THE list for going faster. a work in progress?

slipdrive44

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Dec 3, 2008
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Tucson
So I copied this from a thread I had replied to about nitrous, but I feel it is pretty good. So list anything you feel I missed! I am trying to come up with a nearly absolute list of improvements for performance to market a performance package at Spooky Tooth Tucson.

The way to go faster, really, and this is pretty much the absolute list:
For the MOST out of your ENGINE safely and easily:
1. Port match and polish intake and exhaust
2. Upgraded Carburetor
3. Expansion Chamber a.k.a. Tuned Pipe
4. Best electrical components you can find (high performance plugwire and plug)
5. Boost Port the cylinder
6. Use Bel-Ray Si-7, or AMSOIL Saber (dirtbike racing 2-stroke synthetic oil) in LOW OCTANE fuel (it detonates more violently at the expense of smoothness)

For the Hardware: The idea is to have the bike set up so that you can achieve a desired speed without trying to force the engine to rev beyond what it is made for.
1. Use a 29inch wheel Cyclocross bike- as lightweight and sturdy as possible, made for racing
2. Use either a highspeed low tooth rear sprocket as low as 25-27 teeth OR a shifter kit from SBP OR a modified scooter CVT bolted to the frame (this one is hard to do but it is AMAZING)
3. Keep your tires at maximum running psi

For the rider:
1. weigh as little as possible.
2. ride in bicycle racing attire, to minimize wind resistance ( this includes a helmet for safety)

There you go. This is how to have a top speed bike, a lot of it also comes from luck of the draw on how your engine performs out of the box due to low manufacturing tolerances, few are F1 grade by sheer luck, most are just useable, some fight you every step of the way just to run.

and it is absolutely true that the more you demand from your engine the lower its life expectancy will be. That is the point of doing everything possible to achieve high speeds with lower RPM through gearing. More speed= more vibration... vibrations make EVERYTHING fall apart, even you, so remember that just like in professional racing after every run with a "high performance" motor, you must go through and check and retighten EVERYTHING, because everything is subjected to so much more force than a daily easy rider.

Have fun! and plan to work for every MPH you try to gain! You WILL burn through as much blood sweat and tears as you do fuel trying to get these to go faster, and lets not forget the investment side of the deal!

$1000 High quality 29inch cyclocross bike
$250 High quality SkyHawk engine from spookytooth
$100 for upgraded carburetor
$250 for Andyinchville's or similar custom tuned pipe
$200 for SBP shifter kit
$100+ for labor on professional port and polish
$50+ for Electrical and Fuel/Oil accessories
$50+ for streamlined clothing and various expenses (parts etc.)

TOTAL for "superbike" ~ $2000
(Maybe just buy a motorcycle on craigslist...haha)
 

jasonh

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Jun 23, 2008
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Depends on the individual motor, but usually the piston skirt needs to be notched to allow the intake port to be fully open with the piston at TDC. I got lucky and found a motor that didn't need this.

Also, balancing the crank wouldn't be a bad idea.
 
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slipdrive44

New Member
Dec 3, 2008
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Tucson
Depends on the individual motor, but usually the piston skirt needs to be notched to allow the intake port to be fully open with the piston at TDC. I got lucky and found a motor that didn't need this.

Also, balancing the crank wouldn't be a bad idea.
Balancing the crank was not added to the list because from everything I have heard about it, it is either impossible to really get done, and/or it only assists at a specific RPM to reduce vibrations and all in all is much more trouble than it is worth for a single piston 2 stroke engine, based on researching these forums and internet elsewhere

Feel free to correct me if I am wrong please, if you have it done with good results please let me know, how much did it cost, where, and how much did it noticeably help?
 

TexasDav

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Aug 19, 2008
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Houston
I have read the same thing slipdrive, I know vibration is the bigest killer of everything on these motors including hourse power. But all the research ive read says it is not worth the effort. But I do not know first hand
 

jasonh

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Jun 23, 2008
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Eh, the way I figure, if you're going to pay someone to port/polish, might as well have them balance while they're at it. I haven't had it done, but I've read a couple instances where they had it done and it helped out.

Boost port would be nice, but it's tough to find any detailed info. I want some nice detailed pics and stuff so I can do it myself :)
 

slipdrive44

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Dec 3, 2008
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Tucson
Boost port would be nice, but it's tough to find any detailed info. I want some nice detailed pics and stuff so I can do it myself :)
All you do to boost port your engine it take off the cylinder, then from the bottom up, using a tapered fine grinder in a Dremel or similar make trenches with it up to even with the transfer port tops, and position these ports between the intake port and the transfer ports. This positioning is critical to the function of assisting with Exhaust scavenging. Note the diagram of gas flow in the vertical diagram.

The diagram (crudely rendered) shows a cutaway of the cylinder vertically
and a top down view of port location and gas flow principles that make this help your motor.

Again, as with any mod there is give and take, your piston rings will need to adjust to this setup, and PLEASE do not put a boost port over a ring split. Make sure you know where you piston rings ends are.
 

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tylerlough

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May 28, 2008
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Mishawaka, IN
All you do to boost port your engine it take off the cylinder, then from the bottom up, using a tapered fine grinder in a Dremel or similar make trenches with it up to even with the transfer port tops, and position these ports between the intake port and the transfer ports.
How wide and deep into the cylinder wall do I make the trenches?

Thanks for the good tips for make your mb faster.daxtit
 

slipdrive44

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Dec 3, 2008
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Tucson
I wouldn't go any wider than the width of the bit.
Depthwise pretty much the same, just go easy, don't make the cylinder wall thin.

Dremel sells round/acorn ball bits for their rotary tools, pick up a small one like
144 High Speed Cutter / Model: 144

This should be perfect for the job. Designed to cut into soft metals.
 

mabman

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Oct 4, 2008
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In the wind
This would be the necessary framework for you goals. A 1 grand cyclocross or 29"er would not be dependable enough framewise. This particular frame was actually engineered with a motor in mind.

Highest quality steel constructed specifically designed for use with 29" wheels with angles that will assure handling supremeo.

Behold the Road Warrior!
DSC00811.JPG
 

slipdrive44

New Member
Dec 3, 2008
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Tucson
This is a purpose cast cylinder with BOOST PORTS

this is a superb example.

note the bottom of the cylinder is up in the picture!

 
I was going to say that raising the compression way way up is probably one of the most important mods to the engine too

I run super in mine & cut like .040 off of the head & dont run a gasket at all
I also advanced the timing a little bit taking advantage of the slop in the keyway

I think mid to high 20s gearing on a 29 inch wheel would totally bog one of these engines down
I run a 36 on the back of my 26 incher & cruise 30-35 & can wind it out to about 40MPH
it still climbs hills on the road well but not my driveway without pedaling

have a great week
JAK
 

Egor

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Jan 30, 2008
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Hurricane Utah
Careful with the boost ports. You need to watch out for the ring ends, and poking holes the piston on a piston port engine has to be located away from the intake runner, if your boost holes get near the port the charge just goes back out. Try this. (pic) The second one has the widened ports, this has worked out well, it has a lot of torque. Have fun, Dave
 

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