175 Two Stroker

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Fringedweller Racing
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Joined: Sat Mar 08, 2014 10:03 am

175 Two Stroker

Post by Fringedweller Racing » Mon Mar 17, 2014 9:01 pm

Take one YZ125 bore and stroke to about 160 add various bits lying around in the shed and make it go 130mph.
Famous last words How hard can it be !
Seriously I have found my calling was going to do P6 but this looks like it
So the first build is a 175 class 2 stroke based on a yz125 of 1986 vintage with the addition other bits taking up space in the shed.
Welcome to any ideas or input
Will post some pics soon :roll:
Brad {The Fringedweller}

momec3
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Re: 175 Two Stroker

Post by momec3 » Mon Mar 17, 2014 10:18 pm

Welcome aboard Brad,
Chris

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RGV
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Location: Adelaide Hills

Re: 175 Two Stroker

Post by RGV » Mon Mar 17, 2014 10:39 pm

Welcome here Brad. 130 mph on a 175 is a tall order. Will have to be very streamlined. NA or blown?

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

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AuotonomousRX
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Re: 175 Two Stroker

Post by AuotonomousRX » Tue Mar 18, 2014 8:12 am

Hi Brad

Welcome to the World of Land Speed Racing. Good to see another 2 Stroke added to the Mix. 8)

Given that you have a Bike that is eligible for the Modified 125cc Classes, can I make a suggestion, stay in 125 for your first year, engine wise.

Maybe focus on getting the rest of the Bike into Land Speed Trim for the first year. Including your Tow Vehicle and Trailer etc. :wink:

Check out what speeds are being achieved on what Bikes, it is harder than it looks believe me :

Reducing the Frontal Area, as in, get it as low and narrow as possible is where big gains can be made on the Smaller Capacity Bikes. Don't overlook things like the position and shape of your Handlebars etc.

Find and fit wheels that will give you the best Tyre size options.

Then maybe have a look at Body Work options, even if it's a Tail Section and Front Mudguard and run M-G-125.

Take plenty of Pics from the front and side with you on the Bike with your Race Gear on, it's amazing how much difference there is.

Just a few thoughts,

Pete :D
Metric Target 250 on a 250 on a Red Bike

Pete :shock:
DLRA #866
SATA #49

Fringedweller Racing
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Re: 175 Two Stroker

Post by Fringedweller Racing » Thu Mar 20, 2014 9:38 pm

IMG_0187 (800x526).jpg
Ha Ha Harley
IMG_0187 (800x526).jpg (241.16 KiB) Viewed 4678 times
Thanks for the welcome and input
Making some progress
17inch FZR250 wheels and forks
Motor looks ok and is standard bore with new new piston
IMG_0190 (640x526).jpg
17 inch wheels
IMG_0190 (640x526).jpg (200.24 KiB) Viewed 4678 times
IMG_0132 (640x479).jpg
In the beginning
IMG_0132 (640x479).jpg (242.81 KiB) Viewed 4678 times

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BONES
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Re: 175 Two Stroker

Post by BONES » Sat Mar 22, 2014 9:14 pm

Hey Fringedweller
130 is doable with a 175 but you will need 45 plus hp.
My rs125 went 125 with 40 hp (factory claimed).
Frontal area is everything--- Maybe add about 1meter to the wheelbase (depends on your height) and cut the fork length to give only 50mm of travel.
make the seat height lower than the top of the tyre
60 mm of ground clearance is all that is needed
good luck Bones

Fringedweller Racing
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Re: 175 Two Stroker

Post by Fringedweller Racing » Mon Apr 07, 2014 6:37 pm

Seeking opinions
Its looking like a MPS 125 or 175 depending on how many engines I detonate along the way.
1 In search of maximum horsepower doing away with the power valve setup as it is designed to increase low and midrange and looking at its position at full throttle it would create turbulence in the exhaust port which to my laymans view is not desirable. So weld the power valve in place and grind the port/powervalve to the desired shape.
2. Run an programmable electric water pump with larger radiator to enable better manage water temperature.
3. Run a power shifter with button change to ensure keeping engine in the desired rev range. Crucial on a two stroke with a narrow powerband on salt? Has the added advantage of there being no movement at the rear of the body to potentially upset aerodynamics
Brad

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RGV
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Re: 175 Two Stroker

Post by RGV » Mon Apr 07, 2014 7:38 pm

Hey Brad.

