OzVMX Forum
Marketplace => Wanted => Topic started by: Freakshow on September 17, 2008, 04:28:21 pm
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Howdy i want to run one of my bikes next year in the pre 75 class, as i understand it i can put a non reed barrell on a DT1F and its pre 70 ? does anyone have one for sale or swap ? also do i need to run the 19 inch front or the 21" front ? id prefer to track down a 19" front and hub/ brake etc to slot in if any one also has one for sale of swap. what the story with the forks ? whats size or style does the pre 70 Dt need to have to be legal ?
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The basic DT1F bike can be legally 'back-specced' into a pre-70 bike. The rules say that any DT1 is pre-70 legal when fitted with a non-reed-valve top end - and that's all you need to do. You can, of course, fit any/all of the older model parts if you wish - including the 19" front wheel.
The hub and brake are common to DT1/RT1/DT250/360A, although with a 21" rim. A 19" front wheel with smaller brake from an early DT175 (or a late CT1) might also be a possibility for dirt track, but the skinny little axle on the 175 means that its not just a bolt in.
If you fit a piston port top end to a reed bottom end, you'll discover that the reed conrod is 5mm shorter - so you have to put the barrel into a lathe and take 5mm off the bottom. You'll also have to remove a couple of millimetres from the bottom corners of the piston so that it clears the crank halves.
Of course, all of this buggers up the port timing, but the DT1MX specs are freely available and easily replicated (let me know if you can't find them, and I'll dig them out).
The DT1F also has a slightly wider ratio gearbox than the PP models. I haven't gotten mine running right yet, but as it currently is (not revving out), the closer ratios would be a real help.
Sorry, I can't help you out with parts.
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Hmmm?
thats pretty interesting on the conrod Nathan as i thought all DT1/2/3 and RT1/2/3 shared the same
214 prefix rod.
anyway,
after a dig through the shed Freaky, i've unearthed a very usable
DT1 piston port barrel, 3rd o/s,
a DT360a front hub with brake plate, no axle,
and a NOS set of 19" spokes.
theres definately a dollar bill attatched to the barrel and spokes, so let me know and we'll go from there.
cheers.
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check ya pm
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PM recieved, checked and replyed to.
on this Rod Bizo that Nathans mentioned, i've never heard of differing length rods between the DT1/2/3, can anyone else reading this shed any light on the topic?
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I'd not heard of it either.
I went to bolt the non-reed top end on, and discovered that the piston sat 5mm down at TDC (and that the piston hit on the crank before BDC).
Then I spoke to Nifty (who runs a 'proper' early DT1), and he said that his barrel had obviously had the same thing done, and that he hadn't been able to figure out why.
Finally, the more recent motor that I acquired was the same again - its had the base machined down by about 5mm. Its a DT1F engine number, but has the PP top end and clutch cover.
I'm now somewhat regretting cutting my original barrel, but them's the breaks.
Both of my motors have genuine Yamaha pistons, and I believe that Nifty's does too.
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Are you sure its the rod thats shorter, & not the piston deck height?
I have some old Yam pistons from that era & some are about 5mm taller than others.
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Definitely a possibility, but doesn't explain the piston hitting the crank.
I'll pull the top end off the second motor and work out what rod is in it.
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I've been playing around with DT1s for years and wasn't aware that there was any difference between a reed or piston port rod or anything else other than the actual reed valve itself. It's been a while now but I'm certain the DT2MX crank in my DT1 from Hell has the original rod and I'm certain my barrel hasn't been decked. I'm curious now as I've just bought a DT1 F basket case in Qld purely for the engine to use in my Metisse.
