81 YT125 Clutch Issues

[generallee2005]

I'm still having trouble with my clutch on the Stud Duck. Take off is good, I climbed the side of a building in first, it just goes when I ask every time with no fuss. Second gear is good to go too, I'm still learning but the wheelies are coming easy in 2nd. The trouble comes in 3rd & up, when I am in 3rd, 4th, & 5th gear, the clutch slips when I give more than 1/4 throttle. It has been doing this since I've got it, I have replaced the springs & fiber plates with '81 spec springs & fiber plates. The metal plates are the only thing still "original" in the clutch. They were in spec & level according to the manual. I haven't been getting any metal in the transmission oil, I drained today just to check. I did just finish putting in the new clutch plates & springs in on Monday. I have been using Yamalube 10w40, but had to use the Honda 10w-40 since my cycle shop was out of the Yamalube this past trip. It was today when I was really able to stretch the legs of the machine, & that's when I discovered the clutch still slipping at speed.


When I search for the part numbers for the metal plates, I am coming up with 3 different listings: 3X3-16524-00-00, 3X3-16524-10-00, 3X3-16524-20-00. The description lists them all as " Plate, Clutch 1 U.R." I cannot find the specs giving the thickness of the plates anywhere. Anyone have an old list maybe that would shed some light? Would a new set of plates make a difference? I could see the wear on my original plates, but they were right at the cusp of being in spec. I'm going to take the cover off & measure the clutch spring plate thickness tomorrow.

I haven't come this far to turn around!

Before


After


Before

[Ghostv2]

Well i cannot help but i will compliment you on the work on the trike. It looks very nice, and you got the helmet to match it.

[Larry T Moore]

when I change my clutches I do old an school trick..if the plates are still spec I pour oil on concrete and rescuff the plates by sliding them around in a circular motion....I have done this on several trikes and my buddy's Warrior and have had excellent results...I know it sounds hokey but it works...

[generallee2005]

Hokey or not, I rubbed my plates on some 150 sandpaper until the shine was gone & checked spec. I didn't get the cover back together last night but I should get it today. That was the kind of answer I was looking for, thanks! Also, thanks for the compliment!

[shortline10]

Replace the steel plates and buy HD clutch springs if available . A previous owner might have used a full synthetic car type oil and it impregnates the steel so no mater what you do it will slip under a load . I have rebuilt hundreds of clutches and even though the parts show within spec measurement when heated from slipping they are junk and must be replaced . Also make sure you have a little slack in the clutch cable , a very common mistake

[barnett468]

Hello generallee2005

I have replaced the springs

This is most likely one of your main problems if your bike is a G or H model. Yamaha used different springs on the std J and all Years of Tri Moto models. The last model of either is in 1985 and it uses the 9050113647 springs. Since ALL other clutch parts are identical to ALL other 125 YT models it’s reasonable to theorize that it would use the best parts. My guess is they realized their clutch was weak and slipped when “Dad” rode it so they simply installed either heaver springs or more likely the same rate springs but slightly longer to increase static seat pressure on the clutches. See p/n’s below.

Did you replace springs with original Yamaha ones?

PLAN 1 - First I would simply get some SAE or AN flat washers the same size as the 4 posts on the pressure plate and same od as the spring and using the OLD springs [if the new ones are shorter or not OEM AND if the clutch slipped the same with both] install 2 on each post followed by the spring etc. Adjust clutch properly and assemble enough to test shift it with the motor OFF. The springs may coil bind preventing it from shifting in which case you need to remove 1 washer from each post.

PLAN 2 – If the clutch still slips it still slips with the washers in it I would buy original plates if yours are not and buy new original springs p/n 9050113647 and that should fix it.

SPRINGS

Std G and H use p/n 9050112580 3x3

Std J and Tri Moto K, L, and N use p/n 9050113647 5v6


1985 N MODEL OEM FICHE AND PARTS SUPLIER See part #13.

http://www.cmsnl.com/yamaha-yt125n-t...9.html#results

& fiber plates with '81 spec springs & fiber plates

Are your fiber discs Yamaha or aftermarket? I would use Yamaha only, they are available at the link below.
cmsnl.com

The metal plates are the only thing still "original" in the clutch. They were in spec & level according to the manual.
I cannot find the specs giving the thickness of the plates anywhere. Anyone have an old list maybe that would shed some light?
I rubbed my plates on some 150 sandpaper until the shine was gone & checked spec.
I’m confused, you say you looked up the metal plate spec in the manual but then say you need the spec for the metal plates. Are you referring to the spec for the part numbers you posted, if so the spec for all of them should be the same as in your book. Those p/n plates will ALL be identical thickness.

Your metal plates are most likely fine, they are not likely causing your problem but if it still slips after doing the other things I suggest then buy new original ones if possible.

