400 GS6 cranked backwards

[Steve Minor]

Had a strange thing happen today......only happened one other time since I bought my 1977 400 GS6 new. It cranked backwards. I can tell you that really screws you up when you dump the clutch. It's been kicking back lately when I crank it and I fiddled with the timing recently, bit I thought I set it back to 2.4mm BTDC.

Any ideas?

Steve Minor
Wilmington, NC

[firstturn]

Steve,
  Normally what is happening is that your timing is REALLY questionable.  Check it and double check it. .

Ron Carbaugh

[Mick Milakovic]

Steve, I had that happen to me on a 390 Husky once; turned out it sheared a flywheel key enough to turn the rotor 180 degrees and still fired and ran!  I pulled the flywheel, replaced the key, and it ran perfect.  Hope this helps,

Mick

[Mike Hufnagel]

I had a TZ 350 do that to me. What was really weird was that I had to punish start it. Backing off the timing cured it.

'12 Husaberg TE300
74 Yamaha TY 250
84 Yam IT200
75 Jackpiner w/ 250 eng.
82 KTM GS250II (import)
82 KTM 495 (2)
98 KTM 300mxc
04 KTM 125 SX
00 KTM Duke 2/rd. racer
06 KTM 950 Adv.
08 Suzuki DR70Z

[Ed Chesnut]

Starting backwards on occasion is a prime symptom of advanced timing combined with a slightly less than firm kick.

The piston heads up the bore (a bit more slowly than usual) and the spark comes wayeeee before it is supposed to (relatively speaking), and the piston is powered back down the bore without ever getting to the top of the stroke.  The spark/fuel powered motion is strong enough to drive the engine backwards all the way around and bring the piston up to and thru TDC, the spark comes a bit after the piston starts going down . . . but things are "close enough" for it to simply keep running in the reverse direction.

This can be a relatively frequent occurance on vintage trials engines when the timing is set strongly advanced for crisp throttle response.

Definitely re-check/adjust your ignition timing, that should cure the problem.

Ed

Keep the rubber side down!

[tanz]

I can top that. At this years Reunion ride I went down in a mud hole on my 400, the bike never stalled, when I got it up and started to let the clutch out it went backwards. I had to shut it off and restart it.

Steve

77 GS6 400
73 Hare Scrambler 250
72 Six Days 125
71 Cat 350X

[Big Mac]

Used to happen with my Harescrambler 250 when I kicked it left-footed and sorta wimpy. Timing was right on, just didn't spin it right. Ran perfect otherwise. If it runs good, no pinging from too advanced timing, wouldn't worry about it.

[tomale]

It happened to me at the. Reunion ride in 04,  I had stopped to wait for some of the other guys on my minute and when I gave it a boot it started but I dud know it was running backwards until I tried to take off.  To my surprise I managed to jeep from making a complete fool of myself.  When I got home, I checked the timing,  it was spot on.  Maybe Ed is right, a wimpy attempt at starting the bike contributed to it running backwards.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
74' 1/2 440 maico
70' 400 maico (project)
72' cr125 Husky (project)
93' RMx 250 suzuki
Honda TL 125
2004 Suzuki DL1000

[johnborn]

I had heard of this happening but did not really believe it until i saw it with my own two eyes.I had a 1983 honda cr125,in perfect running condition.My brother started it up,eased the clutch out and she moved backwards.shut it off, restarted it backwards again. shut it off restarted it and it was normal again,and never had this happen again.I always guessed that if the piston is just short of tdc when you kick it, and you dont give it a full kick,the fuel mixture fires just before tdc and drives the piston backwards.

[firstturn]

If it is a real problem and you are sure your timing is correct you can put a in line rectifier and it will only let the current go one way.  Since you brought up Honda most of the older Hondas have one.

Ron Carbaugh