I would like to thank you for the pics and say that this is the kind of info I've been wanting for some time.
I was about to start cleaning up the head (I say cleaning because I really don't "port" --just take casting marks away) when I saw this thread. This head (from e-bay) is destined for a motor that will be rebuilt for a 750 or 800 (haven't decided) and most likely rephased.
My question concerns the short side radius on the intake port. It was my understanding that the small lip that is present on the xs head needed to be smoothed out even with the floor. But after reading (and thinking about the way airflows) I'm not sure that that is the case. There is no easy way to turn the air -- leave the lip and the air that is on the floor of the port hits the lip and shoots up -- into the air that is a little higher -- creating turbulence.
Remove the lip and the air continues straight until it hits the air from the roof of the lport that is already turned down -- creating turbulence.
Seems to be a case of dammed if you do and dammed if you don't. Is there a solution?
I was also wondering about flowtesting in general -- big numbers on the bench don't nessacerily translate to numbers on the street. I do think tho that the bench can tell you about changes in TOTAL airflow. Seems to me that the problem is that you can't see air and can't see turbulence. Why don't porters use smoke ( think cars and windtunnels) to see turbulence? Or even an airflow test that has a substance that erodes as air is run thru the port so the porter can see dead spots?
Thank you for reading -- I don't mean to be critical --I just want to see the theory so I can do the best job that I can.
So the aim for the intake runner would be to smooth all the casting marks out and to have as smooth a transition to the bowl as possible? As well as lowering the short side radius to the point where velocity starts to drop off -- but no more?
I gotta say that your analogy with the water makes things a lot more simple. I always knew those years in the navy staring at the bow wave would come in handy!!
Oh, Dont remove anything from the short side radius, this will kill the HP that the engine will produce, but do gently round the short turn and leave it as rough as you can as this will help to keep the air/fuel mixture together. But now when I say to keep the short turn rough I mean eliminate the sharp edeges and make the radious as gentel as you can but leave the short side as tall as you can as this will help to keep the air speed up and make more flow under the curve of the cam. Now I know the next thing someone is going to say is OK lets raise the short side of the head but in order to do this you also have to raise the top side or the roof as to make the curve the same in order to speed the air up, the problem is that you only have so much room to work with, without getting into trouble in the ports and valve pockets. Another thing that has been asked is if a smoke stream would be helpful to make the heads better, well yes to a point. Because the intake and the carb would also have to be on the engine in order to give a good air flow simulation, due to the throttle blade position and the way that the mounting grommet would change the direction of the flow and the dead spots, but at this point you would need a clear plastic head and carb with the mounting in order to see exactly where the problems will or would arise. So yes this is a good question but there is only so much engine that you are dealing with, in a high HP engine this would be of great concern, but when your dealing with somthing so small CI wise it isnt as great of importance. I would have to lean more towards the valve job and the entrance to the cylinder than to the actual size and shape of the port, this is also true that the amount of air flow that a head has doesnt reflect the HP gain of a engine as the engine is only as efficent as the one putting it together, and the parts used, and the machine work that is done . Keep in mind that just because you have a bigger air flow # doesnt mean that your going to make more power, it just means that you have the potential to make more power. Its up to each individual engine builder to do the necessary mods to get the job done for the need of the customer. ;D I hope this helps to answer your questions.
I was sweatin just thinkin about it -- but the actual doing wasn't that hard. Besides today is a cool 70 in fla today.
Spent about 4 hours using my dremel with a flexshaft and a few pieces of sandpaper on one of the intake runners and the bowl. Noticed as soon as I started that there were "ripples" in the sidewalls (hi and low spots). as well as the usual casting marks.
I think I spent most of the time changing the shape of the valve guide boss to a more pointed shape and cutting it back some -- not much but enough ( I hope).
Noticed that there was a ridge right where the valve seat and valve bowl meet and removed it.
I pretty much left the short side radius alone but there was a piece of casting flash left that was removed.
All in all not too hard but one of you guys should have warned me about the cost in beer!!
I do want to thank you for all your time --bobby and jack and putting up with all the newbiw questions.
Logan, sounds like you did things right, just think if it was one of us doing it for you................what do you think the cost of beer would have been then? ;D Oh and dont worry to much about the ripples in the side walls as most of the air flow is concentrated on the floor of the port and around the guide boss, then a light touch up around the bowl area to remove the flashing and you pretty well have more than the engine will take. Just take your time and Im sure that things will work out just fine, this is one of the major problems to head porting that everyone does is that they try to rush things and screw up from being in a hurry. Also leave the finish on the intake port ruff with heavy scratches, you DONT want it smooth as fuel will puddle and wont mix as well, I prefer to use a 36 grit tootsie roll and spin it as slow as you can, and with light pressure.
Absoulutely not!!!! how can you even SUGGEST I put a dirty engine part in the space where my wife cooks (sometimes) for the family!? Entirely outrageous!!!!
Ok shes gone-- she was reading over my shoulder. 250 degrees --45 minutes then pound them out with a bolt-- got it. I'll have to wait until tomorrow when she's at work! Is this the approved method for the intake valves as well? Since I am going to replace them (the guides) as well I wasn't all that careful with the grinder!
And since we are on the subject what kind of valve guides do you recommend? I know that I've installed bronze alloy guides in chevy heads as well as a porsche my son now owns. Or would this be overkill?
Thanks for your offer about doing one of the ports so I can copy it -- but I can do this (I think) and besides -- this is an extra head I bought on e-bay -- haven't even touched the engine yet!
