Climbing idle once warm

[mercanie77]

Hey!

So today I took out my 83 XS650 and rode fine until about 10 mins into the ride. The startup and ride was fine. When I came to a stop, my idle in neutral started to climb by itself to about 3000rpm and wouldn't come down unless I bogged it by pulling in the clutch. For the rest of the ride coming to stops and lights it would hover again 3000ish rpm without coming down by itself unless I released the clutch, but would automatically climb again.

Upon coming home, thin white smoke was coming from both exhausts, more visible smoke on the left side than right. Any helps to steer me in the right direction would be great.

Thank you.

 

[DogBunny]

EDIT: I just noticed that you stated that you have a 1983, so you don't have an advance mechanism, so ignore that part of my response.

There are two things to consider.

One is the possibility that the springs of your advance mechanism are weak, or the advance rod bushings are gunked up. Either condition will make it hard for the advance mechanism to function correctly. If the mechanism sticks in the advanced position, high idling will ensue. Do a search, there are lots of posts on both causes.

The other thing to consider is that the engine burns fuel more efficiently as it warms up. It is not at all unusual to have to adjust the idle stop screw while riding. You want it screwed in a bit (clockwise) at first to make warming up easier, and then you may have to unscrew it a bit to combat high idling after it has warmed up. With practice, this can be done on the fly, without looking, even with gloves on.

 

[thuban]

It's leaning out. White smoke is oil. Engine could be running too hot.

 

[mercanie77]

@DogBunny

If you don't mind explaining where exactly the screw is, and since it shoots up once warm I should be turning CCW and adjusting while the engine is warm correct?

 

[DogBunny]

thuban makes a good point. You could be lean. That will aslo cause idle to rise as engine warms up. Have you changed the exhaust?


The idle stop screw is on the left side. Turn CCW if idle rises as engine warms up.

 

[mercanie77]

@DogBunny I just got back from a ride. Driving fine. Got back home and let the bike sit a bit. Revs started to climb. I played with the screw and turned it CCW and lowered the revs so that's great. However, the pipes are still smoking and again predominately from the left side. The smoke is white. I do have an aftermarket exhaust on my XS.

@thuban any tips for that problem?

 

[DogBunny]

Look at the left side plug. It will be white. Here is the simplest possible answer for you: go up one size on your pilot jets and three sizes up on your main jets, assuming you put "normal" exhausts on. If you put aggressive exhausts on, and changed the air boxes to pods, then go up two sizes on the pilots and four or five on the mains. There's way more to it, but you don't seem ready for the finer points at this stage in your learning, IMHO.

 

[thuban]

mercanie77. Give me a bit of history on your bike. It has stock exhaust. Is the bike mostly stock? How long have you had it?
If you pull the plug on the left cylinder it should be black and maybe oily if it's smoking much. If it was not smoking I'd be inclined to look for a white plug, lean condition. I wouldn't mess with the carbs until I knew the engine mechanicals were solid. The question is where is the oil coming from; Stuck ring? Hole in the piston...? Just because it has a black box instead of points doesn't mean it would not go full advance as it warms up and the box gets hot. This would bother me more than the idle going high, right now. You have a compression gage? If so, Id pull the plugs and look at them. Run a compression test, key off, gas off, throttle wide open, and kick it thru about five times on both cylinders. I would be more concerned about the overall health of the engine first. Over 100 on both and about even in compression would be a good starting point.
Do the simple things first. Check oil level. Pull an air filter and make sure it's not real oily inside.

 

[kopcicle]

Adjust the valves

 

[mercanie77]

@thuban the bike was a barn find and hadn't been running for several years. When I came in possession of the bike it wasn't running. I did all the basic maintenance and wake up the bike needed to get it running and started. There is an aftermarket exhaust on the bike. I do not own a compression tester but will pick one up. I'm learning as I go with this its all new information for me with this platform so any tips are greatly appreciated. I will check my plugs tomorrow.

 

[thuban]

Adjusting the valves is a good idea, but I wouldn't go there just yet because the timing chain adjustment is involved in that and then timing the engine. Engines running fine so...( Do you have a book?) The bike runs. Evidently doesn't make any funny noise. But it smokes and idle is "hunting".
If the oil level is too high and the breather is picking up oil and "slugging" it to the filter box, that's why it's smoking. But if the box is dry... then it's not so simple.

