1979 YZ 250 Clutch woes - hard to pull?

Related:
Create New Tag

1/29/2018 7:15 PM

Looking for some advice after my first 'field run' on my 79 YZ 250 project yesterday. This bike has one grumpy clutch. Super hard to pull in, feels like it is dragging somewhat when I pull it in with the engine off, and after a few minutes of easy riding it became pretty much ineffective. Pull it in, click in gear, clunk and the bike stalls.
When I had it apart I didn't put in new plates, but I deglazed the metal plates and measured the fiber ones and they all seemed okay. My basket has some grooving, but it doesn't seem like it would account for this level of suck. I did swap a 78 outer cover for the 79 because it seemed in better shape, could there have been some difference in specs?
Any common setup issues for these bikes? Thanks!!

|

1/30/2018 7:00 AM

Good possibility after all these years that you have some sort of aftermarket clutch plates in there. I have seen several brands do this. I try to stay with OE when possible. I've also had good luck with DP clutch kits. The material and thickness have a lot to do with it. Trans oil can make a difference as well......I use Bel-Ray gear saver with good results. The grooving in the clutch basket will usually show up as a grabby pulsing situation when you release the clutch. Hope this helps......cool

|

1/30/2018 7:59 AM
Edited Date/Time: 1/30/2018 8:03 AM

Having raced and serviced my '79 YZ for the last 7 years, I can tell you right now to get rid of the current clutch springs as they are most likely heavy-duty aftermarket junk!

By all means find STOCK Yamaha clutch springs and install them. Accept NO substitutes for OEM Yamaha parts, PERIOD!
Also inspect the clutch-pull actuator arm and make sure there isn't any galling or wear from the shifter rod contact point which spans horizontally and contacts the adjustment screw at the basket. Stiff springs will cause premature wear at these points so keep that in mind during inspection. Sometimes the galled contact point at the arm can be smoothed and polished with various grits of emory cloth.
As far as gearbox lube is concerned, use automotive transmission fluid TYPE F...yes that's right, vintage Ford transmission fluid, nothing else. It's less-expensive and plentiful at virtually any car parts store. I buy it by the case and use it in all my vintage Yamaha's. Clutch life is not compromised and I run OEM Yamaha clutch plates exclusively. No aftermarket garbage.

Also, stay away from cheap, low-quality clutch and brake cables. They are thin, stretch pre-maturely and offer a less positive feel than OEM Yamaha. Sure they cost more....... but worth every penny!

Pull effort on the clutch lever will be smooth and with a lot less tension on your fingers.

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

1/30/2018 8:47 AM

What's up Mark?

All I can add is that I've got a 79 YZ 400 I've raced a handful of times over the last few years. My Grandpa bought it new in '80 and it's completely stock with very low hours (the stock pipe split and I put a DG on it and I mounted some stock RMZ 450 footpegs). The clutch is really smooth and works awesome.....pull is pretty easy. It gives me the least amount of headaches of all my old bikes. I race it, drain the gas.......it sits for months at a time and I dump gas in it and it always fires in a couple kicks.

Photo

|

1/31/2018 3:51 PM

Gentlemen - thanks for the great suggestions! I took the actuator arm out last night and noticed it was rough -- I actually had another one that is in better shape - I swapped it out and that seemed to help. I also found a set of NOS OEM springs on ebay and they are on the way to me now. Will hunt down some plates and hopefully I'll be in business.

Will also try the ATF Type F. Thanks again everyone!

|

1/31/2018 4:16 PM

Way to go! Let us know how it works out.

Never be drawn into aftermarket parts because of low price. OEM all the way that goes for bearings, pistons and rings too.

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

2/1/2018 3:03 AM

wfoyz250 wrote:

Having raced and serviced my '79 YZ for the last 7 years, I can tell you right now to get rid of the current clutch springs as ...more

ok this is a dumb question, but please clarify before i make a dumb mistake. Its easier.
So don't use Yamaha gear oil; Rotella whatever; use typeF???
You got years of this in old Yamis?

You're not the 1st one i've heard this from, but the post never specified "F" & had no real world experience to back up their claim. I had a clutch issue last year i sware was oil related.

Thank you for your input.
Mark

|

2/1/2018 6:40 AM

Historically speaking, I've used quite a few brands of automotive and motorcycle lubricants on my bikes from Royal Purple to Bel-Ray. I'm not saying the others don't work but for value and where lubrication protection are concerned, there isn't any reason to spend more money for a "brand" name.

The hidden "friction modifiers" within oil formulations will cause problems in "wet clutch" systems and that's most likely what is causing your oil-related clutch issue.
My recommendation is the old tried and true Ford TYPE F and you'll be fine.

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

2/1/2018 6:48 AM

Oh.....and FWIW......I sank my bike in a pond last year, the case/gearbox vent tube allowed the entrance of water to the gearbox. The clean-up and elimination of water was flushing 4 quarts of type F fluid through the gearbox and a bottle of HEET.
Raced it the next weekend.

|

Larry Navarro - Spring,TX. Damm glad to meetcha!

2/1/2018 10:08 AM

Like others have mentioned, stick with stock plates and springs. I ruined a few pressure plates and inner hubs running Barnett Kevlars. Live and learn. File and polish out any imperfections you see on any of the components and see how it feels then.

The late John Astleford used to CNC actuating arm extensions for some of the YZ's. I still have one laying around for my 81 YZ250 I still need to install one day.

|

2/2/2018 6:07 AM

Photo

Photo

|

2/2/2018 6:28 AM

|

I was G before the "moto drive" to Vital

2/19/2018 9:25 AM

I wanted to give an update on this...and a funny story. Went back to OEM on the plates and springs. As I was reassembling, the little ball got away from me and rolled away. I ordered a new one....and it was noticeably larger than the one that I lost. Some Yahoo had the wrong ball. It was causing the actuator to deflect and bend. So....I replaced the ball, adjusted it with all of the other new parts in, and it looks like we are good to go now. Yay, I have a clutch! Thanks again everyone, this one is now almost ready to get onto the track!

|