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Old 03-12-2012, 10:43 PM   #16
Andyvh1959
Cheesehead Klompen
 
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Joined: Feb 2012
Location: Da frozen tundra, 1.5 mile west of Lambeau
Oddometer: 601
Well I actually HAVE found success with a Chinese $21 aftermarket NEW Racing CDI, the one on ebay for an AC alternator application. Its a neat looking little unit in a blue anodized finned casing. I made some wiring changes on the installation I was struggling with, and now I have easliy started the bike five times. It warms up quickly and idles steadily. And it seems to rev up real quick compared to using the stock 30 year technology CDI unit. Too bad the ice is all gone for me to test it on an ice track.

I may have to spoon on some street tires for street testing the bike (no lights, horn, etc).

Especially since I also have a Mikuni 36mm VM series round slide carb for it. That may work well with the Supertrapp muffler and foam air filter (no airbox) I have on the bike. Also, I took a die-grinder to the air dam in the intake manifold, and ground it out entirely, to improve high rpm airflow. If this all works out I may consider installing a Wiseco piston from a Honda XR400. The 3rd oversize piston for a XR400 is the same 88mm bore as the stock bore for the GN400, and it has the same 20mm piston pin size. It raises the compression ratio to 10:1 (assuming the pin to piston head distance is ok for valve clearance).

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Old 03-13-2012, 12:44 AM   #17
nanno
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Joined: Aug 2009
Location: Linz, Austria
Oddometer: 271
the biggest issue with the DR250 and GN250 is the head, because the cam-bearing is very often knackered or beyond hope. Engine parts are best bought in China (HK) and there's also a 300cc bigbore piston for it which costs about 100 USD incl. cylinder to match. A new head is around 150USD and cams and followers are about 50 to 60 USD.

All in all a very cheap bike to keep alive.

Cheers,
Greg
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Old 03-13-2012, 07:36 AM   #18
eric123
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Location: Idaho
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Quote:
Originally Posted by Andyvh1959 View Post
Well I actually HAVE found success with a Chinese $21 aftermarket NEW Racing CDI, the one on ebay for an AC alternator application. Its a neat looking little unit in a blue anodized finned casing. I made some wiring changes on the installation I was struggling with, and now I have easliy started the bike five times. It warms up quickly and idles steadily. And it seems to rev up real quick compared to using the stock 30 year technology CDI unit. Too bad the ice is all gone for me to test it on an ice track.

I may have to spoon on some street tires for street testing the bike (no lights, horn, etc).

Especially since I also have a Mikuni 36mm VM series round slide carb for it. That may work well with the Supertrapp muffler and foam air filter (no airbox) I have on the bike. Also, I took a die-grinder to the air dam in the intake manifold, and ground it out entirely, to improve high rpm airflow. If this all works out I may consider installing a Wiseco piston from a Honda XR400. The 3rd oversize piston for a XR400 is the same 88mm bore as the stock bore for the GN400, and it has the same 20mm piston pin size. It raises the compression ratio to 10:1 (assuming the pin to piston head distance is ok for valve clearance).
Do you happen to have a link to the Chinese CDI please?
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Old 04-05-2012, 10:12 AM   #19
Andyvh1959
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Joined: Feb 2012
Location: Da frozen tundra, 1.5 mile west of Lambeau
Oddometer: 601
The "NEW Racing CDI" is commonly available on ebay from many sellers. It is the five-pin AC style CDI meant for use on a bike with no battery. It is the fancy looking (yeah, it suckered me in) blue anodized finned housing CDI unit many sellers have for about $25. Easy to find on ebay, just search "NEW Racing CDI". I bought mine from seller named "1800Coolparts". Shipped quick, within five days or paying for it.

I have started my GN on this CDI many times. Sometimes four kicks, sometimes ten kicks. It idles fine, a bit stumbly, but that may also be caused by the Mikuni VM36 carb I have mounted, which is jetted too rich on the pilot circuit. I found that out by checking the plug color after five minutes of idling, black and sooty. It does rev up quick and high, though it pops at near WFO. That too may be caused by the carb. More to come. I'm mounting rims with dirt track tires so I can test it this summer.

