Help!! Bike won't start and only occasional spark

I recently purchased 1982 xj750 maxim and it ran great when I purchased it. My speedometer started grinding inside the Atari and wouldn't move consistently like it used to. I planned on replacing and updating my speedo at some point, so I decided to get rid of the Atari. I half way got my new speedo hooked up and decide to start my bike. It wouldn't start without me having the throttle down all the way. I could tell it wasn't running right. It was very hesitant and as soon as I let off the throttle it would die. There was also a lot of backfire and it even threw some flames and popped. I tried a few more times but it would only start if I gave it full throttle and didn't let off. Even then, it would rev up however. I walked away from it for a day and came back to it. Did a little more tinkering with the new speedometer and decided to give it another shot. This time it fired right up and idled no problem. I let it run a few minutes and shut it off. I took of the speedo and decided to run around with no speedo or tach for a day or so. Got everything together and it wouldn't start again, only pop and backfire.

At this point, I went through some forums and did some researching and decided it might be the carbs. The guy I bought it from said it may need the carbs cleaned, but up until this point I hadn't had a single issue with it at all, so I figured I would wait until winter until ride it until then. I took of the carbs, cleaned them, and replaced the air filter and deleted the box. I got four air filters that attach right to the carbs, as to make it easier to clean them next time. Got it all back together, and I barely get even a backfire. I smell gas and it seems like I have combustion, but it just keep trying to start. I have headlights, high beam, blinkers , tail lights and break lights. But I can't get it to fire up. I get a little combustion but it was like i need more spark. Checked my plugs and they were all black and coroded so I cleaned them as well. I'm lost as to what to check I'm mostly concerned about just getting it to start right now. As I said, I'd had zero issues after riding for a month straight. I've searched a few places on here and still no luck. Hopefully someone can point me in the right way. Thanks!

 

Replacing airbox and stock filter with four separate air filters (pods) was probably a mistake. If the bike was not running correctly, you probably now have one running worse. Search "Pod filters" on this forum for more information - or see a sample at: http://www.xjbikes.com/forums/threads/air-filters.116420/#post-582047

Other, more expert members, will have to weigh in. I'm guessing (besides needing the airbox/stock filter reinstalled):

Checking and if needed, set proper valve clearances seem to be the first thing to do when trying to get a bike back running correctly.

A complete carb cleaning/rebuild at church of clean is next: http://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/

Ignition/coils/plugs should also be checked.

 

Many of the bikes electrical circuits pass through the Atari. You can't just unplug it; it must be bypassed.
http://www.xjbikes.com/forums/posts/182816/

Before you do that, I strongly suggest that you read the links in my signature, get the bike refurbished in stock condition, and then make sensible modifications (e.g. An Atari delete, but not pods). Your speedometer noise is most likely a problem with the cable, and not the speedometer itself (but the speedometer can be cleaned and lubricated. See the DYI section of this forum).

 

I should also add that I had the same issue initially before installing the pod filters. But yes I see how that could also cause issues. I may just go back to stock then. Partially the reason I changed them is to give more room to take the carbs out next time. I had a hell of a time getting the carb rack out the first and second time. Also, when I cleaned the plugs, I checked them and noticed I only get spark occasionally when I start it.

 

I actually used that diagram in that thread to wire my new speedo, however it's almost as if they didn't include how to do the safety switches from the warning display box. That's why I figured it may not by starting; maybe I need to further bypass it was my thinking. I only got the headlight tailights and break lights crosssover from that diagram/thread.

 

Everything that needs to be bypased is in the thread that I linked.
Undo your work, and plug the Atari back in temporarily for troubleshooting purposes. You may have another issue, and working on a modified wiring harness complicates finding the cause.

 

Makes sense. Guess I know what I'm working on tonight and tomorrow Will keep you posted as to what I find.

 

Quick question also. Any tips or trick on getting the carbs in\out. The manifolds are pretty solid and hard to bend and maneuver

 

I don't want to burst your bubble.... you will need to rejet put carbs in try it...pull carbs change jets ...repeat ...there is NO magic formula for jetting with pods...if you take your carbs to church and do it right the first time ....you will not have to pull carbs for a long time. I can pull the carbs with stock airbox in about 20 min and reinstall in about 30 min so this is not a hard thing to do ....have had mine done for 2 riding seasons and really have not had to mess with them since . This sounds like you need to rebuild the carbs and please realize pods may look "cool"but just realize the challenge of tuning CV carbs do not function well with pods.

 

Use a hairdryer to soften the boots.
Once they are off you can inspect them for cracks.
There is a ethod for resoing them, but I'm not sure that it can be done properly with the intake boots in-situ. Removing the boots can be tricky, since the bolts want to corrode to the head.
The aibox boots can be restored more easily and are really the ones that have to be soft for the carbs to go into place.

 

Just wait until you have to put them back in!

 

Silicone grease inside boots and smear on carb throat and they slip right in .

 

So, granted this is a very delayed post , but I did in fact get my bike running now. New plugs and some carb cleaner through the tank did the trick. Runs almost perfect again. There is a new issue however that I am stumped on. As I indicated above, I removed the factory speedo unit. I did follow the thread to a t regarding what wire to jump to bypass the Atari warning indicators. Everything works now, except my tail light is acting strange. I have no idea what else to try. My tail light only comes on if my high beams are on. Otherwise, no tail light but brake lights do work. Also, if I do have the low beams on, when I apply the brake, my high beams turn until I release the brake. Any ideas as to what the issue could be?

 

as asked in this thread maybe moderators will merge threads
Deleted Atari, no taillights without high beams now?

check your yellow wires one should have a white stripe and is smaller ga wire than headlight yellow sounds like you mixed them up