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Author Topic: 500 four not revving properly on top  (Read 562 times)

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Offline Clasico

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500 four not revving properly on top
« on: May 11, 2014, 12:00:45 PM »
My cb500 k1 revs ok in all gears but in 5th.
On flats takes ages to do 6000. On slight uphills not even that. Going down it goes much better

I guess is not related to carburettors, If it were lack of fuel it should fail on lower gears as well, shouldn't it?
Maybe related to air supply or timing perhaps?

Anybody suffering the same on a 500?
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Offline Deltarider

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Re: 500 four not revving properly on top
« Reply #1 on: May 11, 2014, 12:42:23 PM »
Are plugs properly gapped? Not to wide? Are they still good? New plugs are cheap. How about the drive chain? No brakes binding? Do wheels spin freely?
Quote
On flats takes ages to do 6000.
Usually I don't shift gears before 6000.
Air filter clean? Nothing under the seat that obstructs air intake? Routing fuel tubes OK (no kinks or inlinefilters that hinder fuel flow)?
« Last Edit: May 11, 2014, 12:49:53 PM by Deltarider »
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Offline LesterPiglet

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Re: 500 four not revving properly on top
« Reply #2 on: May 11, 2014, 01:12:54 PM »
Does it have standard sprockets?
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Offline Clasico

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Re: 500 four not revving properly on top
« Reply #3 on: May 11, 2014, 03:10:59 PM »
Quote from: Deltarider on May 11, 2014, 12:42:23 PM
Are plugs properly gapped? Not to wide? Are they still good? New plugs are cheap. How about the drive chain? No brakes binding? Do wheels spin freely?
Quote
On flats takes ages to do 6000.
Usually I don't shift gears before 6000.
Air filter clean? Nothing under the seat that obstructs air intake? Routing fuel tubes OK (no kinks or inlinefilters that hinder fuel flow)?

Plugs are ok, wheels free, drive chain seems fine. Air filter cleaned 300 miles ago but wait i carry a rag there, ill see tomorrow if it is blocking the hole. Fuel tubes ok too.

i can put over 6000 on all other gears although normally change up at 4/5k, donot want to stress the old lady
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Offline Clasico

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Re: 500 four not revving properly on top
« Reply #4 on: May 11, 2014, 03:19:29 PM »
Quote from: LesterPiglet on May 11, 2014, 01:12:54 PM
Does it have standard sprockets?

I think so. If it were too low geared I'd notice a very strong pull in starting which is not the case.

To add more details i've the impression that she is a bit short on fuel in all gears although I've never driven other 500 four to compare with. However, she does less than 40 mpg
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Offline TwoTired

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Re: 500 four not revving properly on top
« Reply #5 on: May 11, 2014, 04:31:39 PM »
Does your bike have one of these on the filter box?
Do you have 649a Carbs?

Have you counted the sprocket teeth front and rear?

Are you certain there is no fuel flow restriction between the tank and the carbs?
Cleaned the sediment bowl lately?
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Re: 500 four not revving properly on top
« Reply #6 on: May 11, 2014, 07:37:23 PM »
Check your ignition timing that it is not retarded. Overly retarded ignition timing can give this feeling of lost power at the mid and top end. If that is ok, then ensure your fuel system and carb's are set correctly with them being clean, with correct float levels, jet sizes and set at the stock needle clip position, by the book if everything is stock.
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Offline scunny

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Re: 500 four not revving properly on top
« Reply #7 on: May 12, 2014, 02:18:28 AM »
Quote
wait i carry a rag there, ill see tomorrow if it is blocking the hole.
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Offline Deltarider

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Re: 500 four not revving properly on top
« Reply #8 on: May 12, 2014, 03:31:05 AM »
Quote
but wait i carry a rag there, ill see tomorrow if it is blocking the hole.
If it is, you will send us a picture, right? For educational reasons  ;D.
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Offline Clasico

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Re: 500 four not revving properly on top
« Reply #9 on: May 16, 2014, 10:50:53 AM »
I checked if the rag was bloking the air supply but it wasn't.

After reading all your advice I think it does not rev up easily over 6k in 5th due to some carburation issues on high which i should be addressing on next 3k revision.

It may also be related to the super long gas action. I keep on forgeting that it has more to come after totally twisting my gas hand!
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