xs400j maxim weak spark

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foundation982

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Hey guys long time honda twin mechanic here, But this one has me stumped. I had a seca 400 as my first bike and loved that thing. Now I picked up a maxim 400 for $150 its a piece of junk. I got a reading on the coils with a resistance of 3.10 manual says it should be 2.75 ohms +10% and I turned it up to 20k and tested the secondary (spark plug cap to coil pigtail) and got a reading of 18.8 ohms manual says it should be 7.9 + 20% ohms. I replaced the spark plug cap with a NGK one I had and it lowered the secondary to 14 ohms. Is the high resistance what's preventing me from getting a strong spark?

I also read that when you flip the key on and it sparks immediately and when you shut the key off you get spark the ignitor is going bad. Mine sparks when the keys on and after it sits for a bit.

Lay your DOHC knowledge upon me. I'm a little stumped.

Also near me is a "$500 scrapper" race I may enter it in because the DOHC motors have some power to them, the cc requirement is 400 or less :thumbsup: but you can only spend $500 on your race bike (excluding tires and brakes) and it has to race for 24 hours.
 
Welcome Foundation!

Keep in mind the accuracy (or lack there of) of your meter. If the readings from both coils are similar to each other and are reasonably close to spec you should be fine. The plug wires are removable from the coils. Unscrew the plastic nut then un-thread the wire. Test the coils without the wires. Then test the wires and caps separately. The TCI shouldn't spark the coils when you turn the key on, but it will shut down the power to the coils if there hasn't been an ignition event in about 20 seconds (I think that's correct), and you will get a spark from both coils at that time. Sounds like your TCI is operating correctly. It may be wise to remove the cover and reflow the solder joints anyways.

FYI, the Euro / Canadian TCI module (TID12-07) has a better advance curve than the US spec module (TID12-08). It will make more torque and top end power.

If you haven't already done so, it would be wise to replace the plugs, even if they look okay. And clean the carbs excessively! Most people take 3 or more cleanings to get them working well. 12 hrs in an ultrasonic cleaner with a mild acid solution should do the trick. Seriously. Been there... ;)

Good luck and keep us posted, including pics!
 
16VGTIDave said:
Welcome Foundation!

Keep in mind the accuracy (or lack there of) of your meter. If the readings from both coils are similar to each other and are reasonably close to spec you should be fine. The plug wires are removable from the coils. Unscrew the plastic nut then un-thread the wire. Test the coils without the wires. Then test the wires and caps separately. The TCI shouldn't spark the coils when you turn the key on, but it will shut down the power to the coils if there hasn't been an ignition event in about 20 seconds (I think that's correct), and you will get a spark from both coils at that time. Sounds like your TCI is operating correctly. It may be wise to remove the cover and reflow the solder joints anyways.

FYI, the Euro / Canadian TCI module (TID12-07) has a better advance curve than the US spec module (TID12-08). It will make more torque and top end power.

If you haven't already done so, it would be wise to replace the plugs, even if they look okay. And clean the carbs excessively! Most people take 3 or more cleanings to get them working well. 12 hrs in an ultrasonic cleaner with a mild acid solution should do the trick. Seriously. Been there... ;)

Good luck and keep us posted, including pics!
Click to expand...

Ahh I was fearing of taking the coils out of the frame :doh: I had such a great experience with my seca when buying this I was like "oh that that thing should also come to life quick and be decently reliable" I currently just relocated to TN from IL and now have limited tools. Definitely living with my parents before was a huge help my dad had almost every tool anyone could possibly need.

Regardless I guess I'll bite the bullet and drop the engine down to get to the coils and properly test them. Also the multimeter I'm using is a free coupon harbor freight crapometer so who knows. It's worked pretty well for me on the past. I think the ignitor is working correctly then, but when I turn the key on the first spark (without cranking) it gives is a good blue arc, but after I start cranking it its a weak yellow/orange spark. (no its not the battery I hooked a higher cranking hour and higher amp hour battery from a different bike on it and it has the same symptoms)

Oh I also took the carbs apart upper diaphragms look perfect and the lower end of the carbs are spotless float bowls move as they should and all the jets needles etc are clear. I think someone cleaned them trying to get it running before me but I think the weak spark ignition problem is whats causing it. I've only got it to back fire a couple times and both times black smoke shot out the tail pipe.
 