Are the manifolds leaking or cracked? I like the KISS method.

 

[mercanie77]

@thuban engine drives and sounds normal.. no bogging.. no knocking... like stated drove normally until I got home and left it on for a bit.. white smoke mainly from right exhaust but also left, some smoke from headers too.. engine running too hot? No noticeable leaks after driving as well. After playing with idle screw in driveway the revs came down to normal but smoke was still present. Ill check my plugs tomorrow and get my hands on a compression tester.

 

[thuban]

@thuban the bike was a barn find and hadn't been running for several years. When I came in possession of the bike it wasn't running. I did all the basic maintenance and wake up the bike needed to get it running and started. There is an aftermarket exhaust on the bike. I do not own a compression tester but will pick one up. I'm learning as I go with this its all new information for me with this platform so any tips are greatly appreciated. I will check my plugs tomorrow.

Not a problem in the world. We'll stay with you. Every bike we get is a new deal and learning experience. If you don't have a book, get that first, and check the plugs. ( I may be asking you questions you have already answered on another page. If so, I'm sorry. I forget where I was at because I'm busy working and just check in here now and again. If your the guy that went thru the BS38's then I'm behind the power curve again!
If it's been sitting a long while, it just may be burning old oil from the pipes and mufflers. That may be a non-issue.

 

[thuban]

Oh, hey and there are no stupid questions! We've all been there and I still ask em'.

 

[TheMonkey]

Is idle getting high only after warmup? Spit balling here, but aluminum expanding causing an air leak? Sounds like maybe from an oil passage? Good luck, you’ll get it.

 

[mercanie77]

@TheMonkey I've played with the idle screw while riding and that seemed to fix it. Been on a couple rides since and that problem can be fixed by playing with the screw.
@thuban this is my plug from the left side (right side is also identical) which has me thinking I'm running rich instead of lean. The current plug that's in the bike is the
NGK Iridium IX Spark Plug BPR7EIX.

 

[thuban]

It looks more like oil fouling. I like NGK plugs but I don't know anything about that one. I believe that plug design is supposed to concentrate the fire making it fire better under high compression conditions - or thru oil fouling. That's a new looking plug yet it's really fouled so... I'm back to burning oil. Clean them good, tough to do without a cleaner. ( or get a new set of standard BP7Es and stick in it. Their cheaper than those. Then run it a bit and see what they look like.)
I'd still like to see a compression test. I hate to see you spending money on test equipment at this point in time.
Edit: Pull the filter on that side and see if it's oily in there.

 

[bosco659]

I agree with thuban on the oil fouling. If it was sitting for a long time could the rings be sticking. Ran ok before but sticking now?

 

[5twins]

Those are resistor plugs. If you still have the original plug caps, they are resistor ones as well. You shouldn't be running two instances of resistance in the system, only one. You might get a weaker spark that way, which would contribute to the black plugs. But, the wet, black look of them and the white smoke does seem to indicate you're burning some oil. That could be because the bike sat for a long time. Maybe the rings just need to re-seat. Put a few hundred miles on it and see if things improve. If not then some topend work may be needed.

 

[kopcicle]

I hate to harp on this but the #1 thing that has to be done is adjust the valves. All else depends on this.
I wrote the following for 4 cylinder dual point but it shouldn't be too hard to translate.
As a get it running method I set the fixed side points to .012" , record the dwell and make the moveable points the same. Check the timing for both points and recheck the dwell, done.
Did I mention adjust the valves?
Synchronize the carbs. Assume that the float levels are correct (assume ? well, float levels are important but...)
Get a reasonable idle speed and adjust mixture screws. Lean misfire should happen between 1 1/2 turn from seat, rich misfire should occur before 3 1/2 turns from seat. If not re-check sync and float levels.
Cam chain adjust is well covered elsewhere.
Now insert fresh spark plugs and go looking for problems.

Just anecdotal. I can't tell you how many times fuel diluted oil from crappy needle valve and seat has contributed to a smoky mess.

I can't tell you how often a complete tune-up has been more a diagnostic tool rather than simple maintenance. If there is a problem, more often than not a tune-up will find it.

By the way, did I mention it begins with adjusting the valves?