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slider84
Level 1 Member
Queensland
17 Posts |
 Posted - 02 Oct 2009 : 6:11:56 PM
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i am building a twin yamaha for post classic racing and need to know what brand and model tyres i can use. i want a 90/90 x 18 on the front and 110x 18 on the rear.
whats the hot ticket.
thanks mark
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Bummers
Level 3 Member
Queensland
244 Posts |
Posted - 02 Oct 2009 : 7:51:53 PM
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Bridgestone BT39s are good & cheaper than Avons.
I use a 2.50x18 BT39SS on a 1.6mm rim on the front of my Championship winning 125  (But I'm looking to change to a 1.85 front rim soon.)
And 100/90x18 on a 2.15mm rim on the rear.
Available from JN's Race Tyres in Brisbane. |
“Racing is life. Anything before or after is just waiting.” Steve McQueen |
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GD66
Senior Member
Western Australia
390 Posts |
Posted - 02 Oct 2009 : 10:21:47 PM
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| What size twin, slider ? I am still using a 90/90 front, 100/90 rear set of Dunlop TT900 GPs,(Card-carrying fat bastard on CB350 Honda)... still good value really at $140 a rear, and almost always available. For sticky Dunlops in the KR range, you'd be better advised to fly them in from the UK. |
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slider84
Level 1 Member
Queensland
17 Posts |
Posted - 03 Oct 2009 : 08:26:47 AM
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| yamaha ds7 250 , rephased crank to 90, special programable ignition,porting pipes modified heads and compression at 18 to 1 and good old methanol. should be a screamer just need tyers to handle it. getting to old to be falling down. |
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GD66
Senior Member
Western Australia
390 Posts |
Posted - 03 Oct 2009 : 11:00:03 PM
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Goodness ! Very interesting project with the 90 deg crank, jampacked with possibilities. Will be following the progress, good luck with your new weapon of choice.  |
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slider84
Level 1 Member
Queensland
17 Posts |
Posted - 06 Oct 2009 : 11:07:50 PM
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yep lots of possibilities. just recieved the ignition today and **** it has some wires
it is going to take a bit of sorting out.it is designed for a rz/banshee so i need to do a bit of machining to make it all fit. also built up the crank today after having it balanced. 300 bucks just in mallory to get the balance factor right, but its good to 12000 and it will last alot longer than 180 deg cranks.by going to 90 you lose 31 % in vibration plus the balancing .i used rz rods bigger and stronger ,had to machine the webs to get them to fit. slowly but surly it is coming together. |
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CB72
Level 2 Member
39 Posts |
Posted - 30 Nov 2009 : 6:18:51 PM
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Bummers,
Did i understand you to say that you are planning on using BT39 in 100/90? How does that compare in grip to say AVON race tyres or to Dunlop TT900s?
I use AVONs in the US but was horrified when I saw what they cost back in OZ and I need a good set of tyres to protect the rims of my CB72 350 that I plan on resurrecting in the next couple of months when I'm back in Melbourne. |
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CB72
Level 2 Member
39 Posts |
Posted - 30 Nov 2009 : 6:28:32 PM
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Slider,
Interesting project. You are obviously thinking about things but 18:1 compression seems high.
I ran a CB72 on methanol but never a 2 stroke, but I keep hearing that 2 strokes don't like the compression with methanol that we expect on a 4 stroke.
My TZ's are around 15:1 static CR but the guys I know in OZ that used to race TZs back in the day claim that they reduced compression for methanol.
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Bummers
Level 3 Member
Queensland
244 Posts |
Posted - 30 Nov 2009 : 10:38:23 PM
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CB72,
The BT39s piss all over TT900s. I could never get enough heat into TT900s to get them to hang on. I tried lowering pressures until they walked all over the place.
I've never tried Avons on my 125 but have ridden a mate's RD250 race bike with them. From that somewhat indirect comparison I'd say the tyres were comparable.
I've been using the 100/90 BT39 on the rear of my bike for several years and the 2.50 on the front. |
“Racing is life. Anything before or after is just waiting.” Steve McQueen |
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CB72
Level 2 Member
39 Posts |
Posted - 01 Dec 2009 : 02:12:37 AM
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Thanks Bummers,
Just to be 100% clear on this are we talking road compounds or the skinny race compound tyres designed for the Honda 50?
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Bummers
Level 3 Member
Queensland
244 Posts |
Posted - 01 Dec 2009 : 07:57:55 AM
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See John Newton's site, that's where I get my tyres:
You must be logged in to see this link. |
“Racing is life. Anything before or after is just waiting.” Steve McQueen |
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john feakes
Advanced Member
Victoria
791 Posts |
Posted - 01 Dec 2009 : 08:16:44 AM
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| My BT39s (2.5x18) say not for highway use. |
125 RIDERS' ALLIANCE
A wise person simplifies the complicated, a fool complicates the simple. |
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CB72
Level 2 Member
39 Posts |
Posted - 01 Dec 2009 : 1:32:52 PM
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Thanks john. that makes perfect sense. they are lighter construction and are designed to fit the Honda CR110 replica for a race series in japan.
Many CB160 pilots in the US run them at both ends on stock WM1 1.60" rims |
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