Jinma 254 clutch adjustment question

[CSH]

Lately I've been having problems with grinding when engaging the PTO, so I figured it was past time to take a look inside the bell housing and adjust the PTO clutch. This tractor has 530 hours on it. I first checked the clearance between the release bearing and fingers, and it was pretty wide (about 3/8"), so I had quite a bit more than the 1" spec for free play. The fingers do show some wear, but I don't think they've worn 1/4" (I think the adjustment was too wide when it was new, but I never looked so I can't say). Anyway, if I use the linkage to adjust the clearance between the release bearing and fingers to 1/8" (for 1" of free travel in the pedal), the pedal is quite a bit further down and I won't have enough travel to disengage the PTO clutch because the safety switch is at the end of it's adjustment range. Should I use the main clutch adjustment to set the free travel between the fingers and the release bearing? If I do it this way should I disconnect the pedal linkage so the release bearing is all the way back? The PTO adjustment seems to be pretty straightforward, but I'm more apprehensive about touching the main clutch. Any guidance or insight would be appreciated.

 

[Rich Waugh]

Whoa! "Free travel" refers to the movement of the clutch pedal before it meets resistance, nothing beyond that. You need to read the manual for the proper clutch adjustment procedure and clearances, or look up one of the several threads on clutch adjustment procedures on this forum or one of the other forums. If I recall, the proper clearance for the PTO finger to throwout bearing is something pretty close to 3/8" , maybe 8.5 or 9 mm. Yours may not be that far off after all.

Rich

 

[CSH]

The proper clearance according to threads I've seen is 1/8". 3/8" between the fingers and release bearing gives a lot more than 1" of free play.

 

[Turbo]

make sure the roll pin in the control arm is not bent or shearing.

 

[greg_g]

Rich's recall failed him this time. The Jinma manual clearly specifies the gap to be 2.5mm (+/- 0.5mm). That's just a hair to either side of 1/10 of an inch, so you're pretty close at 1/8". But if you don't have the owner's manuals, I strongly recommend purchasing a set (of 4). Basic clutch adjustment procedures and specs are in the tractor O & M volume.

//greg//

 

[CSH]

I strongly recommend purchasing a set (of 4). Basic clutch adjustment procedures and specs are in the tractor O & M volume.//greg//

Greg, I have manuals, and the instructions are vague at best. Here's an excerpt from the procedure in Chapter 4, section 1, subsection 1, titled Adjustment of dual stage clutch:

Dual stage clutch should be adjusted on a fixture. The adjusting steps are as follows: Adjust the length of the adjusting bolt (11) to make the distance between between the 3 release levers (19) and the end faces of the PTO clutch pressure plate (4) is 96. 8mm, and the distance difference between 3 release levers and PTO clutch pressure plate is no more than 0.1mm; after adjustment tighten it with nut M10 x 1.

This is exactly as it is written. The diagram that is included shows adjusting bolt (11) as the clutch pedal stop bolt. Turning it in any direction will have no impact on the release levers, not to mention I have no idea how to measure the "96 .8mm" (and yes, it has 2 blank spaces between the 6 and the dot) between the fingers and PTO pressure plate with the clutch pack installed.

 

[greg_g]

Yeah, I said they were basic. I didn't go as far as to say they were clear. The manual language is quite often referred to as "Chinglish". The 96.8mm figure represents stack height, and you're right. That's a measurement typically obtained with the clutchpack on the bench. Or at least with the tractor split. Without coming up with some Rube Goldgerg measuring device, it's not feasible to obtain that adjustment through the inspection windows.

Other than that, let's go back to your opening question(s). The safety switch is adjustable in its bracket. Whenever you adjust the external linkage, you readjust the switch to compensate. The PTO grinding noise is cuz the pedal is striking the stop bolt before the end of full travel. Loosen the jam nut on the stop bolt, screw the stop bolt in far enough so the grinding stops. Tighten the jam nut. When you get to the point where there's no more stop bolt adjustment, it's time to tweak on the clutchpack itself.

//greg//

 

[CSH]

The safety switch is adjustable in its bracket. Whenever you adjust the external linkage, you readjust the switch to compensate. The PTO grinding noise is cuz the pedal is striking the stop bolt before the end of full travel. Loosen the jam nut on the stop bolt, screw the stop bolt in far enough so the grinding stops. Tighten the jam nut. When you get to the point where there's no more stop bolt adjustment, it's time to tweak on the clutchpack itself.//greg//

And this is pretty much where I am right now. I can screw the stop bolt and safety switch in further to get additional pedal travel (there are still threads showing on both), but the back of the safety switch is contacting the bell housing and won't go further back unless I move it (laterally) away from the tractor, and if I do that the pedal will no longer make contact with the switch. Which takes me back to the original question, will I have to work with the main clutch adjustment bolts to move the release fingers closer to the throwout bearing ?

 

[Turbo]

Remember you only have so much room in each cavity to play with, this is why the stack hight is so important.

I made up this diagram to give a visual clue what going on..

any fault with it let me know and I will correct it.. or if its totally out of the ball park I will delete it.:laughing:

the roll pin I would say is the important part in that if it moves or shears you will
not achieve full throw.

As you can see in the diagram when the clutch disk wears the
distance between the fingers and release bearing should decrees to a point that they touch when the disk wears out.
and If it increases the only way it can happen is a new disk installed or the roll pin sheared. IMO.

