Hi folks, I'm fairly new here and to DTs (I also have a '83 IT175).  I'm in the UK where some parts aren't the easiest to find.

I have a 1976 DT400 fitted with a '74 DT360 engine (with desperate piston slap).  I've just bought a 78 DT400 engine (surrounded by a 1999 Husky 410 4T chassis of all things!).  The plan is to swap the 360 engine for the 400.  I know they're different visually but the question is, is there anything major I'm likely to come across when doing the swap?

I'm pretty useful on the tools and good on the electrical stuff so from that side of things I'm ok, I'd just rather set out on the job with other people's knowledge and experience in hand.

A quick look at things shows that the cylinder head fins where the exhaust passes over might need some adjustment, other than that things don't look so bad - am I dreaming or is it going to be an easy swap over?

Any and all help gratefully received.

Thanks, Clive.

Engine swaps aren't a super common thing so not sure anyone here will have direct experience with what you want to do.  I've done a lot with the smaller bikes, just not familiar with the 250/360/400 swap potential.

I will say that Yamaha "recycled" a lot of parts and designs so chances are good it will be an easy swap.

 from near Salisbury, Wiltshire.

Pre 1977 bikes were twin shock, post were mono shock, so I don't know whether or not the engine mounting points changed.

I seem to remember years ago there was a member here that had a twin shock 400 with a later "1M" engine in it.  He was questioning the new intake manifold and reed valve gaskets he ordered being too large.  

I'm pretty sure the engine mounts were untouched.  I do seem to remember it had the twin shock 400 cylinder head.  

I could not find any posts or pictures, but I'm fairly certain mounts are the same.  

(I am certain the 175 engine mounts didn't change from late twin shock to monoshock though the engine designs did change quite a bit during the transition)

Thanks Mark.

Mark - sounds like I'd better make a start on it then :-)

There's a twinshock 400 head on ebay right now so I'll try and get that - it'll be a lot easier than cutting fins off the current head.

As I go along I'll get some photos and info and add it in here; ready for next time this question come up in who knows how many years !

If anyone else has any useful info please feel free to chip in.

Thanks, Clive.

 

I don't remember how well the twin shock head matched the monoshock cylinder.  The bolt pattern is the same, but not sure about the "contour" match to the cylinder fin shape?  I don't remember it being an obnoxious mismatch, but wish I could find a pic.  

(I have seen some obnoxious mismatches like a 1975 DT175 cylinder on a CT1 using the smaller-sized and finned CT1 head, runs fine though)

Obnoxious = Obvious?!

Gotta love these spellcheck jobbies! 

Yeah, let's hope the '75 head I've ordered isn't obnoxious when I fit it atop the '78 cylinder :-) 

I typed and meant "obnoxious".  

That's exactly how it looks to me when the head fin shape and size does not come close to blending into the cylinder fins...  especially if head size is significantly smaller than cylinder fins.... it really looks "wrong".