Here is how I wired the NEW CDI to the old wiring on my GN:
NEW CDI GN400 wiring
BLACK to Black/White, chassis ignition or kill switch, this is the switch ground for the CDI
GREEN to Chassis gound
YELLOW to Black/Yellow, coil primary, this must go directly to the coil input
BLUE to Blue/Red, P1 pulser wire, for the 10 degree BTDC pulser, for idle signal
RED to Black/Red, this is the stator power output to the CDI

The Red/Green wire from the P2 pulser is not used at all, same for the Black and Black/White from the stator. The NEW CDI is an auto advance style, that sets to a retarded ignition timing (10 degree BTDC) if it gets a signal from the timing Pulser.

I am also going to test a CDI from a Honda CH250 (Helix scooter) as I have heard that is a good match. It is the five-pin retangular style CDI from the CH250. A Honda (Nippon-Denso I assume) may be a better name brand than the generic Chinese replacements.

Andyvh1959 screwed with this post 04-05-2012 at 10:39 AM
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Old 05-22-2012, 11:21 AM   #20
Andyvh1959
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Joined: Feb 2012
Location: Da frozen tundra, 1.5 mile west of Lambeau
Oddometer: 601
Some updates on the GN400 CDI replacement:

The Cheapo NEW Racing CDI I think is fried, perhaps it could not handle the non-regulated output of the 6v stator on my bike. I got no more spark with it. So either it needs the regulator in the circuit, or I need a better CDI. One thing about it though, when I'd kick the bike over using a spark tester, it was a smaller less robust spark than the stock 30 year old CDI.

So I have moved on to testing the aftermarket CDI for a Honda CH250 (Elite) scooter. This is the older AC fired style CDI with the 5-pin green connector. I wired it into the Suzuki harness like before with the NEW Racing CDI. Spark produced is nice a fat, strong, easily jumped a .250" gap. Once I got it fired up the bike settled into a nice idle, and the throttle response is real good. I have street tires on the bike now, so down the road for a test ride I go. Easily up through the 5 gears and it seems to max out about 7,000, a bit shy of the 8,000 rpm limit. I have no speedo on the bike, so I guess with the 54 tooth rear sprocket I may be getting about 75 mph. The CH250 CDI goes to full 27 degree BTDC advance at 6,500 rpm, so it does limit the bike. Also, normal Suzuki full advance would be 35 degree BTDC, so I bet the bike is running hotter than it should.

But wait,...there's more! When I try to kick start the little beast, most often it kicks back REAL hard. Please no "try starting it this way" or "use the decomp lever like this" because I have tried them all and it kicks back hard most all the time. When I try to bump start it in 2nd gear, most often it just locks the rear tire and slides. So I assume I have some strange timing issue which has advanced the timing for starting. Next step is to pull the magneto rotor and check the timing for the rotor, cams. valves, all of it. Because these GN400s are actually supposed to be an easy starting bike. But not mine!

Umm. what else. Oh! I have mounted a round slide Mikuni VM36 carb, 130 Pilot jet, needle on the 2nd notch from the top (needle low) and stock main jet (I think is a 420). This carb is a good match for the bike, and is more tuneable than the stock CV carb.

I am also working with a supplier for a new CDI/Coil/Plug wire combo unit, that is adjustable for high rpm ignition advance. The price on the AC fired CDI/Coil unit (all one piece) is $143 which is pretty good considering it includes a matched, new coil and is adjustable. So more testing to come folks!
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Old 05-23-2012, 09:42 AM   #21
Andyvh1959
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Joined: Feb 2012
Location: Da frozen tundra, 1.5 mile west of Lambeau
Oddometer: 601
I'm the "Andy" on that GN400 Yahoo Group forum with the ice bike pictured there.

I should have my new combination CDI/Coil/Plug wire system by next week. Its an adjustable AC fired CDI system that I hope will give me a matched CDI and coil setup. Plus its adjustable for the advanced timing curve, which should give me the range to get the rpm up.

And I should have my magneto rotor puller by this weekend. So I can pull the rotor and make sure the timing is correct, or at least prove the rotor key has not sheared.
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Old 05-24-2012, 07:52 AM   #22
eric123
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Location: Idaho
Oddometer: 1,467
Your bike was my desktop wallpaper for quite awhile...
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Old 10-21-2012, 11:18 AM   #23
royota
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I'm new here and was wondering if there was anymore word on the Chinese cdi unit working on the gn400.... thanks for the info so far..
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Old 10-23-2012, 12:14 PM   #24
jings
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Location: dumfries scotland
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Old 10-24-2012, 08:27 PM   #25
royota
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Thumb

