Ironhead Can't get past 4000 rpm

[bobber58]

Get those baffles out of your drag pipes and go for a ride. Baffles are too restrictive and create a lot of backpressure that chokes the engine. Then either get some performance mufflers or make some lolipops.

[Kingrabbit]

Hey folks thanks for the support. I set the points and the timing and the pushrods based on information on here and in my Clymer manual. I tried running the bike with the baffles out too. None of this has made a difference.
The bike starts up but won't accelerate beyond 4000 rpm in any gear. It overheats and it fouls the plugs.
I think its time to pull the carb and clean it up / rebuild it.

[dablues61]

Did you set thie timing static? (engine not running), if so you might want to put a timing light on it and see if the timing is advancing with rpm increase.

[runingmouse]

Originally Posted by rivethog

if your petcock stil has the screen on it, get rid of the inline filter.

+1

[ryder rick]

Originally Posted by dablues61

Did you set thie timing static? (engine not running), if so you might want to put a timing light on it and see if the timing is advancing with rpm increase.

My thoughts too, but the timing might be too far advanced causing detonation which will make gobs of heat real fast.

[billeuze]

Originally Posted by Kingrabbit

Hey folks thanks for the support. I set the points and the timing and the pushrods based on information on here and in my Clymer manual. I tried running the bike with the baffles out too. None of this has made a difference.
The bike starts up but won't accelerate beyond 4000 rpm in any gear. It overheats and it fouls the plugs.
I think its time to pull the carb and clean it up / rebuild it.

yes and clean the air filter and remove your petcock to clean the screen (if there is one and remove the inline filter). I know I'm repeating what's been said but it all needs doing.

[Kingrabbit]

when you say clean the filter what do you mean? Blow it out wilt compressed air? I have a new filter on there whcih is a little wider than the one the PO used (which was dingy looking).
As an aside, I also have the original '73 round chrome filter thingee - someone says all I need to do is cut a piece of foam and stick it in there for a filter. Any thoughts?

[IronMick]

Air filter ...

Dop not use just any foam. It will not work. It must be motorcycle air filter foam and it must fit correctly.

If it is a paper filter it cannot be cleaned. Replace it.

Foam air filters can be cleaned and re-oiled. Procedure etc in any of the manuals. Or just go to any auto parts shop/indie motorcycle shop and buy the correct cleaning/oiling products.

Best is to buy a reuseable air filter like K&N, and use their cleaning kit.

[billeuze]

so you have a new filter. Is that perhaps what changed recently since the time before you had this problem? For a test, remove your air filter and go for a ride around the block. If that fixes the problem, use a diferent filter.

If you had crud in your inline fuel filter you still need to clean the in tank screen behind your petcock and clean your carb (dissasemble, soak overnight, blow out).

[Kingrabbit]

Excellent advice guys and I do appreciate it.

I will be following up on the in-tank filter (can I access it by pulling the petcock off?) , the A/C and the carburetor and will report progress.

Mick, on the topic of foam filters, given bike was equipped with one in '73 when it rolled off the factory floor, do you think it would be good enough now? Is it too primitive / inefficient?

This 9 to 5 thing has a way of getting in the way of the important stuff.