xt550/xt600 engine difference

[noisy toy]

Can anyone tell me what the differences were between the 550 and 600 engines? I know the bore is different and iron,some 600s were chrome bore(TTs I think) but how about heads,port sizes,cams etc.
I heard the 550 main bearings were bigger? How far can the 550 be bored? The base gaskets are same so a 600 barrel should fit the 550 case, but my bore is good and .75 over. I think the 600 ports would be bigger. I know, why not just chuck in a 600 engine, but mine is in pretty good nick,just want to wake it up a bit.
Cheers, Shane

[LWC82PE]

600 has the twin carbs. Does the 550 have those? There is more than one 600 head aswell. Rather than ask how far it can be bored, see what pistons are available first. Theres plenty for the 600 but for the less popular 550 im not so sure you might be limited to OEM there.

High comp piston will make a huge difference. If get 11:1 ratio they go real good but you wont run on normal fuel. I would look at easier things like exhaust and air box. Im pretty sure you can get aftermarket CDI's for the 550 too. Ive got the details somwhere b ut its a place in NZ who also sells them on ebay.

here

http://www.erd.co.nz/products/index.html

they also sell on ebay aswell.

http://cgi.ebay.com.au/YAMAHA-XT400-XT-400-XT550-XT-550-XT600-XT-600-IGNITION-/200563915811?pt=AU_Motorcycle_Parts_Accessories&hash=item2eb28a7c23

[micks]

there was a change in the heads in the 600`s after the u model the valves were bigger not by much.

[evo550]

Noisy,
The 600 cylinder won't fit the 550 without machine work to the cases.The cylinder liner is to large. I know the 550 head doesn't fit a tt600 cylinder either because of the tacho, although this may be different wih the XT600.
As for big bores, there are a few options. I had a 630 motor built, but it would never run right. I also believe people have had alot of head gasket problems with this option, as no one makes one big enought to suit.
My advice would be to get the 550 running well, and enjoy.

[LWC82PE]

Im sure there are head gaskets out there, well there used to be no so long ago. For standard bore motors use the OEM metal headgasket and not the aftermarket Cometic ones which i found are not as good as the Yamaha ones.

[evo550]

Leith,
If my memory serves me.....well you know the rest. The problem with the 630's was that the piston was from a grizzly (Yamaha)quad and was a couple of mill bigger than the tt600 piston. The only gasket avaliable was the standard tt 600 which would overhang inside the barrel causing sealing issues. There was never an actual big bore kit avaliable, only bigger pistons that fitted....just.

[LWC82PE]

Wiseco, Arias, JE...they all did them/still do them. I have also seen 620 kits and BB importers list a 670 kit aswell. White Brothers used to sell the gasket too. There are ways around it though like making your own gasket from copper sheet.

[Swiss]

On my TT600 I had Arias make me up some 102mm 686cc pistons.  Then I had some custom copper gaskets made up to match the bore.  Not a big deal and you can usually get them in the thickness that you need.  Fairly common to see the Wiseco 640cc kits around sometimes listed on EBay.  With the really big bore you need a custom cylinder liner and case work.  In the early '90s I helped a roadracer in Sweden build up his Yamaha 600 to 686cc and he dyno'd it at just over 70hp.  Of course that was a full race engine with Carillo rod and the big Megacycle cam, porting, FCR carbs and a custom pipe that i designed for him.

You can make a sweet running engine for a LOT less money and be very reliable.  Try to find one of the 640 Wiseco kits.

My TT686cc engine in my Honda Hawk rolling chassis.  Pipes are over dual the engine to dual megaphones to dual underseat custom mufflers.



Swiss