Unstable Idle
Do you have a carb support bracket? If you grab hold of the air cleaner can you wiggle it up and down or side to side even a little?
What do you mean by "The head doesn't have any bolts"? There should be clamps with bolts between the heads and the intake, and between the heads and the exhausts.
Here is my note on checking for leaks ...
Intake And Exhaust Leaks Tests
You cannot get a good tuneup if there are intake leaks or exhaust leaks.
1. Check for Intake Leaks
With the engine idling spray WD-40 or propane gas around the carb/intake/cylinder head joints. WD-40 is said to work well because it has very fine spray droplets. Propane is best because it leaves no mess, and is most easily sucked in thru leaks. Be careful to not allow any of either to get sucked in thru the A/C.
Any change in engine RPM is a leak which must be fixed.
2. Check for Exhaust Leaks
Pour about 1/2 ounce of oil into each cylinder thru the spark plug holes. Run the engine at idle. You will get lots of smoke for about 5 minutes.
All smoke should come from the ends of the exhaust pipes/mufflers. Any other is a leak which must be fixed.
Road Warrior
Joined: Sep 2006
Posts: 1,605
Likes: 82
From: nj
I do have a support for the carb. Now what I meant for the bolts on the intake, there is one band on each intake coming from the head. that is it.There is a rubber boot betwwen the head and the intake. I know on my other bike the intake is bolted to the head. Thanks Iron ( what do you mean A/C )
I do have a support for the carb. Now what I meant for the bolts on the intake, there is one band on each intake coming from the head. that is it.There is a rubber boot betwwen the head and the intake. I know on my other bike the intake is bolted to the head. Thanks Iron ( what do you mean A/C )
If the rubber bands are not detiorated, are neatly installed, and held in place with the clamp then with the support bracket there should be no leaks. These clamps should be installed when the heads are installed and tightened before the head bolts are tightened. For clamps the best are the T-bolt [aircraft style] clamps.
A/C usually means air cleaner. Sorry, i usually don't use these short forms.
Road Warrior
Joined: Sep 2006
Posts: 1,605
Likes: 82
From: nj
My mistake , there is a rubber boot connecting the head to the intake manifold for each side of the intake to the head and there is a band that seals around the boot sealing them. maybe the rubber boot can be dry rotted I will try to check for leaks tommorow. The bike has to be reallly hot for this o happen, for the idle to go down I usually pull the clutch in and give it gas in first gear and then move foward and then pull the clutch back in then she will go down the idle. I did lubricate the cables and did check the idle cam to make sure she is not sticking and everything seems to be free This is why Iam a little confused thanks
My mistake , there is a rubber boot connecting the head to the intake manifold for each side of the intake to the head and there is a band that seals around the boot sealing them. maybe the rubber boot can be dry rotted I will try to check for leaks tommorow. The bike has to be reallly hot for this o happen, for the idle to go down I usually pull the clutch in and give it gas in first gear and then move foward and then pull the clutch back in then she will go down the idle. I did lubricate the cables and did check the idle cam to make sure she is not sticking and everything seems to be free This is why Iam a little confused thanks
I have not experienced this idle problem myself so i am going only by what i recall of what i have read on these forums. When i was working on a couple of Yamaha Virago projects some years ago slow return to idle was a common problem, the cause usually being that the two carbs were not synchronized. Hmmmm, here we have only one carb so that is out.
I would first ensure that there are no intake or exhaust leaks then check the ignition timing. Then i am at the end of my limited knowledge with this.
Cruiser
Joined: Jan 2008
Posts: 161
Likes: 1
I had a problem with the idle coming down real slow sometimes, others it would fall normal. Checked for intake leaks using WD40 but didnt find any. Removed carb and intake anyway and cleaned it up and reinstalled and checked leaks again. Still didnt show any. Rode it around and seemed to be fixed untill the next day I rode to work and it did the same thing. I ended up idling mine at around 850 rpm instead of 1000 and hasnt done it since. But its a little sluggish on take off if you roll the throttle abruptly (has a slight hesitation) which mostly goes away when idling at 1000 rpms. I usually roll the throttle slowly on take off so it was a swap off I decided to just live with. You might try to idle it down just a little, say start with 950 rpm and see if it helps. If not try 900 rpm.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,071
Likes: 1,006
i believe megawatt is on to something. if the flyweights are binding, the idle will move around depending on where they stick at. at idle, it is suposed to retard the ignition timing but if the weights stick full advance, the idle will be high. my 1974 ch went through the same thing and i replaced the whole advancer assy with a stainless steel one with needle bearings on the pivots, end of problem!!
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Seasoned HDF Member
Joined: Aug 2008
Posts: 5,071
Likes: 1,006
hey jcsportster: check your idle mix. if you get carb farts, then you are on the lean side but if it is sluggish then it is too rich. when you blip the throttle, the carb will go rich due to the initial high vac but the air flow will abruptly stop for a brief moment as engine speed isn't high enough to sustain the vac signal. if the mix is right, it should rev on out. i will pass on a little quark i ran across that has to do with alcohol blended fuel. when they started using it here, my idle was screwy and i could not get the mix right until i up the pilot jet one notch.
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