Reading through some of the posts on the internet, I often see well-meaning individuals telling someone to “just stick some gas in it and see what happens,” in response to a question about a bike that has been store for 25 years—or more! The bottom line here is that, while this does work occasionally, the chances are you will damage something inside the engine. Also, it is important to remember that the bike was stored for a reason. (Do you want to seize it solid only to find out that it was parked due to an oil pump failure?)
Although it is very tempting to “try to get it going,” taking a little time to check some essential settings and components will pay dividends in the long run.
What to Check:
- Fuel System
- Oil System
- Cylinder internal condition
One owner in a thousand will go to a bike that has stood for 25 years (for example), and have it fire straight up without any problems. It is not unheard of for some vintage (side valves) motorcycles to be started on old gas that is in the tank, but it is very rare. For every one of these “good news” stories, there are a lot of people wishing they had done some checks.
The fuel mixtures/blends of today are very different from their predecessors. In most cases the fuel inside both the tank and the carburetors (assuming it was not drained) will have deteriorated to the point where it will not combust (even under compression) and is nothing more than a gooey substance in the bottom of the tank and float chambers. That being said, if the fuel was drained from the float chambers, but left in the tank (full), there is a good chance that the inside of the tank will have been protected from corrosion.
If the tank and carb/s do have residues in them (also rust in the tank), the entire system will need to be professionally cleaned. This “professional” cleaning can be done my most dealers, or by specialists with ultrasonic carb cleaning machines. (Note: These machines are available for less than $50 in some cases, but the buyer must research their suitability – check the reviews – for this type of work.)
Once the tank has been cleaned and is rust free, it should be sealed with a proprietarytank sealer such as Red-Kote™.
The entire oil system must be drained and flushed through. On machines that have stood for some time, the majority of the engine oil will have drained to the sump. In the sump, the oil will gradually deteriorate. To get most of the old oil out, the mechanic should leave the drain plug out for some time and if possible warm the base of the engine (with care as oil is of course flammable.) Before removing the drain plug, it will help if the mechanic pours boiling water over the cases; this will help to introduce heat into the engine and oil, but again care must be exercised for safety reasons.
As the oil is draining, the mechanic should remove all of the engine’s external cases – including valve covers – to check inside and to remove any oil that has collected in the pockets of the engine’s castings and covers. The old oil must be inspected for any signs of internal engine damage—the bike was stored for a reason! If there are any metallic pieces coming out with the oil (it is common to see a small amount of aluminum particles in the oil of most old engines), the engine should be fully rebuilt to err on the side of caution.
If the oil looks relatively clean, the mechanic should attempt to rotate the crankshaft via the large nut typically seen on the end of crankshafts to retain the primary drive gear (see below about internal cylinder conditions first). This rotating process must be done slowly and terminated if a lot of resistance is experienced. As the engine is being rotated, the mechanic must check that the valves (on 4-strokes) are opening and closing properly—it is a common problem on motorcycles that have stood for some time to find the valves have stuck open.
Internal Cylinder Condition
If an engine has stood for some time, there will generally be a line where the piston rings came to rest. If the mechanic turns the engine over without cleaning inside the cylinder (ideally, the cylinder should be honed), the rings will scrape any rust or old oil etc. into their groves. Therefore, if the cylinder looks to be in poor condition, the engine should be rebuilt.
Assuming the internal condition looks good, the mechanic should conduct a cranking pressure test, then a leak-down test. Both of these tests will reassure (or otherwise) the owner of the internal mechanical condition of the engine.
Owners of machines with wet plate clutches will invariably find the plates have stuck together over time. Before disassembling the clutch, the mechanic should first try to free the plates by rocking the bike forward and backwards while in gear with the clutch out (obviously without the engine not running).
If all of the above checks out, and the bike was prepared for long term storage, the owner should be able to add new gas and start it up. But the chances of this, as mentioned, are slim. For most owners, the old adage of “better safe than sorry” is the best advice.
source: About autos