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mark you are right the rod is the same one used from 1968 to 1974 mx360a.that is acording to zedder
Part # = 431-11651-00-00
Part Description = ROD,CONNECTING
Model Count = 29
DT1 1968 250 DT1 Dual Purpose
DT1B 1969 250 DT1 Dual Purpose
DT1C 1970 250 DT1 Dual Purpose
DT1C-MX 1970 250 DT1MX Dual Purpose
DT1E 1971 250 DT1 Dual Purpose
DT1MX 1971 250 DT1MX Dual Purpose
DT1S 1969 250 DT1S Dual Purpose
DT2 1973 250 DT2 Dual Purpose
DT2MX 1972 250 DT2MX Dual Purpose
DT3 1973 250 DT3 Dual Purpose
DT360A 1974 360 DT360 Dual Purpose
IT400C 1976 400 IT400 Dual-Purpose
IT400D 1977 400 IT400 Dual-Purpose
IT400E 1978 400 IT400 Dual-Purpose
MX250A 1974 250 MX250 Off-Road
RT1 1970 360 RT1 Off-Road
RT1B 1971 360 RT1 Off-Road
RT1M 1970 360 RT1M Off-Road
RT1MX 1971 360 RT1MX Off-Road
RT2 1973 360 RT2 Off-Road
RT2MX 1972 360 RT2MX Off-Road
RT3 1973 360 RT3 Off-Road
YZ250A 1974 250 YZ250 Competition Motocross
YZ250B 1975 250 YZ250 Competition Motocross
YZ360A 1974 360 YZ360 Competition Motocross
YZ360B 1975 360 YZ360 Competition Motocross
YZ400C 1976 400 YZ400 Competition Motocross
YZ400D 1977 400 YZ400 Competition Motocross
YZ400E 1978 400 YZ400 Competition Motocross
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Jim, i think i'm in love with your Zedder... :)
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Jim, i think i'm in love with your Zedder... :)
does it work with Honda?
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Back in the day Neil keen used to run a 1/4 inch spacer on the dt1's he was building up for the Japs 2 stroke assult on track, so they where going up with the barrell not down.
Maybe JC is onto somthing, maybe for some reason Dt1 ealry piston where scarce in the Act area and they just used later piston and skimed them ?
Hoony, im sure you know but are just being silly, zeeder software comes per maker table, so when you buy it bout $40 online you DL the manufacturer you want , yam , honda suzy etc, the application just looks up tables they cross referance in the specific data base, thats the only differance.
Best money you can spend, you be ammazed at the price differance of the same part with a differant sticker, Zedder keeps you on the cheap :O) and bountiful (also has the supperceeded codes up) ;)
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This has got me intrigued too. When I got my YZB engine it had a 5mm Al spacer under the barrell & unidentified wiseco piston. I figured at the time it was a piston from another engine that was a bit taller than std Yam piston.
Then I noticed DT1 pistons had diff deck ht to reed valve pistons I have (not sure what models they came from except one is IT250D). Just remeasured them all - 19mm for DT1 piston, 24.3mm for everything else, incl the Wiseco one that was in my YZB w the spacer.
So I tho't the barrell hts maybe 5mm diff. Just measured DT1M, DT2M, YZB, several DT2/3, & DT/MX/IT barrells. All are 110mm tall.
I've always been under the impression they used the same (214?) rod, as Zedder shows. So what gives?
The only thing I can think of is the cases may be 5mm lower at the base gasket surface on DT1 & YZ engines, but I no longer have YZ & never had DT1 engine (tho I do have a DT1F of DT2/3 models) to measure. I always tho't they used same cases tho. Might have to pull the barrell on DT1F to check piston deck ht.
Just checked early wiseco catalogues. They list same pistons for YZC-F, DT2/3, MX & IT but NOT incl YZa/b. In the superceded list, 74-75 YZ has separate numbers for it alone. I've found Wiseco listings aren't always accurate, but its the same in 2 diff catalogues.
Can anyone else shed more light?
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i got a stack of YZ and mx piston that are wiseco at home NOS, they are all 234 prefix and say yz 74-76 and i know thay are the same as the mx250a as i used one from that box recently ? they are all reed pistons the only thing i have noticed is the windows shapes changes through the differant piston makes in there as i have some Genuine Yamaha as well.
i have never seen a Yam piston port slug, so cant say on that one, maybe thats what we need to find and suss one of them out.
