Fuel and fuel starvation

Fuel Grade
The Trophy tends to run on most octanes without too many problems. 87 octane seems to be popular, and doesn't cause 'pinking'. In the UK, 91 octane is the basic fuel available at petrol stations. Some report higher octane giving slighter better mpg and lower engine temperatures, but others disagree. Edit: Higher octane fuel is designed to not pink (pre-ignition) in higher compression engines - it is LESS explosive and less calorific......

Gasoline rated 91 octane in Europe will typically be rated 87 octane in the United States or Canada. Octane in the United States is determined differently than in Europe. Europe, including the UK uses RON (Research Octane Number). RON is determined by running the fuel in a test engine under controlled conditions. In the United States and Canada, octane is the average of RON and the Motor Octane Number (MON). MON is measured using different test conditions than RON, and MON is usually about 10 points lower than RON.

Gasoline-Ethanol blends
The United States requires oxygenated gasoline for modern automobiles in order to promote a more complete combustion and to reduce emissions. This gasoline is typically up to 10% ethanol (E10).

Many states allow the use of ethanol-free gasoline for carbureted-engines, such as in boats, cars and trucks, motorcycles, and power equipment. Ethanol-free gasoline may cost significantly more than gasoline mixed with ethanol, but it may also be worth the investment.

Ethanol in gasoline can cause swelling of rubber components in the fuel system. It also contains less chemical energy and will cause lower fuel economy and weaker performance.

Ethanol raises the effective octane of a fuel. It may also cause incomplete burning and carbon deposits in the cylinders. Symptoms of "ethanol poisoning" include poor performance and black, dry spark plugs.

Gasoline containing ethanol is hygroscopic, meaning it absorbs water. E10 gasoline can absorb 50 times more water than non-ethanol gasoline. Ethanol-containing gasoline will separate into gasoline and water if it contains more than 0.4% water. Ethanol-containing gasoline also has a short shelf-life of up to 100 days (Ethanol-free gasoline has a shelf-life of several years). This shelf-life begins when the gasoline is mixed, not when it is pumped. In the United States, "Premium" 93-octane gasoline may sit in the storage tank at the gas station for a significant time before it is pumped, and it may have already gone bad by the time it is pumped into a vehicle.

Several fuel additives, such as Lucas fuel treatment, Sta-bil, SeaFoam, etc. will help to improve the stability of a gasoline-ethanol blend, but they will not reduce the affect of ethanol on fuel system components.

BUT Fresh fuel beats them all.......So drain the fuel particularly from the carb bowls (nice if you loosened them in the last service) and make sure fresh fuel flows freely comensurate with the settings on the fuel tap. Even letting them run dry and switching to prime and seeing fuel eventually flow will reassure you that part of your system at least is working (or sucking on the vac line from dry)....Allow 1 minute for fuel to flow on prime (one elephant, two elephant.....) and if then the bike doesn't start charge the battery.....as stressing the battery wont help. Furthermore Prime setting allows fuel to fill from one pipe, pressing prime in allows fuel to flow faster from both pipes......which eventually makes no difference as the carbs are linked and fuel flows across the filter line....

Fuel Consumption
This is a difficult one. An attempt to compile figures was made from information feedback, but the variations were huge, even taking into account US gallons versus Imperial gallons. One can only assume that different octanes, altitude, state of tune of engines, different make of carburettors all confuse the issue. One thing for sure; the Trophy is not an economical user of fuel if ridden fast ! Ken Hastie's 1998 1200cc Trophy averages 40 mpg (Imperial gallons).

Carburation
A very useful source of information on how to set up your carburettors is available at Factory Pro



Very easy to set up...........Firstly one assumes everything else is working otherwise it is a pointless exercise.....Clean carbs, plugs of the correct colour, no misfires etc.....BUT check plugs after making changes to ensure you have not made an error. Initially, make sure the pilots are set to 2 turns out for mikunis (carbs off the bike) and 3 turns for Keihins (rare late models). These bikes will be harder to start at 1.5 turns and 2 turns respectfully and the plugs will show signs of running hot.

Next make sure the vacuum slides operate by blowing into the adjacent orifices and mechanically adjust the three or four butterflies so that they just crack open together (with the tickover adjuster wound out so it isn't affecting the positions.) when all lift off together then wind in the tickover screw until the butterflies just crack open and a maybe a turn more......With carbs refitted and airbox off - the bike should start and the vacuum sliders should be seen to react together (otherwise suspect air leaks) but 1. Ensure choke operates correctly - opening and closing fully (3/4 open to start)

2. You have allowed 3mm or 1/8" of free play in the throttle cable (otherwise the bike definitely won't start)

If the bike doesn't start 1) charge the battery and check voltages (there has to be a section in this WIKI on Voltage losses at the coils) and 2) wind out the tick over.

This is sufficient to run the bike. set the tickover at 1000rpm (for lots of reasons). Go for a run and reset the tickover once out on the road.....................

Next stage is what I call "fine tuning" which involves balancing the carbs. This will only be noticeable at tickover and tends to allow the engine to tickover more smoothly.

Look up home made manometer carb tuning on YouTube......you will find closed loop setups for multi cylinder bikes (involving some tubing and crosslinked bottles). It is my experience that these simple setups (being closed loop, shared damping, measuring relative pressure) are many factors more accurate than bought products that attempt to measure ABSOLUTE flow, ABSOLUTE pressure with 3 or 4 independent units. (If you are a physicist you will know why)........

In any case the manner you choose to do this will give you readings that will put your mind at ease as to the approximate vacuum that the carbs are creating in their 720 degree suck blow cycle. If you use the manometer you will definitely hear the engine note/pulses become regular and metronomic as the readings come togehter .......if you use a less accurate method you can hunt around with each carb setting until you think it sounds better......

