125cc 2stroke special construction

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Carbon kid
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Joined: Mon Feb 08, 2016 7:12 pm

125cc 2stroke special construction

Post by Carbon kid » Thu Feb 11, 2016 10:49 pm

Hi all !!
New to this so some tricks before I start building would be greatly appreciated thanks !!
Basic plan : 45hp - 55 kg build I HOPE and would love to crack 190kph ?? The rest is Top Secret !!!! Haha
First up RAKE set up ?? Is 45 degrees to much ?
Wear to position most of weight
Wheel base about 2m
19 inch rims F and R with 3.25 Roadrider Avon's ( psi ??? )
Front suspension only @ 75 mm
How best to keep 2 stroke motor going hard as for 3 miles ?? Not at redline but max output !!
Can I run in partial streamlining class as well ??
I've just over a year to build and so excited losing sleep over this already !!!
Appreciate any feed back
Thanks .

gidge348
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Joined: Sat Mar 07, 2009 12:50 am

Re: 125cc 2stroke special construction

Post by gidge348 » Thu Feb 11, 2016 11:29 pm

Hi Carbon Kid and welcome...

First thing I can highly recommend is to read the rule book front to back and over again 99% of all your answers will be there.
http://www.dlra.org.au/technical.htm

There are a huge number of classes so you should be able find a class and a record that fits what you are looking to build.

As far as getting a 2 stroke to last..... well my advice would be put in a 4 stroke (or a turbine :D :D ) but several people have had a lot of success with them.

I will leave others to answer the rest of the questions...

Good luck and hope to see you out there...

Ian...

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RGV
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Re: 125cc 2stroke special construction

Post by RGV » Fri Feb 12, 2016 5:11 am

Hey CK,

If your water cooled you shouldnt have a problem with heat and you wont be running 3 miles as you cant do 175 MPH. Us slow bikes are only allowed to run on the short course, 2 mile max.

You can run in as many classes as you like as long as your bike complies and you have the $$$ for each entry.

I and a few others run RGV's and have no handling problems so that would be a good frame spec to study.

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: 125cc 2stroke special construction

Post by AuotonomousRX » Fri Feb 12, 2016 3:34 pm

Welcome Carbon Kid ...

I agree read the Rule Book over and over and if you don't understand anything contact the relevant Committee Member ....

http://www.dlra.org.au/contacts.htm

For Bike Specific stuff it's our Chief Motorcycle Inspector .....

What engine are you looking at exactly?

it sounds like you would need a late Model Honda RS125 to get close to that sort of power (maybe a TZ but I am not that familiar with them)

Run the Bike one or two Jet sizes Rich and your Oil mixture ++ .....

don't be tempted to chase HP through Jetting ....

if your engine is well assembled with good quality parts, a Smoker will work ok ....

It is when the Mods start and you are moving into the unknown that issues happen ...

Weight is not such an issue in Land Speed but Frontal Area is, especially on lower powered Bikes .....

I ride one of the other RGVs and I found the same as Dave .... with the Std Chassis etc they go dead straight ...... with or without a Fairing .....

If you are making a Frame/Chassis that is a different thing, I am pretty sure you don't need anywhere near 45 degree ...

The Chassis Builders on here can advise you on that stuff ....

the Landracing Forum http://www.landracing.com/forum/ in the USA is also a good resource ...

I found the Load Distribution needs to be have a slightly Forward bias .... some others know better than I do what that is in numbers .... but each Bike is different ...

When I changed my RGV by extending the Swingarm, I also moved myself too far to the rear and the Bike became unstable .... I moved my seating position forward and it was rock solid again ....

I also found my Bike with Full APS type Fairings was very "Aero" sensitive once I went over 120mph ....

The Number 1 thing if you want to run a APS style Fairing .... it MUST BE SYMMETRICAL in shape and in the position it is mounted on the Bike .....

17" Wheels give you the biggest choice of Tyres .... while that might not matter at first ... if your Bike works well then you might need the higher rated Tyres in the future ....

That's it from me ... oh yeah in case no one has mentioned it read the Rule Book over and over :wink: :wink:

Keep us all Posted ...

The main thing is to have Fun and be Safe

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

Pete :shock:
DLRA #866
SATA #49

Stayt`ie
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Re: 125cc 2stroke special construction

Post by Stayt`ie » Fri Feb 12, 2016 10:47 pm

mate with the speeds you will be doing, rake is not necessary, just make sure that "ALL" bearings in wheels, steering head and swingarm are in excellent condition and within manufactures specs, then add a steering dampner,, steering dampners should not be installed to fix a problem, only fit to complement a well setup chassis, :)
First Australian to ride a motorcycle over 200mph at Bonneville,,,

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BONES
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Re: 125cc 2stroke special construction

Post by BONES » Sat Feb 13, 2016 4:35 pm

Hi Carbon
Check my buid diary universal chassis- with the yz80 or tz350
45 is not necessary. 30 is plenty. The important thing is to have some trail. My Hayabusa engined bike is 30deg rake with Kawasaki zx10 tripple
clamps. It's stable as at 205
I think rake more than 30deg is bs
Weight will not be a problem-- you won't have enough HP
You said 45hp--- I guess it is a road race engine
The Avons will be fine. I used them on both my small engine frames. But I used 17" slicks on the front.

Give me a pm if you want, Happy to help

Bones

Carbon kid
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Re: 125cc 2stroke special construction

Post by Carbon kid » Thu Feb 18, 2016 11:35 pm

I have now dropped from 19inch rims to 18 , better tyre choice and a little less frontal area !
Other than aerodynamics what's my next enemy in small 125cc ?, weight ? Rolling resistance ? Or others ??
And where should weight balance be for the salt ?
Starting to test carbon frame options ! Tube only vs part tube part monocoque vs full monocoque ? The fun begins !!
Tube is easiest but heaviest ! Full monocoque becomes complicated in trying to fit every thing in and still be able to work on it !
Won't really know till I get motor and all components and even then with full monocoque will test first with real size plywood mockup .
Thanks for the replies so far everyone .
Will keep you all posted !!

