1978 Yamaha DT400

[barnkat36]

I've recently acquired a dt400 which is missing the exhaust, would like replace with a system that would increase performance. I will be completely striping it down to do a frame off restoration, and will  eliminate stock air box ,oil tank, etc.... which should make fitting a pipe easier, any suggestions would be appreciated .....

Jon 

[The Spanky]

To my knowledge no aftermarket exhaust was ever made for the DT series (I had a DT250). I dint know how the pipe routes on the 400 but if it's anything like the 250 was you aren't adapting any other pipe to fit either.

I did manage to make a YZ silencer work by welding it to the pipe that I cut off the stock silencer after the stock (non- serviceable) silencer became clogged with carbon. It improved top - end pull, but lost low - end, and wad quite a bit louder than stock.

[markit]

I'm thinking all the DT models ran on the rt side but your problem is as above and such an old model, you'll likely have settle for a used stock unit even if you can find one.

[jonboat]

I have a 78 DT400 and yes the exhaust does run along he right ide of the frame. I'm pretty sure you can find exhaust systems on ebay. If you can't find the silencer you can install an FMF universal muffler on it, the universal muffler comes with  small pipe which will need to be bent though. My DT has clogged baffles so I'm going to go the FMF route myself.

If you are a member of yamahaenduro.com you can do a search on the 78 DT400 with the FMF muffler

Edited March 22, 2014 by jonboat

[The Spanky]

I'm thinking all the DT models ran on the rt side but your problem is as above and such an old model, you'll likely have settle for a used stock unit even if you can find one.

My DT250 pipe ran under the tank and then behind the right side panel, with engineered "dents" in the pipe for engine clearance.

[barnkat36]

It does run inside the leftside of frame over clyinder and out rightside on airbox, and the header bolts into clyinder. I located a stock pipe but they crack and aren't very efficent, it will be interesting to see which way I go. I'll post pic when assembly begins. For now I'm just trying to fire it up....

[barnkat36]

This is how the journey began, $75.00 and a dream....

[thejunkman]

I believe Bassani made pipes for some of the DT's including the 400.  Not sure how common they are though.

[Qqqqqqqqqqqq]

J&R made a exhaust for the 400 , I had one on mine back in 79

[sjsingle1]

i remember these monsters.....god they were heavy

[The Spanky]

i remember these monsters.....god they were heavy

I enjoyed my '79 250, I went everywhere with that bike, on and off road. The engine actually ran pretty strong, although the piston and rings did seem to have a short life span.

[sjsingle1]

i had a 78 dt175.....it was half the weight of the 250 or 400.....i sat on them all brand new on the showroom floor

[Supergraphic]

I have a 1978 DT400 parts bike and lots of extra parts available 3/26/2014. Contact me if you want to see and/or buy anything

Glenn

[motoxvet]

I have a 78 DT400 and yes the exhaust does run along he right ide of the frame. I'm pretty sure you can find exhaust systems on ebay. If you can't find the silencer you can install an FMF universal muffler on it, the universal muffler comes with  small pipe which will need to be bent though. My DT has clogged baffles so I'm going to go the FMF route myself.

If you are a member of yamahaenduro.com you can do a search on the 78 DT400 with the FMF muffler

if you can't source some kind of "high performance" exhaust, as johnboat said, a yamahaenduro.com member has experimented with basically gutting the insides of the OEM and the results are pretty good PLUS, since it was OEM, it fits perfectly.  All you'd have to do is find a used pipe on ebay and start cutting.

[Supergraphic]

I've got 2 pipes available

[dt400eman]

PS Tuning based in the Netherlands makes the expansion chamber and silencer that has the same mounts as the stock pipe- plug and play.   http://www.pstuning.nl/shop/index.php?main_page=index&cpath=42_214_220&language=en

 

No, for all the 77/78 DT400 owners out there, it is not a mirage. The real deal from a real company. From e-mail inquires, the pipe adds 3-4 hp peak, more rev capability, and a slight increase in low/mid. It is not based off an IT400, but one designed to work with the stock porting of the DT.Sort of like the stock pipe, which is a real expansion chamber, but just more efficient- without the baffle plates, bumps and dents. With the jolly moto silencer, not including shipping, the price came in at $515.00. It is made from titanium. I suppose you will not have to worry about rust or having to paint.

 One day i hope to purchase the pipe. Frank

[knudsen]

Is there an MX400? Get the jug and pipe off one if there is.

[The Spanky]

Pretty sure the MX and DT engines were completely different.

[knudsen]

On the 250, different porting. Both otherwise a YZ engine. Yam used to sell an Mx kit for the DT. I believe it was the whole top end. I'm pretty sure it's the same story for the 400. Some part no. comparison of the bottom end parts would verify if 400 parts interchange.

[The Spanky]

The DT series was oil injected. The YZ certainly wasn't.