Coil testing

[barelycompetent]

Ok here I am again lol. I finally got my jetting issue resolved, and I put my carbs back on my bike, its an 81 special, with stock ignition, coil, TCI box, everything for the ignition system and charging system is stock. I fired the bike up and it starts up, but its running like complete crap. I put brand new plugs in before firing it up, and I noticed that the right side of the exhaust was barely warm while the left side was hot. I pulled the plugs and the right side is white, pretty much like it just came out of the box while the left side was brown. I only had the bike running for a couple of minutes. So it looks like the I am getting a weak spark or no spark at all on the right side. Now the bike will start and run but only on the left side. I am going to test the coil and see if that is my problem, but I wanted to check on a few things first to make sure I dont damage anything else. I want to swap the plug wires right to left and see if the problem follows, but I want to make sure I am doing that correctly. Is it as simple as unhooking the wires from the plugs and putting them on the opposite plugs and firing the bike, or do I need to unhook them at the coil and swap them from side to side at the coil? By doing this test before I check the Ohms at the coil Im hoping to elimate the wires being bad as well. From there Im going to follow the guides that I have found on this site for testing the Ohms and see what I get. One last question, I know that the original location for the TCI ignitor box on this bike was mounted on the bottom of the stock battery box. I have relocated the ignitor box to a plate that I welded between the frame rails at the back of the bike. It is mounted on the left side of that plate, cant really see it in my second pic though. The wires are not extended in anyway, so they have not been cut and spliced at all. With it mounted to the plate like that would vibration have any affect on it? Would it cause it to go bad or anything like that? Once I test my coil, if thats good I will be moving on to the TCI box, so just thinking ahead. Thanks for any thoughts, advice or help, it really is appreciated!

 

[TwoManyXS1Bs]

Hey, barely, you're getting some real experience there!

If your right side sparkplug was dry when you checked it, you may have a fuel problem instead...

 

[5twins]

Yes, on your ignition type with that single dual fire coil, you can simply swap the plug wires side to side. Your ignition fires the coil every 180° and fires both plugs at the same time. One of those sparks is wasted because only one of the cylinders is at TDC on it's compression stroke and ready to fire (loaded with a gas/air charge). The other cylinder is at TDC on it's exhaust stroke, pushing the spent gases out, so there is no gas/air charge there to ignite. That spark gets wasted.

The way your coil fires both plugs at the same time, it's very uncommon to have one be weak. Usually, if one fires, they both do, or neither do. If you do have a weak or bad spark on only one side, it would probably be related to that side's plug, plug cap, or plug wire, not the coil itself.

Your bad side may not be getting fuel. If it was (but not firing), that plug would be wet. Does that cylinder kick in and come to life when you open the throttle? If so then your sync is off.

 

[barelycompetent]

Thanks for the replies, the plug does have some fuel on it, its not wet, but its not dry, if that makes sense. When I had it running the other day, I cracked the throttle a few times and the right side exhaust did start heating up, by feel it felt about like the left side. The carbs are only bench synced at this point, but my gauge set arrives to today so I am going to do a synch on them as well. 5twins if you remember from my carb posts, the popping I was getting out of the right side, and the PO had a hotter spark plug in the right side when I first bought the bike. Well with the bike running now, it pops and backfires out of the exhaust something fierce, and when the right cylinder warmed up, after it had been running for a few minutes and I cracked the throttle a few times, it did seem like the idle smoothed out a little bit. Right now on my carbs I have 45 pilots, 137.5 mains, and 3 turns out on the screws as my starting baseline. I just want to get the bike running on both sides before I start tweaking and tuning the carbs lol. I hope this information helps.

 

[barelycompetent]

Plus I am going to pick up a spark tester as well and test to see if I have spark on the right side, that can help rule out the coil and wires, I hope lol.

 

[5twins]

Well, if your sync is way off, you may not get the bike running well unless you tweak the carbs (sync setting). If your plug caps are originals, I would just replace them. It's just something you do with 30 year old plug caps, lol. The originals can go bad, gaining resistance. When that resistance starts getting too high, it starts choking off your spark. You can test them by removing them and measuring the resistance through the cap. They were rated some oddball resistance like 9K ohms or something. If yours measure 10, 12, or 15K, they're going bad. It's not a bad idea to remove them anyway and cut 1/4" off the wire, then re-install. That way you get a good connection into fresh wire. Also, fan the wire strands out like so before screwing the cap back on .....

This will insure a good connection. I dab a little dielectric grease on the wire end too before mounting the cap.

 

[barelycompetent]

Ok. Well my sync gauges come in today, so I will hook them up first and see where I am at. Once that is done, if it improves the bike then I know where the problem was, if it doesnt, then I will move on to testing the coil and wires. Somewhere in there I hope to find my problem lol. I appreciate the help, this site has really given me alot of advice and help! I think its someone's signature line on this site, not sure where I saw it at, but it says "experience is something you gain right after you needed it" or something to that effect lol.

 

[retiredgentleman]

Ok. Well my sync gauges come in today, so I will hook them up first and see where I am at. Once that is done, if it improves the bike then I know where the problem was, if it doesnt, then I will move on to testing the coil and wires. Somewhere in there I hope to find my problem lol. I appreciate the help, this site has really given me alot of advice and help! I think its someone's signature line on this site, not sure where I saw it at, but it says "experience is something you gain right after you needed it" or something to that effect lol.

What type of sync gauges do you have? How did you do the bench sync?

