Ok, so I got my bike 99% done. Now it runs great, Lotttts of power Starts right up 10 sec on choke then off too the races Twice, when I got stuck at a light for a while, idle droped 100 rpm and acted like it was running on 3 cyls. Sputtered at take off, then smothed right and ran great again Carbs are "VERY" clean, in sync and adjusted, plugs and wire caps are new with the 1/4" trim done, oil & filter are new, tank has been cleaned (no rust ever) two new inline filters at carbs Once I get it going, it runs fine, idles fine, till I get stuck idleing for several min. any thoughts
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running on 3
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running on 3
1979 XS1100 Special (Mad Max, OEM) Current
1980 XS1100 Special
1990 V Max
1982 KZ750 LTD Twin
1986 700 FZR Yamaha Fazer (faster then expected)
1979 XS750 Special (my 1st Special)
1974 CB750-Four
Past/pres Car's
1961 Catalina 389/1970 Torino GT 351/1967GTO 12to1 comp./ Roller cam/ T-10/ 456 gear/Tri-power/1967 GTO 400, 1969 Camaro, 1968 Z28, 2001 BMW M Roadster 0 to 60 in 4.5 sec. Jaguar XK8Tags: None
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Batt
The battery is new, put in in two months ago, it is a wet cell, but I charged it at 3/4 amp till full voltage.Originally posted by SFerinTEXAS View PostFirst thing I'd do is to give the battery a good look. Age, water level,etc. At idle it supplies the needed juice to keep coils and tci running until you increase the rpm,s and the positive charge rate kicks in.1979 XS1100 Special (Mad Max, OEM) Current
1980 XS1100 Special
1990 V Max
1982 KZ750 LTD Twin
1986 700 FZR Yamaha Fazer (faster then expected)
1979 XS750 Special (my 1st Special)
1974 CB750-Four
Past/pres Car's
1961 Catalina 389/1970 Torino GT 351/1967GTO 12to1 comp./ Roller cam/ T-10/ 456 gear/Tri-power/1967 GTO 400, 1969 Camaro, 1968 Z28, 2001 BMW M Roadster 0 to 60 in 4.5 sec. Jaguar XK8
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The reason the battery comes to mind is I had an Idle stumble, the battery was only 2 months old so I didnt even think of it. Pulled the carbs and to my surprise the pilot jets (1st guess) were spot clean. Pulled the "new battery" out and found the water had dropped below the plates in 2 cells.I try to pull it at least every 2 months to check the water now.79SF
XJ11
78E
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Good point
Good point, I havent checked it sence I installed it, I know they sometimes settle and could need toped off. It works strong and cranks like it is fine, but easy check, will do, thanksOriginally posted by SFerinTEXAS View PostThe reason the battery comes to mind is I had an Idle stumble, the battery was only 2 months old so I didnt even think of it. Pulled the carbs and to my surprise the pilot jets (1st guess) were spot clean. Pulled the "new battery" out and found the water had dropped below the plates in 2 cells.I try to pull it at least every 2 months to check the water now.1979 XS1100 Special (Mad Max, OEM) Current
1980 XS1100 Special
1990 V Max
1982 KZ750 LTD Twin
1986 700 FZR Yamaha Fazer (faster then expected)
1979 XS750 Special (my 1st Special)
1974 CB750-Four
Past/pres Car's
1961 Catalina 389/1970 Torino GT 351/1967GTO 12to1 comp./ Roller cam/ T-10/ 456 gear/Tri-power/1967 GTO 400, 1969 Camaro, 1968 Z28, 2001 BMW M Roadster 0 to 60 in 4.5 sec. Jaguar XK8
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Hey Oem,
Next time you take it out for a little ride, either take your voltmeter with you, or come back home with it warmed up, let it idle and check the voltage after several minutes of idling, and you may find it dropping below 12 volts. The OEM ALT doesn't generate an effective charging voltage at idle, it's best voltage kicks in at 2500+, it's been known for folks to drain a battery working on it while just idling!
It's enough voltage to keep the TCI working, but drops voltage to the spark plug coils, especially if they are running on the ballast resistor circuit. Folks have found that due to the dual plug configuration for a coil, that it can run low on voltage to the point that it will have enough power to fire the main plug that gets lit when the high voltage first comes from the coil to the first plug, but then there's not enough Kv left to travel thru the engine, and then back up thru the second plug.
Another thing could be IF you have the Octy, that under idle there's not enough vacuum to keep the octy valve fully open, and a loss of fuel flow could occur, the bowl could run low and result in stumble/miss? JAT!
T.C.T. C. Gresham
81SH "Godzilla" . . .1179cc super-rat.
79SF "The Teacher" . . .basket case!
History shows again and again,
How nature points out the folly of men!
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Tc
Thanks TC, I also install a new headlight bulb, it was rated 60/55 instead of the 55/60w in the manual dont know if it has a higher pull at idle Dont think it is the octy, could be, but it is my undrestanding that intake manafold vacuum is at its higest when at idle, butterflys shut almost closed and pistons sucking in air, seems like it would be at max like on a car when idleing.Originally posted by TopCatGr58 View PostHey Oem,
Next time you take it out for a little ride, either take your voltmeter with you, or come back home with it warmed up, let it idle and check the voltage after several minutes of idling, and you may find it dropping below 12 volts. The OEM ALT doesn't generate an effective charging voltage at idle, it's best voltage kicks in at 2500+, it's been known for folks to drain a battery working on it while just idling!
