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Message started by stewmills on 12/13/14 at 06:20:10

Title: timing advance (no, not time travel)
Post by stewmills on 12/13/14 at 06:20:10

I'm still tinkering with my 1985 honda atc 70 3 wheeler and read that advancing the timing made it a little more peppy and stronger pulling. what exactly is advancing the timing and does it risk tearing up the engine because of firing out of factory spec? l have the new condensor and points to install and understand very generally how to read the flywheel tdc and firing marks to set it, just curious if i should fool with trying to advance the timing while i am in there?

Title: Re: timing advance (no, not time travel)
Post by Serowbot on 12/13/14 at 06:39:35

You could try it... Advancing 4 to 8 degrees might give you a little boost...
... being that it's only 70cc,... you won't get much (maybe .25hp)...
... and with modern gas,... you might need to switch to premium to avoid knock. (not worth it)...
If you get any knock,... return to stock advance, as it will hurt the little feller....

You'll get more power without any harm, if you have an o-ring chain, by swapping to a non-o-ring... (I did this on a 225cc and the change was very noticeable)...
Adding 5lbs of air to the tires will feel zippier too...

Title: Re: timing advance (no, not time travel)
Post by bobert_FSO on 12/13/14 at 06:49:57

Advancing the timing too far can result in detonation (pinging), which can hurt your engine.

I don't know how applicable this is to motorcycles, but here is a trick we used to do with older cars with distributors to get an optimal spark timing without needing a timing light.

With the engine running, barely loosen the distributor (the points plate on a motorcycle) so that it can be moved, but will stay in place on its own. Increase the engine speed to a high rpm (to ensure the timing advance is fully advanced). Slowly advance the ignition timing by turning the distributor or points plate until the engine starts a high speed miss. Retard the timing until the missing stops. Go for a test ride. If the engine pings on acceleration, retard the timing until the pinging stops.

You may get a small performance increase, but it will be minimal. You probably won't notice it.

Title: Re: timing advance (no, not time travel)
Post by thumperclone on 12/13/14 at 23:53:48

thumper clone is a Chinese ct70 copy tho shes 86ccs its the same confab you have
yes you can advance the pick up off the mag
better to let her breathe
non restrictive air cleaner
free flowing exhaust
sprocket changes(1 in front = 3 in rear)
go to dratv.com
or search small Hondas
ive got a hot engine thall bolt right up but its really not worth it..

Title: Re: timing advance (no, not time travel)
Post by Dave on 12/14/14 at 06:50:45

These little Honda engines can run 40-50.....who knows how many years with no mechanical problems. Just yesterday I rode the little 1966 Honda S65 up to the Sheriff's office to have it inspected as it was from out of state.

Why you wanna' screw around with that kind of reliability in search of a quarter horsepower?

Title: Re: timing advance (no, not time travel)
Post by justin_o_guy2 on 12/14/14 at 09:14:35

You want it quicker off th line? Smaller rear tires,, Instant horsepower..
Its a tiny little motor they designed to run for decades.. COULD you get away with it? Id say yes,, Id say that Because of the way they built them, you could get away with some hop up tuning, Timing, massaging the intake, read THat theory,, Understand an engine doesnt NEED a fancy exhaust to ditch spent air/fuel, the Piston will shove it out,, BUT, Intake flow is crucial and is Only the result of a low pressure pulse. The volume of the air between carb and filter needs to be at least the cylinders volume, larger is better, Of course, a well designed exhaust Helps, nicely, and sounds better, buit few ever consider intake Theory.

OR, you Could just get it running as well as they did Branbd New and see if the potential gain in performance is worth the effort and risk. You May decide that playing with the airflow Thru the engine is more fun and delivers better results at less risk to your toy..

Title: Re: timing advance (no, not time travel)
Post by stewmills on 12/14/14 at 20:28:30

Thanks folks. not being an expert at messing with timing and the potential for some damage, sounds like I'll start with the new points and condenser, double check my intake connections and exhaust gasket (think its missing) and try to fine tune her from there. didn't realize how little the gain was and i may see what I'm looking for when i get it running smooth at stock.

Title: Re: timing advance (no, not time travel)
Post by justin_o_guy2 on 12/14/14 at 20:48:31

Yeah,start with getting it running like new... then think about it.