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Old 11-25-2012, 06:14 AM   #31
argentcorvid
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Joined: Oct 2010
Location: Marshmellow-town, Iowa
Oddometer: 449
Quote:
Originally Posted by ArtCuisin View Post
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.)
Supertrapp.
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Old 11-25-2012, 05:40 PM   #32
NJ-Brett
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Location: Southern New Jersey
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These look like cool bikes.
I wish Suzuki would dust off the gn400 motor and make a TU400.
The old gn250 motor looks very close to the TU250 motor.

It also looks like a great platform for my dream bike, a standard with a good seat, dual shock, street and mellow dirt bike that can do 2 up on the street with some comfort, enough suspension and low weight to do well on dirt roads and trails, robust and easy to service, and cool sounding.

I had a number of old Triumph Daytona's and they fit the bill, but were flawed with a lot of vibration (broke things), a 4 speed trans, a weak clutch and transmission.
If you could fit a modern air cooled motor in that frame, it would have been great.

I will add this bike to the list of great bikes you can no longer get parts for, the sr500, the sl350, gn400, etc.
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Old 12-31-2012, 07:56 PM   #33
royota
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Gn400

Quote:
Originally Posted by eric123 View Post
Damn, yer killing me here. I sold all my GN400 stuff this summer and have been regretting it ever since...
Eric I sold one a couple years ago and regretted it. I kept a titled frame and recently bought a couple motors and parts from the guy you sold your bike and parts to. I'm missing the cdi and dont want to spend the coin on an ebay unit so I have been wanting to get info on a different route.
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Old 01-01-2013, 01:39 PM   #34
eric123
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Quote:
Originally Posted by royota View Post
Eric I sold one a couple years ago and regretted it. I kept a titled frame and recently bought a couple motors and parts from the guy you sold your bike and parts to. I'm missing the cdi and dont want to spend the coin on an ebay unit so I have been wanting to get info on a different route.
Unfortunately I don't have one. The guys at he Chinden shop may have one. They had a old DR400(same motor)awhile back that would have the same unit.

Don't forget to post pics too...
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Old 01-16-2013, 03:41 PM   #35
Andyvh1959
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Location: Da frozen tundra, 1.5 mile west of Lambeau
Oddometer: 610
Newest update on the CDI replacement on my GN400 ice racer/flat-tracker:

The combo CDI/COIL unit proved out to not produce enough spark energy to do anything more than just idle slowly, with the plug gapped at only 0.015". Generally speaking, a coil must produce about 1000 volts output per 0.001" of plug gap. So for the typical 0.025" spark plug gap the coil must output about 25,000 volts. Well, I proved the combo CDI/COIL unit I was testing could only produce maybe 15,000 volts. Enough to make it idle but it would not run on ANY addition throttle.

So I went back to the stock Suzuki coil, fired by a Honda CH250 scooter CDI, using the P1 pulser (red/green wire from the timing plate) signal for 10 degree BTDC static/idle timing. Plug gapped at 0.025", bike fired easily on one kick stone cold. Idled out steadily nice, right away, on the Mikuni VM36 round slide carb I mounted. I played a bit with the carb tuning, have the needle on the middle clip position. I did find out I was using the P2 trigger signal to the CDI previously. Doing that advanced the static timing to 25 degrees BTDC. NO WONDER the damn thing was kicking back SO hard!! Now with the P1 trigger to the CDI it kicks easy and starts right off.

I have heard from some tuners that using the CH250 (Elite scooter) CDI causes the bike to run hotter because of the internal advance curve in the digital CDI. Not sure I agree with that. The bike is using the P1 trigger signal for idle timing and the advance on the CH250 CDI doesn't start until about 2500 rpm. More to come one I get the bike on the ice to test it out. Sure looks cool for a lowly GN400 doesn't it?
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Andyvh1959 screwed with this post 01-16-2013 at 04:10 PM
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Old 01-20-2013, 10:10 PM   #36
royota
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gn400

Thanks Andy for the PM and update is there a wiring diagram you can post, that would be a great help.
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Old 01-21-2013, 12:49 PM   #37
Andyvh1959
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Location: Da frozen tundra, 1.5 mile west of Lambeau
Oddometer: 610
If you go to yahoo.com/groups and look up the GN400 group you'll find all kinds of details on wiring, ignitions, service manuals, mods, etc. Myself and a core group of members have done quite a bit of work on these GN400s.