 

[studor]

but the back of the safety switch is contacting the bell housing and won't go further back unless I move it (laterally) away from the tractor, and if I do that the pedal will no longer make contact with the switch.

You can make the switch shorter by dremeling off some of the threaded part and then the plastic pushrod. On mine there was no way that switch was ever going to be positioned properly without being pinched against the bell housing so for the longest time I did not have a safety switch -- not recommended but I would not let it give me a clutch adjustment problem

 

[greg_g]

Which takes me back to the original question, will I have to work with the main clutch adjustment bolts to move the release fingers closer to the throwout bearing ?

Well, you didn't actually ask that question before, but the answer is yes. I've done several of these clutches, but it takes a lot of typing to list all the steps. Check out this link: JMClutchAdj . If that doesn't do the trick for ya, c'mon back.

//greg//

 

[Turbo]

This is exactly as it is written. The diagram that is included shows adjusting bolt (11) as the clutch pedal stop bolt. Turning it in any direction will have no impact on the release levers, not to mention I have no idea how to measure the "96 .8mm" (and yes, it has 2 blank spaces between the 6 and the dot) between the fingers and PTO pressure plate with the clutch pack installed.

# 11 is wrong, it should read #24

 

[Turbo]

CSH before you throw adjustment at your tractor you need to analyze your problem first.
you say you have 530 hr on the tractor , and now the PTO is grinding when you shift in. Have you always had that problem for the full 530 hr? if not when did it start doing it? has your tractor been sitting awhile, and did it do it last year?
will it disengage at all ? how about an implement attached, will it disengage?
or just take it's time to stop.

I can't believe after 530 hr that you just need to make adjustment to make the problem go away. I think it more like corrosion / rust on the spines, and not allowing the disk to release all the way or even the clutch disk sizing to the fly wheel. were only talking about MM of movement here, and it wouldn't take much to stop it. It could also be a peace of clutch disk thats come off and wedged it self in between the surfaces.

Trying to fix a problem before you understand it will create more problems!

 

[CSH]

Turbo, thank you for the list of things to consider and for correcting what is in the manual. Bolt 24 (and not 11) makes perfect sense. Looking at the diagrams and descriptions online as well as looking inside my tractor I do have a pretty good understanding of how the 2 stage clutch works. I was surprised to see that much space between the release fingers and bearing when I removed the cover. I had never looked inside before so I can't say if it was this way from the beginning. I do understand that the gap should become smaller with wear and not larger.

It started doing this last year and has progressively gotten worse. I don't have any problems with grinding when shifting gears, and the main clutch plate holds really well and doesn't slip. There is also no slipping or unusual noises with the PTO engaged. I checked the roll pins and they are fine. Nothing sheared or backing out. The release bearing looks good and turns very smoothly. I was mistaken about the pedal stop bolt. After cleaning it off I can now see it is only threaded for about half of it's length. It is at the end of it's adjustment. The main clutch pressure plate slides back freely, but not far enough to fully engage the PTO pull rods and move the PTO pressure plate. The gap varies between 0.4 - 0.6 mm for all three bolts.

I don't think corrosion is an issue. This tractor is parked inside my basement when not in use and has never been rained on.

If there are no other obvious considerations, I assume adjustment of the main clutch bolts will be required, and I have a couple of questions about what I should use as a reference for measurements. As discussed earlier, I have no way to measure 96.8 mm for the clutch stack unless I split the tractor, and I'll certainly try the clutch adjustment before I do that. Should I:
1) make adjustments using the gap between the release fingers and bearing (and if I use this gap should I move the push rod back to it's original position when there was a 3/8" gap between release fingers and bearing),
2) make adjustments using the gap between the back of the fingers and clutch cover, or
3) move each bolt an exact number of turns?

I do realize this will affect the gap between the PTO adjusting nut and main pressure plate, which will also require adjustment. Right now this gap varies between 0.4 - 0.6 mm for all three bolts. I'm not apprehensive about making that adjustment (though maybe I should be) since it looks like one could easily use a feeler gauge to get all three gaps equidistant.

Thanks for everyone's help.

 

[greg_g]

I do understand that the gap should become smaller with wear and not larger.

If you're talking about the gap between the finger tips and the throwout bearing face, you have it backwards. I guess that JMclutch adjust link I provided above didn't suit your needs. First, the clutch pedal moves the throwout bearing carrier toward the clutch fingers - not the other way around. Then there's your earlier statement citing visible finger wear. That in itself widens the gap. And as the friction discs and pressure plates wear away, the spring tensions are relieved proportionately - also widening the gap. But maybe you're talking about some other gap (??)

Anyway, adjusting the clutchpack really boils down to preloading the springs again (taking out the slack caused by wear or maladjustment). Doing so necessarily moves the fingers toward the throwout bearing face, once again narrowing the gap in the process. In fact it's not unusual to have to compensate with the external linkage, and move the TOB farther back (away from the fingers). Unfortunately, working through the windows is a best guess procedure (relative to actually achieving specified stack height).

The PTO clutch should be adjusted first (1.2mm gap I believe), then the drive clutch (fingers) if necessary. It's important to make sure all three fingers are equidistant from the TOB face (+/- 0.1mm). When you're done working through the inspection windows, then finish up with the final linkage (2.5mm finger gap +/- 0.5mm) and stop bolt adjustments. The stop bolt adjustment isn't described in the book. But unscrew it to the point where the PTO grinds when you try to engage it with the lever. Then tighten the bolt to the point where the grinding quits.

//greg//

 

[Turbo]

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