Motorcycle build 250 tips

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D Robinson
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Re: Motorcycle build 250 tips

Post by D Robinson » Thu Jun 30, 2016 12:11 am

Thanks Brad for clarifying. I was getting confused between 'gasoline' and 'fuel'. Also been looking at Bonneville bikes that seems to be working on different rules. Standard In line gasoline petcock valve and cut off lanyard sounds good.

* 7D3 says the max overbore is .508mm. I was planning .5mm so my interpretation is this is ok to stay in the 250 modified gasoline class. Am i reading this right?

* Tyre pressure. What's the guidance here. Road pressures (taking into consideration ambient temperatures on the day?). My 'H' tyres are nominally 40PSI.

* Are open pipes ok?. The rules seem to be silent on this.

Thanks for the advice.



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Re: Motorcycle build 250 tips

Post by Stayt`ie » Thu Jun 30, 2016 8:21 am

Pump them donuts up real hard, and put the biggest, loudest meggie on there mate, we gotta drown out the two smokers , :lol: :lol:
First Australian to ride a motorcycle over 200mph at Bonneville,,,

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Re: Motorcycle build 250 tips

Post by psteck727 » Sat Jul 02, 2016 2:54 pm

727 will be there for 2017 racing a 250 rg 2 stroker just having a go / remember if your not having a bit of faith and fun your not trying hard enough :roll: :roll:
Stecky #727 Z500
2009 = 124.739
Sean #836 RG250
Brad #896 Z500 ??

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Re: Motorcycle build 250 tips

Post by DLRA » Sat Jul 02, 2016 4:48 pm

G'Day Darren,
Have you contacted the Chief Motorcycle Inspector yet? If not I strongly recommend it because the questions you are asking and highly technical and will have a significant affect upon the class you want to run.
For all contact details go to
Keep the shiney side up........
DLRA WebMaster / Editor

D Robinson
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Re: Motorcycle build 250 tips

Post by D Robinson » Sun Jul 03, 2016 9:06 pm

Thanks Ed,
I've been in contact with Graham.

D Robinson
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Re: Motorcycle build 250 photos

Post by D Robinson » Sat Aug 06, 2016 2:37 am

Hi all, been a month since last post.
Been finishing a custom cafe racer (red/white). Some pics that some may find of interest in the link below.

Also been working on the salt racer. See link for bike as i got it from a swap meet - very sad. Just so folks know what a 1981 XT250 looks like!!

You'll also see the first mock up of frame just before i attack it with a gas axe. The front shocks will be shortened, rear end converted to hard tail, frame lowered, cowl added.

I've worked the engine head (ported, o.s. piston, etc.) and have wheels, forks, accessories painted. Got a dampener also.

I've gone for 21' front & rear wheels for that flat track racer look -modified the rear hub to fit a second front rim.

Progressing ok.

Darren ... slideshow/

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Re: Motorcycle build 250 tips

Post by gennyshovel » Sun Aug 07, 2016 5:49 pm

Welcome Darren
Is that powder coating you have used on the XT head & barrel ? Remember, we race in 40 degree + temps
!9" rear huh ? have you researched 19" H rated rear tyre availability (unless the tyre you choose is suitable for front or rear use (you must provide documentation that it us @ scrutineering) and is 10 years or less since it was made.
Your final gearing will need to be lowered to compensate for the larger tyre diameter also,
Also, remember the maximum allowed over bore of .020", or will running against 350's
Be careful with porting, The Japs know their stuff when it comes to intake port velocity, you can get away with de-burring the imperfections, but be carefull,,,,
Lastly, cam & pipe it to be happy @ 9,000 rpm
Tiny DLRA# 484
Postiebike Racing , created & funded by TwoBob Engineering

D Robinson
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Re: Motorcycle build 250 tips

Post by D Robinson » Sat Aug 27, 2016 11:17 pm

Thanks for the comments Tiny,
The head and barrel are hi temp wrinkle paint. That bike (red & white) is for the street.

Yeh, gearing is a little mysterious - i've read lots of different recommendations and used a bunch of calculators. So i'm taking a few different options.


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