Fork Seals make me crazy....

[Bob and Mary]

Had a fork seal leak a year ago. Replaced both sides while I was doing it. Left the forks attached to the bike, dropped the wheel and lower tubes. The seal that was leaking has not leaked since I replaced it. However the seal that didn't leak at the time started leaking almost immediately. I replaced it twice now... last time I got about 3,000 miles on it before it blew. Am I cursed, or is there something else I should be looking at when replacing the seal?

 

I use Yamaha original equipment seals. I cover the inner tube with saran wrap and oil it so I can slide the new seal on. It has progressive springs, installed two years ago. I use a 2 piece seal seating tool store bought, not home made. Inner tube has what looks like a small dent in the area above the seal. I cannot feel the dent, but it's visible. I buffed it with a green scotch brite pad, nothing snagged on the pad.

 

On a side note, the front end had begun bottoming out when I go out of my driveway. It's the kind of curb that is a rounded drop to the pavement, not a regular curb cut. The front forks will not hold air pressure. Used soapy water once to try to find the air leak, with no luck.

 

So I'm going to change the seal again... are there any special Yamaha incantations I should be using, or are regular swear words OK?

[Sfahey151]

That small dent, even though it's smooth, will allow a tiny bit of oil and air to escape every time it dips below the seal and returns above the seal. I'm a relative newbie to Ventures so maybe there's some other characteristic flaw in your model,but, I've been a mechanic most of my life and know that those fork tubes need to be pretty much perfect.

 

Steve

[campfire12]

Use All Balls raceing seals made rite here in ohio. You can find them on e-bay. I did the same thing with yamaha seals and the same thing happened. replaced both seals and the oppesite one leaked after installation. The all ballls seals are tougher and much better seals. Give them a try.

[cowpuc]

Couple things here, if your front end is bottoming there is a chance that the springs are actually sacked out. The springs being sacked will also push oil past the seals. If these are new progressive springs - did you remember to add the spacer on the top when installing them? I personnally run 3/4 inch spacers in Tweeks (my scoot) because I do a fair amount of off roading with her BUT - I would say 1/2 inch of spacer is normally adequate. Also, if you have good progressive's you really should never need air in the forks - IMHO.

ANother issue, you mention this "dent" in the tube.. Look at it closely and see if the dent resembles a small "crease".. A crease could indicate that the tube is actually bent. I have seen many tubes thru the years that have been involved in bike crashes that, to the untrained eye appear to be just fine but to the trained eye who knows what to look for (not saying I am one of those "trained" types - lots of folks around here that know wayyyyyy more than I about this stuff - hope they chime in) the tube may actually be bent and need replacing.. Many times finding that is as simple as finding the crease you may or may not be referring to..

Another issue you may be dealing with is fork fluid quantity/height in the tubes. Although sacked springs raises the fluid height and puts pressure on the seals - improper quantity and balance of that quantity can/will result in fluid past the seals. I like to use a fork oil guage (its a syringe with a long metal tube that you preset the height of the oil in the tube with) as well as a measuring cup for getting the new oil close..

Hope this all makes sense and helps in some small way..

Puc

[MiCarl]

I've been a mechanic most of my life and know that those fork tubes need to be pretty much perfect.

 

Any surface defect the seal runs on will damage it. Also, if they're bent, even a little, the seal will die prematurely. You're supposed to pull the tubes off and roll them in v-blocks with a dial indicator on them to make sure they're straight.

 

Also, you didn't mention bushings. Bad bushings will lead to early seal failure, and opening the fork up can damage them. It's good practice to replace bushings every time you tear them apart.

[BlueSky]

Not long after I bought my 85ZN700 Kawasaki that had only 1k miles on it the fork seals leaked. I replaced them with OE Kawasaki seals which did not last long. Then I replaced them with All Balls Racing seals bought off ebay and I haven't had any problems since then. They are advertised to last 3 times as long as OE seals and they do fit tighter than the OE seals. So, a second recommendation for the All Balls Seals.

[jfman]

The problem I have found buying seals and other rubber boots from the dealer is that sometimes tbey have really old stock. Once i bought carb boots from suzuki and one of the two looked much older that the other. It had bee. In inventory for at leas 15 years. I refused that one and made them get me a new boot. YMMV