Question about Harley Davidson XLH 1000 Sportster Motorcycles
I'm trying to reassemble the engine of a 79 Harley Sportster engine. the problem is I'm uncertain which cylinders go on the front and which on the back, because they were not labeled when the engine was tore down. my question is how to determine the which one goes where when they are identical
Hi Andrea, the bottom of the cylinder sleeve will be cut out for rod clearance just have those cutouts facing each other. Good luck
Posted on May 23, 2015
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Posted on Jan 02, 2017
"Backfiring" is a pretty broad term depending on where you live. Some people refer to backfiring as popping from the exhaust while others refer to it as the engine spitting through the carburetor.
I'll assume that you're talking about popping out the exhaust pipe. If it does this after you rev the engine and it backfires on the way back down to idle, this is typical of an exhaust system sucking air. The mixture is extremely rich under these circumstances and will not ignite. But, if your exhaust system is sucking air, it combines with the fuel air mixture already there and bring it to an explosive mixture thus the backfire.
You can check you valves but I've always found that if the valves on an Ironhead are too tight, it's extremely difficult to get it started due to the low compression on that cylinder.
Check you ignition timing and points setting. Also, what kind of condition is your mechanical advance in the distributor in? I'm assuming this is an XLH model and not the magneto equipped XLCH.
What type of carburetor is on the engine? Hopefully not the original Tillotson that it came with. If it's an S&S, the low jet should be a 28 and the main jet a 66 to 70.
Posted on Jun 11, 2010
Ok, first off, this ain't no Yamaha you're messing with. It's a completely different motorcycle in most every way. Not saying it's better or worse than the *** bike but it's different.
It has two cables, this is correct, but only one carb. One cable is the throttle cable and the other is the idle cable. The idle cable pulls the carb shut in the event the throttle plate spring breaks on the carb. It's a safety thing and it was the same way on your Yamaha.
Now, if the front cylinder is not running at idle, I would suspect a vacuum leak somewhere. There are several places where you could have a vacuum leak. Of course, the intake manifold seals could be leaking, the intake carburetor seal could be leaking, or the VOES/ petcock line could be causing a problem. Unless you have taken your air cleaner off for some reason, I'm going to assume that the problem is in the petcock.
Your bike has one of the vacuum operated petcocks in the tank unless it's been changed already. Vacuum from the engine opens the petcock allowing fuel to the carb when the engine is running but when the engine stops, the vacuum disappears and the petcock closes. Supposedly. This is the worst piece of junk Harley ever put on their motorcycles. They do two things, they quit working and won't let fuel into the tank or they cause a small vacuum leak that will cause the bike not to idle properly. I suspect you have the latter case.
Drain your fuel tank by loosening the petcock and allowing the gas to run out around it. Catch the fuel with a large funnel and an empty fuel can large enough to hold the fuel in your tank. Once empty, disconnect the two hoses and remove the petcock. On the backside of the petcock, there is a square plate. Remvove the four small screws and take the plate off. There will be a diaphragm, a spring, and needle under the plate. Remove the plate carefully so you can see how it goes back together. Hold the diphragm up to the light and gently stretch it while looking for holes. If you find a hole, you'll have to either buy a new diaphragm and repair your petcock or , better yet, replace the entire petcock with a manually operated one. A Pingle petcock is a very high quality valve and you'll like it but it is pricey. If you buy an OEM petcock, get one for a 1995 or earlier bike. You will no longer need the vacuum line and you can plug it with a small bolt or something to stop the vacuum leak.
This vacuum line comes off a nipple at the backside of the carb and it feeds vacuum to two things. It's a 3/16" hose that goes up to the VOES switch mounted on the frame under the tank. From there it "Y's" off to the smaller hose that goes to the backside of your petcock. Take your fuel tank off and inspect this hose. Look for cracks. If you go with the manual petcock, eliminate the small portion of the hose by replacing the hose that runs to the VOES with the single hose instead of the "Y'd" hose.
As for the idle speed of you engine, it should be set at about a thousand RPM. Look at the top of the carb. There is a screw near the top on the right side of the carb. That is the throttle stop screw. It controls the idle speed of the engine. Turn the screw clockwise to increase the idle speed.
Ok, try what I've written here. If it doesn't work, get back with me.
Posted on Jul 21, 2010
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