Valve cover donut question for big fitz52

Does anyone know if it is possible to use some sort of rubber washer on the valve cover bolts, using existing donut gaskets, instead of replacing them.

Cut one side of 1-2 rubber washers then slip aroung the bolt between the head of the valve cover bolt and the existing donut gasket. Wouldn't this create sufficient downforce for a new Valve Cover Gasket to prevent leaks.

 

I'm not Fitz...but check out chacal's parts, he's got the right parts for the right job. It would matter what the composition of rubber you are using is, the valve cover gets hot and vibrates alot. Then there's the size, and how much to torque...etc. It's just better to use the right part.

I don't know what kind of bike you have (put it in your signature, hint hint), but I got these donuts from chacal for under $25 for mine. Send him a PM with you bike model, year, and the engine code, and he'll make sure you get the exact part you need.

 

I'm new to this forum and I've heard the name Chacal refered to, is that a site for online parts?

Thanks
82' XJ 750

 

Well, I AM Fitz, and I thank you for your faith in my opinions.

I doubt it would hold up for long. The first time I changed a set of donuts, I tore one up a bit installing it but since I had no replacement handy, I went ahead and used it, just sort of "shoved" the torn bit into place and tightened 'er down.

It leaked at that bolt, almost immediately.

I've got to agree with ManBot, it's better to just use the correct parts. That being said, once you replace the cover gasket and donuts, you won't need to do it again for a long time. I've had the valve cover off/on my '81 twice since replacing everything, and they're holding up fine, no leaks.

chacal is the guy's screen name; he doesn't have a "site" per se, he has a separate "catalog forum" here: http://xjbikes.com/Forums/viewforum/f=23.html and he's the main reason most of us are able to keep these things on the road and operational. Send him a PM or email info @ xj4ever.com with as much info as you can provide and he WILL hook you up.

Welcome aboard, and thanks again. Now do us both a favor and go take your rear brake apart: http://xjbikes.com/Forums/viewtopic/t=15874.html

 

I want to add that if you "shim" your current old donuts you will not likely get the right level of compression on the cover.

Too much and the gasket might distort and leak, or the cover might bend or break.

 

Welcome NickGroves, and +1 on the rear brake delamination.

*Arnold's voice* Do It Now !!

 

Rear brake, check. Thanks guys. This forum has been extremely helpful so far. Especially bigfitz's detailed pics and procedure for Airhead valve Check. Any future "repair" pics would be really great.

I need to take apart and check my starter as well. It doesn't engage everytime the button is pressed. It will click or begin to start and then disengage and wined. I found that if I engage a gear (with key on engine off) rock the bike back and hold there, then hit start it will catch the starter, most times. Any pics or hint would help.

Also, what kind of lube should be used for a speedo cable? My speedo works but reads about 7 mph slower than I'm acutally going. Does this slow reading also affect my miles? Or, do I need to replace?

Sorry, a lot of questions. I have a ton more though. Any input would be appreciated.

Thanks again.

 

You can take your speedo cable off, pull it apart, and lube it with the best synthetic grease or lube, and you will still be 7 MPH off.
The slow reading should not affect the odometer (according to me)

There should be a thread on how to alter the speedo. Magnetically, tweaking the spring, faerie dust . . .
I believe this topic needs attention.

 

Thanks timetoride.

 

There IS a thread on cleaning and lubing: http://xjbikes.com/Forums/viewtopic/t=15303.html

AND: I think I have figured out how it's done (minor adjustments to the speedo) but not quite HOW to do it, or more accurately, re-do it. YET.

I believe calibration could just be a matter of changing the pre-load on the needle (and cup) return spring, thus changing the amount of effect the spinning magnet would have on it. More pre-load, more pull required so slower reading, slightly less pre-load, less pull required so higher reading.

I need to build an RPM-controllable test stand with an accurate electronic rev counter to test my theory.

 

I think you're right. And IF it's like the speedo on the Venture you can change the preload just by holding the cup and twisting the needle on the shaft (it's a press fit).

 

Sorta. The little needle mount bushing is a press-fit on the shaft, the bushing is "embedded" in the needle itself. You have to be careful not to twist the needle off its mount.

This should apply to the mechanical tachometers too, which is why I need to build a test rig.

 

OK, if i were brave enough to dig into my 900's instrument cluster, I would hold the drum and rotate the needle counter clockwise to get rid of the 5 MPH over reading I have at 55.
I would only rotate the 5 MPH amount.
However, at an actual 104 I indicate 115. I would indicate 110 after the fix.
And at low speeds I guess it would read too low (school zone)

I think if I could make the magnet weaker it would be a better fix for me.

Or- - if I were to print a "face" that matched my actual speeds I wouldn't have to change anything.

 

Probably NOT.

But I honestly don't know. I doubt the adjustment would be "linear" as you're assuming; more preload would give greater resistance at higher speeds than at lower, so it would be a greater change at higher speeds.

Maybe if you held the drum so the needle was at 60 and then backed it off to 55... But I don't know.

This is why I need to build a test rig.

 

If he rotates the needle the adjustment will not be linear - it'll be a fixed amount.

If he rotates the needle 5mph it's 5mph for everything above 5.

10 becomes 5
50 becomes 45
100 becomes 95
etc.

Generally, speedometers aren't precision instruments.

 

I disagree. The spring provides more resistance the tighter it gets wound; how much greater is hard to say.

A 5mph "move" may not necessarily produce a 5mph adjustment across the board, because the spring is "softer" at the 5mph position than at the 60mph mark.

So a 5mph "needle adjustment" MAY provide a 10mph difference at low speed and a 2mph difference at high speed; but I don't know. It really depends on the spring itself; generally "clocksprings" are more linear (less "progressive") than other types so it's hard to say. The difference may be minute; it may also explain why a speedomenter that appears to be reasonably accurate at 50 is off quite a bit at 90. The design itself (winding up a spring) is inherently flawed for achieving real accuracy.

The only way to be 100% sure is to build an RPM-controlled test stand and see what effect spring tweakage has on accuracy.

 

Think about it this way:

The drum turns 90 degrees more/less at 50mph. If you don't change the spring or magnets it'll always turn the same 90 degrees at 50mph. The needle just goes along for the ride (the spring is on the drum, not the needle). If you move the needle 5mph then it points to a different spot on the scale, but the drum moves to the same position it always did.

I understand the drum will rest at a different position because moving the needle has the same effect as moving the stop pin. Once it gets off the pin though that has no effect.

 

You forgot that the needle itself is the STOP for the spring's return, and

The spring is on the drum AND needle.

If you move the needle, you are changing the preload on the spring, requiring more (or less) force (therefore more or less rpms from the spinning magnet) to move it off of zero and all the way up the range.

Once in motion, the needle will "hover" at its NEW position at 60mph, true, but the overall curve WILL be different because you started with a tighter (or looser) spring and have more (or less) force to overcome with the spinning magnet through the full arc.

If the needle was not the stop for the spring your theory would hold true.

 

Ahh fitz. I guess you'll have to come by the shop and we'll have to get a box of motors, springs and a speedometer and have us an x-periment.

 

Boy, are you guys in for a treat.........

Don't forget to bring the 4 different styles of 650 speedo/tachs...but leave the 650 Seca's at home, unless you also bring a dremel tool to slice the plastic bucket apart, in order to get to the face and guts..........and the 3 different types of 750's, etc.


Also, be aware that on some models, that brass bushing that the shaft rides in is not removable from the needle, on other models it is.

Who brings the beer, and do you think that'll be strong enough?