SOHC.co.uk Forums > CB500/550

CB550 - full trottle performance

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deltarider:

--- Quote from: Laverda Dave on May 26, 2021, 12:06:36 PM ---I would be tempted to go on a dyno. Might cost a bit more but at least you will have a full read out of what the engine is doing across the entire rev range and this will give you a chance to make small adjustments whilst you are there to potentially fix the problem.

--- End quote ---
Yep, bike as it is now, definitely deserves it IMO. Oh and if you do, please make recordings. :)

Erny:
Short update after today's test ride (~50 miles)

Issue is present in wide range of RPMs, I confim it from ~3500 revs ->
Simply, when at whatever revs I'll open trottle fully, I feel engine does not accelate as good as if I close trottle a bit (approx 1/8-1/4).

After ride I pulled plugs (I installed them new, 55 miles before), all cyls are lean. See attached pics. Good news are are equally lean (I have never achieved that before!)

So, rising needle 1-2 notch looks to be next step..

Erny:
Yes, I know but I cannot avoid resync, right?

philward:

--- Quote from: Erny on May 26, 2021, 08:51:55 PM ---Short update after today's test ride (~50 miles)

Issue is present in wide range of RPMs, I confim it from ~3500 revs ->
Simply, when at whatever revs I'll open trottle fully, I feel engine does not accelate as good as if I close trottle a bit (approx 1/8-1/4).

After ride I pulled plugs (I installed them new, 55 miles before), all cyls are lean. See attached pics. Good news are are equally lean (I have never achieved that before!)

So, rising needle 1-2 notch looks to be next step..

--- End quote ---

Don't ride it too hard for too long with it running that lean Erny

K2-K6:
Ah ha
"Issue is present in wide range of RPMs, I confim it from ~3500 revs ->
Simply, when at whatever revs I'll open trottle fully, I feel engine does not accelate as good as if I close trottle a bit (approx 1/8-1/4)."

That makes it a different problem to initially described,  in as much as it looks like it could take a one size up main jet if it's right across the rev range from about 3,500 upward, and worthwhile trying that first given this information and the plug colours.

You may find that if a jet change was too far,  then in future you could either check with the larger jet plus needle drop, or it would persuade you to use original main jet plus lifted needles as they would be slightly different solutions.

At least you could assess it now with less work if you have any main jets to try just one size larger.

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