Ignition curve
- Thread starter gasto
- Start date
There's actually one in the factory service manual.
I believe it goes from 0° BTDC at idle to ~ 20° BTDC at high rpm's. It's actually fairly simple in that it increases dramatically up to ~4krpm and then levels off.
I believe it goes from 0° BTDC at idle to ~ 20° BTDC at high rpm's. It's actually fairly simple in that it increases dramatically up to ~4krpm and then levels off.
Ahh, it's not even 4k rpm. It's basically straight off idle it increases to ~20° BTDC!
Yes, the only reason is so it does not kick back when starting.
The older points bikes were just fixed. A 250 MX would bruise the bottom of you foot wit kickback!
The DT200 starts the same, advances to over 30 and tapers off with retard with rpm.
This is typical 2 stroke timing, flat or retarding with rpm. Opposite of 4 stroke, although they typically have the under 800rpm retard for starting as well.
Steve
Yeah, I figured the starting part. I just thought it had a more gentle taper to it upto about 4k rpm.
I've seen the curve before in the service manual and marvelled at it but remembered it a little different.
I've seen the curve before in the service manual and marvelled at it but remembered it a little different.
They must have forgot to do it on the old open class bikes. Some of those were shin splitters. I had a YZ490 hurt my once, that was the meanest thing I ever threw a leg over and I've rode about all the big bikes.
Actually it does hit 20 degrees at 4k and holds it till about 6500rpm, book says 16 degrees at 3k, Then about 6500rpm it starts to retard- Does it keep dropping after 8K?
When you advance it +4 are you at 20 degrees at 3K and 24 degrees at 4 up to 6500 rpm?
When you advance it +4 are you at 20 degrees at 3K and 24 degrees at 4 up to 6500 rpm?
Yup, most of them were still points before 1980 and then until 1985 many just had a flat curve that retarded slightly with rpm (more due to the natural delay in the electronics than anything designed in). My 1985 XT600 had the low rpm retard and never ever kicked me back. My 1978 XL500 however, launched me over the handlebars several times!
You are right Slick. A better curve would be:
20 at 3000
24 at 4000
22 at 6000
18 at 8000
or something like that. Due to the "supercharging" effect of the pipe,
you want much less advance at high rpm on the tuned 2 stroke.
The tighter it is tuned, the less advance desired at high rpm.
Yes it will keep declining after 8000 due to the analog nature of the circuit.
Not programed like modern circuits, but done with resistors and capacitors and fancy circuitry tricks!
Yeah I know I'm digging up an old post but I'm having trouble with my Blaster. After checking the timing with my light I'm not seeing any advance. I've tried about everything but this thing has been showing signs of retarded timing for a while. Any ideas why I wouldn't get advance? Thanks.
The things go almost 20° advance off idle. The CDIs for these are incredibly horrible. I'm looking into creating a tuneable cdi. I'vestarted a thread about it under my name. It also covers ignition curves you are dealing with.
For the issues you are having with your ignition timing, check your flywheel and make sure it is lined up to your key way, if you have adjustable standard make sure it is set to standard timing, change your spark plug.
They have near TDC timing to get kickstarted without kicking back, and then jump advanced (18degrees?) at about 800rpm (faster than kick but less than idle) to give good torque. As with most 2strokes, the timing then retards as the rpm goes up to compensate for the pipe tuning. Not enough really. If you wake these motors up with more pipe and port you have to back the timing off even more. The 32hp DT200 had much more retard built into it.
Steve
Rubbersalt Thanks for your response. I read your post last week and would be very interested in one of your adjustable units. My motor is a little special tho. I need more advance and I believe with our setup that would be possible. I have an adjustable stator already running about +8. The motor is worked over pretty well. I'll list the build below. Let me know if your willing to sell one of your adjustable DCIs. I'm even willing to put some dyno time in on one. I need more timing around 3000-5000. Last dyno run I pulled 25.5HP but found a good bit more with the +8 timing.
Best glad to hear from you again. We talked about combustion chambers 3 years ago. I machined my own Toroidal chamber. It turned out way better than I expected as I did it on my all manual lathe. I wanted to try it on my +3 motor for a before and after but after doing all the machining to fit the +3 I found when I tore it down Vito's screwed me and sent me a stock stroke crank and neither I nor my builder checked it.
So my problem is this. This is a street legal build and it gets really hot at steady cruising speeds. It's jetted a bit rich as per the wide band O2 on the dyno.
Build
Ported Vito's 240 at +.50mm
Hot Rods +4mm crank
V4 reeds
PWK35
Toroidal chambered head
Adjustable stator
Billit intake
DT200 gears
Custom LED pipe
Best glad to hear from you again. We talked about combustion chambers 3 years ago. I machined my own Toroidal chamber. It turned out way better than I expected as I did it on my all manual lathe. I wanted to try it on my +3 motor for a before and after but after doing all the machining to fit the +3 I found when I tore it down Vito's screwed me and sent me a stock stroke crank and neither I nor my builder checked it.
So my problem is this. This is a street legal build and it gets really hot at steady cruising speeds. It's jetted a bit rich as per the wide band O2 on the dyno.
Build
Ported Vito's 240 at +.50mm
Hot Rods +4mm crank
V4 reeds
PWK35
Toroidal chambered head
Adjustable stator
Billit intake
DT200 gears
Custom LED pipe
Hey Tim, you won't believe what I'm into these days. Chinese bicycle motors.
Cheap and easy to modify and learn from. Just stuffed a crankcase and ported casehalves this evening.
