Running Question

[jimbyjimb]

Is the following normal:

if I hold my bike at cruise RPM in neutral I can hear very faint popping through the exhaust and has very slight RPM jumping, as in no more than 200 RPM IF that. Undetectable by ear. The bike runs great, has tons of power, does not hesitate and cruises well. Does not SEEM to be missing, as in no change in idle, exhaust note, black smoke or vibration. Also checked the plugs and they are so clean they could be eaten from with over 1k miles on them.

I have much experience with auto's but teeny tiny engines with big 'ol fat cams in them are kind of a new experience for me. I know that a running engine does not hold a constant RPM in any configuration, but I'm curious if the popping is just a result of the near-miss situation created by cam overlap with or without combination of an older, weaker ignition system or if my XS is sick. Thanks in advance.

[mro]

Also checked the plugs and they are so clean they could be eaten from with over 1k miles on them.

Sounds like your just a little on the “lean” side.

I’m sure that Yamahas original intent was to get the best combination of performance and profit it could when it introduced the XS11. In the eyes of the targeted consumer, bigger/more powerful = better. What changed since then is government regulation, emission standards and fuel formulation. Changes to the original XS did not improve HP or performance but the opposite. Since the design of the XS11 engine did not lend it’s self to easy re-design or inexpensive fixes to meet the regulations, they opted to run the fuel mix to the lean side. Less fuel, less emissions …


mro

[CatatonicBug]

Usually, a colortune will get rid of the popping at idle and decelleration.

[jimbyjimb]

I was thinking lean as well since the plugs are still so white. I've never seen a set of plugs without a tan color from normal operation, even after only a couple hundred miles. I'll look into a colortune. I have yet to buy appropriate hardware for dealing with the carbs/valves/other motorcycle specific tasks. I'll dig into some past threads to look for good tool suppliers. Thanks guys.

[TopCatGr58]

Hey Jim,

Before plunking down lots of $$ on tuning tools, check out Ken Tablot's tech tip about tuning the idle circuit by EAR!!!

Also, what if any mods have been done to your bike in the exhaust and intake area? And, have you had the carbs apart, what jets are in there, mains and pilots. I didn't look at your profile before replying, but if you have a later model carbs..the pilot jet SCREWS on the top front may even still have the caps in place, and they would need to be removed to tune/adjust the pilot screws to richen it up!

T.C.

[jimbyjimb]

Hey Jim,

Before plunking down lots of $$ on tuning tools, check out Ken Tablot's tech tip about tuning the idle circuit by EAR!!!

Also, what if any mods have been done to your bike in the exhaust and intake area? And, have you had the carbs apart, what jets are in there, mains and pilots. I didn't look at your profile before replying, but if you have a later model carbs..the pilot jet SCREWS on the top front may even still have the caps in place, and they would need to be removed to tune/adjust the pilot screws to richen it up!

T.C.

I haven't even looked at the carbs yet. I bought it from an old man with several bikes, all in excellent shape. He said he had just had it in for a tune up and I believe him after doing some external work. More than likely whoever tuned it just didn't do it quite right. I'm planning on trying to adjust the carbs without the colortune as it's 60 bucks I doubt I need to spend. I've tuned lots of engines, carbs aren't a mystery to me so far, I just don't have any real motorcycle SPECIFIC knowledge. I'm going to rip into it this week for other things, so I'm going to spray around the carb boots and make sure they aren't leaking and go from there. I may even make my own sync tool as was shown in the Tech Tip section, which after reading yesterday I've found is a gold mine! Thanks for the heads up on the pilot jet screws. That's probably the first place I'll go since it's most likely the source of my woes after a lean idle. The bike obviously has been running lean throughout the entire range by judging from how white the plugs look. I read in tech tips to richen the idle slightly to cure popping on decel, and now with your tip on the pilot jet screws I think I'll try to richen them slightly and see if that cures the problem at cruise. I want to avoid pulling the carbs until the summer's over if I can. If not, well I'm sure you'll all hear about it! Thanks again for the tips! Oh, and the bike is all stock except for XJ exhaust. It's a 1980 SG.

[jimbyjimb]

Also, if anyone happens to read this thread and is from western Washington and doesn't mind having an apprentice in the dark arts, please, let me know if you'll be doing some work on your bike and need a hand and/or someone to BS with. There could be a case of beer/equivilent in it for you. I know most of this stuff isn't particularly complicated but apprenticing under a more experienced XSr isn't an idea that seems unattractive. It's always best to learn from someone who's done it over and over, rather than try to figure it all out by myself.

[DGXSER]

You know, we have a number of local (well, somewhat local) XSives around here. And we have one of our local guys who is very generous with his time and garage space. So periodically, we all decend on his garage and work on whatever needs workin on. We have unofficially nicknamed it the SWOXS MOTLM (Meeting Of The Lost Minds) after the annual meet in Texas.

Those of us with some knowledge and experience that like to tinker also show up to keep some of the less knowledgable or experienced folks out of trouble as well. One day I think there was four bikes being worked on at once. Not bad for only two bays. But its always fun and plenty of jaws get a workout too. And the guy with the garage has some pretty nifty tools he doesn't mind sharing.

[jimbyjimb]

Boy Wonder

So, I figured out why the bike was running lean at cruise. Turns out I was running the bike on "PRI" not "ON." Please slap me at the next available time. The idle is still too lean, popping through the exhaust on decel, but it's not bad. And that's an easy fix. The popping and small RPM surge seems to have magically disappeared when the fuel valve is in the "correct" position. It pays to read and not be a slave to my own stupidity. Thanks again for the help. You guys are on this stuff. I love reading other posts. There is a treasure trove of excellent information and brotherhood here, and nobody seems to have a condescending attitude that is so often found on other sites. Good work on the supportive community atmosphere. The world needs a little more of this.

[TADracer]

Dont know how the difference between prime and on would affect this as prime is only bypassing the octopus. But, dont just go for the jets. You might be opening a can-o-worms. If you are in neutral and at cruise RPM you are probably still on the pilot system since there is no load on the motor requireing you to open the butterflies enough to get into the needle jet system.

The pilot system consist of the pilot jet, pilot air jet and the pilot screw (or idle mixture screw). The pilot system is in play until about 1/4 throttle opening. To cure your symptom might be nothing more than an adjustment of the idle mixture screws and a carb sync. Carbs even slightly out of sync can cause what you are having.

If you are running right under load I do not think re-jetting is the answer. Just my opinion.

[jimbyjimb]

Dont know how the difference between prime and on would affect this as prime is only bypassing the octopus. But, dont just go for the jets. You might be opening a can-o-worms. If you are in neutral and at cruise RPM you are probably still on the pilot system since there is no load on the motor requireing you to open the butterflies enough to get into the needle jet system.

The pilot system consist of the pilot jet, pilot air jet and the pilot screw (or idle mixture screw). The pilot system is in play until about 1/4 throttle opening. To cure your symptom might be nothing more than an adjustment of the idle mixture screws and a carb sync. Carbs even slightly out of sync can cause what you are having.

If you are running right under load I do not think re-jetting is the answer. Just my opinion.

I agree totally and am no longer intent on doing anything until I try richening the idle circuit some.