1965 YJ1K

ztnoo · Posted: Mon Feb 21, 2011 12:10 pm Post subject:

I'm late coming to this thread because I only joined a few weeks ago, but from reading, I believe there are a couple of misconceptions which have been fostered which need correction.
At both the Yamaha Motors site and the Speed & Sport site, the parts list and the diagrams clearly indicated the YJ1K clearly had an automatic oil injection system.
See: http://www.yamaha-motor.com/sport/parts/home.aspx &
http://216.168.60.165/speedandsportinc/index.tpl

The part #: 115-13101-00-00 OIL PUMP ASSEMBLY

Here is a diagram of the oil pump assembly:

Also as to the cylinder head in question, the one on the bike is most certainly not the correct head.
The correct head is squarish and deeply finned. See item 9 in the diagram

Correct part #: 115-11111-61-00 HEAD, CYLINDER

tbirdsp · Posted: Mon Feb 21, 2011 2:27 pm Post subject:

I don't think anyone was doubting that it has oil injection. The factory YF-1 (YJ-1) manual I have doesn't mention it at all though.

I do think you guys are right about the head. The finning all goes one way on the one I have. Anyone have an idea of what it may be off of? I saw some similar looking ones on late 50's Yamahas in some pics, but I don't think any of those were imported to the USA.
Question

ztnoo · Posted: Mon Feb 21, 2011 4:44 pm Post subject:

I have looked high and low for pics of YJ1s on the net.....and they seem to be few and far between.
I found one that is a pic of a primo example, the other two are of something well worn and rough.
However, maybe both will serve you as far identifying certain features.

From all three pics I think you can clearly see the head is very different than what you have.
What you have may work or be working in some fashion, but if it isn't the right head, you maybe eventually headed (no pun intended) for trouble if you keep running it.
Someone probably just slopped it on there because of the bolt spacing and the idea it seemed to fit.
And to maybe get it sold.

I would strongly advise you find the correct head, ASAP, if you intend to actually utilize the bike.
It should look somthing like this....

There's a couple on eBay.
There's also a fair number of parts, even NOS parts for your YJ1.
http://motors.shop.ebay.com/i.html?_trkparms=65%253A10%257C39%253A1&rt=nc&_nkw=YAMAHA%20YJ1&_trksid=p4506.c0.m245.l1513&_pgn=1

tbirdsp · Posted: Mon Feb 21, 2011 6:13 pm Post subject:

The bike seems to run well. I assume the danger of an incorrect head (as long as mechanical clearance is OK) is increased compression ratio and subsequent detonation/piston holing?

Note that the blue bike doesn't have oil injection - no window in the side cover and no oil pump cable.

rdaystrom · Posted: Wed Feb 23, 2011 2:27 pm Post subject:

There is no misconception about oil injection on those bikes. The original 55 did not have oil injection. I was a teenager during that time and my friend had a new 55 at the time among others that had various other Yamaha bikes with no oil injection. The reason I am so certain is that we sat around much of the time admiring the bikes, having extended discussions about the prospect of oil injection, and wondering about the potential reliability of Autolube which came out shortly after that. It wasn't long before everyone had bikes with Autolube and we quickly left the mixer bikes behind. My friend with the 55cc even discussed the prospect of converting his bike over to Autolube but decided it to be a project that wasn't worth the trouble. A couple years later I became a Yamaha mechanic and remained so for a long time having gone to many of their service schools and seminars. The bikes without Autolube quickly disappeared into the past. Autolube was very successful and as reliable as a "Swsis watch". As a side note, during my whole career on Yamaha bikes I saw only one or two bikes with an oil injection problem out of thousands that I worked on.

tbirdsp · Posted: Wed Feb 23, 2011 10:58 pm Post subject:

rdaystrom, any idea what my head is off of? Very Happy

rdaystrom · Posted: Thu Feb 24, 2011 7:44 pm Post subject:

I can't place that head. It just doesn't "ring any bells" with me.

butch8231 · Posted: Sat Apr 09, 2011 1:24 pm Post subject:

That head is off a WARDS riverside 50, It's about a 1961 model. I really am suprised it fits. Just giving my

MR.CHocko · Posted: Sat Apr 09, 2011 1:50 pm Post subject:

Thanks for the diagram. I may just have the head you are looking for. I think I have half one that is used and the the other half NOS. Come to think of it I may have a NOS head for that bike somewhere too. Do the guys who own shops a favor stay off of ebay. Who would you rather buy from? The guys who you see at some of the largest national meets or someone who stays behind a computer screen all day.