When I search for the part numbers for the metal plates, I am coming up with 3 different listings: 3X3-16524-00-00, 3X3-16524-10-00, 3X3-16524-20-00. The description lists them all as " Plate, Clutch 1 U.R."

Where did you get these numbers from? There are no dashes in the p/n or 2 extra 0’s at the end of the original part numbers I got from the original parts fiche below. Any of those part numbers will work, they are ALL interchangeable. All YT 125 models below use the same 7 fiber plates and 6 metal plates and other clutch parts with the single exception of the springs.


cmsnl.com

xxxxx

CLUTCH ADJUSTMENT – I would check it again, see service manual below.


Condensed service manual, see pg 375 for clutch adjustment instructions.

http://www.oscarmayer.net/atc/manual...rvice-data.pdf

xxxxx

GEAR RATIO – If you install a 1 tooth smaller front sprocket on it, it will reduce the load on the clutch in ALL gears thereby reducing the amount of slip it will have.

xxxxx

I have been using Yamalube 10w40, but had to use the Honda 10w-40 since my cycle shop was out of the Yamalube this past trip.

Makes no difference, Honda oil won’t cause your clutch to slip.

xxxxx

1980 - 1982 H MODEL OEM FISCH AND PARTS SUPPLIER. See #13 clutch spring, #11 Pressure plate

http://www.cmsnl.com/yamaha-yt125h-1...0.html#results


1985 N MODEL OEM FISCH AND PARTS SUPPLIER. See #13 clutch spring, #11 Pressure plate

http://www.cmsnl.com/yamaha-yt125n-t...9.html#results


Condensed service manual, see pg 375 for clutch adjustment instructions.

http://www.oscarmayer.net/atc/manual...rvice-data.pdf


Long service manual

http://www.oscarmayer.net/atc/manual...oto_manual.pdf

[Yamaha_Rules69]

The YT 125/175 did not have a clutch cable shortline, they were an "auto" clutch like the utility Hondas. Make sure you have the adjuster screw set correctly. Loosen the lock nut and turn adjuster counterclockwise until slight resistance is felt. Then turn the adjuster 1/8 turn clockwise and tighten the locknut while holding the adjuster to keep it from turning. You can get at the adjuster by removing the smaller right cover, the one directly over the clutch, with the oil cap on the side of it. And I believe the adjuster takes a standard screwdriver if I remember correctly. Hope this helps. ----- Jon.

[generallee2005]

I got it going today, all it needed was the metal plates to be scuffed up! I do think I developed an air leak, I'll track it down later, I seem to remember a propane torch will usually show where the leak is, I'll search & find out exactly how. I imagine the air leak is at the carb boot, I got a little over zealous on a good hill & went a little harder & farther than I intended, but it was worth it! This little guy will go, more than I imagined.

Barnett468, I got the part numbers from www.cyclepartsnation.com, with their part numbers I can sometimes find the part on eBay if it is unavailable, whereas with bikebandit.com, they use an internal sales number that I can't decipher. My YT is the 125H. You are absolutely a wealth of information!

[barnett468]

I got it going today, all it needed was the metal plates to be scuffed up! I do think I developed an air leak, I'll track it down later, I seem to remember a propane torch will usually show where the leak is, I'll search & find out exactly how. I imagine the air leak is at the carb boot, I got a little over zealous on a good hill & went a little harder & farther than I intended, but it was worth it! This little guy will go, more than I imagined.

Barnett468, I got the part numbers from www.cyclepartsnation.com, with their part numbers I can sometimes find the part on eBay if it is unavailable, whereas with bikebandit.com, they use an internal sales number that I can decipher. My YT is the 125H. You are absolutely a wealth of information!

Hello generallee2005


Thanks for the compliment, happy to help.


FUTURE CLUTCH SLIP – Keep in mind that those clutches are apparently weak by design so even though it does not slip now I can pretty much guarantee you it soon will if ridden hard by someone over 100 lbs. This belief is supported by the fact that all you had to do was sand the metal discs to eliminate the slipping. I suggest either shimming the springs like I suggested or buy the updated springs, p/n 9050113647 from the J, K L or N models. See below.


1985 N MODEL OEM FICHE AND PARTS SUPLIER See part #13.

http://www.cmsnl.com/yamaha-yt125n-t...9.html#results



SANDED METAL DISCS – Yeah that sometimes fixes a slip because they “glaze” from previous slipping. If they are blue [from heat] I might replace them anyway.



PART NUMBER DIFFERENCE – Yeah I checked it out, I don’t know which is correct but I think the numbers without the 2 extra 0’s on the end are, either way just check both when searching on ebay or other sites for them etc.



INTAKE LEAK – With propane just start bike and turn propane on lightly but don’t lite it. Pass it around intake, the rpm will change if there is a leak. I use NON chlorinated FLAMMABLE brake cleaner with the long thin nozzle spraying LIGHTLY around suspected areas.