Can someone please tell me the advantages or disadvantages of welding up the heads for a straight spark plug and setting up the squich band. A flat one or an angled one. And what about angling the top of the pistons. Also tips and advice for welding are welcome. How to weld...
Take it to a professional welder and then a machinist. You are welding up the heads in order to make a proper truncated dome type combustion chamber. This style is most resistant to detonation and there fore you can run higher compression values for more rear wheel power due to the increased cylinder pressure. You also want the plug in the center of the chamber to minimize the flame travel time for a most complete burn. As for the squish band, it serves several purposes and for an RS250 motor running stock pistons you want about a 5 degree band. It maximizes turbulence on the compression phase, makes the cylinder more resistant to detonation and should never be flat like the stock one.
Micah, I am impressed, you are learning quite alot, studying I see!! The squish is most important, as you say, for the turbulence and also has an affect on the flame propagation in the combustion process. A narrow squish of 6mm will give more top-end as it allows the cylinder pressure to be fully utilized and dispursed on every stroke. A 10mm wide squish gives it more bottom and midrange as it creates a shelf for a pressure wave to sit in on the combustion stroke. As for the 90 degree plug, I believe it has little to do with detonation, I have seen it in both plug styles, compression is the main factor there. But the flame propogation in the combustion chamber is the main reason, firing directly over the center of the piston creates a more complete burn and a controlled one as well, and so more even pressure on the piston top, i.e. more powerful stroke.
Now for a technical question for Foxter...if the 6/10mm thickness theory works well on a 54mm bore size does this scale down linearly to smaller bores? IE...for peak power on a 47mm bore instead of 6mm squish band is 5.22mm... correct? I got here by dividing 47mm/54mm and then multiplying by 6mm to get the result of 5,22 mm.
Micah, you would divide 54 by 47 and then subtract that number from 6, this would be 5.13 and that is correct. Area and volume are linear in reduction of area or size. Are you goofing around with that RS50 still? It will break entually like my 250 exploded. Like my father always said, you can't stick 3 lbs. of @#%$ in a 2 lb. bag!!!!Never get stuck with stock!!!!!!!!!
im not even going to try and follow what you two are discussing yer both bleeding know it all's.only joking dudes happy new year dudes howie:rollin:
Unfortunantley for me math was always a little vague for me. Thanks for the answer...and I just love messing around with the little RS. Yes, eventually it will explode but, I think I am still about 8-10 bhp from an explosion.
could someone who has modified the head for top end power possibly post pics and dimensions for the mods so I can explain it to my machinist here?
I know what you want to do we do it to mc21s but honda supply a kit which in effect is a top cylinder head swap can you do this to the suzuki engine on the rs.It would cost less.Again i don't no if you can do this to the rs.
Does anybody know the specs (squish clearence and angle) for the RGV kit heads. I know they have a hemispherical combustion chamber - Its just that it might be cheaper to get the kit heads than pay someone to weld then machine the stock heads?
not cheaper for me, I know a welder and a machinist who work cheap cause they enjoy this stuff.
Seeing as I don't know any welders - I'm still interested in the specs for the kit heads ... Also (correct me if I'm wrong) a hemispherical chamber helps prevent detonation, why do the normal heads have a wedge shaped chamer and an offset sparkplug? Why are kit heads only supposed to be used with AVGAS, presumably kit heads have a smaller combustion chamber - hence higher compression than standard?
It's cheaper just to get a set of RGV SP heads.
i think the reason the stock heads have an offset lower head is purely to fit it in the stock bodywork.
You want a truncated dome style combustion chamber and the squish band at about 3 degrees. (for use with flat-top style stock pistons) For peak power in the 11,000 to 12,000 rpm range the squish band should be on the narrow side at say 7-8mm width. For a semi-safe engine combustion chamber volume in the 12cc range would be advisable.
For my project RS250 I am going to try a 1mm spacer plate under the cylinder and a drop chamber head design. I will take pics as soon as I get the bike apart. I am shooting for a .5mm squish clearance.
If anyone has some blown up heads to give away or sell cheap I need them to make my prototype heads and be able to keep the bike running in the mean time. I will be looking at making them from Billet with replaceable combustion domes and straight plugs if they truely work a lot better.
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