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KTM 990 Tubeless

This is my method for sealing spoke type tires to make them tubeless. I have done this to 3 bikes, two Triumph Tigers '99 and '02, and one '07 KTM990S. I have put over 90,000 tubeless miles between the two Tigers and 20,000 miles so far on the KTM tubeless as of Sept 2009 with no problems. My "tubeless rides" included trips all the way to Prudhoe Bay, Alaska and full throttle top-speed speed runs at Bonneville Salt Flats and brutal Nevada desert. Thousands of miles of rocky, bumpy dirt and gravel roads, and temperatures from below freezing to scorching desert pavement temperatures, most often carrying a full set of luggage and often with a passenger. So far I have only used true tubeless tires in my tubeless conversions, such as Metzeler Tourances, Avon Distanzias, Continental TKC-80's (for Tiger), Pirelli Scorpions and Metzeler Karoo T (for 990S). The benefits of running tubeless are cooler running tires that last longer, less unsprung weight for more nimble handling, and super easy to quickly patch typical holes with a plug gun or "gummy worm" type patch kit from the outside, no need to remove tires.

** This information is offered as-is, as a DO AT YOUR OWN RISK project. I do not recommend any of the products or methods used here. This is just what I have done, nothing more.
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Start with wheels true and spokes tight. Brush inner rims with solvent to remove grease and debris. Deburr any rough edges especially in the bead sealing area. Mount wheels on a wheel stand so they can be freely spun while working on them. My stand is homemade from wood and using the bikes axles to hold the wheels.
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Start with wheels true and spokes tight. Brush inner rims with solvent to remove grease and debris. Deburr any rough edges especially in the bead sealing area. Mount wheels on a wheel stand so they can be freely spun while working on them. My stand is homemade from wood and using the bikes axles to hold the wheels.

  • Start with wheels true and spokes tight. Brush inner rims with solvent to remove grease and debris. Deburr any rough edges especially in the bead sealing area. Mount wheels on a wheel stand so they can be freely spun while working on them. My stand is homemade from wood and using the bikes axles to hold the wheels.
  • Stage 1 sealing. I use Seal-All because it is gas and oil resistant. It will resist any oil or gas or solvents that may seep in around the external spoke nipples. This product dries thin. I apply two coats. Apply one coat, let dry then apply second coat.
  • Apply Seal-All with a plastic syringe-type applicator often found in hobby shops or sporting goods stores. Start with the spoke nipple thread hole at the bottom, then squeeze out sealer as you work your way up, to fully fill the thread hole with no big air bubbles. This is the most critical sealing area as this is where most sealed spokes leak if not done correctly. Micro bubbles are OK when the products are dry. Big bubbles are bad and can cause leaking, try to pop them when sealer is still set, or dig it out and re-apply. See following video for how to apply the first Seal-All coat.
  • Work 4 spokes at a time at the top of the rim so Seal-All does not run after being applied. When dry to tackiness or when it does not run, rotate wheel to next 4 spokes at the top and repeat. I never said this was a fast process. Having both wheels mounted allows you to got back and forth between wheels to speed things up. Work on one wheel while the other dries.
  • After 2 coats of Seal-All (or before doing any sealing) you can apply the metal air valve stem. Make sure the valve hole is clean.
  • I use this style metal valve stem that fits in the original rim hole, no drilling needed. Has a gasket to seal itself to the rim.
  • Insert metal valve with gasket on inside.
  • Outside view of metal valve insertion.
  • Tighten the valve housing until the washer just start to squeeze out.
  • Fully installed metal valve stem.
  • After 2 coats of Seal-All have been applied and completely dry, it's time to apply the thicker, more rugged top sealing layer. For this I use GOOP, made by the same company as Seal-All and found in most any hardware store. Any version of GOOP will do, like "Household, Plumbers, Marine, etc", they are basically the same stuff, it's just a marketing thing (I spoke to the chemist at Eclectic, the manufacturer, to be sure). Apply around the spoke nipple cap then spiral in and pull up at the center to form a sealed cap layer. GOOP settles a bit as it dries, so it will flow together. <br /> <br /> Why GOOP? In pull-testing 9 adhesive sealers including aerospace grade stuff, I found GOOP grips aluminum the best for this application, where for example the sealer everyone always thinks of, silicone rubber, does not grip well at all and is easily scraped off. When the GOOP cap is dry, it is tough, and is very difficult to scrape off and seals well, which also makes it very resistant to tire irons and tire tools. No extra rim strips or protective tape wraps are needed, keeping the weight down.
  • This is how it looks when dry. Again micro bubbles are OK when the products are dry. I also apply sealer around the valve stem on the inside for that extra measure of sealing.
  • Tip: I use a bit of tape to mark the last hole I sealed, as I work around the rims, 4 spokes at a time. I found that using all these clear sealers, it's hard to tell what's wet or dry or had it's second coat, etc.<br /> In general, when all sealers are dry, install the tires again, pressure them up, then do a "bathtub test" to detect any leaks. If you find any leaks, wrap that spoke with a food tie or bit of wire, to mark it. Take the tire off again and dig out the sealers and re-do the sealing process on just the spokes that need it. That's what is nice about sealing spoke caps individually, you can also repair them individually. Systems that fill the entite rim well with sealer or fiberglass or other wraps, are in trouble if one or two spokes leak -- you have to peel off the whole mess to fix it.

  • N Nicholson

    on September 9, 2019

    Hi, I'm trying to contact the author of https://cyb.smugmug.com/Motorcycles/KTM/Tubeless#!i=465979239&k=UFqYE
    I've done a successful tubeless 3M 4412 tape and Loctite 290 conversion on a 2010 T100 Triumph Bonneville, which has safety beads on both front and rear rims.
    I am thinking about doing it on a Royal Enfield Himalayan which has no safety beads, but have come across much online advice against this and one actual case of a guy who suffered a sudden deflation on his non-safety bead front conversion https://adventure-motorcycling.com/2012/02/14/converting-spoked-rims-for-tubeless-tyres/
    I've come across many examples of people who say the function of the safety bead in cars is to keep the tyre on the rim when pressure is low/puncture and quoted examples of cars which left the factory with tubeless tyres and rims with no safety bead.
    Obviously a front sudden deflation on a motorbike is nasty. I also am aware this can happen with a tubed system.
    I not in the case of the KTM 990 mentioned above, the front rim does not appear to have a safety bead.
    What is your opinion on the safety bead in a tubeless conversion. I ask because you have done many miles on converted rims. Thanks. Hope you have time to answer my query.

  • MotoHojo

    on July 28, 2015

    Thanks for sharing.! Does the rim have to have a lip for a tubeless tire in order to hold air?

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