Discussion in 'The Garage' started by Team Junk, May 15, 2020.
Well, if I knew the GN250 coil was also 150Ω's I'd be tempted to try it.
I went ahead and got 3 of each. You know... just in case. Your Paypal addy still gggary@blah blah.com .....
changed it to S Claus
Probably should get the one with two leads then. The single lead trigger uses the bracket for one connection.
We don't know for sure who makes these parts for the various manufacturers. The bikes don't care.
Ok guys, I've been fooling around with a GY6 honda cdi on an SR500 parts bike I got with a recent purchase. I got the carb cleaned, tested it today and made a real crappy video. This eBay cdi system came with a coil and harness, which I only used the cdi plug from. Under $20 complete. I don't know if this info will do you twin cylinder elitists any good but here you go.
Well done!! must be the day for "crappy videos."
Here ya go, as requested. Idle advance is at 18-19° and full advance is 34-35°. The rattling you hear is the rear shocks. When it's on the centerstand the springs are unloaded just enough that they rattle. It's barely noticeable in person, but boy that camera sure picks 'em up. I suppose I could re-shoot it with the bike on the sidestand... but it's in the 40's out there and just started to drizzle....and my bonz is achin'. This is all ya get.
Since Gary's footin' the bill, I ordered this one. At least we can compare the electrics of the pickup. Slow boat from China... expected delivery 'tween Dec. 22nd and Feb. 19th.
If you need to know the resistance of the actual pickup coil find a used one for sale on ebay and ask the guy to measure it for you.
Although my hearing took a hit at the sheet metal work This time it perhaps was right
ex for a 78 XS650SE
Ignition Timing 15 " BTDC @ 1200 rpm --that is pretty much idle ---> " Idle advance is at 18-19° "
3 -4 degrees to much advance at idle . I believe that is why it ( bike ) does not have the " Clipp " " The Wow Factor "
at rapid throttle .twist ( and perhaps the kickback + need for Choke mentioned by others comes from )
Hesitates a little.
I believe there is a noticeable difference if the carburetor and ignition are corresponding perfectly -- One notices Wroaaaaaaa...aaa immediately
I don't know if that was it but my first bike had sloppy springs so i made changes ..on the advance unit and it was quick to go full advance.
And most of the times did not retard fully at stops .But there the Wroaaaaaaa...aaa immediately factor was there.
The proverbial kick in the backside and off I went.
The compression was worse than bike 2 .But still the first was quicker to respond " More Rock and Roll "
Have had 2 Boyer ignitions after that on bike 2 not with the same " Clipp " ON - OFF behavior
This year back on engine 1 ( Boyer ) but not past running in procedure.
Does anyone Know the Boyer advance ?
Slowly pondering to go back to points
So if the figures is right there is a bit more advance at idle in relation to those specs.
Advance 41.5 BTDC @ 3300 rpm ----> full advance is 34-35°.
Does it matter and does the average rider care ??? .. Probably not .. But from my view I heard it and there are now digits
in the manual.
Perhaps it has been tested .with lesser idle advance ..already.
I need to think a bit more about this.
1200 is not of practical importance since it quickly goes 2 - 3000 and if the advance curves are linear they cross
and have identical advance at some rpm
15 --- 41.5
Nice Bike .... But perhaps less advance at idle ? ???
OK Jan... sorry for the late response. I been consoling the SG. She took it kinda hard when I told her she had slow throttle response.
Anyway... just like I'd never heard of burnt valves from not enough advance being a thing... too much advance (within reason) causing poor throttle response is another "thing" I'd never heard of. So I googled it. I'll add an interesting video at the end, but here's the gist of what this guy found out with his 70's era hot rod.... advancing the timing at idle actually improved throttle response. He started at 8° and pushed it up from there. I had to re-watch the video to make sure I didn't miss something, but all else being equal, this guys best throttle response was at about 32-33°. That's not a typo... thirty two to thirty three degrees of advance was where his quickest throttle response off idle was.
Does that mean my 18-19° is OK? Of course not. But it is a good indicator that my 3-4° more than stock is most likely not hurting anything. And since I'm now running the highest octane fuel I can get, having it advanced most likely is helping throttle response.
Now, I've responded to this because others are, or are considering using this box. Since @Team Junk hasn't been on the forum since Sept, and since I jumped into this with Jacks encouragement, I feel a bit of an obligation to keep the bus steering between the lines. On that note, this is my last rabbit hole. If anyone puts a fresh query up and I don't respond... well, there's your answer.
Btw, I hope Jack's (teamjunk) OK. Not hearing from someone gets kinda worrisome in these trying times.
