Ironhead Intake And Exhaust Leaks Tests

IronMick · #1 14th October 2006

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 as this will invalidate the results.

Any change in engine RPM is a leak which must be fixed.

EDIT: Experience of forum members since this Sticky was published here is that this procedure will identify larger intake leaks, but it may miss very small leaks that also must be fixed. And that propane is definetly the better choice.

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.

OutlawTexan67 · #2 6th February 2007

I was looking at threads about intake leaks on Ironheads and trying to find a good solution to the never ending problem.So I was sitting here looking at the o-ring gasket that is suppose to fit my 80 sporty and it does fit.I also bought a complett motor gasket set and it includes all gaskets for models 79-81 and I just happened to notice the gaskets for the 79 model and they are the fat rubberband type and they fit perfectly over the intake mani and the intake port on the heads.So my thoughts were why dont you try useing both gaskets at the same time the o-ring on the inside and the rubber band on the outside the only problem is that I will have to get a bigger clamp.I have posted pics to kinda show what I mean.Give me some feedback on your opinions if this looks like a good idea.Thanks OutlawTexan67

IronMick · #3 7th February 2007

Quote:

Originally Posted by OutlawTexan67

I was looking at threads about intake leaks on Ironheads and trying to find a good solution to the never ending problem.So I was sitting here looking at the o-ring gasket that is suppose to fit my 80 sporty and it does fit.I also bought a complett motor gasket set and it includes all gaskets for models 79-81 and I just happened to notice the gaskets for the 79 model and they are the fat rubberband type and they fit perfectly over the intake mani and the intake port on the heads.So my thoughts were why dont you try useing both gaskets at the same time the o-ring on the inside and the rubber band on the outside the only problem is that I will have to get a bigger clamp.I have posted pics to kinda show what I mean.Give me some feedback on your opinions if this looks like a good idea.Thanks OutlawTexan67

I had that same thought at one time. But there is a technique to install the o-rings, and if done correctly it is an easy process and it seals properly and the extra on the outside are unnecessary. You do not need both belt and suspenders, so to speak.

If you want i can review the correct installation technique. Gotta run now or I'll be late.

OutlawTexan67 · #4 7th February 2007

I followed your your instructions on intake mani assembley and am sure that it works fine. I was just sitting here cant do much on my bike right now because the frame is away getting powder coated and I was just doing a little brain storming.

98_1200C · #5 13th March 2007

whats the proper technique for installing the o-rings

IronMick · #6 14th March 2007

Quote:

Originally Posted by 98_1200C

whats the proper technique for installing the o-rings? ...

I just finished doing this again as i just installed a 1986 Sportster carb that i got from eBay. It is a pain to do, even with this technique. But here it is:

The two aircraft clamps have to be opened before they can be installed; so open them up first.

With the manifold in hand install both o-rings onto the manifold. They are to be installed on the next ridge up from where we want them to end up. As you install them ensure that they do not roll on to the ridge as then they will just roll off when you let go; you have to stretch them up over the ridge.

Place the mani+o-rings between the cylinders at the correct location, and flip the o-rings down from the upper ridge to their final resting place.

Now you need to have 3 hands, or an assistant, or a lot of patience [i went with the latter option]. With one of your 3 hands hold the mani+o-rings in place, with the other two hands install one then the other of the aircraft clamps. Make them real tight!

On my bike the rear cyl clamp is best installed with the bolt at the top. With the front cyl if i do it that way the bolt interferes with the choke cable; so i install that one with the bolt at the front facing down.

racerwill · #7 14th March 2007

various O-rings are used as seals throughout the automotive industry... the best, easiest way to install them is to lube them with silicone di-electric grease (tune up grease)... this keeps them from rolling during install and insures a perfect seal

Ww

thewizard · #8 20th May 2007

Another piece of information that you may find helpful for when the top end has been disassembled and re-assembled, and you are trying to re-install the intake manifold. If the manifold does not line up correctly, sometimes you have to loosen the cylinder base nuts, and rotate the jugs a bit until the manifold lines up properly. The jugs will move enough to allow alignment to the manifold. If alignment is that far out to start with, do not just throw in the manifold and hope it seals, it won't, and your motor will never run properly either. Take the extra steps above (it only takes a few extra minutes) and your manifold will seal up properly.

MOREHP · #9 20th May 2007

Great point, I think I just found out why I have alot of intake leaks.

IronMick · #10 21st May 2007

Quote:

Originally Posted by thewizard

... you are trying to re-install the intake manifold. If the manifold does not line up correctly, sometimes you have to loosen the cylinder base nuts, and rotate the jugs a bit until the manifold lines up properly ...

I think the actual proper technique, to avoid this situation in the first place, is to install the heads "just snug do not tighten", then install the manifold, then final tighten the heads. This is the procedure in the manual under "Cylinder Head Installation".