Clutch slipping at speed, need input!
So I have a new (to me) 1988 TRX300FW. Runs really well, but having some issues. I've tried to google this every way from Sunday, but I'm not getting a definitive answer. I've even seen this exact question asked before, the the replies were vague at best.
So here's my situation. When I first got it, I didn't notice any clutch slippage. But as this is my first ATV, I may not have been noticing. To be honest I took it down the dirt road only once, so that was the only time I had it "up to speed". I did ride it around the woods, and back in a quarry behind my house, but in lower gears and never really "full throttle". Put maybe 5 miles on it?
So I changed the oil to Mobile 1 4T motorcycle oil. Took it out afterwords, and noticed in 5th gear and while going up a hill down the street, the clutch was slipping. I wasn't 100% sure that it wasn't doing it before, but it's pretty noticeable. It will "grab" again after a few seconds, but it was defiantly slipping. If it was doing it before the oil change, it wasn't near as bad. (I think)
The next day I got my new tires in. I went 1" bigger. From 23" on front and 24" on the rear to 24" and 25". Now it's REALLY slipping in 4th and 5th gear when I'm out on the road and going 30-40 ish uphill. I also think I'm noticing it slipping in 2nd gear or higher if I'm not downshifting when I could/should and start accelerating. The taller tires really make more difference than I imagined!
Anyway, I have no idea what oil the PO used, but it was pretty black and likely not lubricating at it's best. Do these clutches not like Synthetic oil? The Mobil 1 is rated for wet clutches, but I'm wondering if the fresh and slicker oil might be exposing worn clutches that the old oil was masking?
Either way, I need new clutches. So is slipping at speed the "shift clutch" or the centrifugal clutch? Can the centrifugal clutch get worn enough to slip like that? Or should it be a non issue since my problems are most noticeable at high RPM and not at low RPM? I'm thinking about just replacing both and being done with it, but I'm no expert. I'd like to hear from some of you that know these bikes better than I do!
I've played with the adjuster, and on mine if I did the counter-clockwise till resistance, then 1/4 turn clockwise, it would "creep" forward at idle and "jump" really bad when shifting into SL. I had to adjust it to about 1/8th. That's about where it was when I started. It does sometimes seem like it's not changing gears as easy as it should. It's not "hard" per say, just doesn't always seem like it's going to the next gear. I sometimes have to give it some gas to get it to "seat" in the next gear. This is only from idle. Shifts fine if I'm moving.
Any input appreciated. Haven't had an "auto-manual" since I was a kid and had a 70cc dirt bike that was "auto-shifting" or whatever the proper term is for these setups without a hand clutch. But I've owned many dirt and street bikes. Thumpers to 4 cylinders. This is just my first quad.
1988 TRX300FW Fourtrax