449/511 retard the timing with PCV at low RPM... Flameout Theory...

Theory: Retard the timing at low to very low RPM with PCV to help reduce flameouts.

Thinking, in super-slow-motion, about what is happening during a flameout.

* Piston rises on compression stroke.
* Air/fuel mix is lean (for whatever reason you want to insert here).
* Spark is initiated at 10deg before Top Dead Center
10deg is estimate, doesn't really matter what number you put in here.
* Spark advances quickly with lean mixture.
which is fine at higher engine speeds.
* Rapid advance of flame at Before TDC at slow engine speed causes a downward force of the piston during part of the compression stoke while the piston is still rising.
* The momentum of the flywheel and other factors carries the engine forward in spite of this for several power stokes, but the engine slows down with every revolution causing the situation of compound until...
* At some point, the lean mix and advanced spark ignite the fuel while the piston is still rising in the compression stroke causing the piston to abrupt stop... Flameout!

* Using a tool (PCV) to increase fuel at these engine speeds works because the rich fuel mix is cooler and burns more slowly allowing the piston to complete the compression stroke and move to the power stoke before the fuel reaches maximum burning efficiency.
* Nevertheless, retarding the timing at idle and below would also address the problem without having to add quite as much fuel to the system.
* Addressing the flameout using both strategies may be better than just adding fuel.

* I'm still experimenting but I run -3 on ignition timing at idle and -6 at 1500 - 1700.

ALSO: What I like to see when I start the bike.
* I don't want the engine to just "Spring to life!" I want it to spin a bit and kind of lazily start.
* Why?
* When coming UP from 0 RPM to 2000 RPM, if the engine starts lazily, I know that when the engine is running and begins to dip below idle (headed DOWNWARD) it will also be lazy. There wont be any abrupt surging or stopping (flameouts). It'll just briefly drop down into those slow engine speeds without any drama.
* If my engine Snaps to life when I hit the starter, I know that there's too much drama at those sub-idle RPMs.

* Conclusion: Addressing flameouts by increasing fuel AND slightly retarding timing may be better than using fuel alone.

* Disclaimer: I'm not a mechanic. I'm not an engineer. However, I have published a work of fiction.

Interesting......

We would need to see the factory ignition mapping before just "doing it" Usually reducing base timing or timing at idle will make a vehicle crank faster also which may help.

I want to run my bike on a dyno and see if the zip ty ignition mapping is conservative (increase advance over 7 until it knocks to find the "limit" of the 511).

Nowhere will let me run the bike with myself tuning between runs, they just want to rip it down the dyno to get a hp reading and add some fuel sending you on your way for their 150$+ for "tuning".

Try BHP in Sac. Very laid back and I'm sure he would give you all the time you wanted to make adjustments.

^thank you for the heads up, that seems like the kind of shop I would like to head over too. Hows that wr300 treating you?!

I had mine dyno'ed at BHP. He didn't adjust ignition at all. Only fuel. I dyno'ed at max 46hp. It ran better than before but just loading Zip-Ty's Burson FB map made it run much better... except that I up'ed low end fuel and retarded timing to get rid of flameouts. You're going to have to know more about your bike than BHP does or he'll just adjust your fuel and send you on your way. Have a really good idea what you're looking at on the PCV and what you want to do before making an appointment.

Nice guy though. I got the impression that Tinken knew of him and didn't care for his work. Don't know why and I may have my info off.

I just want the dude to turn the dyno on and hit the throttle, I will do everything with my own laptop or on the PC V software. Its not hard at all, Listen very carefully, advance ignition while monitoring AFR and exhaust temp if possible. If you hear the rattle you got too much advance. I do all the SBF engines I have built by cruising down the freeway in top gear and do a full throttle pull.

Gets dicey tho with the police!

Retarding the timing a bit at idle makes sense to me. I've done the same thing on my Harleys with Screaming Eagle tuners for the ignition on carbureted older twin cam motors ( 2000ish) to be able to open the butterfly up to return idle to its proper setting. This will keep the bike from spitting back through the severely closed carburetor and dying as the butterfly is nearly shut because of advanced timing idle settings.

This works with the PCV on my last few fuel injected baggers as well. No matter how fast you blip the throttle it won't spit back whether hot or cold. Slightly Retarded Timing + Opened Butterfly = proper idle speed. No more spitting back through the intake which means no more flame outs. Works for me on my big twins. Makes sense on my Kymco thumpers too.

* Disclaimer: I'm not a mechanic. I'm not an engineer. However, I have published a work of fiction. Ha ha ha

Certainly worth looking at, not something I'd put much thought into at all actually.

Dirty old Datsun 1600 (510) rally cars I ran years ago were set at 15deg standard but would support 20deg static.
Of course they did not have to produce clean emissions when new or while racing, had only a 2 valve head & were nearly square in the bose/stroke.....

With the 449/511 being so over square, any help in bottom end torque is welcomed for sure.
The huge bore, big ports, big throttle body of all the modern dirt bikes are made more for power up top.
Getting them to do trials type stuff like log hopping etc. is always going to be a tall order I guess.

WHOO HOOO !!
I though of something that, at least on the face of it, isn't ridiculous!

Ha ha ha.

Without a PCV to fiddle with mine, you guys are gonna have to play ball & see.

Ya.. do it! Post the results.

Never met the guy, but I will clear up my findings. Through conversations between Jerbear and myself, I ended up with a copy of his map from BHP. His map settings looked way off to me, so I sent the map over to Dynojet for consultation. Dynojet also agreed that the numbers were much higher than they have ever seen before on this particular make and model. It is not fair of me to assume anything about why the numbers were so elevated. Maybe he was adjusting for an AFR higher than what the 511 needs, I don't know. In any event, I apologized to jerbear for making any assumptions in the quality of BHP's work.

Interesting, I am not exactly sure how far below TDC the oem timing parameters consist of. At the point of flame-out, the air and fuel ratios are at the point just beyond deflagration and move to detonation. Retarding the engine at low rpm makes sense. But there are many variables which could also be addressed. Octane level and compression will be two of those variables. These are two ways to help overcome flame-outs. The fuel that we run in my 511 is always +94 octane or higher. And my engine has had it's compression lowered through the reshaping of the combustion chamber and the piston (not something easily added for most people). But it is something to consider when dealing with a SMR/TE/TXC versus a TC engine. I am mobile at the moment, but will refer to my engineering Kymco documents in the morning.

ALSO, it's my understanding that when I retard the timing by say "-6", that would be 6% slower than the current map. So, if at 2000 RPM spark comes at 10 degrees Before TDC, with a "-6" setting it would be coming at about 9.4 degrees before TDC. Not much of a change, provided my math and concept are correct.

That sounds right, but I want to know for sure that it is percentage and not 'degrees'. Anyone know for sure?

Yaaaaa... that would make a big difference.

The ignition table values are degrees advanced or retarded from the base setting - per the PCV help files.

Thanks!

Interested to see how this turns out! Adding some fuel in the 1500-2500 range seemed to help flame-outs with my setup (for now).


Possibly slightly off topic, but has anyone completely figured out the occasional hard starts with these bikes? Mine is much better after the PCV, but it still likes a touch of throttle on hot starts. Is this a timing, ignition, air, or fuel issue?

Hot restart after a stall/flame out, you mean?
Mine still needs a little throttle if I stall it.
Always has even when it used to flameout.
Unsure why.