XZ400 Discovery Tour

[Riche]

kiwibum

Can you post the files I sent you? Or maybe send them to XZv2. I wil not be able for another week + because the files are on my work computer.

TIA

[XZv2]

Riche, I tried to send the files that I have again to you. Hope they come over now, and that they are better than those used on my website.
XZv2

[Night Vision]

XZv2; I think someone is messing with your email   >:(
I sent you one in February I guess you didn't get either

[XZv2]

I did not receive that, NightVision. I just sent you a mail with two email-adresses. Please try again, XZv2

[kiwibum]

here you go, being busy, just won an exhaust system on ebay and now trying to source some braided brake lines, looking at fork rebuild as well, it's all go.


Higher resolution files here:
PDF 200KB http://www.kiwibum.com/images/stories/projects/xz/XZ400_spec.pdf
JPG 600KB http://www.kiwibum.com/images/stories/projects/xz/XZ400_hires.jpg

hope these are useful, XZv2 has just sent me some useful info and photos on the 400-550 Cylinders and Pistons. Basically the cylinders and pistons are the same length just different bore diameters which means there is a bunch of room for stroking and swaping parts. Since the cylinders are the same length as the 400 which doens't have a fuel pump, I have to question why does the 550 have a fuel pump? I had read it was because the carbs were higher than the petcock and it was needed to get the last of the fuel out, my 400 happily drains down below reserve, haven't been keen to run it out all together though.

Steve

[XZv2]

Thanks for the translations, Kiwibum. Good question on the fuel pump. The engine parts seem to have a similar height between 550 and 400.  The carbs are the same type BD34. The only difference is that the 550 has larger main jets, in size ca 20%, so at top power more fuel is flowing thru 550 carbs than thru 400 ones. I suppose, a 550 can run equally well without a fuel pump. When I have some time I will put the data and photos I sent you on the xz550.nl website so they are available for everybody.
XZv2

[kiwibum]

Don't thank me, thank Richie, I'm just the messenger.

[Tiger]

:) I'm sure that I am right in stating that Brian Mathewson runs his "V" with-out a fuel pump, with no issue's...

                8).......TIGER....... 8)

[XZv2]

Probably Yamaha, desperately looking for possibilities to lower costs for the 400's (that certainly were as expensive to make as 550's), found out they could save a fuel pump without ill effects.
It is in fact surprising they kept the fuel pump on the later 550's.
And it's surprising they sold the 400 with 2 disks.
XZv2

[Riche]

Could it be the 400cc engine had something to do with road tax in the countries they were sold in?

Thanks for posting/hosting kiwibum

[kiwibum]

Not sure about Japan but it wasn't the case here in NZ, 60cc is the brake point and back then there were no new rider restrictions on size of bike.

[don_vanecek]

The dyno run looks like 45 hp from a 400 cc engine? Not too shabby! I still wonder if the Vision had sold better if Yamaha would have done a 650 or 700 cc version like Honda did with the CX500 (do I have the letter correct-the cross wise V twin they made for several years-not the later VT500-come to think of it I guess the VT engines got bigger also). I remember test riding a CX500 sometime before I bought my Vision and thinking to myself, Geez, this thing is hardly any faster then my CB350 twin-needless to say I didn't buy it!

[Superfly]

XZv2,

Just a curious question....
Are the wrist pins for the pistons the same on the 400's & 550's?

[XZv2]

Superfly, do you mean the piston pins (see ill. 11.3 on page 63 Haynes where a circlip of a piston pin is removed)?
The diameter of the pins is the same of 400 and 550, and the connecting rods are the same. The pistons of the 550 fit on a 400 connection rod. I suppose the piston pins of the 550 are longer than of the 400, because the 550 piston is 80 mm diameter and 400 73 mm. I did not measure the length of both pins up to now, but I fitted a 550 piston to a 400 connecting rod, a perfect fit.
XZv2

[Superfly]

Thank you for the response, I was just curious.

[kiwibum]

XZv2
Just to clarify, are you saying:
1. the connecting rods are the same "length"? or
2. the crank and pin holes in the connecting rod are the same for both 550 & 400?

I calculate that the connecting rods must be different lengths since the stoke length changes and that the 550 rod will be shorter than the 400 one since the cylinders are the same length.

Steve

[Riche]

a different deck height on the piston could be used to get the same results. Shorter crank through/same rod length/higher deck. (deck height would be the distance from the centerline of the piston pin to the top of the piston)
economics, use the same rod and it's cheaper. you have to change the piston anyway because of the different bore size. Just a guess on what they might have done :)

[kiwibum]

That's why I asked as I think the pistons are the same height, in a message from XZv2 he mentioned "The pistons have the same heights above the small end bearing." Agreed it would have been easier to use difference piston lengths. I hadn't thought of that, if I build a stroked crank that might be one way to go if there is a problem finding the correct length connecting rod.

[XZv2]

Hi, Kiwibum and Riche, I went yesterday evening back to the workshop to measure again the differences. I mounted the crankshaft of both 550 and 400 in the left carterhalf. The difference in stroke is caused by a different crankshaft. The "throw" of the 400 crankshaft is 47,6 and of the 550 it is 55 mm, measured at the top of the connecting rod. The connecting rods have the same imprinted numbers 11H-00 and seem to be the same length, but it is difficult to measure with the tools at hand (too long distance to use my calipers).
The small end diameter (and piston pin diameter) is exactly the same. With the crankshaft turned up, the connecting rod of the 550 sticks out a few mm more above the "carter level" (the plain on which the cylinder is mounted) than in the 400.
I measured before that the cylinders have similar heights and that the distance between piston pin and piston top are the same, but that cannot be true because both pistons came to the top of their cylinder, and I measure now that the connecting rod of the 550 sticks out more from the carter than the 400.
I will mount a piston and cylinder of a 400 and 550 on each carterhalf with crankshaft and try to measure everything as precise as possible.
Remember the difference here is half the difference in stroke, that is 55-47,6 mm=7,4 mm:2 = 3.7 mm. I do not know now where this difference is situated.
However, I cannot do that now: busy times because I have to go tomorrow to Italy for my work up to March 18. After that I will have some busy days again. I will do the measurements later this month and make pictures of it all. You will have them. My apologies that I cannot do more at this moment. XZv2 

[kiwibum]

Hi XZv2
thank you for all this information, nice to be able to get it, I have no time to build an engine at the moment, just planning for one, so when ever you get the opportunity to do some more measurements and post the information will be fine. The way my work load is stacking up I can't see me attempting anything until the end of the year anyway. Thanks again and have a great day.