 

[barelycompetent]

The gauges I ordered were the kit from Mikes, and the bench sync was done by eyeballing it. I know that is NOT the best method to do that, but I figured I couldnt be that far off. I will definitely be checking it though! Here are the gauges I ordered. http://www.mikesxs.net/product/35-1388.html

 

[retiredgentleman]

The gauges I ordered were the kit from Mikes, and the bench sync was done by eyeballing it. I know that is NOT the best method to do that, but I figured I couldnt be that far off. I will definitely be checking it though! Here are the gauges I ordered. http://www.mikesxs.net/product/35-1388.html

Those gauges are useless for doing an accurate sync. Those gauges are just a marketing gimmick by Mikesxs....................good for their profit, but no good for you. Those 2 gauges could easily read 1 or 2 inches of mercury difference, plus the error of your eyes reading the 2 gauges.Those type of gauges are meant for measuring vacuum, as a rough indicator, where + or - ,1 or 2 inches of mercury is close enough. 1 inch of mercury error is equal to 13.6 inches error on a U tube manometer, using Stabil or ATF, etc.. 2 inches mercury error is about 27 inches on a manometer.

Eyeballing is not very good either. An easy and accurate bench sync uses a slip of paper about 1" wide and 3'' long. Slide the paper "feeler gauge" under each butterfly and adjust until both butterflys have equal drag. This method is far more accurate than those useless vacuum gauges sold by Mikesxs.

A "paper slip" bench sync gets you very close and a manometer puts it right on the perfect sync balance.

 

[barelycompetent]

Wonderful. Wish I had known that before buying those gauges. Yeah I realize the eyeballing method is not the best, so I will give the paper trick a try. I will see if that gets the bike running any better, until I can get a proper sync on them.

 

[Rgconner]

I disagree, I use the same gauges, but in the 4 rack version for the Honda CB550.

I can get all four carbs into sync, as evidenced by smooth idling.

Now, I did have to calibrate them, by putting each gauge on the same cylinder and making sure they read the same across the board.

They were wildly different. Calibrating them meant I could get consistent results.

 

[bergoff]

My bike also ran like crap until is synced the carbs. Stumbled off of idle and would die at stop signs. I made my own sync gauge out of a yard stick 12ft of clear tubing and some atf that I already had. There is a write up on here somewhere about it not by me though. Now it runs like a champ. Good luck and have a fan blowing on the engine it will get hot.

 

[retiredgentleman]

I disagree, I use the same gauges, but in the 4 rack version for the Honda CB550.

I can get all four carbs into sync, as evidenced by smooth idling.

Now, I did have to calibrate them, by putting each gauge on the same cylinder and making sure they read the same across the board.

They were wildly different. Calibrating them meant I could get consistent results.

Well we can agree to disagree. Most lads don't realize they need to calibrate the 2 or 4 gauges to a common vacuum source, which makes the adjustment even more erroneous. However even if you do that, the 2 gauge or 4 gauge method is still a very coarse measuring device to balance 2 negative pressures, and still not as accurate as a manometer. Something as simple as bumping them on a table could take them out of calibration again.

A U tube manometer (for 2 carbs or 4 carbs) is by design, very simple, very accurate, very inexpensive, and never requires calibration.

You can pay $70.00 to $100.00 for 2 to 4 vacuum gauges, or you can pay about $10.00 or less for some plastic tubing and fluid to make up a manometer for 2 or 4 cylinder engines.

 

[barelycompetent]

Well here is where I stand at this moment. I swapped the plug wires and fired the bike up. The left side got hot, and the right side got warmer but not as hot as the left side. This was with the wires crossed again, took the right off the plug and put it on the left plug, and vice versa. So Im thinking my coil and wires are good, but Im going to check those just to make sure. Popped the carbs off, and did a bench sync on them again, this time using the paper method, got what I think is a pretty good bench sync on them, but alas the wife has called me in for dinner lol. Dont know that I am going to get them back on the bike tonight or not, and I havent tried to hook up the new sync gauges to even try them for the heck of it. So, thats where I am at for the moment. Might even pull the jets out again and give them another cleaning just to be safe.

 

[barelycompetent]

Plus the right side plug is wet, not dripping wet but wet and I can smell the gas on it after I have fired it and let it run briefly, so Im getting some fuel at least, not sure what that tells me though.

 

[Rgconner]

You can pay $70.00 to $100.00 for 2 to 4 vacuum gauges, or you can pay about $10.00 or less for some plastic tubing and fluid to make up a manometer for 2 or 4 cylinder engines.

Which works great until you forget to turn off the choke....

*slurp*

I pulled about a teaspoon and a half of mercury out of the CB550 oil pan!

(yeah yeah, we technically don't have chokes on the XS650...)

Every tool has a limitation, and if you know what it is, and how to properly use them, they work fine.

 

[barelycompetent]

Ok did a little more on them. Pulled the pilots and gave them a few squirts of carb cleaner, then blew them out with compressed air. The blew out the passages again with compressed air. Since my mix screws had the original brass plugs covering them, I drilled them out in an earlier thread, and adjusted them to 3 turns out. Now Im wondering, because I havent pulled the mix screws out and checked the o rings, but Im guessing I might need to as everything I have read says the bike will not idle correctly if the o ring is disintegrated. Being as that it is the original one, Im guessing it might be. Looks like more parts to order lol.

 

[5twins]

You can't properly clean the idle circuit with the mix screws in place either.

 

[gggGary]

As I always ask; did you replace the o-rings on the float valve bodies?
Finally got a size I like for the job McMaster Carr

9263K137 Metric Viton(R) Fluoroelastomer O-Ring, 1.6 mm Width, 7.1 mm ID, Packs of 25 6.47 Per Pack