Exhaust, Spark plugs, front shocks QUESTIONS

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Jul 19, 2021
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So I fouled a plug running the, (sounds GREAT, but POS slasher exhaust) and the plugs are these fancy round thing with an E on the porcelain, brand? I'm going to clean them up, throw some NGKs in see if any difference. So while I'm putting factory pipes back on, does it hurt it to run it LOUD for a bit? As in no exhaust.
Will just replacing the seals? on the front shocks fix, ( goes 3-4 inches) there are two per fork, or am I going to need to order more parts?
P.S. I got my 87 Supermagna going pretty good and it's easy to ride, but pretty disappointing on power after riding the Yamaha.
Thanks fellas👍
I wouldn't run it without the exhaust for 2 reasons:

1. It's illegal and you can be cited for it.
2. It will make your bad plug situation even worse.

As for the seals that depends on your forks condition. You'll have to take them apart to find out what shape they're actually in.

If they're obviously leaking fluid then the seals must be replaced, but I would check everything before I ordered anything because you never know what you'll find.

Then again, if you aren't obviously leaking fluid and your forks move that far you may simply have lost all your air pressure.

Get a fork pump and see where they are. I run mine at 8 psi.
Use the factory service manual to buy the correct plugs. Do not use 'fad' plugs.

Running w/o an exhaust will piss-off your neighbors and attract unwanted attention from the Po-Po. Without ear protection it will also harm your hearing. Prolonged exposure to a loud-enough sound can permanently damage your sense of hearing.

Do you have any corrosion or chips in the downtubes where the seals are wiping? If so, changing oil & dust seals is useless.

I'm over 200 lbs in the saddle, ready to ride, and I need the air in the forks for the forks to perform properly. If you don't have a tire gauge, get one and see what your PSI is, something to between 5-14 psi is where it should be unless your bike has Progressive Suspension springs. Using them, the manufacturer says, 'no air pressure needed.' If you use a compressor for filling your forks for air pressure it is very easy to over-fill the psi air pressure. It's a good time to use the pressure regulator function on the compressor. 'Winging-it' with the pressure above that can cause a failure of your fork seals. Having the air pressure PSI too-high, and even a brief 2 or 3 second fill-attempt on one side (like the 1993-'07 bikes have) can be too-long. Also checking the air pressure will drop the PSI several PSI, each time. Either have a low-pressure gauge, or set the air regulator down to what is the maximum PSI you want to use, and only 'touch' the schrader valve for a second at a time, and then read the PSI you have after that. You'll see that the PSI drops quickly with each attempt to read fork air pressure.

Most experienced riders will tell you to use only OEM Yamaha fork seals. Yes there are two seals per side, an oil seal and a dust seal. Setting the seals, you can use the old oil seal as a driver for the new seal, or look for a seal driver kit from someplace like Pit Posse. https://www.pitposse.com/pit-posse-adjustable-fork-driver-set.html This is a bit pricey, but you can use a close-fitting PVC pipe. 1985-'92 downtube is 40 mm O.D. & 1993-'07 are 43 mm O.D. The oil seal is of-course larger than that. The dust seals are much-easier to seat, you can probably do them by hand.
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Will just replacing the seals? on the front shocks fix, ( goes 3-4 inches) there are two per fork, or am I going to need to order more parts?👍
It would be helpful if you could be more precise as to what the problem is.
The way you have written suggests that you have too much fork movement (dive)?

If that is the case then changing the seals will have no effect unless, as has already been suggested, they leak allowing the damping oil to escape.

As you don't know the volume of fluid or its condition you will need to remove the forks and drain what is in there into a measuring beaker.
Refill with the correct amount and and viscosity thenre-assemble and add air as recommended. Measure and adjust as necessary the static sag which should be between 25 and 35 mm.

That will give you the best set-up with OE springs and damping....which isn't that good. If you want a good front end you will need to prise open your wallet and invest in some decent springs and emulators.
something to between 5-14 psi is where it should be unless your bike has Progressive Suspension springs.
This is important. (I had totally forgotten about the progressive spring package).

This is why I was saying "wait until you tear them down before ordering anything". If it turns out you just needed air pressure, cool. No worries.

But if you do in fact need new seals, and you're going to wind up tearing the forks down, you might consider going ahead and getting the progressive spring kit. It'll come with everything you need and be a good improvement overall and it's not that expensive. I think it's around 175 dollars or so; and since you're going in there, might as well go all the way.

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