No spark on my old mans 400 bandit

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gissmo50
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Bike owned: nc24, Cb400n Bobber, Xj600N
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No spark on my old mans 400 bandit

Post by gissmo50 » Sun Jul 23, 2017 7:04 pm

So im here for my old man used to frequent the v4 section quite abit. Dads got a 91 bandit and that engine had come to the end of its life alot of knocking and vibration so he brought a new engine and fitted it thinking will just swap them over and off i go. turns out not that simple hes brought a 93spec engine to replace the 91 and the timing is off on the timing disc so he has no spark and it wont run. ive seen on here that someone swapped the timing disc from a 93 engine to a 91 and it ran perfectly fine. would it work the other way round if we swapped the disc from the 91 onto the newer 93 spec? or is it a case of finding a 93 spec cdi? i know that getting the discs off can be a Pain in the arse but would it work????

Cheers Kyran

SevenThreeSeven
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Re: No spark on my old mans 400 bandit

Post by SevenThreeSeven » Mon Jul 24, 2017 2:44 pm

The answer is that both solutions are easy to implement, if you're properly prepared. And judging from the bikes you have listed in your profile I'd guess you're pretty handy in the garage.

If you're good at electrical things, then changing CDIs would be easy. But you have to be able to accurately read wiring diagrams because the pin placement in the CDI multi-pin connector plug is slightly different between the '91 model and the '93 model.

Did your replacement '93 engine come with its timing disk pickup wiring and connector installed? If the new engine came with its original timing disk pickup wiring in place and you decide to replace the timing disk with a '91-'92 disk you'll have to change the pin-out of the connector to the bike's wiring harness.

If you're good at doing basic wrench-turning things, then the timing disc change would be easy. But you have to have the basic know-how and some patience and the right tools to do the work. I've pulled the timing disc off of my B4 twice or maybe even three times. If you apply heat to the timing disc retaining bolt it will come out pretty easily. Then, if you apply heat to the timing disc the "puller" will be able to pop it off of the crankshaft relatively easily.

If you go with the "replacing the CDI box" option you'll end up with a normal '93 engine. The '93 model engine was slightly de-tuned to 53 horsepower. The '91 engine was a 59 horsepower engine (the '91 has more aggressive camshaft profiles, from the GSX-R400).

Over the years of GSF-400 production Suzuki played confusing game of mix-n-match with specifications with the various GSF-400 models, in Europe there were country-to-country differences. Some European country-specific models got the aggressive camshaft setup while others did not. Some got the BST33SS carbs while others got BST32SS carbs. And in the U.S. there was even a California-specific model that was so horribly de-tuned for California emissions restrictions Suzuki refused to talk about what horsepower it actually produced (you definitely do not want to put a California-specific CDI on your B4).

Here's a link to an old forum thread that shows the differences between the '91-'92 timing disk and the '93 timing disk. You can see the different tooth arrangement. You can also see that the timing of the spark is slightly "retarded" on the lower powered '93 engine (rated at 53 horsepower instead of 59 horsepower). viewtopic.php?f=53&t=51944&p=371660#p371660

If you keep your Dad's bike's original CDI and swap out the timing disc you'll end up with a bit of a strange cross-breed of the B4. The '93 engine was a more relaxed, less stressed version with only 53 horsepower. The '93 engine has less valve lift and less timing advance designed into the timing disc (as a result of the de-tuned nature of the '93 engine Suzuki deleted a spacer under the intake valve springs and opened up the valve clearance specifications a bit). So your '91 CDI would be commanding a bit more timing advance on the '93 engine's less aggressive camshaft action. I guess it might produce a bit more horsepower than a standard '93 engine.

gissmo50
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Re: No spark on my old mans 400 bandit

Post by gissmo50 » Mon Jul 24, 2017 3:16 pm

I'm fairly handy with the spanners so will will give changing the disc a shot along with correcting the pin out for the cdi. He isn't going to miss any power he rides like miss daisy but it's his work bike and was really dishearent when he swapped the engines and it didn't fire up. Said about this forum and I would look for answers and it seems I have them. Looks like I'm in for a fun Sunday.

Cheers Kyran

SevenThreeSeven
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Re: No spark on my old mans 400 bandit

Post by SevenThreeSeven » Tue Jul 25, 2017 12:46 am

just to be sure I'm not confusing anything, the situation I was trying to describe is an "either do this, or do that" but not both...

It was a "pick one of these two solutions" thing:

Solution #1. The CDI connector pin-out would only need to be changed if you decided to keep the new engine's '93 timing disk and replace the bike's '91 CDI with a '93 CDI (in this case the CDI connector plug in your bike's old '91 wiring harness would be a mis-match with the '93 CDI connector plug).

Solution #2. If you're simply going to swap in a '91-'92 timing disk on the bike's new '93 engine then there would be no need to change the CDI connector plug pin-out (because you didn't change the '91 CDI and its connector plug already works with the bike's '91 wiring harness).

gissmo50
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Re: No spark on my old mans 400 bandit

Post by gissmo50 » Mon Aug 07, 2017 11:09 am

yep fully understood this and we went down the timing disc route got the 91 disc off the engine without much fuss tbh three leg puller and a good torch took care of that and just for practice sake we put it back on the engine. Dad buggered off on holiday now so we are going to swap the disc when he comes back. we havent an wont be touching the wiring as you say the cdi and pick up will be the same with as the came off the 91 so no need to mess with them when putting on the 92 disc only if changing to a 93-on cdi which we are not.

Thanks Kyran


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