Fuel Consumption

[Athedra]

Bones all of a sudden started sucking fuel, not just using it. Used to travel 4 days on a tank, now I can do 2 days and half way back.

I am doing no extra travelling, and even started slowing down when I noticed the fuel change.

Any ideas of where to start looking?

No fuel leaks that I can see just in-case that was a thought

[XSokieSPECIAL]

Bones all of a sudden started sucking fuel, not just using it. Used to travel 4 days on a tank, now I can do 2 days and half way back.

I am doing no extra travelling, and even started slowing down when I noticed the fuel change.

Any ideas of where to start looking?

No fuel leaks that I can see just in-case that was a thought

Shift it up out of second gear.

Check your plugs. Is it running rich?

[Athedra]

you mean there is more than one gear?


Plugs seems a bit oil fouled, not rich. Thinking of pulling the carbs again this weekend. Glad I got the pods, saves the problem of forcing the carbs past the stock airbox.

[XSokieSPECIAL]

Are you certain it's oil and not fuel fouling? Is it real black and sooty or just black and greasy. No that is NOT a racist remark---it just came out that way.

Is it all 4 plugs? I don't know how it is in South Africa, but in the southern USA the fuel mixture of ethanol and gas changes from winter to summer with there being more ethanol in the mix in the summer causing a noticable drop in fuel mileage.

I get a rash of people in the shop in late spring every year thinking they need a tune up because thier fuel mileage dropped all of a sudden.

[mxmikie]

check your vac advance

[dbeardslee]

Is it running differently, or is it just increased fuel usage? Seems like you mentioned putting pod filters on your carbs not too long ago - I think you called them 'cones'. What did you do with the vent lines after installation? On 78/79 carbs, a restriction in the vents could cause it to suck gas, but you would probably notice it running kind of 'boggy'. If you put filters over the ends of the lines, and they've got paper elements inside it can be problematic. As the paper absorbs moisture it becomes restrictive, and can eventually cause overflowing float bowls with gas pouring out of the carb bells. You also want to make sure the pods aren't covering, or partially covering the air jet - some have a lip on the rubber that causes problems there. JAT

Note:
Never try to clear the vent lines by putting compressed air into them with the bowls attached - it will increase the air pressure inside the bowl and squish brass floats.

[skids]

I had the same thing suddenly happen to one of mine. It turned out that the baffle in the stock muffs had developed a big hole. Funny thing, it didn't really seem louder.

[redbone]

check and see if one or more of your brake calipers aren't stuck closed.

[Athedra]

Checked the cones (Pods) they dont have an inner lip. Vent pipes? Where?. Didn't have one of those when I took of the original airbox. Apaprt from the pipes running inside the airbox (which I still have no idea what they are used for since they where disconnected in the first place), there was no other pipes.

The cones (pods) are echlin 54mm racing cones (pods). Apparently the best on the market, and at R120,00 each they better be. Had a look at them, and they are definitely not clogged.

I listened to the exhaust and it seems the same, except for a blow on my second exhaust pipe. I am fitting new exhaust gaskets tomorrow night.

The plugs are black and greasy. I need to do the heads sometime in the near future.

The brakes seems ok. Good thing you mentioned brakes, noticed my RH side needs new pads, so will also be done tomorrow.

The fuel change thing, I have no idea. It is summer over here, so if they change the mixtures, I wouldn't know.

I will keep hunting for the problem. Thanks for the lead points so far.

[dbeardslee]

On the '78/79 carbs you should have two sets of "T's". The bottom T's connect to the fuel lines, and the top ones are for the vents. If it's got later model carbs installed there won't be any upper vent lines.

[TopCatGr58]

Hey Athedra,

Check to make sure you are running on all 4 cylinders?? Spritz the pipes after it warms up, are all 4 sizzling? IF one's gotten fouled, it'll just pump the air/fuel mixture thru the cylinder, but you won't get any power benefit from it. I can't remember all the work you've done to it recently, like the pickup coil fix, or new ignition spark coils/wires/plugs, etc.?? Sounds like you've got good quality pods, so you probably are not suffering any restriction of the inlet bell vents.

While you have the carbs off, if there are only 3 small round ports on the inlet bell, then you have the early model carbs, and they vent the bowls thru the upper T's as mentioned by someone else. IF they have 4 small holes, then the have the built in bowl vent going into the inlet bell.

