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Old 02-11-2014, 06:31 AM   #16
IT 400
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Should have kept the TT/XT/SR junk and thrown something together. I've ridden 'em in stock frames, modified stock frames assorted purpose built FT frames in a hunert different engine configurations (serious race prepped 540s to worn out stock junk) we don't want to talk about the variety of tires and swing arms we've thrown at 'em Can't beat 'em as far as "BANG FOR THE BUCK"!!! They make great race or practice bikes... I'm A LOT FASTER on my '77YZ250 Trackmaster after some semi serious practice on a Stock framed, stock motor, GOOD suspension and a custom built swingarm TT500.
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Old 02-11-2014, 06:39 AM   #17
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I still have a pile o' junk in the garage. And, I have thought about putting it together many times in the past six months. I am just being a cheap ass right now. I'd rather throw $600 at my Triumph for suspension, instead of 'glass or wheels and tires for the XT.
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1973 Yamaha DT3 - 250
1973 Yamaha RT3 - 360
2007 Triumph Bonneville America - 865
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Old 02-11-2014, 08:11 AM   #18
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What kind of Triumph?
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Old 02-11-2014, 08:12 AM   #19
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New junk.

'07 America
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250
1973 Yamaha RT3 - 360
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 02-11-2014, 08:43 AM   #20
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I built several TD1-C's and TD2 flattrack bikes in the early to mid 70's at Lynn's in Des Moines.
We used Champions and Trackmasters. Several where outstanding.
I'm pretty sure there is one of them (maybe the best) in Ottumwa.
It's a Champion TD2 built for Mark Oswald. Nice Bike!
I have talked to the man who owns it. Might still have his name.
If you can buy a Chenney Frame for $1650 you should!
The Twins are not as easy to ride as a single or maintain. But when they are right, they are hard to beat! They sound amazing!
I have considerable time with them and would like to hear your progress.
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Old 02-11-2014, 08:56 AM   #21
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I am just starting, and being a cheap ass. I want a Cheney frame for sure. It just might take a couple years to get to that point.

I am hoping to pick up a RT3 to start playing with this weekend. If that works out, I am going to try to have it ready for the short track race at Vintage Torque Fest in May. It will be a test and tune for me, as I will be in the '70's Singles class, and will likely get my ass promptly handed to me. I will also be at the Knoxville event in June, and I would like to do the Davenport event in August.
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250
1973 Yamaha RT3 - 360
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 02-11-2014, 09:08 AM   #22
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I'll look forward to talking with you. I'll probably be at both races.
I am pretty sure I still have the Yamaha Factory Race Spec book that gives port timing, carb sizes, pipe recommendations ect. Contact me if you'd like. Pm me
Wayne
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Old 02-11-2014, 01:28 PM   #23
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The problem with the MX360/DT360/RT360 is finding a conrod is you need to rebuild the crank. They don't use the same rod as the YZ360, but you can sleeve the small end to make one work, if I recall.
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Old 02-11-2014, 02:18 PM   #24
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I am looking to use '72 RT2 and '73 RT3 engines, if that matters.


'70 RT1 and '71 RT1 were piston port 4 bolt cylinders.

'72 RT2 and '73 RT3 were reed valve 4 bolt cylinders.

'74 and '75 YZ360 were reed valve 4 bolt cylinders.


'74 DT360 were the "wide case" six bolt cylinders.

'73 and '74 MX360 were the "wide case" six bolt cylinders with a balance shaft.
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250
1973 Yamaha RT3 - 360
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 07-30-2014, 05:58 PM   #25
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As stated above, I looking at a 1973 RT3, which I have started playing with. I found a frame, but not what I wanted. Although, it gets me going until I find a Champion, like I wish for.

I had a thought the other day. On a half mile, wouldn't the twin have an advantage over the single on certain tracks? With my limited experience, my thoughts were that the 360 single would rock on a groove track, and the 250 twin would own a cushion track. The torque of the single would pull it out of the corners. And, on a cushion track, you would not have to use a compression release, nor downshift to keep the twin within it's power band.

