Maxim Engine question with picture included

Hmmm I dont think this screw is supposed to be here.....I never noticed it until a few days ago.... Any suggestions on this freeze plug that has a screw drilled into its place. I dont know too much about this and I try to pull as much info as I can, but I cant find much.

 

I just went out and looked at my 82 XJ650J Maxim and that screw does not exist on my bike. What size motor is on your bike?

 

Maybe our bikes are from different batches, but my 82 650J DOES have the pictured screw on the right side only.

 

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Hmmm...here is a pic of my plant....wonder of Rick, Fitz or Len knows why some do and some don't....

 

Not WHY, but I know WHAT it is, or where it leads anyway. That "taps into" the oil feed to the intake camshaft. It's either there because of something done in production, or as a "vent" to ensure oil flow after an oil change. If it were for the latter purpose, you'd think it would be mentioned in an owners' manual somewhere but it's not that I know of.

The XS400 twin manuals DO mention it in regard to post- oil change (opening it until oil pukes out.)

My '83 550 has one, my '81 550 is just "blank" and I'll have to look at the 650 when I get home.

 

I have the MAxim with the 750 in it, :/ I just am really shocked I didn't see this....I really just Sorta mind blown, I've looked at quiet a few pictures on google/bing with out finding any with it, saw nothing in the manual..Feeling a bit worried about this, I haven't noticed any oil or fluids leaking out from the head of the screw. Thanks for the answer again bigfit...Your the man no joke...I got this feelin deep inside you could take 1 XJ apart and construct 5 out of it

 

My 82 550 Seca has it but neither of my 81 models have it.

 

pic of my '82 XJ750J Maxim.....no bolts

 

I checked my 650 (pre-YICS motor) and it doesn't have one.

There should be no cause for concern; and I've never had an oil feed problem after an oil change.

Looks like it "phased in" on the YICS motors at different times for different models; again, exactly why remains a bit of a mystery.

 

my 83 xj750mk has that screw on the right side of the engine. just like yours.

 

http://www.2wheelpros.com/oem-parts/yam ... -part.html

Some sort of post-tear down oil flow check? Just a wild guess...

 

my 85 and 86 700 have it...

 

That Fastener Plugs the Top-ends Oil Gallery.
The others had Blind Plugs pressed-in.

This Port serves to provide a convenient spot to attach an Oil Pressure Gauge for evaluating the Plant's pressure.

Also, as dumb place for Oil Pressure Gauge's to be mounted and a very inconvenient spot from which to mount plumbing or a sensor.

 

My '83 Seca 900 has one on the right side of the engine only.

 

That's all there is if you have one.

I have a theory if anyone wants to hear it:

Back in the day, Yamaha had been getting customer complaints about "ticking" sounds from the top end, especially if a bike had been parked, hot, on the sidestand. This is evidenced in Yamaha tech bulletins from '81 that eventually led to a revised cam cap to tighten up the inherent sideplay in the cams.

My theory is that Yamaha introduced the un-plugged drillway so that they could ensure proper top-end oiling on the bikes before they left the factory; or so that dealers could confirm proper oil flow to the cams.

Which is a complete SWAG.

 

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