shoggoth80

ordered a clean bottom end yesterday. should come with everything except for the cranshaft... which is fine by me. if i can get the old engine apart, i should be able to salvage that... provided it is within spec. the engine that that particular piece would comefrom suffered a piston seizure... there were bits of aluminum falling outta the bottom end, as well as a circlip. everything turns freely in there now after a bit of oil... the con rod on it is bent... but since it was piston seizure, and not main bearing seizure, and that the con rod is barely bent, i don't think the crank sustained any damage. so a thorough cleaning, new con rod, big end bearing, seals, and pitson kit should more or less get it up to snuff... then i have to source reeds/'cage, and rebuild the carb i have, or replace it with a better unit. that is still up in the air though. anyone know how to identify the year of the cylinder application? or where i may find a part number? i gave it a quick look over, plopped it on the engine, but have not had a chance to check it out since.

alright! got my YZ400 cylinder... plopped right on without any worries. the cylinder head studs are a shorter length than the DTs, but i have yet to try and remove the studs from one of my DT cylinders to see if i can pull them off. if i can, i could swap them out. the reed cages are different, although the early YZs and DT bikes seem to use the same reeds according to boyesen. so there will still be a bit of research, and parts sourcing... but it's a good start it seems. the head plopped right on too, save for the stud length. just the debate is whether i use a DT series piston, or a YZ series piston? i am leaning towards the YZ series. although i don't have a year range for the part... it was labeled on ebay as a generic YZ400 part. so, i am at a bit of a loss there as far as finding a example to go off of. were the cylinders stamped with a part number? oh yeah...one good thing... NO COMPRESSION RELEASE ON THE JUG! makes my life a bit simpler. now i just have to remove the cable from the cases. which shouldn't be too hard. i was thinking of using JB weld to plug the cable hole in the original aluminum/o-ring plug. should work, and be next to undetectable...or i could always get the hole plugged with a quick tap from a welder. either way, it'd work. now i just need to get that call from the used bike place for the cleaner bottom end... heh.

looked like a close one to me! nice recovery though. looked like a lot of fun, except for the whole almost flipping over backawards part. ha ha ha.

neat pics... that twin headlight tracker-esque model is one of the machines one motocarrera's website... it's a special you can order from them... wait time is like 6 months to 1 year. they have a much better street tracker... very much an inspiration for me... ha ha ha. kinda want that look, without the big square front plate, and something other than yellow. it's cool to see all these strokers cafe'd out. that is closer to their true form in my head. light, and fast.... as far as japan goes, it seems they're having a bit of a two-stroke fit over there. i have seen NEW chambers for the S3/KH400 on ebay coming from japan, and new sets can still be ordered and built there (more than i can say for over here... S3/KH400 chambers are rare as hell)...so it isn't surpsising to see a lot of nice RD examples coming out of the area. if you can find a forum, contact some of the guys in japan, and ask around, that is if communication isn't a barrier. might turn out some really snazzy results. i had a decent pic of a 99% complete RD cafe... but it had no seat padding, but it looked pretty good.

agreed...a quick spin around the block just to feel things out. an overtight chain will affect almost everything... in a bad way... i remember i overtightened a chain once, and it actually slowed the bike down, shop the throttle, and it was like having another brake working somewhere. not to mention it is bad for bearings, seals, shafts, and machined surfaces. chain adjustments are really nothing when you get used to the process for your machine... it's about a 5 minute job on my zook, and about 10 minutes on the kawi... the yamaha doesn't have a chain to adjust at this time. i don't let other people touch my bikes... i do alll the work myself (thus far i have not had to bring it to a shop... but that would be a liscensed mechanic/technician, so i'd have some faith in their abilities). i just find that a good policy... if something is messed up, i only have myself to blame.

i would say what you put in depends entirely on where, and how you ride. i wouldn't worry about synthetic/semi synth stuff... use what is recommended for your conditions... just thoroughly drain your oil, and put a new filter in, and then top off. never heard of synth/semi synth/dino oil problems when you do a full change. those oils aren't compatible with each other (as in don't add a semi synth if you're running a full synthetic, or a dino oil if you're running synth etc.). what is recommended for your bike to start with?