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BONES
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Re: 125cc 2stroke special construction

Post by BONES » Fri Feb 19, 2016 4:39 am

Hey Carbon
Check with Graham Hadley ( head Bike inspector) about the carbon frame.
He might like some stress analysis on it to prove it's strength.
Most of us can look at a tube frame and have a good idea about strength. Carbon looks cool but I know nothing about it structurally.

Don't worry about the weight. Lack of weight will not help here-- maybe when you are loading or unloading the bike.
If you are coming from road racing you will find things a lot different-- If you need a bracket and you think it should be 1.5mm you can use can use 3mm with on disadvantage.
How easy will it be to modify the chassis for an added bracket or fairing mount?

I'm not trying to put you off a carbon chassis,just letting you know some of the differences between Land Speed Racing and ' normal racing'

I'm looking forward to seeing the carbon frame and competing against you with my 125.

Cheers Bones

Stayt`ie
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Re: 125cc 2stroke special construction

Post by Stayt`ie » Fri Feb 19, 2016 6:22 am

Carbon,, Bones always gets a little "guuuuie" when you mention two stroke and 125 in one sentence, :roll: :roll: :lol: :lol: ,, he once took a 125 motor in a esky to the States, :wink:
First Australian to ride a motorcycle over 200mph at Bonneville,,,

Carbon kid
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Re: 125cc 2stroke special construction

Post by Carbon kid » Fri Feb 19, 2016 7:58 am

Thanks Bones , yeah checked with Graham and Ross about carbon fibre frame , not a prob !! It's structurally very strong ,
Very stiff and very light ! The way of the future ! As for add ons it's probably better than welding , no heat treatment loss or distortion and I can create both mechanical and chemical bond !! I used to make bulkheads for America' s Cup boats 3m+ square by 20mm thick you could frisbee across your roof and then put it on a wall at 45 d and drive your car up it !!
I'm always trying to push the boundaries of what I can do with it , some say WHY !! I say because I CAN !
But I can't weld for S:#*t And to save some $ $ I'm not to concerned about the weight factor as much !
Too funny stayt\ ie

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dplecko
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Re: 125cc 2stroke special construction

Post by dplecko » Fri Feb 19, 2016 10:17 am

BONES wrote: Don't worry about the weight. Lack of weight will not help here-- maybe when you are loading or unloading the bike.
You guys have a lot more experience on the salt than me but my understanding is that with relatively low powered bikes the rolling resistance becomes a factor to look at and a lighter bike will have proportionally less rolling resistance. My simulator shows (depending on your package weight/weight%/CoGheight/CDa/HPcurve/ratios...salt/airdensity) lighter is better up to a point, i think around 50-70 HP?

Image

SlowRobo
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Re: 125cc 2stroke special construction

Post by SlowRobo » Fri Feb 19, 2016 9:08 pm

Hi Carbon,
Yes, we all know the benefits of a good carbon lay up. Just google R C Dynamic Soaring, now pulling speeds in excess of 500mph with out a motor. Didn't seem that long ago they couldn't build a wing to exceed 200mph.

I struggle with every day f/glass, So I'll stick with the std RS 125 Aprilia frame. Best of luck with the build.

Cheers, #1215

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BONES
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Re: 125cc 2stroke special construction

Post by BONES » Sat Feb 20, 2016 2:57 pm

OK Carbon
We will need pics you know.
Frontal area is everything if you don't have any streamlining. What sort of forks will you use??
Maybe a girder style with streamlined carbon legs-- maybe 2 sets :-)
My RS125 went 125mph in stock road race trim and me-- 185cm
I think 125 should be doable with a good 'A' chassis.

My TZ 350 is faster as a naked bike than it was in road race trim.
I'll weigh the 125 A bike

cheers Bones

Carbon kid
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Re: 125cc 2stroke special construction

Post by Carbon kid » Sat Feb 20, 2016 8:40 pm

Hey Bones
No pics as yet nothing to see except lots of drawings in scale and a few full size on the factory floor !!!
Are you familiar with Nigel Petrie's 350 cc KTM A class from last year ?? Similar to that !?!?
I'd like to see some pics of your rs 125 though !!
How much work was done on the engine ?? And HP ?
125mph is impressive for 125 cc !! You must be happy with that effort ?
We run a 3 mile course yeah?
Thanks
Cheers Waz


Thanks dplecko and Slowrobo !

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BONES
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Re: 125cc 2stroke special construction

Post by BONES » Sun Feb 21, 2016 12:12 pm

Hay Waz
The RS125 was standard-- as it came off the race track. The book says 40HP.
If I remember right the KTM is very similar to mine. I thought it was a 500--
I thought it was a great job.
I think he used stock forks off the dirt bike--- way too long.
The forks on my 350 are 560mm long. I used a str of conventional forks and shortened the sliders and tubes--- lots of work.
For the 100cc bike I used Thumster USD forks- 580mm long but much easier to shorten. 50mm travel for both .
I use a 17" slick off the 125 on the front of both bikes

We do run on the 3mile course but it is nit necessary to flog the engine for that long.
I have been riding easily (maybe 60mph) until I see the flags for the beginning of timing and thenchange down a couple of gears and GO.
The little engine may be done by the 1/4 mile. Keep it flat until the end of the first mile. It may increase speed a little. You will need to see how your bike works.

Have a look in the build diaries--- universal chassis-- These are my bikes

cheers Bones

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