Having some fun with my Baja 250 - Page 2

TheRealWorld · 02-21-2011, 10:11 AM

No, I had not, but I will, and thanks for your info. I will let you know what I hear.

cliftstuff · 03-12-2011, 10:01 AM

Careful because there are dc fired cdi's and ac fired cdi's...(I learnt the hard way by blowing the main fuse). I get my parts from scrappydogscooters.com out of here in vegas. Nice people and Mo is knowledgeable.

culcune · 03-12-2011, 01:18 PM

Cliftstuff, that link seems to have alot of parts. They seem to have parts for the Hensim/Baja and the Ventos, too...Good link!

Weldangrind · 03-12-2011, 03:21 PM

Quote:

Originally Posted by cliftstuff

Careful because there are dc fired cdi's and ac fired cdi's...(I learnt the hard way by blowing the main fuse). I get my parts from scrappydogscooters.com out of here in vegas. Nice people and Mo is knowledgeable.

I was looking at their stuff on eBay, and I'm not sure how to tell if an AC or DC CDI is required. How do you tell?

cliftstuff · 03-12-2011, 03:59 PM

This is off his tech talk page about weather ac fired or dc fired:

Here is somewhat simplified checklist to determine type:
Headlights turn on with key, DC. Headlights turn on with engine,AC
Engine does not run without batter, DC. Engine runs without battery, AC
CDI box is pretty large, DC. CDI box is smaller, AC (note: our new digital DC units are smaller)
There is one wire on the two part plug, DC. There is two wires on the two part plug, DC.

Like I said Im happy with these guys and they seem to have a good rating on ebay.

Weldangrind · 03-12-2011, 04:22 PM

Thanks for the reply.

This is fantastic tech: http://www.scrappydogscooters.com/Te..._with_Mo_.html

TheRealWorld · 03-12-2011, 11:35 PM

Thanks for the info guys, I have been very busy, but I will be getting to this soon. I did try to call scrappydog today and got a message, I will call again.

humanbeing · 03-14-2011, 05:25 PM

This is a better "chinese" replacment (:P Qlink XF/ XF stock is that brand & so did other big players in China ...)
Currently ~$12 in China
Any cheaper CDI with similar curve will work, BUT reliability not guarantee

Weldangrind · 03-15-2011, 12:05 AM

Wow, zero degrees at 1500rpm, but 16 degrees BTDC at 3000rpm. That's a really steep curve, but it's nowhere near the total advance that I imagined. Typical four stroke engines are happy at around 35 degrees BTDC (initial plus centrifugal if applicable).

TheRealWorld · 03-15-2011, 12:11 AM

Thanks for the comment, but I have to admit you are way over my head, I have no idea what you are talking about!

Weldangrind · 03-15-2011, 12:33 AM

What I mean is that the spark needs to occur sooner than TDC (top dead center) as the engine spins faster. The CDI makes the spark occur earlier and earlier as rpm increases, so that the air / fuel mixture can properly ignite by the time the piston has reached the top of its travel. This is referred to as ignition advance, and it is expressed in crankshaft degrees before top dead center (BTDC).

You can't get too carried away with advance, or the ignited air / fuel mixture will be trying to force the piston down while it is still travelling upwards. The result is detonation, and it sounds like rocks rattling in a coffee can. If you're lucky, you'll only break a spark plug. It can certainly result in broken rings or a broken piston.

All that said, I'm still surprised by the rather weak advance curve shown in the specs. I expected the curve to take advance to well past 30 degrees BTDC.

FastDoc · 03-15-2011, 12:44 AM

That was a really intellegent, concise explanation, Brother Weld.

humanbeing · 03-15-2011, 01:29 AM

Quote:

Originally Posted by Weldangrind

expected the curve to take advance to well past 30 degrees BTDC.

Stock (AC) = Reliability 1st & meet emission laws

Curve from a programmable (DC / coils) : http://motorcycle.sh.cn/t_248815.htm
4 curves kit (DC / coils) for "lazy" guys: http://item.taobao.com/item.htm?id=7935554522

Weldangrind · 03-15-2011, 11:12 AM

Ok, that makes more sense. The link you showed us is for a stock replacement, not a performance CDI.

