Ducati Monster Motorcycle Forum banner
1 - 17 of 17 Posts

·
Premium Member
Joined
·
510 Posts
Discussion Starter · #1 ·
I did some searching but could not find any thing.
At what temp does the bike need to be to check the clearences on the valves. All of the articals I have seen don't mention it.
 

·
Registered
Joined
·
393 Posts
That would suck if you had to check them warm.
 

·
Premium Member
Joined
·
508 Posts
Aguacate said:
That would suck if you had to check them warm.
+1 because checking them cold isn't a pain in the nuts to start with. Last thing I would want is to try it at operating temp.
 

·
Registered
Joined
·
8,324 Posts
Maybe he's asking a min temp. How does 60 deg F sound?
 

·
Premium Member
Joined
·
510 Posts
Discussion Starter · #7 ·
The problem is that at what ambient? These are very tight tolerences and the temprature makes a very big difference so does the manual say "60 f" or does some one know of a proper temp. I will do this during the winter and 20 F can make a major difference than 60F.
 

·
Premium Member
Joined
·
5,076 Posts
I've never heard any specific temperature mentioned. I think the range of ambient temperature on earth is minimal for these purposed. Of course, if you move to Mars..................
 

·
Registered
Joined
·
8,324 Posts
98yell750 said:
The problem is that at what ambient? These are very tight tolerences and the temprature makes a very big difference so does the manual say "60 f" or does some one know of a proper temp. I will do this during the winter and 20 F can make a major difference than 60F.
The guy that does mine(when they need it) is a certified tech. He won't do them below 60. I have to bring the bike in the shop and let it warm up to room temp. As always YMMV.
 

·
Registered
Joined
·
241 Posts
I guess this would be a way to see if it makes a difference (or rather, a significant difference):

Get two shims of the same size and put one in the fridge and one at room temp (let's make it a 50 degree F difference just for the sake of this argument); measure and let us know the size change based on temp.

I'd be interested to know how much of a difference it would make, as here's a scenario for you:

Shim sitting in engine that's 50 degrees F; you measure and it's too small. You pull out another shim that's the right size, but it's been sitting in your 98.6 degree hand for a couple of minutes... then you put in in the bike and it's heading back down to 50... so will it still be the right size?

My thought is that if this was such an issue, you'd be keeping your clearances much looser than we currently do. After all, you might measure at 60 degrees, but then the shim is at 200+ while operating (not to mention the additional stress of getting pounded by the rocker arms, that adds heat too).

Ken
 

·
Registered
Joined
·
126 Posts
I'm a land surveyor, and in days of old we used to measure land with steel measuring tapes, made out of a spring steel (they first made them from women's hoop skirts). The tapes are calibrated at 68 deg. F, and we had to make corrections for systematic errors such as expansion/contraction.

For 100 ft (that would be a pretty thick shim) the temperature correction for 100 degrees (as in the steel would be 68F plus 100F = 168 degrees) difference from the standard calibration temperature is 0.065 ft. Thats basically 3/4 of an inch per 100 feet. BTW, a typical survey correction would be something like 15 degrees x 0.0000065 x 5,280 ft (1 mile) = 0.51 ft (so thats 6 inches per mile on a 83F day). If it is warmer than 68F, the measuring tape has lengthened, so you are measuring a shorter distance, so the temperature correction is ADDED to your measurement.

So I don't see how the shim temperature is going to be a measureable effect. The trick is how warm/cool the valve train is, at least thats what I suspect. The length of the valve stems & push rods (do Ducati's have pushrods?) are about 11billion times longer than the shim is thick. BMW's, which have short valve stems & really short (1/2 inch?) pushrods (remember, they are all in those heads that stick out, so BMW tries to minimize the length) can have the valves adjusted after the bike sits for a couple of hours, which is convienient as you can ride to the shop & wait for the service. Kind of a bummer to have to wait overnight. I suspect they would kick you out.
 

