Topic: Porting...

[Falken]

gunna have to take my motor apart to getting it running again...been giving some serious thought to porting the heads while i'm in there (Searchs have lead me to believe that it is one of the best things you can do to wake up the engine).

If I port the heads...what else needs to be done?

[grcamna2]

Just increase your carb jetting a bit to compensate for the extra flow your newly ported head will produce.

[Danno]

yes porting done well will wake up the response of the engine as it can get fuel faster you may or may not have to increase jet sizes but you may want to raise the needle one notch so the flow of fuel more closely mimics the need of the ported engine

you will know if raising the needle is a good idea when you twist the throttle quick and there is a sudden lull and then it takes off that means it is getting to big a shot of air without enough fuel to go with it which means raise the needle

note these carbs will do this if opened too quickly any way what I mean is if it worked fine to open the throttle at that speed before and now after porting it is noticeable then it needs the needle raised

[andrewk]

I think that it's important to note that botched head work will make it run worse.  I wouldn't try to port the head unless you know what you're doing.

[wrenchmuch]

Others have ported heads themselves with good results . They posted pics and waited for suggestions on a course of action . Basic porting (cleaning up casting marks and blending ) is within the abilities of most who are capable of tearing down an engine and putting it back together . If you want to get the most from a port job its best to leave this someone who does it all the time like MRieck or APE . Post some pics of your ports (use the macro setting on your camera , light the port from the valve side and take pic from the port side and then do the reverse ) .

[andrewk]

I agree.  I didn't mean to imply that it couldn't be done, just that it takes some care, and that carelessness can leave you with a heck of a mess.

[dave500]

you can get good results by looking at each port and buzzing of irregular casting or dags,make them all the same but try not to just enlarge them,also bolt the inlet manifolds on and look and feel with your finger if there is a mismatch and buzz any step away to give a direct join,you dont need to go nuts enlarging everything.

[grcamna2]

you can get good results by looking at each port and buzzing of irregular casting or dags,make them all the same but try not to just enlarge them,also bolt the inlet manifolds on and look and feel with your finger if there is a mismatch and buzz any step away to give a direct join,you dont need to go nuts enlarging everything.

Dave,
   Did you do head porting on your CB500/550 head ?

[dave500]

yeah grcamna,anytime i have a head apart i just like to tidy up any production flaws that are obvious without going to any extremes,i do like to clean the bowl area aswell but without removing too much metal,blend where the valve seat insert sits,some dont need anything done here,sometimes its only one or two seats need a touch,i used to do a bit of two stroke porting,but thats a different kettle of fish,i limit that to my chainsaws these days,my neighbours love using my chainsaws.

[camelman]

Porting makes a world of difference, even if you aren't the best porter in the world.  Read up on it as much as you can, and you'll likely be happy with your results.  Your carb jetting will likely not need to change much either.  I installed a 466 kit and bored carbs on what was a 400F, and I only raised the mains one step to get smooth operation from the carbs.  I was using the stock airbox.

Camelman

[dave500]

dont be too keen to go radical,just clean up factory slight faults,they would have made the ports twice as big from the outset if it was that easy to make free power!its a bit like just bolting on a bigger carb,,its not the simple power gain you think it is,the flow factors and shape of the "wind blast"are all to complex for anyone at home to measure and shape what hes doing.

[malcolmgb]

It's also a help to tell people what engine you are talking about.

[Falken]

It's also a help to tell people what engine you are talking about.

K7 CB750F