Yes Sir and thank you for the answer Sorry if it appears overly Critical
But it is really Combustion engine Physical laws And not so much personal view or opinions
Please look at the curves
Ignition advance is there for giving the mixture time to burn and create the driving force for the piston
If we accept a little later advance at full advance so we not risk pinging
Why cant we accept the same at the retarded position ( or that there is an optimum )
Assume a too early ignition -- to much advance curve b
Clockwise rotation seen from right side.
To high pressure at the wrong time
The piston is on it s way up and the ignition lights the mixture the pressure builds and the piston is till moving upwards.
Compressing .. then one gets a rotational preventing force on the piston --less Effect .
If it is to late say exactly at top dead center. curve d
Then the piston is already on the way down and combustion chamber pressure is less at the wrong time
..even with fully burnt mixture
There exist a optimum advance curve c
If the ignition spark occurs at a position that is too advanced relative to piston position, the rapidly expanding air-fuel mixture can actually push against the piston still moving up, causing knocking (pinking or pinging) and possible engine damage, this usually occurs at low RPM and is known as pre-ignition or in severe cases detonation. If the spark occurs too retarded relative to the piston position, maximum cylinder pressure will occur after the piston is already traveling too far down the cylinder. This results in lost power, overheating tendencies, high emissions, and unburned fuel.
Yamaha has designed the engine with at the retarded end 13 -15 degrees BTDC
And it is a Machine sold with that in for about 15 years. If it was off in some sense with over 250 000 machines sold they would have changed it.
For me that is a indication that it should be around there.
There can be changes needed mostly because perhaps Fuels and other things Coils spark etc. .Other advance settings can be better .. What do I know.
I dont know how much testing has been done to reach the 18-19 and the Gonzo but it can by no means be 250 000 bikes under 15 years
Please understand the view that the Mentioned Physics and 250 000 bikes give an indication that less advance at idle can be better.
I do believe most enthusiast today at least in their setting would like to have the possibility to test factory specs.
At the lower end.
If no adjustment possibilities exists there is the risk that holes are drilled in rotors for magnets 5 - 6 degrees wrong
Please bare with us / me .. We / I don't know all and has not test driven the bike.
What we do know is the factory setting and the big number driven with that spec
And has some knowledge of the combustion process
As well as of the bike for 35 years
This can be better ....But we don't know that .. And it will be seen after more people install the Gonzo box.
People are gonna try moving the advance a little as they do with other ignitions.
And every man makes his own decisions and chose how his bike shall run. The curves are there.
Jan, there's more to it than that. Everything they sell is a compromise. When they set the timing specs they allowed for error during manufacturing and ownership. Of course they're conservative with specs. Better to play it safe. Then they also had to deal with emissions. Since you're studying timing do some research on the effect of retarded timing on emissions. (Spoiler; it helps) Really, worrying about 4 or 5 degrees of extra timing is pointless.
mrriggs ran his bike with the advance lock at full advance.
His thread explains how he was able to do it.
Good link there Greg! some interesting info regarding advance and kickback. Kickback always been my advance limit. advance till it kicks back, back timing off a bit, done.
BUT the stock mechanical advance tends to allow OVER advance as it wears out. Full advance timing should always be checked with a timing light.
Want to run more advance, increase the beer and bratwurst intake.
I'll just add this before I move on... small aircraft engines, Continentals, Lycomings and such have no advance mechanism. They use a magneto that's fixed... normally about 25-30°. For starting they use what's called an impulse coupling. The coupling serves 2 purposes. First it stops the mag about 25-30° before TDC. As the crankshaft continues to rotate, that energy (kinetic) is stored in the couplings spring. When the crank reaches TDC, a pin releases a catch and the spring is released, imparting a rapid spin to the mag. That gives you a nice fat spark at the plug. The other purpose, by way of freezing the mag, is that the spark is delayed until TDC... a mechanical retard system for starting. Once started, flyweights keep the coupling disengaged so that the mag fires at it's set advance... 25-30° depending on engine spec.
So... a 540 cubic inch 6 cylinder will happily idle at 500rpm and take a full throttle shove with no problem. It will rapidly accelerate to redline with no hesitation.... all the while with 30° advance.
So, for the last time... our 18-19° advance is neither unheard of... nor is it a concern. End of discussion... at least on my end. You guys can, and likely will... continue the flogging. Carry on.
Don't beat the pony! I do believe my 47 John Deere uses an Impulse mag! Set it, forget it.. Pop, Pop, Pop.
I'm wondering if the pickup from a bicycle speedo could be used to trigger the GN250 box? They use a magnet for the signal. Pretty compact.
Would the end of the motor shaft on a small flat motor like a cd tray motor act as a sensor? I'm thinking the magnetized shaft would energize the rotor coils which could be read as a voltage on the input leads.
How many of us have at least one Yamaha relay sitting on a shelf with a nice little coil inside it?
Good info, as usual, makes me feel a little better about my "idea" in the works.
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