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Remembering that all three of my motors are stamped DT1F:
This is my untouched DT1F (reed valve) motor for my resto bike. It has a 311 rod. Its on the original bore, so I assuming that its the original rod.
(http://i46.photobucket.com/albums/f128/annaandnathan/Wed2186.jpg)
This is my race bike motor (and no, I'm not going to pull it apart to take photos). Note the small lump on the side of the barrel just above the base gasket - this is the top of the pad that used to have "246cc" cast into it, before I took to it with the lathe.
(http://i46.photobucket.com/albums/f128/annaandnathan/Wed2179.jpg)
This is my 'spare' motor. Note that its missing material from the bottom of the barrel, but less than my bike's barrel. Nifty's is like this too.
(http://i46.photobucket.com/albums/f128/annaandnathan/Wed2175.jpg)
214 rod in the spare motor:
(http://i46.photobucket.com/albums/f128/annaandnathan/Wed2176.jpg)
Yamaha piston from spare motor. This one hasn't had anything removed from the bottom of the skirt, which makes me think that there are two or three different piston-port pistons.
(http://i46.photobucket.com/albums/f128/annaandnathan/Wed2177.jpg)
Finally, the spare motor with piston installed, shown that the deck height is well and truly in the ball-park (if not ideal):
(http://i46.photobucket.com/albums/f128/annaandnathan/Wed2173.jpg)
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Freaky,
I'm just going on what 2 early Wiseco manuals say. They list # 234 for "YZC,D,E,F, DT2,3, MX,IT" only.
# 230 & 398 are listed for 74-75 YZ. I suspect they're 5mm shorter deck-ht like DT1. And that fits w my YZb engine using #234 piston, not the proper #230 or 398 & needing 5mm spacer under barrell. The YZa/b was said to be developed from the DT1 engine (ie not DT2/3)
AS mentioned previously, I've measured DT1 piston-port piston (several times) & its 5mm lower deck-ht than DT2/3, but barrels are same ht (110mm)
Nathan, Yeh seems to me there's 2 diff cases too. My DT1F (DT2/3) engine has 311 rod also. I'm fairly sure the YZ had 214, but its obviously the same length cos yr engines have both & both need decked barrell.
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im lost . nathans other motor shows a 214 rod ? so are we now agreeing its the pistons that change in hieght not the motors ? make life easier if thats the story.
the Yz was alway a reed was it not ? so the piston should be the same all the way. I have a 234 and the 230 piston at home so i might pull them out and measure them up, but i just assumed they were the same i have never had them side by side as they were both i thought reed window pistons.
i got 2 Dt1 motors here somewhere after next week i might pull of the heads and suss the rods, be inerested to see how many are 214 or the 3 series.
i have a Dt2mx barrel on a yz bottom end, and thats fine, so too if i fit a dt1 barrell - they all line up fine. i dont have a PP barrell to sit on it to see if there is a differace to agree with ya finding there, but ill have a hunt up through the Dt1 c, f or mx Bottom ends i got and see if there is some kind of a pattern in there.
interesting thread fellas :O) thanks for all the pics Nat makes it easy to see what were all talking about here.
Neal told me he only fitted 1/4 spacer ( which later became a GYT kit) and had an angled intake inlet set up to a mag carby yam gave him with a pancake air cleaner, when i sussed him out about his go fast in the day set up, there was no mention of rod changes, but if i speak to him later ill quiz him on that too, because he ran the PP and then into the reeds before he retired in 74, they dont call him proffessor for nothing.
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most interesting indeed fella's!
Freaky, i just measured my PP barrel and it's 110mm from base gasket to head gasket and so is obviously "undecked" and STD.
i have no DT motors at my disposal so i can't measure anything else and only have the one RT motor. prefer the big bike.