·
Registered
Joined
·
393 Posts
KenSwift said:
I guess this would be a way to see if it makes a difference (or rather, a significant difference):

Get two shims of the same size and put one in the fridge and one at room temp (let's make it a 50 degree F difference just for the sake of this argument); measure and let us know the size change based on temp.

I'd be interested to know how much of a difference it would make, as here's a scenario for you:

Shim sitting in engine that's 50 degrees F; you measure and it's too small. You pull out another shim that's the right size, but it's been sitting in your 98.6 degree hand for a couple of minutes... then you put in in the bike and it's heading back down to 50... so will it still be the right size?

My thought is that if this was such an issue, you'd be keeping your clearances much looser than we currently do. After all, you might measure at 60 degrees, but then the shim is at 200+ while operating (not to mention the additional stress of getting pounded by the rocker arms, that adds heat too).

Ken
Yeah, but the clearances can be adjusted to be measured at any temperature. Just like tire pressure. You put in less pressure than what the tires run at because you know when they heat up the pressure will rise to what they should be. Maybe it's more of a compromise between warm and cold tires, but that's beyond the point.

I think also, that the shims wouldn't be the primary concern but rather the rocker arms, along with whatever else they directly or indirectly touch. If the relative change in the size of a shim doesn't make a difference, the relative change in the rocker arms and everything else might.


This is interesting though: http://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html

Although I don't know why they don't friggin solve the differential equation and give you the formula. What is the constant of integration??!

From http://www.engineeringtoolbox.com/thermal-expansion-pipes-d_931.html if the engine were made out of copper or stainless steel I calculate that your clearance readings will be off by .04 % between 20 F and 60 F. And you can look at the first page and see how the coefficents match up between different metals. They're not all that different, but it'd be nice to know what all the parts are made of (anyone?)

Don't know what all is involved as far as what attached to what moves what and affects what, but if you have a piece of stainless steel 12 inches long, the change from 60 F to 20 F is .0048". Steel 3 inches long gives .0012".

Now the question is what metal is involved, and what effective length are we dealing with for expansion. Just from these examples however, it looks like it might make a difference

I say the empirical test should be for one person to check his clearances in the snow and for another person to check his clearances in a warm garage within 5 minutes of running his bike!
 

·
Registered
Joined
·
3,755 Posts
Before I started doing my own valve adjusts, I'd ride up to BCM early. I'd get there an hour before the shop opened and the tech would do all the other service tasks first; saving the valve adjust to last. NBD.
 

·
Premium Member
Joined
·
510 Posts
Discussion Starter · #15 ·
There will be a difference between hot (200+) and ambient (60). I was an engineer that was involved in design of heavy duty diesels that required lash adjustments. You had to perform them at a certain temperature (60 to 70) or it will come out wrong. the lash they tell you to measure is what you should have cold so when the engine warms up the clearances are correct. This is with a conventional valve train, nothing at all like the ducati contraption.

Aguacate,socalrob, you have the same thought process as me and you are on the right track. I would look it up but the books are in storage. I would figure that the manual or dealer would know instead of us having to do all the math. Much easier too.

I think i will just have to run the bike and then let it cool down with the heater on until the bike is at like 60 or 70 and then the garage will be warm too or I could wait till spring. :) Thanks for the help.

If any one runs into this kind of info we should include it into the sticky for valve adjustment. Because if you run it with the wrong clearances you can break things, burn a valve, or loose power. :-X
 

·
Registered
Joined
·
4,309 Posts
Any difference in the clearances at temperatures in which a person could perform a valve adjust are probably less than the accuracy of said person and equipment. (ie, with a typical person and a typical micrometer, you can't measure the difference between say 50 and 90 degrees, which are probably the extremes at which you would do the measurement.)

So the answer - ambient temperature.
 

·
Registered
Joined
·
3,755 Posts
When I did a winter valve adjust a couple of years ago, I didn't bother running the bike. Just stoked up the wood stove the day before and kept the shop at about 70 for 24 hours.

But then my shop doesn't drop below 40 or 45 even with the stove cold. The abutting greenhouse leaks a little heat in.
 
1 - 17 of 17 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top