But don't despair as tomorrow the conditions will have changed and your carbs may be perfect for the day......and no-one rides around at tickover....

A2

Fuel Starvation
Fuel starvation is a common problem on many Trophies. This is a situation where some bikes apparently run out of fuel, but the tank still holds a good supply. It is a phenomenon which happens somewhere between 1/4 full and empty on the fuel gauge. There has been a huge amount of discussion on various groups about this problem, and there are many different views as to why it happens. Not ideal, but the simplest solution is to refill your tank before it hits the 1/4 full mark!

The fuel tap is a diaphragm valve, which opens when a vacuum is present. There are fuel selection markings "ON", "RES", and "PRI" on the selector knob. The fuel tap has a separate vacuum line running from it, and many owners have found this line to be kinked, preventing the fuel tap from either opening to pass fuel, or from closing to shut off fuel when the engine is off. Each time the fuel tank is removed and replaced, you must make sure this line is not kinked. Many owners replace the fuel lines with a better quality (more rigid) line to solve the problem. Tygon lines are recommended by some owners and others are known to run their bikes with the fuel tap in the PRIME position, to bypass the vacuum operated part of the switch. The diaphragm sometimes sticks open. This means the fuel does not shut off, particularly noticeable when you remove the tank! By removing the vacuum line, the diaphragm can be carefully 'popped' shut by inserting a thin probe.

Another reported problem leading to the 'Fuel Starvation' problem is rust from the inside of the fuel tank clogging the vacuum controlled fuel shut-off valve. This could not be determined by riding on "Prime" due to fuel only flowing freely when the valve is in the "Prime" position AND depressed 1 mm or so. Rust can both clog the shuttle and eat up the internal o-rings. The cure in this case is to fit a whole new petcock assembly ($95+) and clean the substantial iron deposits (3/8" deep!) out of the bottom of the float bowls. Apparently, the height of the fuel in the tank may exert enough pressure to assist the vacuum shuttle in opening. Thus the bike may start sputtering at 1/4 tank and below. This is now completely cured and the bike runs great all the way down to empty. If you have the "1/4 tank splutter" you may want to check your tank for rust, and drain the carbs onto a paper towel and look for excessive rust in the float bowls.

Yahoo group member Tony Dagostino has written in the files section of the Yahoogroup about the Roll Over Valve with a description of his (and local Triumph mechanics from two different dealerships) view of the problem, together with a scanned-in page from the shop manual. They say that removing the roll-over valve has usually solved the tank venting problems, which lead to fuel starvation. However, the roll over valve is a safety feature (prevents spillage of fuel in a lay-down), and great consideration must be given to any thoughts of removing it.

Theories abound - I suffer from quarter tank syndrome in certain geographical circumstances that I associate with the rib in the tank......On one particular route that is generally downhill over 20 miles I can seemingly run out of fuel - or even splutter - until I reach the valley bottom and start to climb and the fuel level eventually makes it to the back of the tank and no doubt from right to left over the spine too (variations apply depending on fuel level). Alternatively a very quick stab of the brakes (very quick - not life threateningly) will force fuel over the spine and my spluttering ends.....Next scenario is a long motorway run on smooth roads where the fuel stays on the right hand side of the rib and passing on to reserve does not have the desired effect until forced to stop then the bike can be lent over to the left (or the jab on the brakes technique). Leaning to the left when moving doesn't displace the fuel.- Yes I could fill up more often but I may as well take the car....My particular commute allowed me to fill on a Sunday and again on the Wednesday PM without usually hitting reserve but I would occasionally just hit the "quarter tank syndrome" instead....depending on how much enthusiasm I had shown on the previous runs.

Fuel Lines
Fuel lines do not last. There is a common tendency for the fuel lines which lie along the carburettors to crack and leak. Members have recommended Tygon replacement line. Fuel lines are 5/16" and the vacuum line is 3/16". OEM replacements are available and are pre-formed thus easier to reconnect. Fuel injection hose can be used (I use this with quick release connectors over the battery (with permanent long 1/2 leads to the tank and long 1/2 leads to the carbs) as it is easier to connect and check) but automotive fuel hose with a braided cloth covering has a particularly short life.

Fuel Filters
The Trophy uses the fuel "sock" inside the fuel tank as the main fuel filter. Beyond the fuel sock, it also is manufactured with line fuel filters that are situated inside the tees that deliver fuel to the carburetors. These tees are easily clogged with any debris that passes the fuel sock. They are the last protection before the needle and seat valves in the carburetors. Rust or grit in the fuel tank that gets past the fuel sock might become lodged in the fuel tap, preventing it from closing when the engine is shut off. In addition, rust or grit that gets past the fuel filters (if they haven't been removed), might become lodged in a carburetor needle and seat. If both of these happen at the same time, fuel will overflow the carburetor bowls and drain downhill into the cylinder, flooding the engine. If this condition happens, the bike could become hydro-locked, preventing it from starting, and the engine oil could become contaminated with a large amount of gasoline.

Rust passes through the filters in suspension in the water (dissolved). The filters tend to hold back water in the tank due to it higher capillary attraction but eventually water droplets pass down to the carbs carrying rust which is immediately dropped when the water comes in contact with the aluminium in the carbs. At the same time the engine tends to misfire on sharp openings of the throttle as the heavier water eventually gets lifted.

A greater risk from jammed open Petcock and Carb floats is fuel making its way back into the air filter where a fuel fire may be possible or the fuel carries on down the breather pipe and fills the engine casing. This has an aggressive action on the main bearing shells - possibly due to a reduction in the Oil's effectiveness. Edit : more likely that fuel leaking into the carbs will get into the airbox and drain down into the oil sump causing catastrophic engine failure