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It is a bit of a conundrum.
The pistons are definitely diff hts. PP pistons (& YZa/b as far as I can tell) are definitely 5mm lower from gudgeon to top than all other reedvalve pistons. But the barrells are all 110mm high & the rods all seem to be same length whether 311 or 214.
So if the rods & barrels are same length/ht & pistons 5mm shorter something else must be 5mm shorter also. The only thing it can be (it seems to me) is the cases are different, w the vertical distance between base-gasket surface & centre of crankshaft 5mm less on the PP DT1 (&YZa/b) cases than on all later reedvalve engine cases.
I measured that distance on a DT2/3 (DT1F) engine & later DT engine. Its 80mm (or v close to it) on both, but I don't have a PP DT1 (or YZa/b) engine .
Another way around decking the bottom of the barrell 5mm when putting DT1 barrell on DT2/3 cases would be to use a 5mm taller piston. I'm fairly sure the TM/TS250 pistons were about that, cos when DirtBike mag built a project DT1 in early 70's they used a Suz piston w a spacer under the barrell. I'll have to check what thickness.
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when putting DT1 barrell on DT2/3 cases
Hang on i thought we were talking about a PP barrel on a DT1F reed rebottom end ? thats what Nathan has up in pic's. IM wanting to put a Dt1F bottom end onto a PP barrel, thats what i though we were nutting out. can we be sure we are talking about that specific set up when we conclude this delema.
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Does this help?
214 rod is 130mm between centers, 311 rod is 125mm between centers.
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and so it is, the jigsaw pieces are coming together
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Brilliant post, thanks Kurt.
That explains half the mystery - but I'm not sure why Nifty's or my spare motor have needed material removed from the bottom of the barrel.
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if you used a 311 rod with a Dt1 piston you get that short stroke so the only way to pick up that squish is to drop the barrel or head, maybe the barrell was easy for them to do b8ut why you needed to re cut the ports to the specs you did .
Sounds to me like a 214 with a Dt1 PP piston is correct hieght
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Yes, that solves it. Rods are diff lengths, so Zedder listing of same rod in all those bikes must be wrong.
214 rod w DT1 PP piston should be right Freaky (w'out moodification). By the way, DT1F engine # is DT2/3 engine.
Suz TS250 piston is 6mm taller from gudgeaon to top than DT1 PP piston, so that could be used w 311 rod & a couple of extra base gaskets as an alternative to decking the barrell when using 311 rod.
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I have a DT2MX crank, presumably with 214 rod in original DT1 early number cases and a twin ring piston port piston. Am I reading correctly that this setup shouldn't work? I'm not about to pull the engine apart to check but I'm 99.9% certain that's what I've got and the engine runs fine and has for twenty years. The slight doubt I have is that Gary Treadwell modified the barrel and Peter Reynolds the head and I can't remember the details.
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the way i read your situaton mark is that you have the "long" 214 rod with a "short" DT1 piston.
as opposed to a "short" 311 rod "long" DT{reed}piston.
it's early but i think i need beer!
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yes to all that, its obviously the combination of rod and reed that can make a problem. but 214 and PP as you say JC seems like thats how it was.
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Yes Mark, I think yr combination should be right too.
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My head hurts................................ ::)
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What's the go with PRe 70 mods then, like are there restriction on a round slide carby etc ?
Obviously you have to use a flange set up or do you ? can you just then make up a flange to rubber and run a 34mm mukuni or somthing, or does it have to be an original 30mm style Flanged carby ?
Anything else im missing that has to be Dt1 etc to be legal or is everything else free ( not era specific - ie 74 mdl Dt forks etc )
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got your PM Freaky and we'll work it out.
my RT1 carby is a 34mm unit and jetted to the RT1 specs straight from the manual and runs fine.
i needed to get a rubber boot from T.D. Hatricks {mikuni guys} to make it work and they're pre~70 legal no probs.
any yammie 34mm forks with straight leg bottoms and the correct travel amount will do the job for pre~70 but the earlier type with the mudguard mount brackets "look" the part for that era {my opinion only}.
bascically, any DT/RT 1,2,3 as long as they're converted back to a piston port barrel, will be fine for pre~70.
