Foton 254: How to take measurement of clutch fingers

[D0TC0M]

Now that snow season is over I have the time to go over my tractor with a fine toothed comb. I have the cab off to access the tranny cover(s) to fix my shuttle shifter and I thought it would be a good idea to check the clutch while I have easy access to it. I was reading through the service manual and they say to measure between the 3 main clutch finger tips and the face of the flywheel. Looking through the small clutch inspection hole I am wondering how in **** am I going to accurately measure this because the tolerance is 0.12mm. Anyone have any tips on how to take the measurements without taking the tranny apart. If I have to split the tranny from the engine I will because I have only to remove the bell housing bolts.

 

[quicksandfarmer]

On my Jinma it's .1 inch, not mm.

The way I do it is to loosen the lock nut, put the feeler gauge in the gap, tighten the adjustment screw until the feeler is trapped, back the adjustment off about an eighth of a turn and tighten the lock nut. You don't need to be able to see the gap, you just have to reach it. The key is to rotate the flywheel so that the adjustment point is right in front of the access hole, if you do you can do the adjustment through the hole. I put a 27mm socket on the crankshaft next to the radiator and use it to turn the engine. Make sure the fuel is off and the compression open!

Detailed instructions are here: 354 Clutch Adjustments | CHINESE TRACTOR WORLD FORUMS

It's a good idea to tie a string to your tools when working through the access hole. I did drop a wrench in the hole once, I had to bribe my ten year old son to stick his hand in and get it.

 

[D0TC0M]

Thanks for the link. It was an interesting read. Since my cab including the clutch pedal and linkage are removed I'm not sure if I should adjust the clutch as mentioned in the link because the release bearing is backed out against its mechanical stop.

Even if my clutch pedal and linkage were installed I know the previous owner adjusted the clutch linkage so the release bearing is probably not normally against its mechanical stop with the linkage installed. With the release bearing fully backed out there's about 6-8mm of gap between the release bearing and the main clutch levers. In the service manual they specify setting the height of the levers in reference to the flywheel mating surface. The measurements are 86.5mm +/-0.12mm for the main clutch levers and 78.5mm +/-0.12mm. Once the levers are set then you set the length of the clutch pedal rod length to achieve the 2.5mm +/-0.5mm clearance between the release bearing and main clutch levers. In the link you provided they adjusted the clutch levers I'm not sure why they didn't just adjust the linkage to the clutch pedal to set the 2.5mm gap instead.

 

[quicksandfarmer]

The only reason to adjust the fingers rather than the linkage is to make sure all three fingers are equal.

 

[D0TC0M]

The only reason to adjust the fingers rather than the linkage is to make sure all three fingers are equal.

I agree with your statement the only thing I find weird is why the service manual says do it as I mentioned above.

 

[greg_g]

I agree with your statement the only thing I find weird is why the service manual says do it as I mentioned above.

That procedure is done as part of the stack height adjustment, and only when the tractor is split. It can be done on the flywheel, but is more accurately done on the bench. What I haven't seen mentioned here is the overall stack height spec. I'd have to see the FT254 manual to make sure which spec is to which clutch. Mechanically it's PTO friction disc and PTO clutch + gap + Drive clutch and fingers = stack height. When distances between flywheel and all undamaged finger tips - to include the gap between both clutches - are equal to all fingertips, fingers should default to equal height. If not, tweak them in. The goal is to get all fingers to make simultaneous contact with the vertical throwout bearing face. Once the tractor halves area mated again, then you adjust the position of the bearing carrier relative to the finger tips to achieve the final 2.5mm gap. But this can't be done until the clutch pedal is properly connected to the clutch release arm. The 2.5mm spec is achieved by adjusting the length of external threaded rod that connects the pedals with the release lever. Stop bolt depth may need adjusting as well, and clutch interlock switch may need to be repositioned slightly.

//greg//

 

[D0TC0M]

In the service manual they specify setting the height of the levers in reference to the flywheel mating surface. The measurements are 86.5mm +/-0.12mm for the main clutch levers and 78.5mm +/-0.12mm. Once the levers are set then you set the length of the clutch pedal rod length to achieve the 2.5mm +/-0.5mm clearance between the release bearing and main clutch levers.

greg_g isn't these the measurements your talking about? Also how do you set the stop depth bolt and what exactly does it do?

 

[greg_g]

Well, I was talking general Chinese tractor clutch design thru maybe 2006, but your use of the word "levers" suggests a different design. I've worked on Jinmas, TaiShan, Kama, Foton (but only the 454) and none incorporated levers. So I might be off base here.

Stop bolt just keeps your clutch foot from overstretching the springs. But if it's set too high, you can't depress the pedal far enough to fully disengage the clutchpack. If you floor the clutch pedal, yet still have to do some grinding to get into gear, it might be a simple case of screwing in the stop bolt a turn or two for more pedal travel. But too far in, and you're mashing the bearing face into the release fingers unnecessarily hard. Not good for the finger tips, finger springs, bearing face, or the carrier spring.

//greg//

 

[quicksandfarmer]

Well, I was talking general Chinese tractor clutch design thru maybe 2006, but your use of the word "levers" suggests a different design. I've worked on Jinmas, TaiShan, Kama, Foton (but only the 454) and none incorporated levers. So I might be off base here.

Stop bolt just keeps your clutch foot from overstretching the springs. But if it's set too high, you can't depress the pedal far enough to fully disengage the clutchpack. If you floor the clutch pedal, yet still have to do some grinding to get into gear, it might be a simple case of screwing in the stop bolt a turn or two for more pedal travel. But too far in, and you're mashing the bearing face into the release fingers unnecessarily hard. Not good for the finger tips, finger springs, bearing face, or the carrier spring.

//greg//

When you adjust the stop bolt you also have to adjust the clutch safety switch. That switch is very susceptible to getting smashed if the pedal is pushed too far into it. Best practice is to loosen the clutch switch before adjusting the stop, get the stop where you want it and then adjust the switch so that it closes when the clutch is fully depressed.

 

[D0TC0M]

Thanks for the heads up