The pipes on the inside of the airbox were to route the scavanged exhaust gases from the crankcase hose...the LARGE one that you probably have routed down behind the engine to air, or hopefully have put a canister filter on the end of it; that hose would have gone into the front of the OEM airbox. The airbox may have had some smaller nipples for other smaller hoses, but IF your carbs didn't have the uppper T vents, then those nipples would have just been closed/sealed off, just for show, not functional.

Hope you figure it out soon, with your 750 FD mod, you definitely should be seeing good mileage. Have you noticed any other noises in the middle gear or final drive? Have plenty of hypoid gear oil in there, not getting dry and partially burning up the bearings?

T.C.

[Athedra]

Thanx TC. Your post arranged my Saturday for me. (Kept me busy for the day). Had a whole day to kill, and your info gave me something to do.

Did the following and found the following:

Started by removing my exhaust and checking it front to back. Had two blown exhaust gaskets in there (2 and 3). Replaced all four and sealed it up with some fire gum. (White glue type goo that swells when heated and then becomes hard as a rock). Started her up and she was silent in the front and extremely noisy at the back. Took my silencer off, looked inside and saw that I have no baffles left in there. Order me a new slip-on Cowley Silencer, will be here next week (R1000-00 for it).

Checked oil levels on all my drives and also the motor. Decided to do an oil change on my motor oil. The oil that came out was still ok, but had nothing else to do at that time. I then stripped off the cones (Pods), washed them in petrol and just to as a test while it was wet, stuck my mouth into the carb side and breathed in. (Don't try this at home.......MAJOR HEAD RUSH), after the head rush, I figured that there is definitely no restriction on the cones (Pods) when soaked. Took off the carbs, and decided to remove the intake rubbers while I have everything open. Gave them a few more coats of tool grip and then reinstalled them.

Now it is round about here where my problems started. I installed the Rubbers according to the numbers I wrote on them. Leaned down and realized that the rubbers are pointing upwards. Removed them again did a few measurements, re-installed and got the same problem. I went to out local bike shop, and he pulled out a set of rubbers for a TL1000 out of his store room for us to see where the problem could be. As he placed them on the table I realized two is marked LH and the other two is marked RH. Took my rubbers out of the bag, placed them on the table and with a bit of mixing and matching found that they where the wrong way round in the bike. (I didn't know that they are different since I have vacuum outlets top and bottom on my rubbers) Went back home (Feeling really stupid) and fitted the rubbers the right way. Since then the leak on carb 2 stopped.

While I had the seat off, I lifted the tank a bit to make it easier for my gorilla hands to fit inside the carb area. After I lifted the tank and getting ready to remove it, I noticed that my left hand pipe clamp is missing. I now have a funny suspicion that my heavy fuel usage is by donating some fuel to someone else who needed it much more than I did. After my above venture, I took some Hydraulic crimp clamps, and crimped my fuel lines into place. If who ever wants some free fuel in the future, they will have to cut the pipes.

Little trick I learned from my father on the two stroke side. Filled a bottle with exactly 1 Liter fuel. Filled another with two liters. Made a feed pipe on the 1 liter ones cap, and connected it to my carbs. Took the other and put it in my bag. Started her up on the one liter, and took her for a drive. Got 18km on 1 liter. Took the two liter bottle, filled up the one liter, and came back home. She died in the driveway coming back, so am truely getting 18km's on a liter.

Had a look at the vacuum t-piece. I been using those to fill by float bowls after working on my carbs. Would it be safe to add breather filters to them?

So in short, my leaking carb two was due to stupidity on my side, and the fuel consumption boils down to the same explanation as my leaking carb two.

The clever people on here will have to do the miles to the gallon conversion. I have no idea, but 18km's per liter is realy good milage over here.

[Rasputin]

I believe this is the pod restriction they are talking about. Maybe this pic will help you. From http://www.xs11.com/forum/showthread.php?t=8269

[Athedra]

Nice pic. My cones (pods) are different inside. It has a very narrow lip inside. I would assume just to stop it from being forced in to far. Also if I push the cones (pods) in up against the tabs on the carb, I still have a gap between the cones (pods) lip and the carb. WIll pull one off tomorrow and take a picture for you guys.

[Rasputin]

I then stripped off the cones (Pods), washed them in petrol and just to as a test while it was wet, stuck my mouth into the carb side and breathed in. (Don't try this at home.......MAJOR HEAD RUSH), after the head rush, I figured that there is definitely no restriction on the cones (Pods) when soaked.

I was just trying to point out where the restricition would be as opposed to using your method . Not all have this type of rubber but the cheaper ones are more prone to being restrictive. My Pods also have the narrow inner lip and those do not hamper the breathing.