Author Topic: 400c running backwards  (Read 513 times)

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Offline iranana

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400c running backwards
« on: October 03, 2018, 11:46:48 PM »
Hi all, just wanting to pick your brains. I also made a post about this on the 2SW forums since my 400c is using a Vintage Smoke/Dyna S ignition:

http://www.2strokeworld.com/forum/index.php?topic=34728

Needless to say I am a bit concerned about this incident (and the other reports of it don't help), but from what I can tell it's not necessarily 'unnatural' for a two stroke to do this. Has anyone else had experience with their RD running in reverse (whether using points, stock CDI, aftermarket CDI etc), and what did you do to address the issue? My best guess is that I didn't kick the bike hard enough for it to push past TDC, so the piston just got shot back down before TDC, turning the crank in reverse. But, I've never had this happen on my 250E under any circumstance...

Offline Lute

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Re: 400c running backwards
« Reply #1 on: October 04, 2018, 03:42:47 AM »
Hi,

I am new here. I’ve owned my 1975 RD350B for a few weeks. I have experienced the same phenomenon twice now. I can’t explain it. But, I’ve heard that running in reverse can happen. I have just killed the engine and restarted without any apparent problem. It is a little unnerving to release the clutch and backup as if I am in reverse gear.

Offline magbuster

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Re: 400c running backwards
« Reply #2 on: October 04, 2018, 09:03:00 AM »
Hi

Seen it happen on a Garelli.

Deliberately stalled and re-started and then engine remembered  the way it is required to run.


Offline Sneck

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Re: 400c running backwards
« Reply #3 on: October 04, 2018, 02:10:12 PM »
Had this happen on a 400E in 1979 , no body believed me , I realised when I put it in gear.
If it ain't smokin it's broken

Offline D Peacock

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Re: 400c running backwards
« Reply #4 on: October 05, 2018, 07:11:56 AM »
The original Powerdynamo system could do this (usually sign was the tacho stopped working). The later versions have tapered magnets so it can only spark in one direction.
Yes I am this abrupt in real life but I don't lie or talk sh*t so live with it.

GSXR1100 - The behemoth and every day commuter
GSXR400RKSP - Mainly track tart
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Online splant

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Re: 400c running backwards
« Reply #5 on: October 05, 2018, 09:34:31 AM »
Must have fired the very first upstroke of the piston ,if your leg swung to the bottom  of kickstart stroke it would be fine I should think .
oops i think my powerbands snapped .

Offline hamsav

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Re: 400c running backwards
« Reply #6 on: October 10, 2018, 04:35:31 AM »
Seen it once  ( Suzuki OM 50 ), unbeknown to the rider  who started the bike in the garage  , leaned right over the handle bars in anticipation of a full rev dropping of the clutch.........anyway the thing took off backwards leaving a black stripe  a short distance  to the back wall of the shed and up over some planks laid on the floor against the wall  and up the wall of the shed where upon the bike flipped right over and landed on the un witting pilot,  funniest thing I ever saw.... 'cept maybe the look on the guys face mid  flight  :D...............after a few more beers we all tried to ride it round the yard backwards.......with predictable results  and a lot more laughing
« Last Edit: October 10, 2018, 04:38:56 AM by hamsav »
My biggest fear in life is that when I die my wife will sell my bikes for what I told her I paid for them

Offline (F5)

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Re: 400c running backwards
« Reply #7 on: October 10, 2018, 06:34:03 AM »
Yeah hold your horses and don't just rush in to fix it.

YouTube the attempts like above post.

Then when you tire of that fix the ignition timing.  It is retarded which means it is firing too close to top dead centre.

Offline iranana

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Re: 400c running backwards
« Reply #8 on: October 10, 2018, 10:53:34 AM »
After some investigation, it looks like it was able to run backwards due to the magnetic trigger losing strength. This was probably caused by my failed voltage regulator (forgot to check it!!!). The heat in the rotor and stator was enough to damage the magnets in the trigger.

Instead of getting one spark per cylinder, I was getting three sparks (there's three magnets in those triggers), creating the opportunity for the engine to fire backwards when it kicked back (and keep running backwards). It ran pretty badly before I pulled it apart, I had thought my timing had somehow drifted way off (which I guess it had).

So in light of this, I'm ditching it all for a Powerdynamo setup. A slightly expensive mistake, but nothing too major at the end of the day ;)

Offline Blackhat400

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Re: 400c running backwards
« Reply #9 on: October 10, 2018, 11:25:55 PM »
My DT400 did this,  [rex speed shop cdi ],  the revcounter not working is the first sign,  and it fooked the oil pump,. Any way it was too far Advanced,  i retarded the stator plate fully on the slots, and it still did it,,  notified   Rex,  he said were having issues ,[ only bench tested ].  but when fitted to the bikes, he hadnt taken in that the flywheels keyways wernt all the same,betwen models,,  so i had to slot the back plate, by 20mm  ,to solve the problem,
you"l be to far Advanced,

Offline Aardvark

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Re: 400c running backwards
« Reply #10 on: October 11, 2018, 07:26:35 PM »
My brother had a jawa 250, he could get it running backwards and ride round the pub carpark. He became very good at riding in reverse.

I had forgotten about that until I saw the post.

Good times.

Offline Blackhat400

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Re: 400c running backwards
« Reply #11 on: October 11, 2018, 10:16:35 PM »
I"v met you Advark , at the Blackpool rally[ 2012]  Whiles on the subject, [timing]  here a good read,  about Rex speed shop,  admission that his units were wrong,
https://yamaha-enduros.com/index.php/forum/performance-improvements/7305-rex-s-electronic-ignitions?start=0

Offline Aardvark

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Re: 400c running backwards
« Reply #12 on: October 12, 2018, 06:18:26 PM »
Hi Tophat

I remember you, hope you are well and enjoying this storm at the moment.

I have just had a hell of a trip back home through the lakes.

Time to sit and relax and let the weather pass over.

Aardvark