Petcock positioning

OK. Here's the photo of the petcock on my 83 XJ750. (It's different than the one on my 82. My 82 doesn't have any PRI, and the positioning of the petcock is logical. The "On" is down, and I turn the petcock clockwise to get to the reserve.) The arrow on the petcock on the 83 is pointing down, to "On", and it's turned as far clockwise as it will go. So I have to turn it counterclockwise to get to the reserve. This does not make sense to me, because the long tube for the reserve has to be up when the petcock is set to "On", and the only way to make it come down is to turn the petcock clockwise, not counterclockwise. What am I missing?

 

The arrow on the end of the selector lever should point to the faceplate POSITION indicator word. If the arrow is not pointing to the proper word, the selector lever handle has been installed improperly, and thus, the POSITION that the handle is pointing towards is not going to be the operation (mode) that the petcock is actually performing.

 

So I should trust logic (and physics) and have the lever's arrow pointing to "RES" (which is, in fact, actually "On") for normal riding, then turn the lever clockwise in order to engage the "RES" tank, if needed, even though it will then be pointing to "On".

 

Ha-ha! No, I think the proper solution would be to determine why it is acting in reverse of what it should, and solve the fundamental issue..........either the selector lever is installed in the improper position, of the in-tank filter unit is reversed, having the "reserve" straw or section located where "ON" should be, and vice-versa. The lever may be installed/operating as designed, but if the input (the filter) positions are reversed........

 

Well yeah...there's that.

 

thats how the petcock on my 82 750 looks and works. when on you turn past prime to reserve to work. ccw

I will look on my 83 to see if it is the same

 

So you're saying you turn yours counterclockwise to get to the reserve tank (from "On", up past the PRI, to Res)? On my 82 it's the exact opposite.

 

Let my go confirm but yes

 

confirmed
both 82 and 83 750 maxim point down for on then turn ccw to 9:00 for reserve then ccw to 12:00 to reserve.

makes sense to me to go through reserve first to fill carbs as I am rolling down the road, instant gas to carbs then to reserve.
I can hear and feel the death shudder just before i have to turn petcock.

also the way your wrist works this also makes perfect sense as it would be hard to turn clock wise while riding from on to reservs

 

i think your clockwise petcock was from a bike that had petcock on right side i also suspect that it is not a vacuum petcock. does it have an off position. and a vacuum hose

if by long tube you mean tubes in tank maybe they are on the wrong tube

 

I'm trying to conceptualize how that would work with the straws and I can't wrap my head around it. It would seem that the lever would have to be turned clockwise in order to get the longer reserve straw situated deep into part of the tank furthest away from the gas cap. But I guess counterclockwise could accomplish that as well, lifting the regular straw up and out of the way while positioning the reserve straw deep into the reserve area of the tank.

 

the straws do not move but again your petcock could be ment for a right side tank.

think of how hard it is to turn petcock clock wise while reaching down riding it also scares me to be releasing the throttle to do this

 

think of an ignition key in your car right side and clockwise if it were on the left side of the coloum you would have to turn it ccw to start car with out discomfort to the wrist

 

The straws don't move?

(I know on my Magna it's pretty easy to reach down, roll the petcock forward in a clockwise fashion, and engage the reserve. It's much easier to turn. The petcock on my 83 is very stiff and difficult to turn.)

 

len,you are a genius.My petcock looks like this one, I never questioned ccw for prime, mine is correct I assume.i am just curious.My specialty is critical care medicine. I have done it for 42 years.I am an expert.Were you a factory trained motorcycle mechanic, selftaught, and why did you focus on the xj bikes? I am sure glad you did, for selfish reasons.

 

yes the lever turns counterclockwise from "on" at the bottom, through "pri" to "res" at the top. maybe the rubber selector inside the tap has been flipped over , or in the wrong position

 

Maybe it's backwards on my 82. On my 83 it does turn counterclockwise, and the petcock looks original. The one on my 82 does not.

 

is your 82 petcock vacuum operated?
does it have 2 hoses?

if it only has on and reserve and is not vacuum operated there is no need to have a prime position because the fuel will flow when turned to on.
got a photo of the 82 petcock?

 

now for the yamaha curve ball. on 550 and 650
petcock is on when lever is in down 6:00 position
turn clockwise from on to 9:00 and it is on reserve
turn counter clockwise from on to 3: position it is on prime

the position of the petcock allows me to reach it with just index finger and pull it up to reserve.

 

I'll grab a photo of the 82 tomorrow and post it.

 

Here's the 82's petcock. It would appear there is no vacuum connection.

 

that is an aftermarket manual petcock you can see the arrow on the handle pointing to off. looks like it rotates ccw to on and cw to reserve from the off position.

no prime because on would serve the same purpose as on

the cutout part on the disc handle is mounted to tells me it turns in both directions from the off position

in the first photo it is turned to on

when tank is full gas should flow out the fuel line in on or reserve position.

remember to turn it off when bike is not running

make sure all the vacuum ports are capped on the intake manifolds
in your second photo you can see the cap and clamp check all the manifold boots

 

you can see the tubes in this photo they are stationary the tall on is on short one reserve
link is larger photo
https://s20.postimg.cc/a181zvxsd/manpcock.jpg

 

I always leave the petcock on the 82 in the "Off" position when the bike is not running. Now, however, since the bike is off the road/a parts bike, I'll drain the gas tank and empty the carbs.

 

LOL. Yeah. I don't know why I thought the straws turned with the petcock. (Well, the reason is I don't know that much about how motorcycles work.)

 

now you know and will learn much more on this site

 

fog the gas tank so it will not rust inside

 

Sadly...the gas tank is rusted. That's one of the reasons I got this 83 XJ750. Now that I can actually take it off the bike I might try to find someone who can fix it. I always felt it was a ticking time bomb.

 

we have threads on derusting a gas tank very easy every thing from electroliss to tumbling in a drier

this link has several links to methods it is good rainy day reading
The Information Overload Hour


The following websites outline the most common methods used to de-rust iron or steel parts:

http://www.mopedarmy.com/wiki/Removing_rust_from_a_gas_tank

http://users.eastlink.ca/~pspencer/nsaeta/electrolysis.html

http://www.moreg.org.au/dissolving_rust.htm

http://www.htpaa.org.au/article-electro.php

http://xjbikes.com/forums/index.php?threads/32838

http://xjbikes.com/forums/index.php...val-no-frills-easiest-fastest-cheapest.48196/

http://www.robertscycle.com/chrome-clean.html

http://www.xjbikes.com/forums/threads/teds-2nd-82-xj750-maxim-bobber-project.47929/#post-478002

http://www.practicalmachinist.com/vb/general-archive/rust-removal-using-molasses-90452/

 

Absolutely. (The strange thing is that I never felt any "buzziness" on the 82. It had those ugly rectangular handlebars that were non-standard and wouldn't accept normal accessories. The 83 has normal 7/8" handlebars. I'm wondering if those ugly rectangular handlebars did a better job isolating vibrations than the normal bars.)

 

Cool. Thanks. I will definitely check those threads out.

(Tumbling in a dryer? Now THAT I have to see!!)

 

yup put a bag of fish tank gravel or other media in the tank seal all holes put in trash bag pack foam or pillows all around tank set drier to no heat and you have a giant rock tumbler.
just wait untill your wife ,girlfriend , mother ect are away.

 

I'll be damned! I can't wait to tell my buddy about this technique. (He's a big Magna Man and has re-painted several Magna tanks.)

 

Great stuff man. Thanks.