Hi Jack, I was at Homestead-Miami raceway at the weekend with a friend who races CCS vintage class ( Honda 350) Anyway, I mentioned Megacycle cams and didnt get a very good response. I was told by another vintage racer (who just put a couple of grand into a 350) that they are having quality issues and the time frame for re-grinds was pretty unacceptable (up to 6 months) Just wondering on your (or anyone elses) experience with Megacycle PJ
There are three types of people in the world, those who can count and those who can't I dabble in rocket science, when I'm not picking my nose
So I'm still very much in the dark on this head porting thing, and the allure of it being a DIY job is keeping me from letting it go, but I have a TON of questions and need a LOT of clarification.
I'm gonna try to ask in stages, cause a single post would be way too much to read with all the specifics.
First off, how realistic is a 'mild' head porting for someone like me who has never done this before, and is a true novice at machine work? I don't think it is at all beyond my capabilities to do this sort of work, and learning by doing is the best way. I'll probably try to pick up a spare head on Ebay or something to practice on, and I've read all the material in Jack's previous threads concerning this topic, but haven't searched the archives for much older posts.
So the first thing is tools. I don't have an air compressor, die grinder, welder or a flow bench. I do have a dremel tool. I've seen it mentioned in this thread that one was used, so I'm assuming that I can use this, but what bits/cutters are recommended for use with a dremel to port a head? Dremel or other manufacturer's model numbers would be ideal. And I assume that the flex shaft attachment would be absolutely necessary for this too?
Let me say that I hope not to frustrate anyone here with the depth and what will probably be viewed as repetition of questions, but I'm a very deep thinker and need to feel I have a very strong understanding from concepts to execution of a given task before I even start. So please be patient with me, and hopefully what I ask and discover may help contribute to the topic at large.
r80rt: :)This is a splendid write up, THANK YOU!!!!
Dec 26, 2015 16:54:05 GMT -5
mashermoto: What the what is this shoutbox for? Or should I shout, WHAT THE WHAT IS THIS SHOUTBOX FOR!
May 12, 2016 22:22:21 GMT -5
motormike: Good Day ...just a FYI.. Wild Cat is this Labor Day weekend. Still go'n on. A few 650's still make the scene. Various rides at different skill levels each day.. awards dinner sunday eve. BS in the park'n lot after dinner.
Aug 23, 2016 7:57:01 GMT -5
lsettle: First post in over 6 years!
Aug 28, 2016 19:45:17 GMT -5
kardon: Wow quiet here, where did they all go.
Oct 7, 2016 2:18:13 GMT -5
gggGary: XS650.com LOL
Feb 16, 2017 20:49:02 GMT -5
buell88: Anybody have any idea who built the xs650 tracker used in the Draggin Jeans Ad on Pipeburn?
May 16, 2017 16:24:09 GMT -5
joshua: The regulator/rectifier unit I got from Mikes PMA has closer hole spacing than original. Are we supposed to mill the holes to fit?
Jun 7, 2017 19:25:58 GMT -5
joshua: My bad. I found the bracket they supplied to mount the rectifier/regulator... Uh oh. How is this meant to work? Which way is it meant to mount? Looks like I have to use some spacers or something. Good instructions would be nice.
Jun 7, 2017 22:09:52 GMT -5
craig8johnson: Not sure if this is the right spot or not but oh well...
Jul 11, 2017 18:04:15 GMT -5
craig8johnson: I'm checking the charging system. I'm afraid I might have fried the last battery. With the solid state regulator (after market) what should it be charging at. The book says, I think, 15 volts. I'm hitting 17 when revved. Is that too high?
Jul 11, 2017 18:06:19 GMT -5
gggGary: Yes 17 volts is too high, about 14 volts is max, sounds like you don't have the right regulator or it's wired wrong.
Jul 13, 2017 6:54:33 GMT -5
dean: Just saying Hello, new member who is going to fix up a 79 XS650 that has seen its better days. I will definitely have lots of questions coming up.
Jun 23, 2018 16:45:32 GMT -5
tt650: Trying to breathe life into a 1980 that's been stored (indoors) for 25 yrs. Air filters are dry rotted. Have cleaned carbs but she only runs briefly on choke then stops. Need jet setting info and other ideas that might help her idle and rev.
Jul 3, 2018 19:15:19 GMT -5
trix13: Hey everyone! New to the forum and am fighting those gremlins!! New charging system, ignition switch, coil and fuse box. Resistance is higher than normal on the ignition pick up so I'm trying to find one. No such luck yet.
Aug 16, 2018 8:50:48 GMT -5
trix13: Also, even though all of my connections are clean, I cannot seem to find out why , when at higher rpms, I hit the signals and the rpms pulse with the signals...hahah. same with the brake light. I appreciate all input!!
Aug 16, 2018 8:55:08 GMT -5
bob99: how do I post a question. I am new to the forum
Jun 6, 2019 10:52:10 GMT -5
adlpc: Hello all! Been enjoying your edifying posts and discussions - and as a fan of the XS650 since my early teenage years happy that I now own a 1980 Special which I plan to turn into a vintage half faired racer. Thank you all for being here!
Oct 1, 2019 0:58:56 GMT -5
jimothyj: Hello everyone, I just joined & wish would have known about this site in 2014 when I brought my 1974 TX650A back from the grave. I have spent a good deal of $$ and alot of time on it. Just painted it and working on electrical, I will post pics soon,
Apr 10, 2021 2:14:13 GMT -5
louisvan: trix13 - I had a problem with my 1975 SX650. When I got to highway speeds, the engine lost power. The problem was in the connectors. At a certain vibration and the wind pushing on the wiring loom, the connector lost continuity. A bad crimp to the wire.
May 20, 2021 1:19:09 GMT -5