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Do you have a part number for that flange boot ? IS it like the TM suzi one.
SO a set of 74 Dt250 forks are ok then ?
any thing else im missing ?
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What's the go with Pee 70 mods then, like are there restriction on a round slide carby etc ?
Obviously you have to use a flange set up or do you
No Freaky you aren't limited to the flange mount carby. I used a rubber boot and a 34mm Amal off a Weslake speedway bike on my DT1 which worked great. I'm initially using a 34mm flange mount Mikuni on the Cheney RT1 to simplify things but will probably go over to a 34mm in a similar setup as Vandy.
I used 35mm Betor forks from an OSSA on my DT1 but to simplify the job I'd be using 34mm Yamaha forks with alloy sliders from a later model and fitting PDF valves which overcomes the lack of adequate performance of the Yammy forks . I don't think the conical style Yammy front wheel is legal for pre '70 so I'd be use fork sliders that easily accept the old DT1 full width hub.
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kewl thanx firko, ill try to get a heads up from vandy on the rubber bit, 34 muks i got and boxes of jets so iid like to stick to what i know.
i got a set of betor here somewhere i might have a look at them , but from what your saying a full width front drum is the go ? i have a 75 TS 250 front end which is full width and might be an easy bolt on F/end ? thoughts, it looks way old school particulaly with the big drum andi thik it also has a brake stay too not a tab.
what trees can i use then that are legit to take the 34mm forks or do i get the 32mm reemmned ?
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I don't think the conical style Yammy front wheel is legal for pre '70 so I'd be use fork sliders that easily accept the old DT1 full width hub.
Mmmmm... Interesting point... According to the on-line parts catalogues, the conical hub was first fitted to the 1972 RT2MX, which was reed valved.
However, the wording of the rules says that 'any' RT1 with a non-reed barrel is legal for pre-70.
The obvious debate then centres on whether an RT2 is really an RT1 (they've all got RT1 stamped into the frame and engine).
Meh - I'm running the full-width DT1 type hub on both my DT1 and RT1, because there's no argument over legality and because the brakes are awesome.
Firko, all of the 34mm in-line forks have the same brake lug - so you'll have no drama fitting the early brake/hub to later 34mm forks, or visa-versa.
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so nat what did you do to the triples to take the 34mm forks .
If im reading it right your saying the 34mm forks are OK and there also is no need to modify the DT1 axle or shim to slot later DT 34mm forks, the axles etc the same.
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Found this bit of info on the DT1mx when i was going through some stuff on the GYT mods etc for my next project.
Any ow remebered this debate and not sure if it relates to it, anyhow it mentions a differant hieght and window on that piston spec, which maybe where all that sizing crossed over, also noticed they head volume changed and on the other pages it also mentions window and timing changes for the 1 mx version ?
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so nat what did you do to the triples to take the 34mm forks .
If im reading it right your saying the 34mm forks are OK and there also is no need to modify the DT1 axle or shim to slot later DT 34mm forks, the axles etc the same.
Sorry, I missed this when you first posted it.
All DT1 forks are 34mm, so there's no need to do anything to the triple clamps or brakes or anything - what changes is the lower legs. Early models are chrome plated steel, while later ones are alloy. The alloy-leg forks apparently have better internals, as well as the improvement in weight and stiffness.
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Any advance on whatr the flange rubber mount is for the 34/36mm Carb ?
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Come accross a PP with a deck barrell, what am i lookng for piston wise to make this work. > bottoms i have are 214 rods, any idea what the piston was that used the decked barrell ? before i go making up a spacer ?
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bump