Question about 1972 Yamaha XS2

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1972 yam xs650 burning oil from right hand cylinder oil in intake port

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Probably a worn out valve seal. Maybe a bad ring. You can do a leak down test to see. Try a compression test anyway and see if the compression is still good in there. It will need a top end job most likely. Not too hard on that bike.
I'm curious as to how you know there is oil in the intake port. Are the carbs off? Most oil will blow out through the exhaust ports.

Posted on Jul 31, 2009

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Where do i find the serial number on a 4 cylinder toyota engine,early 70s?

Try Oil Pan / Or above it cast in block near frost plug / block heater ... maybe intake manifold ## s may cross reference ???

Nov 28, 2014 | 1972 Toyota Corolla

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I have a 1972 Yamaha 650XS Special. I am wondering if you can cut the gas valve off the tank to move it so it doesnt hit the top of the engine anymore

By gas valve, you mean the fuel petcock? That should just unscrew right from the tank. However, you'd then need to weld in a new drain port at a low portion of the tank where you could re-attach it. It's a big, annoying job, as the current petcock location is designed to permit the maximum amount of gas to drain out of the tank. Plus, not every welder will agree to work on a gas tank, even if it's been boiled out to minimize the risk of residual gas vapor.

On the other hand, it's also possible that you don't have a correct tank for your motorcycle frame. In 1972, Yamaha sold an XS650, but not an XS650 Special. The "special" series didn't start until, if I remember correctly, 1979. So, it's possible that the original tank for your bike was replaced or upgraded at some point in its life. "Special" and standard XS650 tanks have noticeably different shapes. I have worked on a variety of XS650s, and I've never seen the fuel petcock physically touch the engine at any point, even when going over big bumps and chuckholes. Luckily, if this turns out to be the problem, XS650 tanks are relatively plentiful, for bikes of that vintage.

If you are pretty certain that you do have the correct tank for your year Yamaha, I would double-check the condition of the rubber mounting buttons on which the tank rests. These harden and crumble over time. Without the rubber shock-absorbing buttons, the tank is resting directly on the metal supports. This will lower the tank but a good .5-1.5" from where it should be resting. I can see how this could cause interference with the fuel petcock and the engine.

Good luck figuring out if there's an easier fix for your tank issue!

May 20, 2011 | Yamaha XS2 Motorcycles

1 Answer

I am rebuilding a 1972 yamaha xs2, the forks are rusted and need replacing. Can you tell me what size the tubes are?

Hi there.
The 72 XS650 uses 34mm OD fork tubes. You can easily get replacements from MikesXS for US$129 a set. They have all of the parts you may need to overhaul the forks. The OEM part number for these is . # 306-23124-60-00
regards robotek

Mar 16, 2010 | 1972 Yamaha XS2

2 Answers

2003 expedition misfire on #5 cylinder...what should i do

Check the valves for that cylinder. Open the valve cover and turn the engine by hand and watch the valve as the 5th cylinder opens. Both the intake and out valves have to open then seal right back down. One of them may be stuck or burned out.

Dec 29, 2009 | 2003 Ford Expedition

1 Answer

Idles normal with hand over carb and gets to much air with hand off

You have a major air leak on the carb intake, cylinder, head or seals. Tighten down the head to start with. Tighten down the carb and the manifold it is bolted to. If that doesn't fix it, as old as the bike is, I would find a gasket set with crank seals and then replace the crank seals. When replacing seals tighten the center case screws. Then I would move on to replace intake manifold gaskets and head/ cylinder gaskets.

Check the crank bearings. Hold the flywheel in your hand. Lift it up and down then move it left and right. Any movement or is it rock solid? If movement then you will need to take the engine apart and install new crank bearings.

While you are checking things, pull the cylinder head and de-carbon the head and cylinder. Run the piston down and check the exhaust port. Over the years carbon may have built up in the port and plugged it nearly closed. It should be about the size of the intake port. Remove the buildup to allow the engine to breathe.

Please rate this answer. Thanks!

Apr 20, 2009 | Honda Fusion Motorcycles

1 Answer

Dead pw 50 and sad boy.

Many things could cause the problem. Let me see if I can help out.
You have spark, but is it enough spark? A weak battery can rob power from the coil so only a weak spark is present. Get a new stock NGK spark plug to eliminate the possibility of a problem plug.

It is good that you cleaned the carb because that would be my second target. Reset the air and idle screws. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Clean or replace the air filter and be sure the bolts are tight on the carb manifold. INSTALL AN IN-LINE FUEL FILTER. Let the float bowl fill then start the engine. Set the idle speed with the idle screw.

