'92 Bandit 400 won't fire

[Fishfried]

Hello folks! 

  I'm new here, I've been reading lots of posts on the GSF400.  Great info!  I am by no stretch of the imagination a mechanic.  I'm more suited with welding and fabrication.
  I just purchased a 1992 Bandit 400.  The bike has 6,200 miles on it and looks nearly new.  VERY little wear.  Bad news is that it won't run.
  Here is the story from the second owner:  Bike purchased from original owner with 4,000 miles in 2011.  Ridden for 2,000 miles in summer of 2011 until on day while riding in a sudden rain the bike ran rough and stalled out.  Carbs were gone through and cleaned at this point and bike still refused to run so it was put in the corner of a garage and left until now.
  Fast forward 4 years...I come along and buy the bike for not much money.  I have the bike at a mechanic shop that specializes in Suzuki and is really experienced with fuel system, carbs and such.
  He put a new battery in, cleaned the carbs entirely (pointed out that they had been drilled, he said the screws were backed out quite a bit, four turns I think) new spark plugs.  He has an IV bag hooked up with fuel and the engine cranks strong but won't fire.  He will clean the tank when he gets the bike to run and will change oil and oil filter.  With starting fluid (ether) still nothing. He says the plugs spark against the block but not as bright blue as he thinks they should.  He is stumped and asked that I look up some info on the web.
   Using the search function here I came across a few posts that make me think that it may be the CDI.  I can get capacitors and have an IT guy at work that can easily swap them out, he is great with circuit boards and such .  I'll wait to do this until I for sure know it is the problem.
 I keep thinking back on what the guy said about it stalling out in the rain, anyways, can anyone help troubleshoot this?

  Thanks in advance, I know a heck of a first post 

[greg737]

I think you probably got a really good deal on a motorcycle that can easily be fixed.  A time-capsule bike. Congratulations on the "barn find".

It's good to hear that you've got access to somebody who really knows electronics.  I think that's where you're going to find the problem.

The back-story that the prior owner told you is probably all true but I'm betting he left out some important information (because he didn't realize it was important).  The problem that caused the bike to quit during the rainstorm probably isn't the same issue that's currently preventing it from starting.

When a bike refuses to start people get frustrated and they get abusive, they crank the bike until its battery goes flat then they put jumper cables from a running car onto it which seems to be a contributing factor to CDI death.

Of course, the cause of your Bandit's failure to start could be completely unrelated to the rainstorm.  It could be that the true problem simply happened to occur then (during the rainstorm) and the prior owner became convinced the two were related.

For example: It could be that the wiring for your Bandit's pulse generator (the Variable Reluctance sensor) located under the engine's left-side cover has been broken or chafed and grounded out on metal.  The wiring for the pulse generator (two wires: one brown, one black) are very small and easy to break.  Without a recognizable signal from the pulse generator the CDI will not fire the spark plugs.

Although, if there really is a water-related issue with this Bandit, you could end up finding and fixing some sort of owner-caused follow-on damage (like a fried CDI) but still have the original water-related problem.  When I got my Bandit (a multi-owner 1993 model in pretty rough cosmetic condition) I found that every drain-hole for the spark plug recesses had been plugged by some sort of mud-dauber wasp (the holes were plugged tight with a natural cement made from wasp spit and tan colored dirt).

[ventYl]

google, download and read through bandit service manual. it is available on the internet from many different places. section 6 contains description of electrical system. section 6 page 5 onward contains description and instructions for inspection of ignition system. if inspection shows that all CDI peripherials (signal generator, wiring, relays, ignition coils, spark plugs, HT wires) are OK then the CDI is at least half-dead.

personally i won't be so scared of cranking the bike connected to running car as I did it several times on several bikes with no damage at all.

if you find out that CDI is most probably bad then either you can try to measure drop of the voltage on ignition coil driving pin while cranking. Right now I don't remember actual values but at least if values for left and right coil will be significantly different (let's say more than 30%) and/or if voltage won't drop below 3 volts you can freely give the CDI to IT guy.

For me personally replacement of final stage switching transistors made more success than changing capacitors. If capacitors are fried (which can be examined by looking at their top, fried capacitors usually have top side bent out) timing is unstable but bike should at least cough while in cranking mode both IC charge impulse and spark fire advance are fixed. If switching circuitry is fried nothing happens even with correct timing.

For me, TIP150 switching transistors worked as drop-in replacement even if they don't have required parameters (transistors used originally are not available anymore nor any other suitable replacement). But with price around 5 Eur per unit with two units required and drop-in replacement character i opted for tryout and it worked. Capacitor replacements are generally available.

PS: One information i found meanwhile is that Bosch is producing switching transistors which may have required specs. They are used in Bosch's own devices and often used in things like megasquirt.

[Fishfried]

Thanks fellas!  The bike does sputter and cough.

