misfires when accelerating hard

[bernardofeio]

hello

my bike misfires when accelerating hard however when rolling on the power gently there is no problem. If I role back the throttle it will be OK again.

it's a dual plug with electronic advance ignition set to +22 degree.

the carburetors are clean and adjusted. needle is 1 notch richer

if it was from ignition failure I should have backfire but it does not happens. valve clearance it's ok.

any ideas? in my view I don't see any justification to fuel starvation. to rich eventually?

 

[scooter paul]

Check your float bowl fuel level. I’ve had a bike that did this and adjusting the tab to allow more fuel to fill the bowl cured it.

 

[Mad Hatter]

I had same problem and it was the float levels set too low as Paul says

 

[bernardofeio]

Yesterday I changed the needle one notch to be a little less rich. I didn't notice any difference. Today I will try to do the opposite. After I will try to see the float level. thks

 

[bernardofeio]

today I removed the fuel filters to check if it would make any difference ( no difference at all)....

 

[Nin]

If you’ve checked the timing with a strobe and it’s ok, I’d be looking at coil, and/or ignition leads.

 

[2gses]

What exhaust system is fitted to your motorcycle? If it’s the same as mine I may have the answer, do you have a collector box fitted?

 

[DrFarkoff]

I would suspect Coil connections, Coil, Leads, Plugs, in that order

"Under load" being a clue

 

[Bubb]

Try changing the plugs. I had a similar problem once, and it was a plug starting to break down. Easy fix once I had gone thru the carbs, timing, etc etc…..

 

[chopper_harris]

Don't change more that one parameter before testing, else you will not have a clear view on the fault/resolution.

 

[Gelandestrasse]

Don't change more that one parameter before testing, else you will not have a clear view on the fault/resolution.

Where's the fun in that?!!

 

[bernardofeio]

If you’ve checked the timing with a strobe and it’s ok, I’d be looking at coil, and/or ignition leads.

yes. timing is correctly adjusted with a strobe at aprox 6 (1000rmp) + 28 (3500rmp). but anyway could be one of the possibilities

 

[bernardofeio]

What exhaust system is fitted to your motorcycle? If it’s the same as mine I may have the answer, do you have a collector box fitted?

y- pipe. I still have the original collector box that I can use to make some tests

 

[bernardofeio]

I would suspect Coil connections, Coil, Leads, Plugs, in that order

"Under load" being a clue

this is my main suspicious but I'm not fully sure how to check.

1- the plugs are new
lower - NGK BPR8EIX
upper - NGK BPR7EIX

2 - how can I check the leads? what should be the resistance knowing that I'm already using the "R" plugs?

3- I'm using two PVL 356100 coils that have 0.6 ohm each. Mounted in a parallel circuit
https://pvlignitions.com/shop-us/product/pvl-coil-356100-356-100/

 

[DrFarkoff]

this is my main suspicious but I'm not fully sure how to check.

1- the plugs are new
lower - NGK BPR8EIX
upper - NGK BPR7EIX

2 - how can I check the leads? what should be the resistance knowing that I'm already using the "R" plugs?

3- I'm using two PVL 356100 coils that have 0.6 ohm each. Mounted in a parallel circuit
https://pvlignitions.com/shop-us/product/pvl-coil-356100-356-100/

Stop fecking about with meters and schit! Fit a known good part !! Do this ONE part at a time Do not just load a parts cannon and fire it at the bike and then think , "I wonder what fixed it?"

If it stops doing the misfire then you have found the fault!

WHY are you running iridium plugs is it 10.5 to 1 compression or something special??

 

[2gses]

y- pipe. I still have the original collector box that I can use to make some tests

Try the collector box first , I’ve a siebenrock silencer I removed the removal pipe and the flat spot has gone. Sounds a bit fruity but the main thing is that it runs lots better

 

[bernardofeio]

Try the collector box first , I’ve a siebenrock silencer I removed the removal pipe and the flat spot has gone. Sounds a bit fruity but the main thing is that it runs lots better

thks "2gses". the problem is not a flat spot during acceleration... it's a real lack of ignition/combustion during some moments that can only be fixed reducing the throttle a bit.

 

[bernardofeio]

Stop fecking about with meters and schit! Fit a known good part !! Do this ONE part at a time Do not just load a parts cannon and fire it at the bike and then think , "I wonder what fixed it?"

If it stops doing the misfire then you have found the fault!

WHY are you running iridium plugs is it 10.5 to 1 compression or something special??

)

I have aprox 11:1 compression
98,00 mm pistons
dual plug
electronic ignition
bla bla bla

I'm waiting for new leads that in fact are the only thing that it's not new

my suspicious is that should be coils/ignition/timming related. Does any one has experience with these coils?

 

[The Other PaulG]

Not sure about your aftermarket coils, but the OE ones could develop barely visible hairline cracks that made them fail when damp and possibly when under load.

 

[warmshed]

Had the same problem but it turned out to be the ignition amolifier, fitted new one and fine now