Remove the cylinder head. run the piston down to the bottom of the cylinder. look inside the cylinder. On th carb side (intake) you will see an intake port > a large hole that lets gas into the cylinder. Now look at the exhaust port. It is possible the exhaust port is pretty plugged up with carbon. The intake and exhaust ports should be approximately the same size. Are they? If not then remove the muffler and take a screw driver and plastic hammer and knock the carbon into the cylinder, thus enlarging the exhaust port to its' proper size and allowing the exhaust gases to escape. Vacuum the carbon out of the cylinder. De-carbon the piston top and the cylinder head.

Get back to me and tell me what you find. If more is needed we will go further.

Apr 12, 2009 | 1972 Yamaha XS2

2 Answers

Grey smoke high oil usage

It sound like you have a set of worn intake valve guides and seals. When your engine is idling , the intake manifold vacuum is high. If the guides or seal are bad, the manifold vacuum draw oil pass the valve stem. then in intake ports.

Apr 03, 2009 | 1999 Chevrolet Silverado 2500

1 Answer

Tail light wiring? 1972 xs650???

no problems at all black yellow and blue

Jan 17, 2009 | 1972 Yamaha XS2

1 Answer

4jb1 engine

I can tell about a couple of odors from oils that are quite indicative of the places where they oil is leaking into the exhaust though.

You've got a few internal places where oil can get into the engine and even some can get into the combustion chambers. They have distinctive odors and can really help diagnose the cause or reason for the oil consumption.

First let's start with the "sweet-smells".

This means that the oil have gone through the combustion process along with the engine's fuel (gasoline or diesels too!). It is about the same smell you get whiffing the exhaust on a 2-cycle engine with gas-oil premix.

Places where this CAN happen:

1) Cylinder walls ie; piston rings, worn or broken.
2) PCV system where the oil is sucked into the manifold under vacuum and is entrained into the combustion chamber in the normal air-flow to the engine for combustion.
3) Intake runner-to-head surface gasket(s) where the intake can actually **** oil from the cam tray area or the inner valley between the heads and the intake manifold.
4) Occasionally from changing spark plugs in "well" type plug chambers that let the plug get very close to the head through the head casting. Taking a plug out and letting the collected oil fall into the cylinder is usually a temporary situation, but can scare you when it happens.
5) Cracked head or blown head gasket: this usually has to happen where the head has a high pressure passageway for the oil to travel through the head to get to a cam tower on top of the head.
6) Now - here's something that's gonna get debated, fer sure! ONLY the intake valves can leak past their stem seals and allow oil to travel down the stem onto the combustion process. Remember that I am speaking or "sweet" oil smell here.

Now some of the "not sweet" or bitter oil smell:

1) Exhaust guides or stem seals on the EXHAUST valves ONLY can cause a very acrid smell of nasty, eye watering and cough-inducing stink.
2) CVCC or pre-combustion chambers can also cause this problem. The Honda CVCC engines were notorious for this! The auxiliary valve can leak oil into the pre-chamber and then it opens the valve and dumps the burning mess into the main cylinder head area and the results are a bad BAD stink and lots of white/blue smoke.
3) RARELY...very rarely the exhaust port AFTER the exhaust valve seat can become perforated and allow oil to get into the exhaust stream. It does NOT burn here - rather it just cooks-off with a very bad smell.


Acrid oil smell
- the oil has NOT gone through the combustion process in the cylinder head but is rather "cooked" into a stinky odor. It may or may not smoke too much too.

Sweet oil-burning smell - oil that has been burned as part of the combustion process in the combustion chamber on one or more or even all cylinders.

Sep 16, 2008 | 1993 Isuzu Trooper

1 Answer

Thick blue smoke. no oil leaks new spark plugs and spark plug wires. checked all cylenders cant figure out why its smoking.

Hi! Chris, There are many causes of oil burning or exhaust smoke. There are three different causes of normal oil burning, 1; worn valve guides (smoking during deceleration), 2; worn cylinders and piston rings (smoking during acceleration), 3; split or worn out valve seal, or damaged intake manifold gasket (smoking all the time). Of course there are several variables in this equation. Sometimes coolant can also get into a cylinder and cause a blueish smoke. If you remove the spark plugs and use a pressure pump on the coolant system (radiator), coolant should leak into the intake manifold or cylinder. Coolant leaking into the intake manifold will leak into several cylinder through the valves. So, what year and how many miles are on the Jaguar?

Aug 08, 2008 | Jaguar XJ6 Cars & Trucks

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