advanced timing?

#1
I've heard that some people advance the timing on their engines and I was thinking to do it also... but my question is, what does advancing the timing really do? and how much can you advance the timing? I saw that Small Engine Cams.com sells up to 12deg timing advance
 
#2
You ask a really good question:

AS built the electronics in a dumb Gx/clone has a propagation delay that at high RPM starts to retard timing.

To put it simply it takes time to fire the plug from the point the ignition senses its time to fire, but the amount of time require to deliver that spark decreases as RPM increases.

It work out to about 1 deg per 1000 rpm....

So if you plan on running 6000 rpm you should add 3 deg of static timing to get the spark to happen at the right moment.
BUT the right moment is a moving target too!
the flame front in the combustion chamber also moves at a roughly set speed, so we need to add some additional advance to compensate for this too!

How much?

I dunno.....

A LOT OF OTHER FACTORS come into play.

I run a lazy 25 BDTC for my clone that seldom goes over 5000.
This still preserves some top end without too much power killing lead at the bottom.

Your millage may vary....
 
#3
ooooohh okay, I get it now... thanks for clearing that up for me :thumbsup:
so I guess I'll do some testing, as my build progresses .
also I have another question... is there a point where the engine won't run correctly because of the timing,and modification combo? say I install my header, and slap on 8deg., do you know if there would be a problem with that?
not trying to annoy you, I'm just curious :laugh:
 
#6
ooooohh okay, I get it now... thanks for clearing that up for me :thumbsup:
so I guess I'll do some testing, as my build progresses .
also I have another question... is there a point where the engine won't run correctly because of the timing,and modification combo? say I install my header, and slap on 8deg., do you know if there would be a problem with that?
not trying to annoy you, I'm just curious :laugh:
If that is all your gong to do then yes I think you may find you have a problem, a loss of performance...

The header will allow more flow, but without more fuel the engine will lean out and run poorly.
So consider some jets and filter kit to fix that.

The 8 deg of timing will make the engine a bit cranky at low rpm, it will suffer in performance at low speed, but it will wake up above 5000.
Do you intend on having an engine built that will run often at high rpm?
You will need an valve train and billet upgrade to run up there, not to mention a better cam.

You need to plan this out
 
#7
well I'm putting new jets in, so that should help it a little bit, but I guess I won't advance it yet because I'm keeping the governer in until I get my billet parts
 
#8
You can't ad hock build something that works well.
Buy a Predator to build into an engine and keep the one you have now functional so you have something to ride.
Try a 4 deg key ( file your own if you have a vice ).
Get a timing light and find out exactly what your starting with and try and get to around 25 ( but no more that is the upper limit for something to still run well at low speed ).

Out of the box all these engines are lean, but your going to have to richen it up and within the limits of your carb and exhaust.
How much depends on a lot of things.

Find a 14 cc head and bolt that on.
Its a cheap easy find at most small engine shops and it will build power at all RPM ranges and still allow you to use a governor and stock internals.
You might luck out and find a GXV160 mower engine around ( commercial Honda mower ) this has a flywheel that is as strong as billet, lighter than stock and has about 5 deg of timing advance built in ( hard to screw up ).

Header, filter kit, timing, 14cc head, GXV flywheel all this is cheap stuff you can find locally or make yourself, you can even drill your own jets ( but I suggest you get some scrap carbs to practice on ).
The idea with these suggestions is they are relatively easy bolt on changes that can be undone easily too.
 
#11
don't worry I'm listening
Your listening to a guy on the internet....
Next let me tell you about my Sasquatch hunting excursion ruined by the KGB and their alien masters.
I was so close when my jammed up.....

Take every suggestion with a grain of salt.
Read, plan study and ask a lot of questions.
I have my opinion and I am not trying to mislead you, but you need a plan of your own that starts with you deciding the kind of riding you will do and then build an engine around your needs, not other people opinions.
 
#12
Your listening to a guy on the internet....
Next let me tell you about my Sasquatch hunting excursion ruined by the KGB and their alien masters.
I was so close when my jammed up.....

Take every suggestion with a grain of salt.
Read, plan study and ask a lot of questions.
I have my opinion and I am not trying to mislead you, but you need a plan of your own that starts with you deciding the kind of riding you will do and then build an engine around your needs, not other people opinions.
lol........... I just needed some more background information before I start experimenting with modifications and all that cool stuff
 
#15
He's talking about the RLV aftermarket ignition.

A lo of money for nothing
There is a relatively new Honda CDI system for one of the big V twins that gives all the advantages of the PLV with a stock Honda flywheel and a low RPM retard function so its easier to start and runs better at low Rpm.
 
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