Low RPM issue

[jimbyjimb]

Ok, I'll ohm test the coils. It's idled at 1100 as long as I've owned it and it used to be happy there, so that's my aim. Still, if there were something wrong with the pickups I'd think I'd see it when checking firing at the coils, but maybe not.

I'm still going to test the boots (tomorrow) and per BA80's recommendation run some fuel system cleaner through. I just so happen to have a bottle of gumout carb cleaner, so a ride up north on the interstate is in order. I'll set the idle to 1500 in the meantime, unless I find a problem with the pickups tomorrow.

Thanks for the suggestions and butting heads with me on this.

[TopCatGr58]

Just another thought, you state the MikesXS coils, which ones, the black ones, or the green ones? When were they put on, how many years/miles ago.

If the black ones, and you have ~10k mile on them, then they are probably nearing their failure point! Regrettably we found out that they were prone to failure around the 10k mile mark. I didn't find mine to fail for 4 years since I only put a few k miles every year, but it finally did fail right around the 10k mile mark!

I've since updated the MikesXS coil upgrade tip with the condemnation of these inferior coils, and NOW suggest Dyna or other branded high output coil. Several have installed the MikesXS Green monster coils, and so far have not reported any failures with them!

Also, how's your charging system working, have you checked your voltage at idle?? If the charging system is developing a problem it could be dropping near or below the critical 10.5 volts that the TCI needs to run properly!

But yes, pour a 1/2 bottle of sea foam and run it, you may get pleasantly surprised! Also, put your petcocks to PRIME, at idle the OCTY may be malfunctioning and not opening adequately at idle restricting fuel flow?

T.C.

[jimbyjimb]

My idle voltage (haven't checked) is so weak that if I'm using the brake light the turn signals won't flash, they're just solid. But, it's been that way ever since I bought the bike and this has never been an issue before now. Doesn;t mean it couldn't be contributing, but in four years time I'd think it would have cropped up at some point. Will still be good to add to my ever growing list of things to check.

I do have the black Mike's XS coils, but they're only a month old. Thanks for the tip on that though. Maybe 200 miles.

I think before I jump the gun on anything else I'll do the vacuum test and try the carb cleaner. I really should check the voltage at idle too. The only recent change in the electrical system was the Mike's coils, but it did run well for a couple weeks with them. I just have a feeling about the carbs since they've had fuel in them for four years and I only put 4k tops on my bike in the previous years. It also sat much more than usual last year. We had a crappy summer.

[motoman]

I think before I jump the gun on anything else I'll do the vacuum test and try the carb cleaner.

You'll only be jumpin' the gun IF you go to thinkin its a carb issue.......just a word to the wise...

[jimbyjimb]

Being the coils are the only thing I've messed with you're probably right. It'd just be amazing if the ignition were behaving exactly like a vacuum leak. Stranger things have happened.

[petejw]

pull the sparkplugs out and see what they
look like, ull be surprised what they can tell u.

[jimbyjimb]

Well the plugs were changed with the coils so there's about 200 miles on them. That's enough time to tell if there were a serious problem, but not enough to tell anything more subtle than a serious issue. Plugs are the first, middle and last place I look for any running issue. Thanks for checking though.

Today when I get home, 1PM PST, I'm going to do a better check on the pickups, ohm them, ohm the harness. If that checks out, I'm going to pull the tank and ohm the Mike's coils. I may put the originals back on and see if that makes a difference.

If that still doesn't do it it's on to hosing the boots/carbs with brake cleaner while the engine is running to try and find a vacuum leak. Regardless I'm going to run cleaner through the carbs via the fuel tank on the next ride I take.

I know there isn't a fuel restriction in the lines and the bike has no problems revving high so I think that rules out anything beyond the idle circuit as far as the fuel system is concerned. I really wonder about those Mike's coils. The timing light showed no problems BUT timing lights aren't exactly precision tools. An engine scope would be nice.

Whether or not it makes a difference I run the bike on premium, 92. I used to run it on 89. I have used premium occasionally in the past, but not regularly until recently. Never noticed any knocking or pinging on the 89, or the 92.

[jimbyjimb]

I had a thought-

When I did the Mike's coil swap I did so assuming (I know, ass out of u and me) there was no resistor. I thought 80 SG's didn't have the resistor. If I'm uncorrect in this assumption and there is a resistor, could this be the cause of my woes?

