked to have been wrecked (no), so maybe some that have been reported as defective are reall a result of a crash.

Now, back to the exhaust issue. I first noticed the sound. Personally, I like a quiet machine, but the raspy sounding exhaust was not too annoying considering what you get in return.

In return for the extra noise, I seemed to have felt much more bottom end power. I don't think this was an issue of it sounding faster because I found that I could lug it at a lower speed in second and even third while putting around in my yard. Also, in second gear, I let it go as slow as possible without killing it, and then would full throttle it in the gravel. It spun the tires up to speed much quicker than with the arrestor in. When removing the arrestor, you will notice that the engine idles at a higher speed, so that alone tells you that if the engine is laboring extra just at idle because of the restrictions, it is really restrictive at high rpm.

On top end, I couldn't tell much of a difference, but I did a plug check and found that it looks like it is running lean (I reinstalled my arrestor until I can rejet) from the plug check. I'm no expert, so take a look and tell me what you think http://www.vci.net/~bash/ceramic.jpg

I'm fairly certain that if it is running lean, it won't show much improvement in top end until it is jetted correctly, but at least I know that there is potential. (I think)

I just thought I'd share this with you all. Feel free to comment, and if you remove your arrestor, be sure and do a plug check so that you don't run your machine if it is lean!

 

Your Plug looked dead lean. I wouldn't ride it like that.

 

hi bash
that plug is not running lean , remember it is a 4 stroke not a 2 stroke.if the core turns a yellow-green colour you are lean (premium gas)

paul

 

well well, we seem to have a disagreement already.
To clear things up, I haven't rejetted because they didn't have them in stock. Instead, I just put the spark arrestor back in place until I can be sure of what I'm doing..

I was thinking that I was looking for a cardboard brown/tan look on the electrode for it to be correct.???

thanks for the posts, keep them coming...

 

It looks a little lean to me. By lean I mean not fat enough for maximum power/acceleration. If you run a free flowing exhaust and K&N filter with open airbox, you should fatten the jetting so that you are gaining or maintaining midrange and topend power, not loosing it due to leaning out.

 

Definately a bit lean...you are looking for a light tan/brown color. Was that plug-check from just putting around the yard or from a high RPM test followed by cutting the engine off? Did it seem like it was running a bit hot?

 

I didn't run it really long, because if it was running lean, I didn't want to do any damage.

 

paul,

That plug is with the intake restriction in place. It would probably be even whiter if I had taken it out.

Is the power advantage that I described similar to what you have experienced? If so, did it pull harder on top end too? It's hard to tell for me because of the extra noise.

 

bash
i have removed the intake restriction and the spark-arrestor.i normally ride at 5000 ft but the past weekend i rode at 3000 ft and did top-end runs (full throttle) for 10 + km with no problems.
the exhaust burns a nice gray colour.i use 93 premium pump gas.

paul

 

Any idea of what your top speed was in either km/h or mph?