How wrong am I?
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Justin Calkins - Iowa Falls, Iowa USA
1973 Yamaha DT3 - 250
1973 Yamaha RT3 - 360
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 07-30-2014, 10:13 PM   #26
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I raced flat track at the pro level for about a dozen years into the early '80's. Spent most of that time running short track at Santa Fe Speedway outside Chicago. I built a Champion frame bike (which I still have and will never sell) and over the years used 3 engines...a DT-1, RT 2 and a YZ 250 A. It handled excellently and was very competitive with similar bikes like the Ossa DMR and the Bultaco Astro. I must admit though...if given the chance to live through it all again I'd go with the Trackmaster frame instead. Champions were good frames but, Trackmasters were better...The only reason Champions got popular was because they paid Kenny Roberts to use them...when that money went away KR started to make his own frames.

I recommend you go with a single engine. Handles better and much easier on the pocketbook for maintainance.

The twins were actually outlawed by the AMA because they were incredibly fast and unruly and didn't work at all on the short tracks and were a handful for the novice racers. The reasoning behind the ban was also to give the novice riders a level playing field and not be forced to have 2 bikes to be competitive on both short tracks & half miles.

The biggest problem you will run into if you try to mix the use of the RT2 and RT3 engines is they have different cases and mounts. You can't mount an RT 3 into a frame made for an RT 2 or vice versa.
Post '71 stock frames will work for track racing...their biggest drawback was weight. '71 and earlier frames handle like you're riding a greased pig backwards! Framecrafters in Union IL can build you either a Champion or Trackmaster replica if you're dead set on an after market frame. I don't know about Champion but the last I heard Trackmaster frames were available through Gary Davis on a special order basis.

As to your questions on the handling of the single vs. twin I'd say you "sorta" have it opposite...assuming you don't plan to run brakeless...the twin would have a horsepower advantage on any 1/2 mile track but would handle better on a groove because on a groove you can "road race" it into and around the turns. The single would give you more oomph on the cush because it has less power but more torque you can really make her slide and steer with the throttle without overcooking it.

I'll be glad to answer any questions I can...Good luck to you.
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Old 07-31-2014, 06:51 AM   #27
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That is what WRW9751 said as well, that I had it backwards.

I have a RT3 and a spare DT3 engine. As far as I have seen with my months of research, the 1968 to 1973 engines (and frames) were basically the same (DT and RT). For 1972 and '73, they added reed valves. 1974 was a total rebuild. The frames were a closer copy to the Champion flat trackers. The engines were more along the lines of the MX series, and they were all called DT (DT250, DT360, DT400, etc.).

As far as the RD250 goes, it is just a neat thing to think about. After I get my 360 finished, and to my liking, I will probably step up to a XT500.
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1973 Yamaha DT3 - 250
1973 Yamaha RT3 - 360
2007 Triumph Bonneville America - 865
WANTED - Boss Flat Track Frames - WANTED
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Old 07-31-2014, 10:03 PM   #28
OldTimeBiker
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Quote:
Originally Posted by Calkins View Post
That is what WRW9751 said as well, that I had it backwards.

I have a RT3 and a spare DT3 engine. As far as I have seen with my months of research, the 1968 to 1973 engines (and frames) were basically the same (DT and RT). For 1972 and '73, they added reed valves. 1974 was a total rebuild. The frames were a closer copy to the Champion flat trackers. The engines were more along the lines of the MX series, and they were all called DT (DT250, DT360, DT400, etc.).

As far as the RD250 goes, it is just a neat thing to think about. After I get my 360 finished, and to my liking, I will probably step up to a XT500.
The MX frames and engines for both the DT (250cc) and RT (360cc) changed in '72. It was the model year that the frames got changed and worked MUCH better and it was also the model year that the engines went from 5 port induction to 7 port torque induction with reed valves. I may have a clouded memory but I believe that in '73 they changed the engine cases and frame mounts...at least in the MX line and I'm positive the original engine mount locations returned in '74 in the YZ line. Enduros after '72 I didn't keep track of.
One bit of advice for your engine...replace the stock metal reeds with the fiber Boyesen reeds...the stock ones were prone to cracking in the high stress of flat track and would do tremendous damage compared to what would happen if a fiber reed let go...Strangly the fiber reeds were much more durable.
I'll be at Davenport...let me know what number and class you plan to run and I'll try to look you up.
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Old 08-01-2014, 09:17 AM   #29
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Just tracking along the old Enduro topic - we have opened up a brand new website with forum and a lot of other resources dedicated to the 1968-1981 Yamaha Enduros. We don't exclude the other vintage models, but that is the focus. If you are interested in the old enduros, come take a look Membership is free and worth every penny!

http://yamaha-enduros.com/

This is NOT the Enduro forum that has been around for many years - but many of the same folks are associated with it
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