Convert poor running |
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Hyline
Falcone Joined: 08 Oct 2017 Location: Bristol Status: Offline Points: 82 |
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Posted: 06 Apr 2018 at 14:38 |
Had a nice ride today in the spring sunshine apart from the following problem!
The bike started fine, acceleration seemed sluggish, but I put that down to the engine being cold. Pretty soon it became apparent that the bike would happily cruise at 50mph, but if I tried to accelerate beyond that, the motor would become "fluffy" and lose power until I closed the throttle a bit, and which point it would resume cruising at 40-50mph. On encountering any uphill sections, the bike would lose speed and only managed to stagger up them at 20-30mph. Very embarrassing and left me wondering several times if it was going to get me home (which it did). I don't think I had a problem of only firing on one cylinder and I checked the spark plugs when I got home, and both are the same shade of pale grey. I am thinking either a carb problem (the throttle cables seem to be running smoothly) or something electrical, but where to start looking?
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iansoady
Senior Member Joined: 23 Jul 2017 Location: Redditch Status: Offline Points: 2402 |
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If it was cold and damp I would suggest carb icing but probably not in this case.
If you stop and wait for 5 minutes or so does it get better? May be worth checking the fuel cap breather hole. |
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Ian
1952 Norton ES2 1986 Honda XBR500 1958-ish Greeves/Triumph in progress |
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Hyline
Falcone Joined: 08 Oct 2017 Location: Bristol Status: Offline Points: 82 |
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No, I stopped for coffee, and it re-started OK, but the running got progressively worse.
I will go out and check the filler cap. Thanks.
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Dukedesmo
Senior Member Joined: 17 Apr 2015 Location: Leics Status: Offline Points: 856 |
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Dirt/water in the carb floatbowls?
I had similar with my LM2, removing and cleaning the float bowls solved it.
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Le Mans 2
Ducati 916 Ducati M900 |
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cyclobutch
Senior Member Joined: 08 Sep 2015 Location: Essex Branch Status: Offline Points: 750 |
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Slipped ign timing?
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Butch
V50 II - 'The Black Pearl' T3 - 'Blue' Eldo Loop - 'Jug' |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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My prime suspect would be carbs & fuel supply, hoses, filters, tank tap filters. Sounds like it may be fuel starved.
Modern petrol wreaks havoc in carbs these days, cited examples being swollen floats (which jam up against the float chamber walls), hard green or brown deposits (which literally have to be scraped & chipped off), blocked jets and galleries. Carb cleaner etc. won't touch it. It got to the stage where I would be draining the carbs and leaving them dry if bike was going to be left unused for more than a few days. +1 re check tank vent. |
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"Chicken nuggets don't dance on a Tuesday."
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Ken-Guzzibear
Moderator Group Joined: 13 May 2014 Location: Sileby Leics Status: Offline Points: 9454 |
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yep fuel redex after cleaning and checking
btw Wilko is best price on redex |
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The Older i Get, The Better I Was
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ranton_rambler
Senior Member Joined: 13 Feb 2015 Location: Stafford Status: Offline Points: 1147 |
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I always think ignition is responsible for 90% of problems. What system does this have? Could be heat-related breakdown of coil, condenser, HT lead etc.
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c13pep
Senior Member Joined: 31 Aug 2017 Location: Doncaster Status: Offline Points: 2110 |
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Oh for the days when a real person came out to fill up your petrol tank (in gallons of course) accompanied by a free shot of Redex CHRIS |
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you can`t have any fun in a straight line
Monza Honda CB77 project |
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Hyline
Falcone Joined: 08 Oct 2017 Location: Bristol Status: Offline Points: 82 |
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Well its not the tank vent unfortunately. The bike has conventional points.
My knowledge is sorely limited when it comes to taking carbs apart and sorting issues with coils etc, so I may take it to a local classic bike specialist for them to look at. Thanks for all the help.
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Dave P.
Senior Member Joined: 12 Jan 2015 Location: Northants Status: Offline Points: 5573 |
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Is the auto advance mechanism, erm......auto advancing? Or might it be sticking before full advance is reached?
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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Jerry atric
Senior Member Joined: 24 Nov 2014 Location: Wiltshire Status: Offline Points: 3367 |
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Thats fair enough but can you take the bottom of each carb off and just see what falls out? It only takes a tiny bit of muck or water to give your symptoms. |
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Hyline
Falcone Joined: 08 Oct 2017 Location: Bristol Status: Offline Points: 82 |
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Ha Ha, it's bits falling out that worries me, and then wondering how it goes back together. Hopefully tomorrow I will be able to have another look.
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Ken-Guzzibear
Moderator Group Joined: 13 May 2014 Location: Sileby Leics Status: Offline Points: 9454 |
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The carbs are easy big nut undo let the crap fall out re do ....job done new fuel try it if it is the points , Which by the way on my 250k V1000 have rarely given a major issue either have the condensers ...if you have limited skills take to a dealer simple job ....
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The Older i Get, The Better I Was
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Wait a minute folks, on small throttle opening it goes fine, open the throttle more, it gags and loses power & speed, close the throttle it picks up and goes fine again, doesn't sound like any ignition behaviour that I've heard of.
It does sound like more neat air is going in rather than the correct air + petrol. Of course it's possible the opposite could be happening, could be going very rich. Looking at the spark plugs will show which way it's going. HTH |
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"Chicken nuggets don't dance on a Tuesday."
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