Weldangrind · 03-15-2011, 11:12 AM

Doc, you're very kind.

03-12-2011, 10:01 AM	#2
cliftstuff Join Date: May 2007 Posts: 11	cdi replacements Careful because there are dc fired cdi's and ac fired cdi's...(I learnt the hard way by blowing the main fuse). I get my parts from scrappydogscooters.com out of here in vegas. Nice people and Mo is knowledgeable.
	0

03-12-2011, 04:22 PM	#6
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Thanks for the reply. This is fantastic tech: http://www.scrappydogscooters.com/Te..._with_Mo_.html __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

03-15-2011, 12:05 AM	#9
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Wow, zero degrees at 1500rpm, but 16 degrees BTDC at 3000rpm. That's a really steep curve, but it's nowhere near the total advance that I imagined. Typical four stroke engines are happy at around 35 degrees BTDC (initial plus centrifugal if applicable). __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

03-15-2011, 12:33 AM	#11
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	What I mean is that the spark needs to occur sooner than TDC (top dead center) as the engine spins faster. The CDI makes the spark occur earlier and earlier as rpm increases, so that the air / fuel mixture can properly ignite by the time the piston has reached the top of its travel. This is referred to as ignition advance, and it is expressed in crankshaft degrees before top dead center (BTDC). You can't get too carried away with advance, or the ignited air / fuel mixture will be trying to force the piston down while it is still travelling upwards. The result is detonation, and it sounds like rocks rattling in a coffee can. If you're lucky, you'll only break a spark plug. It can certainly result in broken rings or a broken piston. All that said, I'm still surprised by the rather weak advance curve shown in the specs. I expected the curve to take advance to well past 30 degrees BTDC. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

03-15-2011, 12:44 AM	#12
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	That was a really intellegent, concise explanation, Brother Weld. __________________ Happy to serve.
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02-21-2011, 10:11 AM	#1
TheRealWorld Join Date: Jun 2008 Posts: 817	No, I had not, but I will, and thanks for your info. I will let you know what I hear.
	0

03-12-2011, 01:18 PM	#3
culcune Join Date: May 2006 Location: Yuma, Arizona Posts: 9,035	Cliftstuff, that link seems to have alot of parts. They seem to have parts for the Hensim/Baja and the Ventos, too...Good link!
	0

03-12-2011, 03:59 PM	#5
cliftstuff Join Date: May 2007 Posts: 11	This is off his tech talk page about weather ac fired or dc fired: Here is somewhat simplified checklist to determine type: Headlights turn on with key, DC. Headlights turn on with engine,AC Engine does not run without batter, DC. Engine runs without battery, AC CDI box is pretty large, DC. CDI box is smaller, AC (note: our new digital DC units are smaller) There is one wire on the two part plug, DC. There is two wires on the two part plug, DC. Like I said Im happy with these guys and they seem to have a good rating on ebay.
	0

03-12-2011, 11:35 PM	#7
TheRealWorld Join Date: Jun 2008 Posts: 817	Thanks for the info guys, I have been very busy, but I will be getting to this soon. I did try to call scrappydog today and got a message, I will call again.
	0

03-14-2011, 05:25 PM	#8
humanbeing Join Date: Mar 2008 Posts: 2,436	This is a better "chinese" replacment (:P Qlink XF/ XF stock is that brand & so did other big players in China ...) Currently ~$12 in China Any cheaper CDI with similar curve will work, BUT reliability not guarantee
	0

03-15-2011, 12:11 AM	#10
TheRealWorld Join Date: Jun 2008 Posts: 817	Thanks for the comment, but I have to admit you are way over my head, I have no idea what you are talking about!
	0

03-15-2011, 11:12 AM	#14
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Ok, that makes more sense. The link you showed us is for a stock replacement, not a performance CDI. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

03-15-2011, 11:12 AM	#15
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Doc, you're very kind. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0