those are some killer shots! been a long time since i went up any mountains.... though i was usually driving over. really pretty scenery... i don't think i have ever been to mount hood. i know there are a couple places in the olympic mountains where the trails offer you a killer view across the straight, and a nice look at the canadian shore across the way. perhaps sometime this summer i'll actually be able to do a little motorcycle "touring" (long disctance rides... been meaning to ride up to canada for a while).

ha ha ha!! that's the best!

man, my first bike was a 1973 honda XR75. it is a great little machine to learn on... and tough as nails... very hard to kill. my parents stil have that little honda, and my nephew is learning on it little by little. good luck.

well, the dealer was amazingly not helpful... the parts department guy claims that he doesn't have info, or access to info for older bikes. somehoe i think that is BS, but whatever. looks like i do this the hard way! i won that YZ clinder on auction. trying to imagine what could be different as far as bore/stroke numbers.... but i honestly believe that they are the same... same bore would pretty much have to equal the same stroke... unless a shorter rod was used and a longer piston, or longer rod/shorter piston... either way with enough research, it should pan out. the YZ jug idea was suggested by one of the guys from motocarrera, so perhaps this was a more common mod to do "back in the day" to get some more oomph out of the DT series machines? who knows... i DO know that the early DTs and YZs use the same part number for boyesen power reeds. that makes getting that part set up pretty smooth. what would be schweet is if i could find a boyesen RAD valve to accomodate the reeds... but it would be tough to find one with the right size, and bolt patterns i imagine... i can always shoot another email to boyesen for that... would definitely add more grunt to the powerplant if they had something that would work. the question now comes down to heads... i have one that has some slight scoring inside, could be cleaned up with sandpaper, and one that has a small screw imprint in it (it was embedded in the piston!), with no other marks on it. which would serve as a better unit? i am under the impression that the screw imprint is less offensive, since the scratch/score marks on the other head look like the result of really sloppy decarbonizing, or broken piston ring pieces. should i trim down the fins on the other side of the head to accomodate the YZ pipe (while the pipes on both the YZ, and the DT exit at the same side, they cross over opposite sides of the head... one is a straight shot back, and the other crosses over close to the rear of the frame)? maybe just get a YZ400 head? i don't thing the combustion chamber is shaped differently. although more research may be needed here. this is a pretty adventurous and ambitious project, since i am bringing a bike back to life from virtually nothing. should be fun to watch the transformation process, as well as a major learning experience. should i use aluminum, or steel to block off the compression release unit? o-rings almost seem a no brainer to add in there for extra security, and dirt cheap to boot. maybe make little copper crush gaskets?

go to bel-ray's website... www.bel-ray.com thy're full synth or semi synth ought to suit you pretty nicely. redline also makes some nice oils... they'd be worth checking out. you can always email their tech departments for some input as well. doesn't yamalube make a synthetic yet? i really don't see how you could go wrong with the manufacturer's blends.

they do appear to use the same bottom end bearing, there are a bunch of internal bottom end part numbers that are shared... which is always promising.

maybe, although i imagine it as unlikely. i wished i had a site that would give me part numbers. i emailed the yamaha dealer that is closest to me (their parts department anyway), and fired away a few questions. even if the con rod is a different length i'd be willing to bet the bottom end bearing is the same. with what little i could dig up it seems like i lot was shared between the DT/YZ/MX series bikes in terms of internal specs/clearances.

sweet deal on the front end! i'll be doing one of three things, by my planning: looking for DT400 forks, looking for street forks of the same diameter, or looking to find another front end altogether... perhaps a yamaha XS series machine... they all used 19'' front wheels from what i have been told, and it would allow me to get the tracker sized front wheel, as well as a disc brake front unit. rear wheel, some random wheel that fits the swinger perhaps... not very good at making spacers and whatnot, so it may just be easier to nab a DT400 wheel/axle/spacer, and get a 19'' wheel laced to that. and since i still have the rear shocks on the DT, that would take care of the rolling chassis... and well, i dunno about upgrading suspension yet... i figure i might as well see how the rear feels. before committing myself to spending more money... cheaper to use what you've got right? i'll be shooting some emails to the yamaha dealer, see if they can nab reeds for a YZ400, or a DT400 (if by some chance the jug gets sold before i can nab it, i have a backup contingency). good times.

