Mystery Heads on 83' XJ900RK

Hi all,

I recently ordered another valve cover gasket for my XJ900RK project...and once again it did not fit.

I ordered it from XJ4ever, and after some correspondence regarding the matter, he suggested that the bike may have a different head on it. While the engine and frame codes match (yes, I took the time to read the write up on decoding VINS), I can only conclude that this must be the case.

It was suggested to me to locate a serial number on the head. I am still poking around looking for it, but am wondering if any of you have come across this situation...i.e. which heads are compatible with the RK? I would appreciate any insight into the matter.

Thanks!

 

I reckon it could be a cam cover from a 750 Maxim. Look at this picture on ebay picture number 4 in the ad>http://www.ebay.co.uk/itm/1983-YAMA...249542?hash=item5d59f5f406:g:R~gAAOSwjVVVhKbb and compare your picture you posted up a few posts back.
Also, you haven't actually told us what engine and frame numbers you've got. You might have a 750, just a thought.

 

Thanks for the response. You're right, the cover looks just like mine...as does that of the 550.

Although the bike was not running when it was donated to me, I presume that such a swap could be a common thing? That is presuming that it did run at one point run!

Hopefully, I can put it to rest today after some time spent in the garage.


As for the engine and frame numbers on mine...

JYA35H009DA000815

35H-000815

 

http://www.ebay.com/itm/Yamaha-750-...ash=item236bb98cc2:g:JhcAAOSwc1FXYfj7&vxp=mtr

Look at the next to last picture (showing the bottom of the head/two combustion chambers) towards the front of the head (exhaust port side), use the "zoom" feature if necessary, you can see the casting numbers (5G200 in this case, 5G2 being the model ID code for a 750cc model)....it's right in-between cylinders #3 and #4, in front of the head stud hole.

I haven't double-checked, but I believe that the 900 head (North America) will show 35H00 as the casting number.


What else might have been changed? Possibly the jugs, too. Check for the ID code and cc's on the front of the jugs, see the 4th image in this listing:

http://www.ebay.com/itm/Yamaha-750-...ash=item235330e515:g:E-AAAOSwLVZVhGdH&vxp=mtr

XJ750 engines (most of them) are actually 748cc's.............

P.S. a 900 engine will show 853cc's

 

Chacal,

Thank you for your response and also the time you have taken to assist during my recent parts order.

I did locate the casting number on the head and it is indeed that of a 750cc model. However, the ID code on the front of the jugs is 853.

Now it makes more sense as to why the intakes on the head appear to have been slightly bored out...

As that I have no history on the bike, I don't know how it came to the state that it is in or how it ran (before it didn't)

My gut says to find the right head and then proceed, but maybe it is worth going ahead with as is?

Thanks!

 

Your gut is telling you the right thing!


P.S. does the bike have the correct carbs on it (Mikuni)?

 

Yes, the carbs are correct.

Unfortunately, it doesn't look like there are troves of 900 heads for sale. No surprise there!