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Old 01-15-2014, 07:40 AM   #1
Calkins OP
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Question Need Flat Track Advise - RD250 & DT360

The past few years I have been slowly trying to get a flat tracker together. I had a TT500, was ready to race (I think), and had an offer to sell. Recently, I bought back my old pile of spare TT/XT parts, thinking I would going to build another one. But, an old family friend of mine wants to help me put a two smoke together. He was a Yamaha mechanic back in the '70's and '80's, and that is what he would like me to build.

So, this is what I would like to do. There is a "local" series, the Classic Flat Track National Championship Series (http://bikedays.com/id52.html), that has a few half mile races a year. Usually, two are held here in Iowa, Davenport and Knoxville. I want to run the V250/360 class. Back in the day (1973 to 1976) that meant 250cc two stroke twins, 360cc two stroke singles, and 360cc four stroke singles and twins. From what I have seen, the Honda XL350 owns the class. I have not seen many smokers. For me that is great, because I would rather be unique.

So, what I am questing for is technical information. I would like to put together a RD250 and a DT/RT/YZ360 powered Champion. Which engine/year/model, for each, was/is the hot setup? The reason I am wanting to build both, is because I think it will be harder to find a Champion frame for the RD, so the DT will probably get built first as I find RD parts. Then, the DT will probably get switched to a short tracker or TT bike.
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 01-17-2014, 07:12 AM   #2
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Need Flat Track Advise - DT360

I talked to a guy that has been racing a Yamaha two stroke twin for the past 15 years, I think that is not the way I should go.

So, DT360 tune ups. Any advise?
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 01-17-2014, 05:21 PM   #3
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Old 01-17-2014, 06:25 PM   #4
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Quote:
Originally Posted by Calkins View Post

So, DT360 tune ups. Any advise?
mx360 may work better than dt360.
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Old 01-17-2014, 07:27 PM   #5
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There was an old thread on the FT.com about the old 250 and 360 Yamahas. The old boys thought the DT and RT were tuned pretty close to each other, and the MX was a little hotter, and the YZ was a little hotter yet. The MX had a balance shaft in it. If that was removed, the MX would work well. The MX and around '74 on up DT got wider engine cases, that would scrape the ground in the corners.

This is all here-say from old foggy minds. That is why I started threads, to get some answers.
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1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 01-28-2014, 07:50 AM   #6
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If you want to be truly "unique" AND FAST, you should be on a Bultaco 360 ASTRO. Torque like a 4 stroke off corners and revs like the Yamaha.Lighter than any of them...... But alas, you seem to be a Yamaha guy.
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Old 01-28-2014, 08:19 AM   #7
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Actually, I am into Triumph and Husqvarna.

I would love an Astro. But, I do not have $5000+ to throw at a toy like that.
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1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 01-28-2014, 02:47 PM   #8
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Quote:
Originally Posted by buls4evr View Post
If you want to be truly "unique" AND FAST, you should be on a Bultaco 360 ASTRO.
i like the astros too, but wouldn't call them unique at a flat track event..
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Old 02-01-2014, 08:51 AM   #9
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i like the astros too, but wouldn't call them unique at a flat track event..
Not "unique" to see the 3 Astros battling 20 Yams and Hondas in the class?And at least 1 of them ends up on the podium. They come off corners much better than an MX360 and have a lot more power than an XL. They are worth that money if you want to win. Ability to pass on corner exit is everything in flatrack.
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Old 02-01-2014, 08:56 AM   #10
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Having a Bul is on my wish list. I would like to get some seat time with this Yam 360 deal first. I have a feeling that I have much to learn with riding a two stroke. Heck, I have plenty to learn with just the flat track part of it!
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1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 02-02-2014, 07:26 AM   #11
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Quote:
Originally Posted by buls4evr View Post
Not "unique" to see the 3 Astros battling 20 Yams and Hondas in the class?And at least 1 of them ends up on the podium. They come off corners much better than an MX360 and have a lot more power than an XL. They are worth that money if you want to win. Ability to pass on corner exit is everything in flatrack.
sorry if i was not clear, the only place an astro is not unique is at a flat track event. i.e. it's the only place you would expect to see them. that being said, surely there is more to flat track than the ability to pass on corner exit..
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Old 02-02-2014, 08:38 AM   #12
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Sure Stainlesscycle, a lot more to it. But that type of pass is the most solid and certain. Some believe the fastest bike at the end of the strip is best. If that were the case then an RD250 would win. It is seldom the case that a "going in" type of pass sticks as you often go "off line,high", and get passed right back. So a coming off corner pass is most certain because your immediate opponent has no answer for it.
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Old 02-05-2014, 05:49 PM   #13
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I had a coworker send me an ad for a '75 RD250 today. I called my coworker a bunch of names for that. Anywho, it is super cheap, and local. I am going to check it out next weekend.

What makes the stock frame a pile to flat track? If I could make the stock bike handle well enough to last me a little bit, it would buy me time to find a proper purpose built frame.
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 02-06-2014, 07:28 AM   #14
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Calkins, a stock frame is not rigid enough in the steering head area or the swingarm area. It also has too much rake..... Angle is wrong so it will not "turn in" well. That means you will be on a high wobbly line, in corners. It is also weighted incorrectly front to back. You want a Champion or Knight frame with Barnes wheels so you can change gearing readily also.Those frames fit a variety of engines that I mentioned. You need to buy,build motor mounts for them and the RD250 ones are probably available on vintage forums.The RD engine has the most HP of all of these engines except the Bul, but it makes it way too late down the straights.Really bad for shorttrack, barely passable for 1/2 mile. 2 expansion chambers are also a nightmare in that environment.Hope this all helps.
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Old 02-06-2014, 07:32 AM   #15
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Thank you!!
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1973 Yamaha DT3 - 250 - Flat Tracker Parts
Boss Framed Yamaha RT3 Flat Tracker
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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