Nice bike do you have more pics of it..
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Old 10-25-2012, 02:45 AM   #26
jings
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Location: dumfries scotland
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Nice bike do you have more pics of it..
no only one ive got think it was off the pipeburn site
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Old 10-26-2012, 08:13 PM   #27
dpforth
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Joined: Oct 2010
Location: Fantasy, I mean Vancouver Island
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Quote:
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Nice bike do you have more pics of it..
Here's a bit more
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Old 10-28-2012, 05:54 AM   #28
plugeye
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Joined: May 2007
Location: Garland, Texas
Oddometer: 3,297
i love them.
trying to get my buddy to sell me his basket case
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Old 11-24-2012, 03:35 PM   #29
ArtCuisin
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Joined: Sep 2011
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I had one back in the eighties. It was a commuter for me. I had
a huge topbox on the rear rack. I treated it gently as though that
was all it was. Every night, I would ride this 270 degree downhill onramp.
Over time, I rode it faster and faster. One night, I hung the rear
end out accidentally and it felt fine. After that, things were
never the same. Even though a commuter, Suzuki did use
tapered roller bearings in the steering head. I always wondered
if that was the reason for the good (to me) frontend feedback.

After about 40K of commuting, I stripped it down for the winter
and painted every nut and bolt on the bike. I added clubman
bars--really comfortable because the steering head is really
high, like that of a cruiser, but it looked pretty cool. I kept
the chrome fenders. They looked good against the flat-black.
At the time, Powroll in Oregon still existed and they had a
simple slide-needle carb kit to replace the constant velocity
diaphragm type that was on it. They said it would add 5 hp.
I removed the airbox and put on a K&N sock. And I had somebody
weld up hanger for a shorty XXXXXXX muffler. (Darn, I'm
drawing a total blank for that exhaust manufacturer that
used to have those removable discs--more discs, louder,
fewer discs, quieter.) Anyway, that all made for an even
lighter bike. Of course, I got rid of the battery and all that.
You could see through it. No turn signals, but I used my
hand signals religiously--do I get points? Anyway, it all
made for a blast of a bike from my vantage point. I also
put some stiffer, longer shocks on it, so the modus
operandi on every commuter corner was to hang out
the back end. That was the beauty of the bike's low
power and light weight. You could nail it in every gear
as you slammed it on its side and the thing would do
no wrong. Okay, in the rain one day, the back end
went out too far....,but that was poor judgement. :)

Great bike. I miss mine.
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Old 11-24-2012, 08:55 PM   #30
eric123
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Joined: Mar 2009
Location: Idaho
Oddometer: 1,467
Quote:
Originally Posted by ArtCuisin View Post
I had one back in the eighties. It was a commuter for me. I had
a huge topbox on the rear rack. I treated it gently as though that
was all it was. Every night, I would ride this 270 degree downhill onramp.
Over time, I rode it faster and faster. One night, I hung the rear
end out accidentally and it felt fine. After that, things were
never the same. Even though a commuter, Suzuki did use
tapered roller bearings in the steering head. I always wondered
if that was the reason for the good (to me) frontend feedback.

After about 40K of commuting, I stripped it down for the winter
and painted every nut and bolt on the bike. I added clubman
bars--really comfortable because the steering head is really
high, like that of a cruiser, but it looked pretty cool. I kept
the chrome fenders. They looked good against the flat-black.
At the time, Powroll in Oregon still existed and they had a
simple slide-needle carb kit to replace the constant velocity
diaphragm type that was on it. They said it would add 5 hp.
I removed the airbox and put on a K&N sock. And I had somebody
weld up hanger for a shorty XXXXXXX muffler. (Darn, I'm
drawing a total blank for that exhaust manufacturer that
used to have those removable discs--more discs, louder,
fewer discs, quieter.) Anyway, that all made for an even
lighter bike. Of course, I got rid of the battery and all that.
You could see through it. No turn signals, but I used my
hand signals religiously--do I get points? Anyway, it all
made for a blast of a bike from my vantage point. I also
put some stiffer, longer shocks on it, so the modus
operandi on every commuter corner was to hang out
the back end. That was the beauty of the bike's low
power and light weight. You could nail it in every gear
as you slammed it on its side and the thing would do
no wrong. Okay, in the rain one day, the back end
went out too far....,but that was poor judgement. :)

Great bike. I miss mine.
Damn, yer killing me here. I sold all my GN400 stuff this summer and have been regretting it ever since...
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