Try this:
http://autos.groups.yahoo.com/group/GN400/

My next test will be of a CDI for a newer model GN250. I found one on ebay for $30. Worth a try.
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Andyvh1959 screwed with this post 01-22-2013 at 08:07 AM
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Old 01-21-2013, 02:48 PM   #38
jjgres
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My pop rode a GN400 from Miami to San Diego and back.

No problems.
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Old 01-23-2013, 07:20 AM   #39
Turbo Ghost
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I had an 81 GN400 from 1990-91. It was the black and gold model with the Enkei mag wheels. Bought it for $500. I rode the heck out of that thing! Had a lot of fun on group rides firing Meguires! (hit kill switch at speed and pin throttle then switch back on for a massive boom!) I eventually traded it for a Virago but, I put several thousands of miles on it while I had it. Great little bike!
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Old 03-01-2013, 08:47 AM   #40
Andyvh1959
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Location: Da frozen tundra, 1.5 mile west of Lambeau
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I'm working with a aftermarket producer of CDI units to develop a reliable, inexpensive, modern CDI to replace the heavy, ancient 33+ year old NipponsDenso CDI on the GN.

I'll be testing four different CDI units, along with tracking the advance curve and max rpm capability, and butt-dyno evaluations.
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Old 03-02-2013, 09:33 AM   #41
nanno
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Quote:
Originally Posted by Andyvh1959 View Post
I'm working with a aftermarket producer of CDI units to develop a reliable, inexpensive, modern CDI to replace the heavy, ancient 33+ year old NipponsDenso CDI on the GN.

I'll be testing four different CDI units, along with tracking the advance curve and max rpm capability, and butt-dyno evaluations.
That's when the name Ignitech.cz springs to mind... they have been making those for quite a few years. Additionally they're available for next to nothing from Hong Kong... maybe you want to check them out, before you invest lots of money in R&D.

Cheers,
Greg
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Old 03-04-2013, 06:48 PM   #42
Nessman
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Hey Eric123:

http://www.dotheton.com/forum/index.php?topic=35688.0

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Old 03-04-2013, 06:50 PM   #43
Nessman
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[/QUOTE]

Sweet, I had a GN for a while but couldn't see that bike in it...it ran sweet with some fiddling, now I'm wishing I had it back.
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Old 03-05-2013, 03:04 PM   #44
argentcorvid
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Quote:
Originally Posted by nanno View Post
Additionally they're available for next to nothing from Hong Kong...
is this just a GN thing? Or CDIs on general? I know about ignitech, but the possibility of an cheap alternative is interesting. Got a CB400 that needs a new spark box.

Posted during work using magic
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Old 03-05-2013, 03:21 PM   #45
Andyvh1959
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Location: Da frozen tundra, 1.5 mile west of Lambeau
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I look at it this way, CDIs dating back to the mid 70s into the mid 80s are heavy, clunky, prone to vibration induced solder joint failures (somewhat common on the old Nippon-Denso Gen 1 series CDI unit). To buy a salvage CDI is a crap-shoot at best, and all you're getting is a possible copy of your problem CDI for a lot of bucks. There are more and more modern tech CDIs that are inexpensive (damn near cheap!), lightweight, readily available, durable, that can easily replace the ancient OEM units. Its not entirely hard to match CDIs for current engines to many of the older/vintage/classic bikes we enjoy to wrench and ride.

Hey Marshalltown! Been through there on a RAGBRAI ride, on my homebuilt/scratchbuilt recumbent. Nice town, like most back roads Iowa towns are.

That GN is actually a fun bike to work on and learn from. Like I have been doing for the past two years. Cheap to buy, some people nearly give them away. Simple little two-valve long stroke thumper that is cheap to buy and update. Responds well to home-tweaking, like VM36 Mikuni carb and Supertrapp pipe. Now I hope to find a bit more oommph via the ignition system.

The engine in my GN right now is one I bought for $40. Pulled the head, cleaned it up, checked the piston and rings, ring gap, bore condition, etc. Reassembled and set the valves, cam timing, etc, starts easily on the 1st kick. So now I have an extra engine to build up, bore out, shave the deck, cam, etc. I have heard of this lowly engine pushing well past 40 hp.

Since I stripped most of the street stuff off this bike, it now weighs in at only 285 pounds fueled up.
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Andyvh1959 screwed with this post 10-09-2013 at 11:50 AM
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