Could premium fuel have caused power loss?

[Ian]

Ok well, firstly this isn’t dealing with a car, its regarding a 1975 suzuki gt185 motorcycle, but that pretty irrelevant to the topic at hand…
(btw the manual recommends anything between 85 and 95 oct fuel)
it was running fine last week…about 4 days ago i decided that it deserved some premium fuel, something like 90 octane from a circle k. couple days later i refilled the tank with more premium fuel, some 91 octane from a sunoco…

pretty much around that time it started running weird, power loss across the whole range, trouble getting up hills, a little more backfire, weird and delayed throttle response, a sort of “hollow” sounding exhaust at times… all these symptoms seem to get worse when the engine is nice and hot. idling is perfectly normal though, symptoms are only present under load

so my first thought that comes to mind is the gas… particularly the sunoco gas… now everything intuitive tells me that the fuels in the right octane range so it shouldn’t be the culprit… but the place i got it from doesn’t have that much traffic trough it ever, and it’s run and owned by indians, maybe not following regulations idk… :whistle:
so that combined with the thought of how rarely drivers buy anything but regular unleaded fuel…leads me to believe i may have gotten a batch of some old, dank, expired premium gas thats funking things up?

obviously ill know if that was the problem when i put some more gas in (which i will update on here), but hopefully the results will be useful to anyone finding them in a similar confusion.

p.s. if its not that i’m thinking carburetors, timing, coils, or if i’m really unlucky, rings or possibly seizing….eek :woohoo:

Topic

[Richard Kirshy]

Wondering if you got water mixed in with the fuel.
It wouldn’t be the first time that has happened.

Might try a bottle of dry gas and see if things improve.

[Rob]

[quote=”Chuzzlepuff” post=170928]Ok well, firstly this isn’t dealing with a car, its regarding a 1975 suzuki gt185 motorcycle, but that pretty irrelevant to the topic at hand…
(btw the manual recommends anything between 85 and 95 oct fuel)
it was running fine last week…about 4 days ago i decided that it deserved some premium fuel, something like 90 octane from a circle k. couple days later i refilled the tank with more premium fuel, some 91 octane from a sunoco…

pretty much around that time it started running weird, power loss across the whole range, trouble getting up hills, a little more backfire, weird and delayed throttle response, a sort of “hollow” sounding exhaust at times… all these symptoms seem to get worse when the engine is nice and hot. idling is perfectly normal though, symptoms are only present under load

so my first thought that comes to mind is the gas… particularly the sunoco gas… now everything intuitive tells me that the fuels in the right octane range so it shouldn’t be the culprit… but the place i got it from doesn’t have that much traffic trough it ever, and it’s run and owned by indians, maybe not following regulations idk… :whistle:
so that combined with the thought of how rarely drivers buy anything but regular unleaded fuel…leads me to believe i may have gotten a batch of some old, dank, expired premium gas thats funking things up?

obviously ill know if that was the problem when i put some more gas in (which i will update on here), but hopefully the results will be useful to anyone finding them in a similar confusion.

p.s. if its not that i’m thinking carburetors, timing, coils, or if i’m really unlucky, rings or possibly seizing….eek :woohoo:[/quote]
sounds like something else in the gas to me… it should run fine on both…. if its a motacycle… they should be easy to dump the tank of gas… because if you have something like particals in it… it could damage your system… like water is the gas could do somethign like that… personlly what like 3 gallons are in a bike… I would dump it out fully and add fresh… run it for a little bit if it sounds better… then I would change the fuel filter incause that had some dirt from the gas… and problly not by gas from that pump… because there might be something bad like there tank or there gas mixxer or the pump… but thats me I would dump it and try new good gas from another station like 20 miles way.. so hopefully not from same gas truck

[Mike]

Remove the float bowl and check for water and sediment at the bottom of it. You’d be surprised what can collect in there.

Also, if the fuel line from the tank is a rubber line that is a push-fit over barbed fittings, remove the line and check inside the tank and carb fittings. With age, the rubber deteriorates and goo gets sloughed off the inside of the line, which will collect inside the connections and restrict fuel flow. You may have to clean the passages out with toothpicks, pipe cleaners, compressed air, the red extension straws from spray cans, shots of WD-40, or whatever. You get the idea.

This bike is a 2-stroke, right? Make sure you get the fuel/oil mix correct.

[Stuart Tierney]

I’d check for water like everyone else has said, and if that doesn’t work, clean the carb (pull it to pieces, clean everything, re-assemble) and then drain and clean out all the fuel.

That ‘premium’ might have been just that, and included a little more ‘cleaner’ than usual, which might have dislodged something in the fuel system and caused some grief, as in a chunk of gunk stuck in a narrow passage. No effect at idle, lots of effect when it needs more fuel.

Stupider things have happened…

(DAMHIKT. Helped a friend rebuild a triplet of SU carbs because of something getting into the fuel system and giving it all a clean out…)

Stu.

[Ian]

Howdy guys, i figured that this warranted an update to help people in the future with similar problems… today i finally got around to pulling the plugs and checking compression… compared to the 130 i got on the cylinders last year, it was only a few pounds of difference, and that was with the engine decently hot…so rings are good. Now onto the actual problem… i noticed when i pulled the plugs, that they were SUPER oil fouled… like i know 2 strokes just burn oil, but this was clearly getting way too much. now this 2 stroke doesn’t require you to mix oil with fuel, instead its got its own little oil pump that squirts 2 stroke oil directly into the crankcase and comb chamber via banjo bolts…. now a few months ago i adjusted the oil pump outward a decent amount from where it was when i bought the bike… enough to match a notch on the pump lever with a notch on the housing… well clearly those weren’t meant to match up because the engine was getting bukkaked in oil… not really a bad thing i guess from a long term standpoint…

anyway, i adjusted the oil pump nut back down and it seems fine now, WAY more power… WAY more throttle response… I like to make the thing buck a little in 2nd gear, which it could’t do at all previously;)

[Author]

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