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Convert poor running

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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: 07 Apr 2018 at 17:30
Oh by the way have you checked all the fluid levels low fluid to the torque converter will affect running .....
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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 17:31
Disclaimer: of course the ignition timing and operation should be checked, if only to eliminate.

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 19:03
Have you checked the fuel filters on the taps? If they get blocked you would have exactly your symptoms.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ianboydsnr Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2018 at 19:27
Check the sparks good even new bits are a hit and miss nowerdays, and the advance is working and timing is good,, then fuel,
On mine I run one side of the tank to one carb, the other side to the other carb, because I struggled to get a decent non bent fuel pipe connection if I joined them, and it would also get a vapour lock occasionally,

Check the float height, that the choke comes off, and the fair filters clean.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hyline Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2018 at 11:14
Fuel getting through OK to both carbs - there was a kink in one fuel pipe which I thought might be the culprit, but not so, still running poorly after removing there kink.
Spark OK to both plugs, air filter new, AT fluid in the converter up to level.
Removed the bottom of the carbs, couldn't see anything untoward, and the gauze filters on the carb banjos are OK.
I think it must be an electrical issue, and I want the bike to run reliably so I am going to resort to taking it to someone who knows what they are doing.
Thank you for all the helpful advice offered - I will update when I find out what the problem is.

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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: 09 Apr 2018 at 16:19
Did the behaviour start after when you changed the air filter?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hyline Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2018 at 16:48
Replacing the paper air filter was one of the jobs I did over the winter whilst the bike was off the road. Since then i have done a short (5 miles) run all in 20/30 mph limits and no problem was apparent, but that could have been because of the low speeds.
Last week, I took the bike out on a longer run on faster roads, and the problem was immediately apparent when picking up speed or attempting an overtake.
The air filter was a bugger to install, but I am fairly sure it eventually went back in OK - what would be the potential issue with it?
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Post Options Post Options   Thanks (1) Thanks(1)   Quote jpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2018 at 18:19
A good rule with engine trouble is DIC, 1 distribution, 2 ignition, 3 carburation.
You save time checking and fixing things in that order, instead of doing a headless chicken impression.

On a big block it comes down to checking valve clearances, using a strobe light to check ign. timing and auto advance operation, then fuel supply, jets & needles, float height and air supply. At least you have a plan. Smile
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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: 10 Apr 2018 at 15:17
Originally posted by Hyline Hyline wrote:

Replacing the paper air filter was one of the jobs I did over the winter whilst the bike was off the road. Since then i have done a short (5 miles) run all in 20/30 mph limits and no problem was apparent, but that could have been because of the low speeds.
Last week, I took the bike out on a longer run on faster roads, and the problem was immediately apparent when picking up speed or attempting an overtake.
The air filter was a bugger to install, but I am fairly sure it eventually went back in OK - what would be the potential issue with it?

Right, so you did something to the bike, and now it won't accelelate.

Murphy's Law says most likely caused by something you did. Big smile

Where did the new filter come from?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hyline Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2018 at 15:30
You may well be right, although I have not touched the distributor, coils or carbs. I did replace the spark plugs and caps (bought from a motor factor, not t'internet), and the air filter came from Gutsibits and it is he same as the old one.
Although I found the new air filter difficult to fit, it all went in Ok eventually, so I don't imagine that could be causing the problem?
Also, I assume that a problem with one of the plugs or caps would lead to a permanent mis-fire/running on one cylinder, not the loss of power when winding on the throttle that I am experiencing.
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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: 10 Apr 2018 at 15:53
I would have the filter out again to see what's going on. With those long conical filters it has been known for the pleats to close up under vacuum, thus restricting air flow. One suggested trick was to put a coil of stiff wire up inside it to hold it out. Must say when I first did one of these filters I was less than impressed. I ended up putting big oval K&N's on, but which required buying the Le Mans crankcase breather box. Motomecca used to do a 'conversion kit', which I bought for the Spada.


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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: 10 Apr 2018 at 16:48
OK, I will have a look at that. Must admit, I have it in mind to switch to K&N's at some time in the future.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2018 at 21:18
What you describe is very symptomatic of fuel restriction, or air restriction, both of which will cause considerable loss of power under increasing load.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote wheelybin Quote  Post ReplyReply Direct Link To This Post Posted: 11 Apr 2018 at 12:20
is the issue revs related? I had a a KH250 years ago, it ran fine up to a point where it just would not rev any higher, turned out one of the condensors had given up the ghost. Running with the points cover off, it looked like the points giving a "firework" display at higher revs.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 11 Apr 2018 at 16:37
Originally posted by Brian UK Brian UK wrote:

What you describe is very symptomatic of fuel restriction, or air restriction, both of which will cause considerable loss of power under increasing load.

What do spark plugs look like?


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