It's enough voltage to keep the TCI working, but drops voltage to the spark plug coils, especially if they are running on the ballast resistor circuit. Folks have found that due to the dual plug configuration for a coil, that it can run low on voltage to the point that it will have enough power to fire the main plug that gets lit when the high voltage first comes from the coil to the first plug, but then there's not enough Kv left to travel thru the engine, and then back up thru the second plug.
Another thing could be IF you have the Octy, that under idle there's not enough vacuum to keep the octy valve fully open, and a loss of fuel flow could occur, the bowl could run low and result in stumble/miss? JAT!
T.C.1979 XS1100 Special (Mad Max, OEM) Current
1980 XS1100 Special
1990 V Max
1982 KZ750 LTD Twin
1986 700 FZR Yamaha Fazer (faster then expected)
1979 XS750 Special (my 1st Special)
1974 CB750-Four
Past/pres Car's
1961 Catalina 389/1970 Torino GT 351/1967GTO 12to1 comp./ Roller cam/ T-10/ 456 gear/Tri-power/1967 GTO 400, 1969 Camaro, 1968 Z28, 2001 BMW M Roadster 0 to 60 in 4.5 sec. Jaguar XK8
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My understanding is that intake manifold isn't necessarily highest at idle, but it's high when the carb butterfly valves are almost closed. When under strong throttle the butterflies are more open, less vacuum being directed to the vac. adv. port, so less advance of the vacuum advance mechanism which actually retards the advance timing to the more powerful range of 30 or so degrees btdc.
But when running at let's say 5k rpm, but cruising...the butterflies are closer to being closed which directs more vacuum to the advance pot increasing the advance more towards the max of 52 degrees it can reach. But that's because the engine is generating more vacuum running at 5k rpm than at idle. Otherwise at idle, the vacuum advance to pull to full throw and cause the engine to race just from the idle vacuum level...so that's why I don't think it's generating max vacuum at idle, therefore less vacuum pulling on the OCTY to keep it open flowing vs. when running at 4K or such.
T.C.T. C. Gresham
81SH "Godzilla" . . .1179cc super-rat.
79SF "The Teacher" . . .basket case!
History shows again and again,
How nature points out the folly of men!
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Thanks, Like I said, just trying to figure out what is causing this miss after idle, I am thinking it might be a plug fowling after idleing, I am a little rich on the mix screws (by the book, that is) Going to pull the plugs and look, clean and adj any that look rich, thanksOriginally posted by TopCatGr58 View PostMy understanding is that intake manifold isn't necessarily highest at idle, but it's high when the carb butterfly valves are almost closed. When under strong throttle the butterflies are more open, less vacuum being directed to the vac. adv. port, so less advance of the vacuum advance mechanism which actually retards the advance timing to the more powerful range of 30 or so degrees btdc.
But when running at let's say 5k rpm, but cruising...the butterflies are closer to being closed which directs more vacuum to the advance pot increasing the advance more towards the max of 52 degrees it can reach. But that's because the engine is generating more vacuum running at 5k rpm than at idle. Otherwise at idle, the vacuum advance to pull to full throw and cause the engine to race just from the idle vacuum level...so that's why I don't think it's generating max vacuum at idle, therefore less vacuum pulling on the OCTY to keep it open flowing vs. when running at 4K or such.
T.C.1979 XS1100 Special (Mad Max, OEM) Current
1980 XS1100 Special
1990 V Max
1982 KZ750 LTD Twin
1986 700 FZR Yamaha Fazer (faster then expected)
1979 XS750 Special (my 1st Special)
1974 CB750-Four
Past/pres Car's
1961 Catalina 389/1970 Torino GT 351/1967GTO 12to1 comp./ Roller cam/ T-10/ 456 gear/Tri-power/1967 GTO 400, 1969 Camaro, 1968 Z28, 2001 BMW M Roadster 0 to 60 in 4.5 sec. Jaguar XK8
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When she starts misfiring, take a wet rag and touch each one of the headers, maybe find out which cylinder is cool. I had a similar problem recently and it turned out to be a bad spark plug. JAT2H7 (79) owned since '89
3H3 owned since '06
"If it ain't broke, modify it"
☮
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Good thought, that is what i am thinking, one is weak and fowling at idle, and thanks Phill for all your help with sooo many other problems, you have helped keep this old bike one the road Hope you had a great Thanksgiving and wishing you and yours a Merry Christmas God Bless
Originally posted by bikerphil View PostWhen she starts misfiring, take a wet rag and touch each one of the headers, maybe find out which cylinder is cool. I had a similar problem recently and it turned out to be a bad spark plug. JAT1979 XS1100 Special (Mad Max, OEM) Current
1980 XS1100 Special
1990 V Max
1982 KZ750 LTD Twin
1986 700 FZR Yamaha Fazer (faster then expected)
1979 XS750 Special (my 1st Special)
1974 CB750-Four
Past/pres Car's
1961 Catalina 389/1970 Torino GT 351/1967GTO 12to1 comp./ Roller cam/ T-10/ 456 gear/Tri-power/1967 GTO 400, 1969 Camaro, 1968 Z28, 2001 BMW M Roadster 0 to 60 in 4.5 sec. Jaguar XK8
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All an interesting read but betting the issue is #3 carb...................81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.
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Bet your right Ken..........I'll see that two and raise ya one pick-up wire.81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.
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Picked this up at Harbor Freight today... Trying to find a place in the fairing to make a 1.5" hole. I think it would be very useful to keep track of electric system before she starts missing or won't start. Good information for $7.
When the horse is dead, dismount.
Bagapotomus - '80G Attempted Rescue, '78 Engine, Vetter Bags and Trunk.
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