Torque spec for Gen2 front brake reservoir screws (be kind)?

[no rain]

I suspect that the most common answer to this question will be "snug". That kind of vague instruction absent of a definite standard, though practical for many, can be dangerous for a recovering engr. I have an excellent low range torque wrench that I primarily use on my mtn bike. Thanks!

 

[Bogus]

Would this be of any help? But seriously, "snug" should be more than sufficient.

https://www.federalscrewproducts.com/torque-chart.htm

 

[Fred W]

Somewhat surprisingly, there is a torque spec for the front brake master cylinder's 6mm screws.

It is listed in the FSM (Factory Service Manual) as 10 nm / 1.0 m-kg / 7.2 ft-lb.

On a fastener this small I would convert the 7.2 ft-lbs to 86 in-lbs and use an appropriate torque wrench with that scale.

OTOH, snug is certainly good enuff.

 

[Twigg]

These are M4 machine screws .... they are made of something approaching the consistency of cheese, as is the housing. Any more than "snug" runs the risk of stripping or shearing them. All they do is seal liquid at zero pressure under a rubber gasket.

Engineers usually understand terms like "snug"

Other measures are "Standard British (or American) Handful

A "Smidge"

Gaps measured in the dimensions of a Gnat's cock. A full "Gnats" or "half a gnats".

 

[Ignacio]

That kind of vague instruction absent of a definite standard, though practical for many, can be dangerous for a recovering engr.

I guess my question is why the recovering engineer doesn't have their own service manual? It would be the OCD thing to do.

 

[ionbeam]

Welcome to an engineering black hole, it just sucks you in and there is no escape.

The Phillips® screws on the FJR are made to JIS specifications. A US pattern Phillips screwdriver is highly likely to 'cam out' and damage the screw head if not going in, then when removing. Because the US Phillips screwdriver can't fully insert in the JIS screw it is hard to over torque the screw, even using the Good 'n Tite torque technique. Using a JIS screwdriver which does fully engage the JIS screw, you should not exceed the FSM torque spec that Fred W mentions (and even converts into a more practical unit). If using a torque wrench, be sure that the torque value is someplace between 25% and 75% of the torque wrench range, because if you are outside this sweet spot, torque wrenches are notoriously inaccurate.

Or, you can use a US Phillips screwdriver and push down on the handle end with one hand and with the other hand, turn the screwdriver until you no longer feel the rubber gasket being compressed. The pressure will help prevent cam-out. I prefer to turn both screws until they both equally start to snug, then go back and fully tighten the screws.

A good engineer should be able to over complicate a toothpick, yet be completely accurate in all aspects of design and fabrication. Next time you need to crack an egg, PM me and I'll fix ya right up.

 

[no rain]

Thanks guys. I had intended to mount a RAM ball cover plate, which installs over the stock plate. Problem I just found was that one of the intended center slots was not machined all the way through the plate. I also question the blanket instructions to use the nylon spacers for a two-fastener cover. I am going to return that part and order a MCL replacement cover instead that accepts a RAM ball.

 

[SouthernCruizer]

IMHO, the most dangerous tool in your tool chest is the torque gauge when it comes to anything smaller than 17mm bolts on the FJR.

 

[no rain]

Advice well taken. Although I appreciate Fred's input above, and I don't doubt his reference, I have to question a torque of 10 Nm on those screws. I think I will allow common sense to prevail and let the sleeping torque wrench lie this time. See, I told you I was recovering!

 

[ULEWZ]

We never list torque values for screws that small in aviation (1/4-20 and above). Too tight and you will know it rather quick. Those screws are in tension, but don't hold much, so snug is the correct choice. Must be an electrical engineer.

 

[creg-ny-baa]

Other units or levels of torque include RFT or PFT (indicating real f***ing or pretty f***ing tight).

A commonly used measure of clearance is an RCH...if you don't know that one, I'll leave it to others to edumacate you.

What our recovering engineer probably doesn't know is this: Ft. Lbs or Nm are only units of tightening torque. The unit of loosening torque, across both SAE and metric is motherf***ers. You can look it up.

 

[no rain]

We never list torque values for screws that small in aviation (1/4-20 and above). Too tight and you will know it rather quick. Those screws are in tension, but don't hold much, so snug is the correct choice. Must be an electrical engineer.

Indeed I are.

 

[Bogus]

IMHO, the most dangerous tool in your tool chest is the torque gauge when it comes to anything smaller than 17mm bolts on the FJR.

That is one of the most profound statements I have seen on this forum!

 

[Fred W]

My spec of 10nM was not for the little 4mm JIS (cross headed) screws that hold the reservoir lid on. Those screws do not have a torque spec in the FSM. They merely compress the rubber gasket under the lid so, as others have said, "snug" is fine. A generic spec for a 4mm screw in an alloy thread would be around 10 in-lbs. But don't try measuring that with your 3/8" drive torque wrench. You'll need a wrench with a scale more appropriate to the measurement. Torque wrenches that small are usually of a screw-driver design. Yes I do own one, and yes many manufacturers do torque fasteners that small as a means of maintaining repeatability and reproducibility of the assembly, the buzz words of Quality Control.

The 10nm torque spec that I quoted earlier is for the 6mm (I even said as much) Allen head cap bolts that mount the entire master cylinder to the handlebars. Though I have never felt it necessary to torque those screws either, I think they would easily withstand 86 in-lbs of dry thread torque.

The problems associated with using a torque wrench on any sized fastener are primarily operator error (like using the wrong sized wrench for the job, greasing threads that are supposed to be dry, using Loctite when not called for, etc.) or having an improper torque specification from the manufacturer (like the FJR drain plug fiasco).

Like a gun, a torque wrench is just another tool. It is not dangerous. It's the operator who can be dangerous.

 

[wheatonFJR]

Torque wrenches don't strip threads, people do.

 

[ionbeam]

...Those screws are in tension, but don't hold much, so snug is the correct choice. Must be an electrical engineer.

Indeed I are.

Rain, I would generally rather have an electrical engineer work on my FJR than have a mechanical engineer work on my microwave

Either engineer would be better than some of the Forum Pipe Fitters. If it absolutely, positively must be broken beyond all recovery, you need to get in touch with a Nuclear Metrologist

(that has his own personal disaster recovery team to bail him out from the ensuing basket cases such as 6 cylinder Kawasakis and BMWs).

 

[RadioHowie]

Alan, I could only "like" once, dadgum it!

 

[08FJR4ME]

My theory would be tighten it till it doesn't leak anymore. Has always worked for me. Now I gotta go buy me a Jis screwdriver whatever that is.That's what I like about this place your always learning somethin new.

JSNS,

Dave

 

[mcatrophy]

...Now I gotta go buy me a Jis screwdriver whatever that is....Dave

You should have one in your OEM toolkit.Click on image for larger view