I do have a Vitos bigbore and +3 crank sitting in another Blaster right now, but no working stator. Gotta buy parts and so many other things to do.
What is with all the advance? Normally a bit of compression, a pipe and a turbulent head will speed up the burn enough that you have to retard the timing. Well burning engines need less timing advance.
I run a KTM 125 on the street. Who knows the hp? It does highway speeds easily and about 85mph peaked out on rpm. I had some troubles fine tuning it for steady speed driving. First I was overly rich in all carb ranges. Steady speed is mainly pilot and needle. Had to lean pilot quite a bit, and carefully tune needle. You may need to do the same. If you are using more than 1/4 throttle to hold 50mph, something is wrong.
Part of the retarded timing is to time the burn toward the exhaust so the pipe will do its thing and not pump the heat into the cylinder. Timing and compression are bad for heating up pistons. Make the pipe and ports do the work. My thoughts.
More explaination here: http://www.blasterforum.com/threads/a-crash-course-in-ignition-timing.45181/page-2#post-596433
Steve
Cheap and easy to modify and learn from. Just stuffed a crankcase and ported casehalves this evening.
I do have a Vitos bigbore and +3 crank sitting in another Blaster right now, but no working stator. Gotta buy parts and so many other things to do.
What is with all the advance? Normally a bit of compression, a pipe and a turbulent head will speed up the burn enough that you have to retard the timing. Well burning engines need less timing advance.
I run a KTM 125 on the street. Who knows the hp? It does highway speeds easily and about 85mph peaked out on rpm. I had some troubles fine tuning it for steady speed driving. First I was overly rich in all carb ranges. Steady speed is mainly pilot and needle. Had to lean pilot quite a bit, and carefully tune needle. You may need to do the same. If you are using more than 1/4 throttle to hold 50mph, something is wrong.
Part of the retarded timing is to time the burn toward the exhaust so the pipe will do its thing and not pump the heat into the cylinder. Timing and compression are bad for heating up pistons. Make the pipe and ports do the work. My thoughts.
More explaination here: http://www.blasterforum.com/threads/a-crash-course-in-ignition-timing.45181/page-2#post-596433
Steve
I'm not sure what the deals is. The temp just starts to creep up as I cruise. I need to see if it is actually retarding at idle. I may not have the idle low enough to see it advance. I didn't realize the advance come on so low (or the retard goes away). I've been through about everything on this thing. That's why I reached out on here. I've pressure tested it. I've had it on the dyno with the wide band to check my jetting. And the worst thing is I was having the same problem with my last motor too. So when I build this one I didn't reuse anything from the last motor. I'm going to try and get the timing light on it again tomorrow.
They are still in the developmental stage. When i get one going that is adjustable, or at least may better suit your needs, I'll hit you up. I hope by the end of August, I'll have something worth looking showing.
As for stators, very easy to rewind. Ohm it out, and see what it shows. If bad, simply rewrap the dead coil. You can pick up some 34 guage magnet wire for cheap. 1/4lb is more than enough for 1. 1/2lb is usually a little better of a deal at $12. 1/2lb is typically around 5000 feet or so worth of wire.
To rewind them, remove the old wire (cut it off with a dremel or something), insulate the iron laminates, then begin winding. Be sure to leave part of the wire hanging out so you have something to solder too when it's complete. I typically solder a piece of heavy wire to the magnet wire and let the heavy wire stick out. It's more resilient and durable than 34g wire.
To do the actual winding, which is hundreds of turns... I thread the wire through a coffee stirrer and check the iron laminates(stater winding core) into a drill, and let it rip. Gotta keep slight tension on the wire. The source coil isn't picky on the way it's wound. The pick up coil can be. If you wind the pick up coil and it doesn't work right, then switch the leads coming off around and it will.
When your done wrapping, some cheap epoxy that isn't jb weld or anything that can disrupt the magnetic field. I've used that harbor freight clear epoxy weld. haven't had a failure yet (but I'm also removing and experimenting!)
As for stators, very easy to rewind. Ohm it out, and see what it shows. If bad, simply rewrap the dead coil. You can pick up some 34 guage magnet wire for cheap. 1/4lb is more than enough for 1. 1/2lb is usually a little better of a deal at $12. 1/2lb is typically around 5000 feet or so worth of wire.
To rewind them, remove the old wire (cut it off with a dremel or something), insulate the iron laminates, then begin winding. Be sure to leave part of the wire hanging out so you have something to solder too when it's complete. I typically solder a piece of heavy wire to the magnet wire and let the heavy wire stick out. It's more resilient and durable than 34g wire.
To do the actual winding, which is hundreds of turns... I thread the wire through a coffee stirrer and check the iron laminates(stater winding core) into a drill, and let it rip. Gotta keep slight tension on the wire. The source coil isn't picky on the way it's wound. The pick up coil can be. If you wind the pick up coil and it doesn't work right, then switch the leads coming off around and it will.
When your done wrapping, some cheap epoxy that isn't jb weld or anything that can disrupt the magnetic field. I've used that harbor freight clear epoxy weld. haven't had a failure yet (but I'm also removing and experimenting!)
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I don't think it's a problem with the stator as this is the second one. I think I stated earlier (not sure but not going to dig either) I changed everything when I did this motor. I have the old engine sitting on a shelf in the garage and the only parts I would have to put back are the carb, pipe and CDI and I could start it on the floor. Those parts were pulled to remove the engine but not reused on my current setup. I didn't get out to work on it today so maybe I'll see how low I can get it to idle tomorrow and put the timing light on it.