The bike look like its coming along nicely.

1: Ive installed springs to hold my power valves open. No heat distortion from welding.

2: Std water pump and radiator should work fine. I warm my bike up to 55 deg before leaving the line (forged pistons need to be up to operating temp. before being thrashed) and it cools down during the run

to around 51 deg. by the end with std cooling system. Your cooling system is designed to operate with a radiator 1/2 full of mud at low speeds around a MX track so should cope easily. Money better spent on

programmable ignition. Not sure if one of these is suitable for your bike. Its what Pete and I run. http://zeeltronic.com/page/pcdi-10v.php

3: Havnt had the need for a power shifter, (Zeeltronic has quick shift) and mines pretty peaky. Ive heard they are hard on gear boxes and I like the KISS principal.

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

Fringedweller Racing
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Joined: Sat Mar 08, 2014 10:03 am

Re: 175 Two Stroker

Post by Fringedweller Racing » Tue Apr 08, 2014 8:15 pm

Thanks Dave,
Yea tend to get a bit ahead of myself with ideas and spending money I don't have.
Whats the best value spend( in terms of performance for $$$) you have had putting your bike together
Brad

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RGV
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Re: 175 Two Stroker

Post by RGV » Tue Apr 08, 2014 10:29 pm

Probably a chamber or mod yours if its close, there's a few free and some cheap chamber design programs that might give you an idea as to how close yours is. Its probably designed more for mid range like your porting. Air filter/box mods, squish will be pretty conservative from standard, set it to 0.8 mm if your head has enough cc. Find a 125 road racer with the same bore and stroke and compare your ports. Ive heard that 190 deg exhaust and 130 deg transfer is a good starting point. What size carby have you got. 38 mm round slide will give you the best top end and their cheap second hand. If you have a 38 flat slide I wouldnt bother changing it. 80's 2 strokes had small crank case volume so a reed valve spacer might help.
Get your bike as low as you can get it. Good aero if easier/cheaper than HP after you get to a certain level. What class are you aiming for?

It took Milton (RIP) quite a lot to get his RM125 to the 100 record.

http://s4.photobucket.com/user/dlra2/me ... 2.jpg.html

Dave

Last Minute Racing "its a 2-stroke ya twit - Its supposed to smoke"
DLRA #928
SATA #10

2010 MPS/G 250 118 MPH:)
2011 Washed Out:(
2012 Washed Out:(
2013 MPS/G 250 131 MPH (RECORD):)
2014 MPS/G 250 140 MPH (RECORD):)
2015 MPS/F 250 DNF:(

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BONES
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Location: Killara Sydney

Re: 175 Two Stroker

Post by BONES » Wed Apr 09, 2014 6:11 pm

Hey Brad
If you are handy with a welder (not stick) or have a mate who is willing to help, IMO you are best to modify the chassis
to make it as low as possible and long- so you lay on it.
frontal area is EVERYTHING.
It takes a bit of doing but you need to get the forks as short as possible. Maybe even change them to a set of road forks off a 125.
The stock forks probably have 200 mm of travel-- even if you shorten them to 50mm travel the sliders are designed to have 200mm and will be
too long.
Have a look in my build diary-- universal chassis. Very simple and easy.
Is the engine crank case reed?
If not, see if you can turn the cylinder and put the pipe straight out the back. A hell of a lot easier to make a pipe and a better package.

happy fabricating
Bones

Fringedweller Racing
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Re: 175 Two Stroker

Post by Fringedweller Racing » Sun Jun 08, 2014 5:19 pm

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Did a bit of a mock up
Running rigid rear end braced under swingarm.
Many more questions than answers so far

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