Rough running 2,000 rpm

[John Roberts]

Engine's running rough at 2,000 rpm, it idles OK, but I suspect down on power at higher revs, 3,000plus. It's just had a new second hand trigger unit, which seems to work ok, i.e. it advances smoothly from 2,000rpm as seen with the timing light. Valve clearances OK. Carbs adjusted by ear as I've done for the last 30 years and idling OK.

Where should I start looking?

 

[Beemerboff]

Looks like no one else runs their bike at 2000rpm - they do go a bit better with a few more revs on the dial.

Try keeping the motor around 600 revs either side of peak torque ,which is around 3200 to 4400 revs, and see how it goes.

Or if you really must run at 2000 revs you could try fitting a diesel - the Gardiner fours in the old London buses and Drott skid shovels pulled really well at 2000 revs.

 

[John Roberts]

Are you really saying that nobody else ever rides slowly in, say, traffic for instance, or country lanes at 2,000rpm? Or perhaps that they all slip the clutch until well over that speed?

It does run a lot smoother at higher speeds. Thank you so much for your input.

 

[Beemerboff]

Most people have worked out how to change gears, and this helps a lot.

But seriously, Airheads have a short stroke, short rod engine and are not designed for low revs, and this is quite clear in the riders handbook, if you have one.

Any problem with tune will also show up much more at slow revs / small throttle openings and the only answer to that is meticulously checking everything.

I think the timing should start to advance before 2000 revs so you may have a problem somewhere , and the factory full advance setting is is also really only a starting point - the best spot could be 2/3 degrees either side.

After 30 years the needles and jets might be a bit worn and causing it to run a bit rich too.

Obscure faults that I have experienced have been a resistor plug caps with four times the resistance, excessive voltage drop through a well worn ignition switch, gummed up passageways in the carbs, a new plug which missed under load, and a partially clogged muffler.

Setting the fuel level in the bowls by measuring the depth also works better for me.

A stiff dose of Auto injection cleaner in the tank cleaned out the carbs, but some of the others took a bit more finding.

Sorry if the previous post caused any offence - I usually post last thing at night when I get back from the pub and as they say they don't always look as good in the morning!

 

[John Roberts]

Looks like no one else runs their bike at 2000rpm - they do go a bit better with a few more revs on the dial.

Or if you really must run at 2000 revs you could try fitting a diesel - the Gardiner fours in the old London buses and Drott skid shovels pulled really well at 2000 revs.

Sorry if the previous post caused any offence - I usually post last thing at night when I get back from the pub and as they say they don't always look as good in the morning!

Most people have worked out how to change gears, and this helps a lot.

So you left the pub just a bit earlier this time. Yeah, right.