Misfiring test

[Steve in Sunny Fla]

If you are experiencing lower rpm / light throttle / lower gear misfiring, I have a test for you to perform...

Remove the vacuum line from the igniter, block the vac line with a nail, screw, etc, and ride the bike. If the misfire is gone, post it up here. Mine was doing this, i worked on the carbs enough to realize it wasn't carb related. I found and fixed the problem with a trick I learned power tuning cars many years ago. I'm not going to post it up unless there's others here who have the exact same issue I had. Steve

[flip18436572]

I had tried that after I still had a miss after Carl had rebuild the carbs and sync'd them about 2 years ago. I didn't know where to go after that, but I didn't want to cause problems with my Ignitor and break my starter chain. I can't afford a lot of repair, so I checked the line for problems, and trimmed the end of the line to possibly remove a vacuum leak at the ignitor. Still had the miss, but not 100% of the time.

I was thinking maybe I had a spark plug or plug wire problem, so I replaced all of them also. Still no fix.

[Steve in Sunny Fla]

did you leave the line off and ride the bike, trying to get it to do the misfiring?

On mine - and I suspect alot of others, the misfiring was bad if I had very light throttle / 1st gear / 3000 rpm / light cruise. That's not a way I would often use the bike since I don't ordinarily ride it in traffic, but it was also really noticeble on back roads - 3rd gear/ 40 mph / 3000rpm. Seemed liked lean misfire, but it's not - I richened the carbs, and just went through some "over-fixing" by raising and even changing the needles, and the misfire persisted, though when it got rich it did suppress it quite a bit. That told me to go to the ignition timing. Steve

[flip18436572]

I took it out on the highway for a little bit and the misfire never went away completely. I don't ride it around town, mostly highway miles.

[Steve in Sunny Fla]

OK, You guys need to explain something to me - there are 2 other threads going about low speed misfires. I offer a test to do, and NOBODY gives any feedback on trying what I suggested? Is it that My bike is the only one with this problem or that there's no way "despicable Steve the over-fixer" could figure anything out? Isn't anyone even interesting in trying the test? Steve

[Chris near Kansas City]

flip1843658290210 is in Iowa. His bike is in my garage in Kansas City. I'm in New York. A test ride will have to wait until the logistics improve some, LOL.

[twigpig]

I've been working 13-14 hour days at work, plus I am helping my inlaws move and I sold my old bike. No time yet. I appreciate your input but my summers are crazy busy.

[Me Again]

I've been working 13-14 hour days at work

Half this countries out of work and you're taking up all those hours? You outta give them to someone who really needs them.

Now go for a ride.

[flip18436572]

I am working 10-12 hours a day and don't have time to ride other than to work and back. Currently my ride is in K.C. and I am riding my SV650S to work everyday.

[usmalenurse]

OK, You guys need to explain something to me - there are 2 other threads going about low speed misfires. I offer a test to do, and NOBODY gives any feedback on trying what I suggested? Is it that My bike is the only one with this problem or that there's no way "despicable Steve the over-fixer" could figure anything out? Isn't anyone even interesting in trying the test? Steve

I'll give it a shot when I can. Mine misses at idle and low speeds but runs like a top on the road. I figured it was probably the carbs since it's a '97 model and hasn't been ridden much. I've only put about 500 miles on the bike so far and still experimenting with it. Did get the stereo up and running this afternoon...both fuses behind the headlight were blown (thanks Carl). Will try it and post when I can.

Charles

[Steve in Sunny Fla]

it's really easy to do - remove the faux fuel tank, the igniter is right under it with a couple wire connectors and a vacuum line going to it. you can even leave the tank off when you do the test ride. it SEEMS just like a carb issue, but it isn't. Steve

[PKarl]

ok so what is the fix for it if it makes it quit missing when you unhook the line..leave it plugged?

[Steve in Sunny Fla]

no, but the fix IS pretty easy. did you do the test? Steve

[PKarl]

No havent had a chance to test it yet..that why was wondering what the fix was so could do it all at one time to see if theres a difference dont know why it has to be a big secret just tell us what it is
Paul

[Steve in Sunny Fla]

The reason I asked for the tests to be done and then reported back was to get a feel for how widespread the problem is, and to get some forum participation to see if we all will benefit from my findings. I know when I told it to Carl, he was pretty excited. Steve

[ekap1200]

ok heres a shot in the dark , is it just the plastic vacum delay valve thats the culprit ?

[Steve in Sunny Fla]

Gene - no, and it's more an anti - backfire valve than a vacuum delay valve (I pulled vacuum on it). The issue is that the vacuum line goes to a vacuum advance unit in the igniter, just like you and I are used to in automotive applications. I "t"'d a vacuum gauge in and rode the bike, finding that the misfire occurred when the vacuum exceeded 5" vacuum although advance was present from 1" vacuum up. Of course the vacuum advance is a critical component to fuel economy, so completely omitting the vacuum advance unit wasn't my intention. Knowing how vacuum advance works, it's easy to see that the engine would pull higher vacuum in the lower gears, which is why this misfire isn't an issue in high gear cruising. I figured an easy way to mitigate the vacuum over 5", and the misfire is gone. Steve

[twigpig]

I finally got a chance to work on and ride the bike some. I plugged both the vacume line and the intake on the igniter. It did not help. If anything it made it a little worse and extended the range of rpms that the miss occurred. I tried your sugestion with the enrichiner and that helped smooth out the low rpm rough running. I got 42 mpg on a 120 mile ride in mixed highway town riding. Some was stop and go rush hour although since I was on a motorcycle I could use the HOV lanes most of the time. That is with the enrichener off. I checked the float levels. 1,3 and 4 are 2 mm above the gasket line and 2 is right on the gasket line. spark plugs are new and gapped I checked the spark plug boots and they are all ok. The carbs are balanced. Rubber boot clamps on carbs are tight. Like I posted in the other thread both idle and a little above 2500 rpms is smooth. It is smooth at all rpms with heavy throttle. It is rough in that band above idle to a little above 2500 in all gears but is more noticable in the lower gears probably because there is less road noise and the rough running is easier to detect. Using 87 octane 10% ethanol.
I know what some of you are going to say. Just use heavy throttle all the time. Problem solved. Ha! Beat ya to it.

[Steve in Sunny Fla]

OK, then in your case it's not the igniter, it's in the fuel system. although the fuel levels are to high, it's still to lean down low, probably cruddy pilot jets or transition ports, I've even seen varnish on the slide needles and that'll do it too. My bike definitely responded by running better when I pulled the enrichener before i went through the carbs, but when the misfire persisted after the carbs were done, I went to the igniter. I assume all the voyagers don't have this problem, my 87 didn't. I think I'm starting to miss that bike... Steve

[usmalenurse]

Finally got around to trying the igniter vacuum line and doesn't seem to be my problem either. Made mine a little worse instead of helping. Guess mine is in the carbs. Mine just idles a little rough and wants to miss when you're trying to ease off in 1st gear. Will occasionally just die when you let off the throttle at speed coming up to a stop sign or something. Cruising along at speed or accelerating she runs like a top.
Charles