Dt1 vs Yza barrell

[Freakshow]

how do you tell the DT1 barrel from the YZa barrel from the side ? do the fin breaks happen in differant spots, staggered vs straight or somthing like that  

[Freakshow]

I found a 73 article on this so all good.  NExt question is though is there seem to be a few dt1 prefixes in differant bodies.  did the dt1F prefix run from 68 to 72 or am i missing somthing here, can someone tell me the differances in the production numbers or are they all the same internals and stators etc  i have been rereading from my Gorden Jennings pile and noted in one he works on a pipe and port solution for the Dt1 information is very spot on and i going to try some of his results on one of the Dt 1f motors i have here for a little flat tracker project, but im not real clear on the story of the dt1 motors any one explain or point me to where i can find out what models these came in and if they are infact identical in port layout and internal, or if changes what prefixes or numbering to the move from.  they seem to be a fairly simple reliable little motor and would be a lot of fun to have a couple build up to take to the track.   the parts and holes look to line up with 2mx and yza flavours or am i missing somthing there as well.

Speak o forum of wisdom.

[Freakshow]

Must have fell on deaf ears. OK how about someone talk to me about a 1/4 " spacer plate and what decked head with a centre hole should i look to squish up to get this rocken.  Apparently this was all the rage in 72-73 onb the Dt 1 apart from blowing the rod into next week or the head bolt, any one had success in a realistic spacer and did the timing change still make usable power ?

anyone ?

[vandy010]

i'll kick it along for ya freaky,
but i ain't no expert.
DT1=piston port, as in, no reed block so inlet porting would be different to DT2 etc
my guess is that they're all basically the same. Dt2 onwards that is.
as for differences to the YZa barrel. dunno! Adam would be the one to answer that i reckon.
Ignitions? anything you can get to fit making sure the stator/flywheel/cdi all work together.
Deck hieghts/spacers? i only thought this was done when fitting the 250 top end onto the 360 bottom end so as to make for a long stroke motor,
250 bore & stroke is 70 x 64
360 bore & stroke is 80 x 70
the spacer would allow the 250 barrel on the 360 bottom end making it a DT269 which would mean you'd have to get a new sticker made up for the side panels of course and i'm not sure what would happen to the crankcase pressure. i remember firko saying something about it a while back.
heads? dunno... webco i guess.
cheers mate

[Freakshow]

the SPACER SHOULD LIFT ALL THE PORT s UP sort of a poor mans port job and reversable :O)

Well i got the Dt1 here so the motor says, but it has reeds ? was this the 69 -72 motor the same all the way along but the chassis changed ?

Whats the DT1F- bit really mean is it the same other than the barrel/no reeds in the early ones, then the change to reeds like this one fit another use ?   with the reeds if looks like the YZ but assume way differant ports, but i see a lot of US guys run dt1 barrels on Nikasil bores on YZa bottom ends is there a reason for that other than cost ?, one also assume they  can be profiled inside the same or that set up is a flatter power band ?

I got 2 motors that say DT1F- i have no idea what they are off, but they are years appart but they look the same

[David Lahey]

Yes DT1, DT2 and DT3 all have engine number prefix DT1-F.

If an engine has a 1/4" barrell spacer, it usually means that a different length conrod or a piston with a different height between the pin and crown has been fitted.

Yes you can fiddle the port timing by raising the barrell but 1/4" is way too much. More like fitting two base gaskets was the go back in 1972. Don't forget that when people fitted two base gaskets, they had to reduce the head volume to get the compression ratio back right again.

[Freakshow]

So are you saying all the Dt1F motors are identical - just the chassis 1/2/3 changed ?

If i fit one up to this frame, i want to have 2 motors  the same and the ones i have know all start DT1F - but i have no idea if they are the same inside, they look a little differant o the outside ?

[vandy010]

they should all bolt up ok freaky.
motor changes in the early dt's, rt's were very minor up until the 'A' model dt which had a different donk altogether, even though some parts still were interchangable.
as for the frames being different, not by much me thinks. different tank/seat combo but the frame rails stayed pretty consistant through the early models with the exception of the dt2mx{same motor basically}.
build em up, bolt em in and go like the clappers dude!

[Freakshow]

I got one running motor, but i did nt want to piss about building the second up as a spare if it ended up being all differant, would be dead weight taking it along with me then.  Do any other heads fit them as these look very agricultural

[LWC82PE]

http://cgi.ebay.com/ebaymotors/YAMAHA-YZ250-YZ-250-DG-HEAD-RARE-AHRMA-NOS_W0QQcmdZViewItemQQcategoryZ35595QQihZ011QQitemZ320200016613QQrdZ1QQsspagenameZWDVW

i asked the seller and it has 94mm bolt spacing

webco heads are always on ebay.

compare head gasket part numbers. im sure there would be a YZ/MX/IT head that may fit