40mph speed secrets revealed

foureasy

foureasy

New Member
i will periodically add pictures and the reasons why, for a few of the things that i have done in the quest for speed.

i did this to my combustion chamber to make it a more efficient "squish" type chamber. it helps to promote a more even flame travel and less risk of detonation. not to mention the added benefits of increased compression. the ideal size of the squish band is 1/2 of the bore area, which i have come pretty close to.

weld it up
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face it and grind it out
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i got five on it
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Nice job with the fill welding trick (^)

I wondered about attempting that on a spare head I have but the welding guy I talked to said it would likely warp real bad...looks like yours survived so I may take it back and tell him to go for it.

To others that try foureasy's mod a nice finishing trick to use once you've roughed out the combustion chamber shape by hand or in a lathe is as follows...

Grab a few lengths of 1 1/2" - 2" hardwood dowel and shape the ends to the desired combustion chamber shape with a belt or disc sander. Get some various grits of sand paper and glue them smoothly to the shaped dowel ends with contact cement. Starting with a 180 or so grit work the dowels in the combustion chamber like your starting a fire the hard way...the end result should look real nice and be smooth enough to avoid any possible detonation issues.


PS: foureasy is this your finished and running head? Wondering if you touched up the pitted areas on the squish band or not? I'm concerned glowing deposits could get in lodged in them and cause some unexpected detonation...
 
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it runs great, this thread is based on the things that i have already done to do 40mph at 8000 rpms.

rock, those pitted areas are as good as i have the patience for. they are right where the filler rod meets the base metal, (whatever that is). i have seen no evidence of detonation so far. the only issue i've had with this motor is the connecting rod bearing on the small end. i picked up some nice american made bearings to replace the stocker.
sometime in the near future i'm gonna mill up a billet head that is hugely oversize, to combat the heat issue here in tucson.
 
sometime soon, i'll port a used cylinder i have laying around and show some of the layout tricks

here is a sneak peek of my exhaust port


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here is an intake port

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that is a lot of drilling !!!
does it help you enough to be worth the expense/effort ???
enquiring minds want to know :)
 
i was having huge headgasket issues. every cold start resulted in a whistling head gasket until operating temp was reached. i think i need to go back and drill the holes a little bigger, it still seems to get too hot. i still want to get a billet chunk twice as thick and put some radial fins in it like the old two strokes
 
Hey there easy, I'm sure you know that more comp. = more heat, and the extra mass of your billet head may be holding heat. Even with the holes you may not be getting the air flow though them for efective cooling. you might even try making some bolt on fins before you go for another billet. Keep us updated, this old Marine dosen't have the toys that you do to play with.
 
scooterhoot said:
Hey there easy, I'm sure you know that more comp. = more heat, and the extra mass of your billet head may be holding heat. Even with the holes you may not be getting the air flow though them for efective cooling. you might even try making some bolt on fins before you go for another billet. Keep us updated, this old Marine dosen't have the toys that you do to play with.
Click to expand...

exactly! i think i need to go back and make those holes 3/8 instead of 5/16. i was thinking of welding on a few fins, but it might look stupid welding on billet. not to mention the heat transfer wont be that great.
 
i didn't have 80 bucks to spend on the dellorto carb that this motor needed, so i built the manifold and used two carbs instead. they work great, and look sweet too.
 
wow... I will be surprised if that first head doesnt blow your motor at WOT.


A flat squish is an incredibly bad idea as these are not flattop pistons. Also, all your little nooks and crannies in your combustion area are storing heat. You need to get that smooth as possible.



As for the billet head, Id just scrap that... lol. Youd have been better off leaving it a solid chunk and bolting on nice radiator fins from a CPU and putting thermal paste between the two.


Really though you should grab a slant head and have it decked properly.


Your ports edges also look a bit rough, did you chamfer and radius them? How much did you raise your port timing?
 
Foximus said:
wow... I will be surprised if that first head doesnt blow your motor at WOT.


A flat squish is an incredibly bad idea as these are not flattop pistons. Also, all your little nooks and crannies in your combustion area are storing heat. You need to get that smooth as possible.



As for the billet head, Id just scrap that... lol. Youd have been better off leaving it a solid chunk and bolting on nice radiator fins from a CPU and putting thermal paste between the two.


Really though you should grab a slant head and have it decked properly.


Your ports edges also look a bit rough, did you chamfer and radius them? How much did you raise your port timing?
Click to expand...


If you read the post you would see that this bike goes faster than most... why do you think that is? Do you have a domed piston? im lookin at 3 right now flat as a pancake.
Got nothin nice to say......
 
I am not intending to knock you. Perhaps that is how it was perceived but not meant as such.

Purely comments from one builder to another. There is nothing derogitory in my post at all.


I commend you for trying new methods.
 
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