well, both being strokers, and of similar displacement.... it really isn't all that surprising. twin VS triple... do the RD series bikes have reed valves? i was under the impression that yamaha used them pretty widely on their 2 stroke bikes.

i think the tripe will be getting a bit better mileage now, since i readjusted the carb settings. i am running size 25 idle jets (stock was 22), and 95 mains (stock was 62.5), and now the carb needle is in the second to bottom position, whereas the last time i put any serious distance on it, it was in the bottom! i was just trying to get a ballpark range for the yamaha mileage so i'd know whether to carry oil on me or not, or whether i should pack extra fuel like you would in bikepacking.

yeah, i am pretty antsy about getting the thing rolling... i figure i'll start with the motor, and nab up any bits that happen to be convenient... but getting a good solid powerplant is fits priority for it. after that, rolling gear, and then after that, i would say the electrics, then and only then, after everything else has been sorted, the bodywork. two strokes are a blast to ride on the pavement, and since i live in city, and well, have a dirt bike (with my parents...they live in the sticks), why not make it as fun (intepret peppy) as possible on a budget? most of this stuff doesn't appear to be too pricey, and it is only a single (a top end job for my kawasaki would be like...$900 or so ). top end for a DT? somewhere between $60-110 new and most likely includes the rings (kawasaki=sold seperately). good luck with your XT mods!

anyone ever use a oil pump block off plate on this model? results? does anyone know if the compression release is a necessity with this model? never messed with either of these mods before, don't even know if the compression release bypass is possible. help?

man, i burned a hardly on the freeway with my KH400... sure, it's not a yamaha stroker (no reeds ) but it still whizzed by. downshifted to hit powerband. he thought he was gonna pass me in the right hand lane, and got sooo mad when i took off that he passed the car in front of him by using the merging traffics on ramp/acceleration lane. by that time, i slowed down... i like bursts of speed, even extended bursts of speed... but i know where to back off to avoid cops in my area.

indeed! the kawasaki KH400 is a 3 cylinder 2 stroke street machine... it's one of the smaller triples, but is still a blast and a half to ride. the H2 is it's larger brother... that's gota long ways to go though... it's just a frame, a front end, a caliper, a swingarm (with no shocks to mount it up yet), and a pair of wheels/clapped out tires. one day it'll be a monster (parts are HARD to come by for that one, and they aren't cheap). my idea for the tracker: DT400 bottom end, YZ400 jug, YZ400 expansion chamber, DT400 head, boyesen rad vavles if they make them for the old YZ, flat slide carb with a pod/uni air filter, 19'' wheels (wouldn't be a true tracker otherwise) and whatever good front end i can cram on there. anyone know the fork diameter for a '76 DT400?

hey guys... new to the forum... seems like a pretty cool place. i got my first yamaha last week. it needs a lot of help, but should be a fun overall project.. it's a 1976 DT400. own a number of other machines, but this one is pretty greek to me (a bunch of little bits like compression releases that i have never messed with before, and apparently a 6 volt electrical system). i am hoping to build a street tracker out of the thing... just think that would be pretty fun way to go with it, and look pretty sharp in the process. figured i would find people who know more than i do on here, and attempt to pick some brains, and add what i can to the forum while i am at it. well, that's it for now!

Hey all... JUST registered with the site. I have a 1976 DT400 that I know next to nothing about, and would like to pick some brains if I may. 1) Has anyone here ever owned one, and could lend advice? 2)If so, have you ever converted the engine to premix by using a pump block off plate? Any issues with under-oiling in this situation? 3)Can the compression release unit be safely removed, and blocked? I have NO experience with compression releases, all I know is that they are typically used to make starting the bike easier. 4)Have you ever used a different model cylinder (ie: MX, or YZ 400 models)? 5) What would you recommend to make the bike more spirited, and streetable? This is a street-tracker project in the works. I got the bike really cheap, and the motor needs a rebuild... I am already sourcing pieces for this, and happened across a pretty good deal on a used (2nd overbore) YZ400 jug from a breaker yard. Any and all input would be really appreciated. Thanks in advance for any info you can lend!