blowit Posted April 28, 2010 Report Share Posted April 28, 2010 I try not to either. I have a good method problem is I don't have a protractor handy. I will also add that my ghetto fabulous ideas will work IF you have the knowledge understanding AND foresight to make every cut and calculate every angle duration ect correctly. It is not something that anyone can do, but, like I said if you have the right guidance I believe something like what I explain can be done by almost anyone. I know I've made some dumb (apparently) topics but rest assured I was probably trying to get something out of it that I couldn't have got by asking directly. And I believe I have done a fair job. In a woods or play application where max performance doesn't matter I wouldn't hesitate to try something myself, but make no mistake if I wanted something competitive I would definately send my engine to a builder. You should not need anything but a scientific calculator to get any number you need. Again, get in the Bell book, bust out the calcs in excel, and test your work. Should be able to do this in an evening. Not sure what the protractor would even be used for. Rod angle?? Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted April 28, 2010 Report Share Posted April 28, 2010 You should not need anything but a scientific calculator to get any number you need. Again, get in the Bell book, bust out the calcs in excel, and test your work. Should be able to do this in an evening. Not sure what the protractor would even be used for. Rod angle?? What I do is make a graph two line horizontally the lines are 58 mm apart the top line is my theoredical tdc, the bottom bdc then I measure down from the top line the distance form tdc to the top of my exhaust, then another from the top line to a point where my transfer roof would be next I draw a line 110 mm long from the top line down and this point will be the top of a circle 58mm in diameted. next I draw a line 110mm long from the theoredical top of my exhaust port and make a mark on the circle where the end of the line falls. If I measure f4rom the top of the circle to the line goig to the exhaust it will give me the degrees atdc. Same goes for the transfer. I can't be accurate tho w/o a protractor Quote Link to comment Share on other sites More sharing options...
blowit Posted April 29, 2010 Report Share Posted April 29, 2010 What I do is make a graph two line horizontally the lines are 58 mm apart the top line is my theoredical tdc, the bottom bdc then I measure down from the top line the distance form tdc to the top of my exhaust, then another from the top line to a point where my transfer roof would be next I draw a line 110 mm long from the top line down and this point will be the top of a circle 58mm in diameted. next I draw a line 110mm long from the theoredical top of my exhaust port and make a mark on the circle where the end of the line falls. If I measure f4rom the top of the circle to the line goig to the exhaust it will give me the degrees atdc. Same goes for the transfer. I can't be accurate tho w/o a protractor I am not sure if you will ever be accurate with that method. I would say if you were going to do something like this, you are better to get a degree wheel and mock up your engine. I really feel the mathematical way is the only way but many have built good engines with a degree wheel. That might be the best route for you. Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted April 29, 2010 Report Share Posted April 29, 2010 (edited) I am not sure if you will ever be accurate with that method. I would say if you were going to do something like this, you are better to get a degree wheel and mock up your engine. I really feel the mathematical way is the only way but many have built good engines with a degree wheel. That might be the best route for you. You can get within 2-3 degrees. Good enough for me to get a feel for if there are any big changes in duration.. I would definately use a degree wheel for my final cuts Edited April 29, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted April 29, 2010 Report Share Posted April 29, 2010 (edited) HA! Got it. 2mm spacer would give you too much transfer timing in most all applications. No spacer would be better for trails but the bd would be a little low w/ no porting. Seems like decking the bottom of the cylinders with some minor porting and custom domes would be a killer woods machine with a pipe such as the fmf gnarly. 4mill, 1mm spacer and some minor porting would be my cup of tea though.And it appears i could leave my head bone stock;) Edited April 29, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
blowit Posted April 29, 2010 Report Share Posted April 29, 2010 HA! Got it. 2mm spacer would give you too much transfer timing in most all applications. No spacer would be better for trails but the bd would be a little low w/ no porting. Seems like decking the bottom of the cylinders with some minor porting and custom domes would be a killer woods machine with a pipe such as the fmf gnarly. 4mill, 1mm spacer and some minor porting would be my cup of tea though.And it appears i could leave my head bone stock;) Sounds like you are catching on!! Right on... Quote Link to comment Share on other sites More sharing options...
AKheathen Posted April 29, 2010 Report Share Posted April 29, 2010 there ya go now, lol.....and just a little tid-bit...the plate is actually 1.5mm, and "shiney" is bad...you wnt a machined surface or similar for sealing...like "grip' for the gaskets. for killer woods, like you are thinkin, the best thing would be a sleve/welded cyl to re-port. i would personally chose something other than gnarley, too....based on real aplication needs.....on another note, i have used a protractor before to get a rough estimate on the stock porting for the "pocket bike" 50cc in my daughters' little quad, lol...then i made my first "failure" pipe that still performed, but not as great as i wanted......curious on how you factoed everything to leave your head bone stock with a 1mm plate.......stock deck and head clearance with the gaskets is only about 060" if i'm not mistaken, so you take the 1mmstroke with the plate, and .040 out of the head to leave you with .020 squish, and i guess you will use a stock, plus 015-020 extra base gasket? Quote Link to comment Share on other sites More sharing options...
SLORYDER Posted April 29, 2010 Report Share Posted April 29, 2010 (edited) there ya go now, lol.....and just a little tid-bit...the plate is actually 1.5mm, and "shiney" is bad...you wnt a machined surface or similar for sealing...like "grip' for the gaskets. for killer woods, like you are thinkin, the best thing would be a sleve/welded cyl to re-port. i would personally chose something other than gnarley, too....based on real aplication needs.....on another note, i have used a protractor before to get a rough estimate on the stock porting for the "pocket bike" 50cc in my daughters' little quad, lol...then i made my first "failure" pipe that still performed, but not as great as i wanted......curious on how you factoed everything to leave your head bone stock with a 1mm plate.......stock deck and head clearance with the gaskets is only about 060" if i'm not mistaken, so you take the 1mmstroke with the plate, and .040 out of the head to leave you with .020 squish, and i guess you will use a stock, plus 015-020 extra base gasket? I believe the stock piston to head clearance is about .080" with a .020" deck height BTW I made my calculations using 1 and 2mm combined thickness of the gasket plus plate so it should be correct Edited April 29, 2010 by SLORYDER Quote Link to comment Share on other sites More sharing options...
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