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Hey there, on a trip (see other thread) and the 550 lost a lot of its power in southwest Colorado. Bike runs fine at low speed and idles fine but can't really get above 45 mph and starts lurching once it gets going. So far we have a couple of thoughts: my friend thinks there's a chance he put 85 octane gas when we last filled up and the issue started shortly after that, normally we put 87 in (MA minimum octane rating is 87) so we were wondering if anyone has any experience running 85 and if that could account for the loss of power. We checked the points and the 1-4 point looked worn. At first thought the spark plugs were fouled and after checking them the 1-4 plugs were really corroded and the 2-3 plugs looked white, but we changed them and the problem persisted. After about 30 miles we checked the plugs again and the 2-3 plugs were white (getting there the throttle was wide open the whole way to keep it around 50). Took pictures of both sets of plugs see below. Let me know if you have any thoughts, thanks!
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1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
1977 GS550
1977 GS750 - Cross country trip thread -
Picture in OP is #4 plug at first below is #2 after 30 miles.1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
1977 GS550
1977 GS750 - Cross country trip thread -
#3 plug after 30 miles:1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
1977 GS550
1977 GS750 - Cross country trip threadComment
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At your higher elevation, 85 octane is acceptable.
Take your points cover off, start the engine. Do you see sparking at the points? If you do, change the condensors.
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mine: 2000 Honda GoldWing GL1500SE and 1980 GS850G'K' "Junior"
hers: 1982 GS850GL - "Angel" and 1969 Suzuki T250 Scrambler
#1 son: 1986 Yamaha Venture Royale 1300 and 1982 GS650GL "Rat Bagger"
#2 son: 1980 GS1000G
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New points and condensors needed
Octane is not an issue
Also, sounds like you have air leaks on 2-3. Your bike should be running richer at altitudeLast edited by Big T; 07-28-2017, 12:32 AM.1978 GS 1000 (since new)
1979 GS 1000 (The Fridge, superbike replica project)
1978 GS 1000 (parts)
1981 GS 850 (anyone want a project?)
1981 GPZ 550 (backroad screamer)
1970 450 Mk IIID (THUMP!)
2007 DRz 400S
1999 ATK 490ES
1994 DR 350SESComment
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Yup it was the condensers swapped out the ones from my gs750 and it ran fine. Luckily I had a spare set at home and got them fedexed over. They should be here today.1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
1977 GS550
1977 GS750 - Cross country trip threadComment
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