Last edited:
Clean your engine ground. A bad engine ground will cause weak spark when cranking. Sometimes the fuses don't make good connection. Carefully clean the terminals, they are very fragile!

Once you get it running, you may find the carbs aren't as clean as they look. There are some very small passages and ports that can get plugged with corrosion. One of our forum t-shirts says it all... You've been warned! :)
 
16VGTIDave said:
Clean your engine ground. A bad engine ground will cause weak spark when cranking. Sometimes the fuses don't make good connection. Carefully clean the terminals, they are very fragile!

Once you get it running, you may find the carbs aren't as clean as they look. There are some very small passages and ports that can get plugged with corrosion. One of our forum t-shirts says it all... You've been warned! :)
Click to expand...

I took the coils out and primary still 3.1 ohms, Secondary is 9.2 ohms. I also bought new plugs and put them in and I'm getting the same weak spark. I once again tried my brand new battery from my other bike and tried to get good spark.

I'm starting to think something is going on in the left cover with the timing contactors.
 
Sounds like your coils are ok. Did you replace the plug wires? Or trim them a bit? Did you clean the engine ground and the fuse connections? The ignition switch and kill switch are other possible areas for poor connections.

If you are getting sparks when the engine is cranking, I doubt that the triggers are faulty.

Keep at it and be thorough. You have 30+ years of previous owners and their poor maintenance/storage to work through.
 
16VGTIDave said:
Sounds like your coils are ok. Did you replace the plug wires? Or trim them a bit? Did you clean the engine ground and the fuse connections? The ignition switch and kill switch are other possible areas for poor connections.

If you are getting sparks when the engine is cranking, I doubt that the triggers are faulty.

Keep at it and be thorough. You have 30+ years of previous owners and their poor maintenance/storage to work through.
Click to expand...

I trimmed them back a bit and they're resistance seems fine. I cleaned the fuse connections although the plastic bits that hold the fuse in place are cracked off I may get an external fuse holder or a replacement. I just want to hear the thing run to know if its worth investing more money into. I'll have to look into the ignition switch and kill switch.
 
I'm going to sound like a broken record, but what about the engine ground cable? Cleaned both ends and making good connection? Or at least connect a jumper cable directly to the engine and the battery negative for testing...
 
16VGTIDave said:
I'm going to sound like a broken record, but what about the engine ground cable? Cleaned both ends and making good connection? Or at least connect a jumper cable directly to the engine and the battery negative for testing...
Click to expand...

Haha Did this test exactly today. Is there another ground you were referring to before? This is the one I checked and cleaned I also did the jumper able trick and still had weak spark.
 
Are you using resistor plugs? If your spark plug is labeled with an R on it that means resistance. Try finding the proper spark plug (NGK D8EA) which is non resistance. Should improve the quality of the spark
 
I'm running resistor plugs (NGK Iridium) and boots (NGK 5 Ohm) without issue. My spark is an intense blue white and I don't have any misfiring, even when riding in a torrential downpour.

If the coils, wires, etc. are in good shape, having more resistance isn't a problem and will produce a hotter but shorter duration spark.
 
Figured out the problem, I took all the coils apart they all tested out fine, Cut the wires back a bit and cleaned up all the contacts. I found the ground near the ignitor wasn't making good connection and starting getting bright blue spark! I plugged the coils in and it fired right up idled perfect too.
 
Does anyone know what calipers can switch over to the maxim 400? the Maxim is completely missing it's caliper. My SR500 has the same caliper but I see a lot of xj750 calipers cheap on ebay can anyone confirm fitment?
 

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