Retarding Ignition advance

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Indawoods
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Retarding Ignition advance

Post by Indawoods »

Has anyone retarded their ignition advance a tad to reduce spoo? I was going to try that this winter.... but just a tad.
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Indawoods
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Post by Indawoods »

I read this article and has me wondering .... supposedly you can retard your ignition, jet leaner and run a hotter plug, get more power and run cleaner.
Read the third to last paragraph....

http://www.strappe.com/plugs.html
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Post by TopperHarley »

I wouldn't mess with that myself. I belive, changing your octane actually can change your ignition timing a bit. Works in v-8's anyway. I would try that first. higher octane-higher flashpoint-advanced timing and vice versa. Not sure how the premix will affect flash point. But considering Ron cuts heads to run off different fuels, tells me that the pressure and flash point do come into play with 2 stroke engines& pre-mix fuel. Low octane fuel has a lower flash piont, burns at lower pressure and lower heat levels. If your octane is too high for your heat and pressure level, you may not be getting a full burn. In my 02(the bike I ride 90%of the time) I run 93 pump gas w/amsoil50:1, RB pump gas head, RB modded carb. 42pilot 152 main.clip in#3 position. Polished exhaust ports, procircuit exhaust, snorkel removed, Iridium plug, Air filter oil squeezed out fairly well. I don't have a spoo problem. The bike did when I got it from Hellbender but that was with KLOTZ 20:1 stock carb and head.
Ron pre-jetted the RB carb but I went up a size on my main. Once i did my mods and changed to amsoil w/ irridium plug- no more spoo. I did overheat a couple times over the summer on some turtle pace technical stuff but turning my air screw in a tad cured it.
this is my 02 after a last sundays ride and no cleaning. Of course, you do not want to forget where this info is coming from. This could just be some fantasy I have made up in my head, like the rest of my existance. :rolleyes:
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Post by TopperHarley »

looks like some of what I said in my fantasy ramble is stated in that article. Maybe I'm a fart smeller after all...um.. smart feller, I mean.
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Post by Indawoods »

Well... I have everything you have down to the octain of gas except for the iridium plug. Still getting spoo.... Some of it may be residual left in the pipe though. I jetted it to a nats ass last time.
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Post by TopperHarley »

if you had spoo build up in your pipe, it will continue to come out for a while. it will make it difficult to tell if its spooing less. have you repacked? perhaps pull the pipe, plug the end and swish some xylene around in it and reinstall. I really think the iridium plug helps. If you clean out your pipe and run iridium, leaving everything else as it is, it would be a good test for the rest orf us. We will get to the bottom of this spoo issue.

I thin that ring blow by may contribute to the spoo factor also.
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Post by Jeb »

Inda - FWIW because I've got the 220 AND I did this at the same time I bolted on Ron's race-gas-shaped head mod:

I retarded my timing about 1/2 of the distance between the middle mark and the mark next to it (turned in a counter-clockwise direction). Obviously the mod made a difference in power, but I got more revs and more punch up top.

I retarded my timing the rest of the way (in a counter-clockwise direction) and I got MORE punch between midrange and top.

In both cases my spoo disappeared. I'm running 50/50 VP110/pump
Last edited by Jeb on 08:14 pm Nov 10 2007, edited 1 time in total.
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Post by TopperHarley »

Maybe that is the key to the no spoo
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Post by Indawoods »

I think I will give it a go...
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Post by TopperHarley »

so you dont think it could be the plug?
If you run into Heidi, have her look me up in her little black book and give me a call.
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Post by Indawoods »

I had an EG in it before... didn't do diddle. Went back to the ES and she runs great. With a timing change it may make a difference though...
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Post by Jeb »

Please note that I changed "clockwise" to "counterclockwise" in my first reponse. Turning the plate counterclockwise retards the timing . . .
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Post by Indawoods »

10-4 Jeb!
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Post by TopperHarley »

Keep us posted on how that works out. Everybody I ride with has a spoo problem.
If you run into Heidi, have her look me up in her little black book and give me a call.
Im feelin a little wild today.
http://stores.shop.ebay.com/GATEWAY2-STROKE
2005 KDX220 mine
2003 KDX220 mine(under construction)
1998 KDX220 1/2 Brother-in-laws, soon his own
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Post by canyncarvr »

We ran a 250cc road racer at the drags a few months ago, and found that retarding the spark about five degrees from the manufacturer's setting raised the trap speed from 106 to 110 mph. Similarly, there's a 125cc motocross machine residing in our shop which runs a lot stronger and cleaner since it has been retimed for less advance, jetted leaner, and been given a hotter spark plug.
Road racer?

Motocross machine?


Not the same animals as woods bikes.

I've been all around the 'get rid of spoo' horn. I gave up a long time ago. I tune for the best running bike I can get. If it spoos in the end (out the end? :hmm:)..I don't care.

Oh..that includes timing changes, too. Although, it may be time to try that all over again.

Remember to check the key after you put the rotor back on!! If you don't, you may end up with a whole lot more retarded bike than you planned on.

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Post by Jeb »

One thing to add that dawned on me today as I was doing some maintaining on the kiddos little RM.

Before his last race I was trying to get a little more bottom end. These little 65s don't really do much until about 6k-7k and then all of a sudden here it comes (if you ever get a chance to ride one of these little things do so - they are impressive). Power reeds and shortening the silencer by an inch helped. So a couple of weeks ago I advanced the timing to see how that changed things. It looks like it did, got a little more snap coming out of the curves without having to wind it out . . .

but I noticed the trails of spoo coming out of the silencer, noticeably different than before (which was for all practical purposes non-existent).

The only other thing that's changed, besides advanced timing, is the weather's gotten cooler. But that would mean the additional spoo would have started showing up as a result of leaner operating conditions and, maybe I'm wrong but that don't sound right. Could the cooler air mean ever-so-slightly lower combustion temperatures, enough to cause the excess unburned fuel?

Or DOES the timing thing really play a role?
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Post by canyncarvr »

I'd like to hear the take on why starting the spark later leads to less spoo, all other things remaining equal.

..didn't say I don't have one.

Thanks!

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Post by skipro3 »

If the spark is later, then that means the whole mix is more compressed, seeing as the piston is closer to TDC than if the spark was advanced. Perhaps the additional compression before lighting it off is resulting in a better burn? Also, the retarded timing gives the fuel charge a little more time to vaporize before lighting it off. Every knows raw fuel won't burn but must be vapor before it ignites. Spoo is unburned fuel, so it seems to me that unburned fuel is also unvaporized fuel. Get the fuel to vapor and you end your spoo problem.

More power in a retarded timing would also be accounted for if there is more vaporized fuel to ignite than unvaporized fuel.

Does any of that make sense? And more to the point, does any of that have any credence?
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Post by TopperHarley »

skipro3 wrote:
does any of that have any credence?
I have some credence.....old credence clearwarter revival,CCR that is.
anyone for "Run Through The Jungle" or maybe a little "Proud Mary" :lol:



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2003 KDX220 mine(under construction)
1998 KDX220 1/2 Brother-in-laws, soon his own
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Post by canyncarvr »

Re: ' Perhaps the additional compression before lighting it off'.... 'a little more time to vaporize before lighting it off.'

The more pressure a vapor is under, the more time it's under that pressure, the LESS it tends to stay a vapor. Gee...haven't you watched any scary submarine (We're past crush depth Cap'n!!!') movies?

'More power' is an unqualified term. More power in a road racer? A motocrosser? What's the point of that example?

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