4000rpm bog

[Salman_z8]

New to me cbx1000 79’
Had sat for a few months before i got it, in very good condition.
The PO had it sitting without the airbox, but carbs were on and intake venturi’s sealed with tape.

Tank was like new inside.
A new battery and fresh gas, and it fired up and idled perfect once warm.

Airbox was put on, but i didnt have a filter or lid yet.

A little test run, bike ran good off the start, and would bog around 4k first gear. Ran through the gears, all seemed good.
I chalked it up to no filter and lid being present.

Fast forward, all the missing pieces on, bike runs better but still gets stuck at 4k, almost like a rev limiter.
My first thought was ignition, but since all ignition problems are usually carb problems, i am suspecting clogged jets ?

So before i yank those bad boys off, can someone else chime in if i am on the right path. But in my experience if it was an ignitor issue, the cylinder would either be dead, or die as it would fail ( temp or whatever ) not fail at a certain load, correct ?

Have a tiny oil leak, but thats irrelevant at this point.
The rest of the bike is actually too good for what i had expected.

[Salman_z8]

Might add, i have a fair bit if carb experience, just dont want to be tilting the engine and fighting the carb manifolds unnecessarily.
Thanks

[tevan]

I would check your advancer. Make sure it operates smoothly. Simple check.

[bobcat]

If adding the filter and air box lid made it better, it sounds like a lean mixture condition.
Is the filter a paper or other aftermarket ? If the bog (or stumble?) begins at 4000 rpm
it's not likely to be the slow (pilot) jets which would be the first to be clogged from sitting
too long.

Also, do you know what the PO had done to the carbs, if anything ? New tank ?

[Salman_z8]

No history on the carbs, but the bike starts, and idles perfectly.
Accelerator pump works the way it should.
It sounds exactly like it hit the rev limiter.

Air filter is oem, and with new oem foam from louis.

[Salman_z8]

The slides, if i remember correctly, all seemed to fall at the same rate once lifted.
I have always had pilots clog, while the main being bigger is almost never an issue on conventional carbs.

[Salman_z8]

I would check your advancer. Make sure it operates smoothly. Simple check.

Will do that

[Salman_z8]

Tank is original, repainted in some yellow. But pristine inside

[NobleHops]

Here’s a little tutorial on servicing the advancer.

https://www.facebook.com/media/set/?set ... 039&type=3

[Salman_z8]

Here’s a little tutorial on servicing the advancer.

https://www.facebook.com/media/set/?set ... 039&type=3

Thanks alot

[Salman_z8]

I would check your advancer. Make sure it operates smoothly. Simple check.

Will do that

Advancer is nice, clean and smooth.

[bobcat]

This is a long shot but remove a float bowl and check to see if the primary and secondary
main jets have been installed backwards, switched by error. I've seen it before and it would
run exactly as you describe. Check the plugs first. If the jets are switched the plugs will be black
or very dark.

[Salman_z8]

This is a long shot but remove a float bowl and check to see if the primary and secondary
main jets have been installed backwards, switched by error. I've seen it before and it would
run exactly as you describe. Check the plugs first. If the jets are switched the plugs will be black
or very dark.

So i guess the carbs will be coming off then ?
Is there enough room to get a bowl off while mounted ? Doesnt seem like it.

I will pull em next week, if there is anything else, please feel free. I hate tilting the motor

[Salman_z8]

This is a long shot but remove a float bowl and check to see if the primary and secondary
main jets have been installed backwards, switched by error. I've seen it before and it would
run exactly as you describe. Check the plugs first. If the jets are switched the plugs will be black
or very dark.

So i guess the carbs will be coming off then ?
Is there enough room to get a bowl off while mounted ? Doesnt seem like it.

I will pull em next week, if there is anything else, please feel free. I hate tilting the motor

[bobcat]

Check the plugs first ! You should be able to get no.6 off without too much trouble.
If you don't know the history of the carbs, there's all kinds of possibilities.

Edmonton, nearly 2200 ft. elevation, I doubt that it needs much, if any re-jetting.