I just got a 78 in decent shape, 2500 miles with no carb. It's complete aside from that and the rear signals. Ebay doesn't have a lot to offer and those that are there are pretty expensive. This is a cheap bike and I would like for it to stay that way! I have seen others recommend this - http://www.ebay.com/itm/KEIHIN-PJ34...Parts_Accessories&vxp=mtr&hash=item232e6cc563 And also this - https://www.denniskirk.com/_.p16465.prd How much work would setting these up entail? The Mikuni looks almost exactly like the stocker, could I simply install stock size jets and be done with it? Everybody loves pics... I have the fenders and exhaust...
After a metric shit ton of research and getting sniped on the only reasonably priced carb on ebay I'm leaning to the Mikuni in the second link. You can add a port for the oil injector and I'm hoping if I set it up with stock size jets it will get me close.
stick with the vm. reliable, cheap, easy to get parts... 32/34/36 will all work i believe - depends on what you plan on doing - i dunno about adding the injector part - the oil pump is the very first thing i remove..
i'd go for a new carb 99% of the time over a used/original one. get a new mikuni VM (like the one in the 2nd link), jet accordingly and ride happily. get the VM, a few main jets & a few pilot jets and start tuning. if the standard main for the DT400 is a 160 (seem to remember that's what it was on the '77 i had), i'd get 145, 150, 155, 160, 165 & 170. same with whatever the pilot jet is... the standard size + 3 smaller and 2 larger. that should about have ya covered, depending on your elevation. i know there's "better" carbs out now, lots of people love the $49 taiwan Keihin knock-off, flat slides, etc... but i've messed with the mikuni VM for ages, it's easy to tune, makes good enough power, etc. stubborn, i am.
Yeah Stainless I'm not sold on the pump port either but want to have the option. I have an rd with one and it has been very reliable. I think premix on a streetbike will be a big PITA. This bike will do mostly street duty, maybe some light fire road stuff.
if you're gonna ride more than 2 hours at a time, i think the oil pump makes things a heckuvalot easier..
not the large hex 4/042 main jets the VM 34 uses... at least none i've ever seen. not in the mikuni/sudco catalog either.
i like the vm too - they ALWAYS idle.. lotsa carbs make more power, but the idle circuit on the vm is so predictable - it makes tuning so much easier when you're not fighting a bike to keep it running..
OKO flat slide available from Ebay for $49, works much better than any round slide carb, and Keihin jets fit no problem. These carbs will greatly improve running, increase top end power, and in most cases reduce fuel consumption.
I'm more concerned with drive-ability, ease of setup and fitment. Would a flat side radically change any of these things? This one looks to already have a hole for the injection nozzle. http://www.ebay.com/itm/YAMAHA-YZ-S...Parts_Accessories&hash=item3f2912aa8b&vxp=mtr
tmx's suck. vm or if you gotta flat slide/d-slide, pwk/oko.. the vm's are the easiest. pwk/oko is not bad to tune, they make more power everywhere than the vm.. tmx is a nightmare. if you're just riding it casually the vm is by far the easiest to deal with.
can't say i'm not beginning to be tempted by the pwk or oko. i have some kinda issue around the oko being a knock off, but that price tag is forgiving. that being said, VMs sure are easy and i can't say the carb is why i've lost so many races
Interestingly enough the carbs marketed by JRC in the US as "PWK" are made by Koso in China, and are a copy of a copy. OKO are better quality than Koso, work almost as well as Keihin, and in most cases can be tuned to work on any bike in less than an hour. For competition use though there is an awful lot of BS related to what carbs are allowed, with some classes insisting on the appalling Anal carbs even...................
aside from pp land speed racing classes, i cannot think of a race series which requires only oem carb and not allowing a period carb switch.
i've got twin amals (anals) on a triumph in my garage. they seriously are appalling. i also have and have run on the street and/or off road with a number of tillotsons, linkert, mikunis of various flavors (VM, HSR), kehins (harley CV, early butterfly, CR), S&S, amal, SU, bing... though all mostly on 4 stroke twins. of the one carb out of that list that i feel is universally easy to run and reliable, it's the mikuni VM. plus i've a drawer full of spares so never need anything "new" for 'em
if you'd like a challenge for your dt400 carburetion - get an irz of of an ossa, or a jikov from an mz. - both are probably better than an amal though (and that tm for that matter)..
