1979 Honda XL 125, only 600 miles on it. The

Water and vapor (steam) coming from the tail pipe is normal and will stop after a few miles when everything is hot. That is one of the reasons exhausts need replacing as they rot with rust and is more evident on cars that only do low mileage as the exhaust does not get hot enough to boil off the water and it sits in the pipe slowly rusting it away. What you see as smoke is probably steam and is more evident on cold mornings. If the car is not using oil then I wouldn't worry.

Might be a drain. Next time you ride past the Honda shop, drop in and ask the friendly guy or gal behind the parts counter. I would expect to see some smoke after a prolonged out of service period.

Making friends at the parts counter will pay you BIG dividends in the future.

Thanks for your interest in FixYa.com

Backfiring out of the exhaust pipes usually indicates an ignition problem. What happens is that the fuel air mixture in the cylinder is not burned and is exhausted into the exhaust pipes. The next time the cylinder fires and the exhaust valves open and allows the residual flame to exhaust into the pipe, it ignites the unburned fuel in the pipe from the previous misfire. What kind of igniton system is on the bike. And, spark plugs will foul within minutes in an Ironhead Sporty if the mixture is too rich. Your super "E" is still a quite large carburetor for that engine. It should have a #26.5 slow jet and a #66 main jet. Make sure that your accelerator pump is not adjusted to put too much fuel in the cylinder when you open the throttle. Go to S&S's tech site and download files 51-1012 and 51-1013. This will tell you everything you need to know about your carb. http://www.sscycle.com/instructions/instructionslist.php?x_cat=24 If you are running open drag pipes on your Ironhead, you don't have enough backpressure on the exhaust system and you've probably got a flat spot at about 55-60 mph. If so, look on the backside of the exit end of the pipes. There may be a hole in the pipe for the bolt to hold the baffles in the pipe. If this hole is open, install a 1/4" bolt that is 1 1/4" long in the pipe with three nuts on the bolt on the inside of the pipe. Put one of these bolts in each pipe. This will give you just enough backpressure to almost eliminate the flat spot and the bike will perform much better. Due to the hemispherical design of the heads, the Ironhead must have some backpressure. I hope this helps.

Good Luck and Ride Safe
Steve

At least 100 psi to run, but should be 125-140 psi
If your not getting any compression and you don't think the rings are bad, then check you valve clearances. If a valve is stuck open, you wont get much compession.
Put motor on TDC. Put are hose in exhaust pipe and listen to see if air is passing through head.
If so the exhaust valve is open.
Blow air into intake side and listen if air is escaping through head. If so, the intake vaklve is open

At TDC both valves should be closed on the compression stroke.

use plenty of penetrating oil
normally a exhaust shop would apply a lot of heat to the join as that breaks down the carbon/rust and allows it to tap apart

It's rust. You can try to use some penetrating oil on it, WD-40 is a close second. And if you were able to heat it up (running it) sometimes that helps, but you can end up burning yourself. The middle DOES come apart, and all you do is loosen that clamp and slide it out. No special procedure on this one. Rust will hold things in place very well. If you have to, find a way to grind the nut off the clamp, and buy a new one...but find one before you do this or you may wind up with more of a headache. The schematic I saw looks as though the exhaust will come off just after it bends to match the frame, so you can take both exhaust pipes off at that point and maybe slide it out from under the rear tire (if the bike is on its center stand?) Here's a link to BikeBandit, they have schematics for all the parts of your bike.

http://www.bikebandit.com/houseofmotorcycles/1979-yamaha-motorcycle-xs650-2f/o/m8268#sch215387

Hope it all goes well.

Bruno

The exhaust maniifold to head nuts are 23 ft lbs.

The manifold to exhaust pipe nuts are 40 ft lbs.

Changing the oil pan gasket on a GMC Yukon XL is realtively simple, but does require removal of the exhaust pipe. You will need a new oil pan gasket and a new exhaust pipe flange gasket.
Put the car on ramps or jacks to access the undercarriage.
Remove the exhaust pipe by removing the 3 nuts holding the exhaust pipe flange to the exhaust manifold. These nuts often rust and prior application of penetrating oil may be required to remove them without damage. Once the pipe is unbolted, work the exhaust system loose from the hanging brackets. In most cases the entire system does not have to be removed since there is enough room to remove the pan with only the front hangers removed.
Drain the oil from the engine
Remove the 10 mm bolts holding the pan to the block.
Remove the old gasket material and scrape any remaining gasket from the block and pan.
Install the new gasket. Forma-Gasket or a similar product may be used in small quantities to "glue" the new gasket in place and prevent shifting while the pan is reattached to the block.
Reinsall the 10 mm bolts in a cross pattern to ensure the gasket is compressed evenly. Do not overtighten the bolts.
Replace the pipe to flange gasket between the exhaust pipe and the exhaust manifold with a new part.
Reattach the exhuast pipe to the hangers.
Install the 3 bolts connecting the pipe flange to the exhaust manifold.
Fill the engine with oil.

This is the closest manual to your bike I can find.
http://www.autorepairmanuals.biz/site/57...
As you can see, it covers from 1979 - 2003 - Honda rarely change their engine configurations when they make something that works.
This manual was probably last printed in 2003 - and later year bikes just added updated pages (Honda does that quite often to save on re-printing new manuals).
The XL model is exactly the same as the XR, except the XL has additional components to make it street legal - battery, head light, tail light, turn signals, horn and street legal tires