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Convert poor running

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Hyline View Drop Down
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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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iansoady Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 14:45
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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Hyline View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hyline Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 14:57
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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Post Options Post Options   Thanks (1) Thanks(1)   Quote Dukedesmo Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 16:10
Dirt/water in the carb floatbowls?

I had similar with my LM2, removing and cleaning the float bowls solved it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyclobutch Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 17:33
Slipped ign timing?
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 18:58
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. Ouch

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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Ken-Guzzibear View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 19:52
yep fuel redex after cleaning and checking
btw Wilko is best price on redex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 20:14
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 06 Apr 2018 at 20:18
Originally posted by Ken-Guzzibear Ken-Guzzibear wrote:

yep fuel redex after cleaning and checking
btw Wilko is best price on redex


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
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Hyline View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hyline Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 13:25
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. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 14:11
Is the auto advance mechanism, erm......auto advancing? Or might it be sticking before full advance is reached?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry atric Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 15:48
Originally posted by Hyline Hyline wrote:

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.

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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hyline Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 16:59
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 17:28
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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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 17:29
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.

Big smile

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


"Chicken nuggets don't dance on a Tuesday."
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