 
 
For example: It could be that the wiring for your Bandit's pulse generator (the Variable Reluctance sensor) located under the engine's left-side cover has been broken or chafed and grounded out on metal.  The wiring for the pulse generator (two wires: one brown, one black) are very small and easy to break.  Without a recognizable signal from the pulse generator the CDI will not fire the spark plugs.

I will look for this tonight, in the manual.  We haven't thought of this.

[Fishfried]

google, download and read through bandit service manual.

I do have this manual.

For me, TIP150 switching transistors worked as drop-in replacement even if they don't have required parameters (transistors used originally are not available anymore nor any other suitable replacement). But with price around 5 Eur per unit with two units required and drop-in replacement character i opted for tryout and it worked.
 
I can only find TIP120 here locally at the electronics parts store, you think these will work?

Thanks!

[ventYl]

TIP120 has lower h_FE coefficient than TIP150 one. If there is some store which is able to deliver them wait for them. Or order them via internet. The h_FE is the most significant difference between TIP series and original switching circuitry and makes the biggest concern for me.

[Fishfried]

TIP120 has lower h_FE coefficient than TIP150 one. If there is some store which is able to deliver them wait for them. Or order them via internet. The h_FE is the most significant difference between TIP series and original switching circuitry and makes the biggest concern for me.

I went to NTE Parts Direct and got the TIP150's and the proper capacitors (all three types). All are heat rated, the ones at Radio Shack were not.

[Squishy]

Have a look at the spark plug wires and connectors. My 400 ran rough very often in heavy rain because the plug didn't connect properly on the valve cover or the drainage was glogged. New spark plugs should've fixed that unless your wiring to them got damaged.

If it's not that.. it kinda has to be the CDI....

...If you trust your mechanic, that is.
If the carbs are clean and functioning, and you have clean fuel... If you airbox is stock and clean... if all 4 cylinders have proper compression.. only spark/ignition remains.

That is if the 2nd owner told the truth and it really has only so few miles on it.


Don't forget to check on other "logical" things. It could've been just worn spark plugs because of rain - only after rebuild something like the choke-mechanism got stuck. Stuff like that!

[Fishfried]

 

Have a look at the spark plug wires and connectors. My 400 ran rough very often in heavy rain because the plug didn't connect properly on the valve cover or the drainage was glogged. New spark plugs should've fixed that unless your wiring to them got damaged.

If it's not that.. it kinda has to be the CDI....

...If you trust your mechanic, that is.
If the carbs are clean and functioning, and you have clean fuel... If you airbox is stock and clean... if all 4 cylinders have proper compression.. only spark/ignition remains.

We checked the wires, coil, magneto etc. last night with a meter.  I pulled the CDI and took it apart, nothing visually looks bad.  I'll update early next week if the CDI repair works. 

That is if the 2nd owner told the truth and it really has only so few miles on it.


Don't forget to check on other "logical" things. It could've been just worn spark plugs because of rain - only after rebuild something like the choke-mechanism got stuck. Stuff like that!

[ventYl]

New spark plugs of correct type and spark plug leads won't hurt in any way. But IMHO spark plugs would be the cause only if bike ran fine during warm weather which isn't.

[Fishfried]

UPDATE!: 

  Here is the deal.  I got all the 5 big capacitors and the two transistors for the CDI and gave it to the IT guy at work.  After a week he brought it in today and and I went straight to the mechanics after work tonight and plugged it in.  wewewewwewehVRRRRROOOOOOMMMM!  Fired up in about 5 seconds.  Last time it ran was 2011.  It blew out some smoke for a minute but settled down.  Purred nicely, engine ran smooth.


  Now for the bad.  Mechanic had a spray bottle of water and 3 of the 4 pipes were crazy hot the one on the right was hot, but obviously not as hot as the others.  Maybe the carb has a clogged jet, valve stuck?  Where do I go from here? 

[Fishfried]

Here is the bike.

[greg737]

Nice looking Bandit!

I'm not betting on a carb problem here.  With 3 out of 4 cylinders firing nicely the odds on it being a carb problem falls into the long-shot range.  In fact, if the cold cylinder had a weak carb it would still be helped along by the other three and would probably fire eventually (as the bike warmed up).

Instead I'm betting on it being an ignition problem.  But just a small problem.

I'm sticking with the abusive-prior owner theory (which I believe is backed by the burned up CDI box).  I think the next thing you should check is the HT lead for the cold cylinder.

Because you've got 3 hot and 1 not that means both of your coils are healthy.  I'm betting that the HT lead to the cold cylinder's spark plug has been compromised (roughly handled) in some way by the prior owner.

[Squishy]

I don't agree.
My 400 has had many 3 cyl problems and they were always caused by either fouled spark plug or because the pilot jet was clogged with stuff.

I cleaned the pilot jet and problem solved.

[El Gringo]

Blocked Pilot Jet 99.9% Guaranteed

Mines has done it 3 times, now have a filter fitted