[cywelchjr]

My idle voltage (haven't checked) is so weak that if I'm using the brake light the turn signals won't flash, they're just solid. But, it's been that way ever since I bought the bike and this has never been an issue before now. Doesn;t mean it couldn't be contributing, but in four years time I'd think it would have cropped up at some point. Will still be good to add to my ever growing list of things to check.

I do have the black Mike's XS coils, but they're only a month old. Thanks for the tip on that though. Maybe 200 miles.

I think before I jump the gun on anything else I'll do the vacuum test and try the carb cleaner. I really should check the voltage at idle too. The only recent change in the electrical system was the Mike's coils, but it did run well for a couple weeks with them. I just have a feeling about the carbs since they've had fuel in them for four years and I only put 4k tops on my bike in the previous years. It also sat much more than usual last year. We had a crappy summer.

Did you remove the ballast resistor when you installed them? And over 4 years your battery will have aged and a battery that may have held the system up enough to keep the coils firing well enough to keep it running well 4 years ago may not do so now. It's also possible that the new coils can't handle the lower voltage as well, although this is not something I've heard of. That said, many ignition system problems will mimic the symptoms of a vacuum leak almost exactly, and any time you have made a change and a symptom shows up afterwards, it's almost guaranteed to be related. The MikesXS coils are rather not recommended any more, as just about everyone recommends spending the extra for higher quality high output coils from elsewhere that actually have a warranty and a track record for not failing, rather than such an incredibly higher failure rate as the MikesXS coils

[cywelchjr]

I had a thought-

When I did the Mike's coil swap I did so assuming (I know, ass out of u and me) there was no resistor. I thought 80 SG's didn't have the resistor. If I'm uncorrect in this assumption and there is a resistor, could this be the cause of my woes?

That would do it. The resistor didn't go away till 81. Leaving it in would make the voltage too low for good spark at idle.

[jimbyjimb]

Aha!

Well, I'll just remove that and see what happens. I didn't know about the Mike's coils being no good when I got them last month. I'll get rid of the resistor and plan on getting better coils sometime in the near future. T.C. said they would last about 10k though, so I should have a while before they really become an issue.

This must be it. I really appreciate the help and being able to bounce ideas off of other people who've done the groundwork. The tech writeups in particular are spectacular.

I think I'll still check the battery and charging system though, just to be academic if nothing else.

[cywelchjr]

Aha!

Well, I'll just remove that and see what happens. I didn't know about the Mike's coils being no good when I got them last month. I'll get rid of the resistor and plan on getting better coils sometime in the near future. T.C. said they would last about 10k though, so I should have a while before they really become an issue.

This must be it. I really appreciate the help and being able to bounce ideas off of other people who've done the groundwork. The tech writeups in particular are spectacular.

I think I'll still check the battery and charging system though, just to be academic if nothing else.

If you didn't remove the ballast resistor, that's almost for sure your problem, as the coils aren't getting enough voltage at idle to work properly, actually they are probably just barely getting enough to work properly above idle anyways.

[jimbyjimb]

Eliminated the resistor and holy moly that thing fired to life with purpose like it never has!

I ran it for a little over five minutes, enough to get the choke off and checked sync. It idled at 1k no problem with all carbs at 9 in/hg. No hunting, no stalling, no hesitating, one rock solid smooth needle. Thanks for the suggestions along the way. I now have a pretty good idea what to check first if/when I have other similar issues.

[tweeleft]

I noticed that no one said anything about Idle mixture srews during this topic. Just a thought

[cywelchjr]

I noticed that no one said anything about Idle mixture srews during this topic. Just a thought

Notice that he removed the ballast resistor from the circuit with the aftermarket coils and the problem went away. Had the troubleshooting steps pointed to the idle mixture screws we would certainly have suggested that. However it was known that something was changed and the problem started after that, so it was down to determining what the change was, and then working from there. While nice suggestion, troubleshooting is a process, and a science. What those of us who have been around a while have learned (both by personal experience and that of others) is that very often what looks like fuel problems can often be ignition or electrical in nature, so since the electrical is the easiest to confirm as being good or bad first, it's almost always best to either confirm or rule out electrical issues before messing with carbs that were working fine 2 weeks ago, especially when problems started without them being touched.