Timing Question.

[Boz]

I'm somewhat newer to this modification thing. I've been told that one of the changes I should make to my 1993 Yamaha, is in the timing. It's a Pro-V 200, 2.6. ; carbed as well. I believe it's 22 degrees at present stock? I've been told to advance to 26 degrees. The only mod to date is a tuner but a set of 220 heads are going on before thaw. My question is this.........What does timing do and how would this benefit what I'm trying to do; which is top speed on a lake. If it matters, I'll be running 90 octane fuel; at the pump...... I'm Curious as to what your thoughts are on the best place to start w/ modifications.

Thanks, in advance, for any feedback.:D :D

[Markus]

The reason to increase the ignition advance is that you give the flame front more time to propagate which gives you a more complete burn and therefore a more efficient engine.

22 degrees is probably stock timing on your engine and moving to 26 degrees is reasonable.

Increasing the timing increases the risk of detonation, which is the downside.

Therefore, depending on your compression, 90 octane fuel may or may not be sufficient if you increase advance.

You should make some test runs at 26 degrees with fresh plugs and closely monitor them for signs of detonation or excessive advance - there is a link on my links page to an excellent article by Gordon Jennings that shows you what to look for - and compare your top speed to what you get with 22 degrees. If you cannot notice the difference, I would recommend that you go back to 22 degrees.

[Boz]

That was great info. Thanks for that and I'll check that article out. :cool:

[Markus]

Glad to be able to be of help.

Please keep us posted on how your Yamaha project is progressing, how much speed you get from different mods etc.

Btw, how much have you picked up with the mods you have done this far?

[Boz]

how I make out. From speaking to some reputable Yamaha guys, they tell me that with what I've done to date, I've made decent gains. I have removed the stock tuner; the Pro-V I have, shares the same powerhead as the 225. That stock tuner choked it down to a 200. I have an aftermarket tuner, removed the liner, and drilled 4, 3/8 inch holes on either side of the cavitation plate. I hear this has gotten me to 240ish hp, give or take (likley take!)
A have a set of 220 heads going on and these are from my 88' (in parts in my garage); this was a sweet find. I never new I had those particular heads until 3 days ago and I was all set to buy some! Merry x-mas too me!! I run this on an HST (it's in Readers Rides) and guess that I'm running near 85 mph? No radar or GPS to claim anything. I run a 29 srx w/ 12 inches of set back. :D