same happend to me. i have always ran mobil-1 v-twin oil in mine. last summer i tried lucas oil. my clutch started slipping like all get out. i only left it in there for a couple days and drained it and put mobil back in. took it for a 75 mile run and my clutch was back normal.

I love my Mobil 1 VTwin Air Cooled 20w50 Motorcycle oil... I also use Mobil 1 in all my cars, Never a Failure...

Amsoil "Motorcycle" oil has JASO classification and is recommended for wet clutch applications. It should not make the clutch slip. Were you running Amsoil for motorcycles, or just Amsoil? There is a difference.

I just started experiencing clutch slippage under hard WOT accell in 3rd, 4th & 5th gear only after re-jetting carb and poormans BAK to stock airbox and stage 2 stock exhaust mod. All was good last fall before the winter mods. The oil in the engine was Yamalube from the dealer when they did the trans recall last fall (I had Ams/Oil 20/50 in it from when I first purchased the bike). I tried the seafoam treatment in the oil last week and though there was an improvement it still slipped a bit. I changed out the oil and filter today for my usual AmsOil 20/50. We'll see how this goes. My 99 only has a little over 17,000 miles on it but I have been reading on issues with the factory weak clutch. It works just fine under normal everyday easy riding. Just the extreem "Get On It" runs is when it slips. BTW, I am and have been only using the motorcycle AmsOil.

I been following trend on clutch slippage . I'm experiencing clutch slippage my self ever since I had my oil changed. I had Castrol oil put in my 06 Roadstar. Where can I buy Amsoil motorcycle 20W50?

Thanks for your help
Willy

How many miles,and what type of castrol? You may just need to adjust it at the lever.
Most motorcycle shops carry AmsOil or you can get it from their site.

About 28,000 miles on bike. Don't remember what kind of Castrol. Mechanic from shop that does work on the side got it for me. Tried to adjust lever and cable , didn't help. Going to do an oil change to see if that helps.

Willy

If the castrol oil was car oil it has friction modifiers in it which will cause the clutch to slip. Oil change to a jaso-ma rated oil should help. Just don't use any oil that has the energy conserving label on it.

ok, now this is weird because I just changed the oil and oil filter with mobile 1 V-twin oil 20/50 and i started to notice the clutch to slip. now i have been using mobile 1 V-twin oil 20/50 syth since last year with no problem but this time i have notice it. Now are there any guys out there that have been using mobile 1 V-twin syth for a long time with out any problems?

I am and have always been a Mobil 1 fan. I do not disrespect those who choose others. Mobile offers a 4 quart Non EC 15-50 that works great. Since the engine in my valk is very much a performance engine, i use 0-30 European non ec formula. I also use that oils on all my bikes unless i plan to do parade duty with the PGR. I could write a novel on the benefits of synthetic oils, however, i would not recommend running an extended change interval because you are running synth.

Just my .02