Sach forks topping out? E.g. Clunking when fully extended?

[betajuice]

hey guys, anyone's sach forks topping out? e.g. front suspension's clunking regularly when fully extended?

summary: it seems the 2015 and earlier top out springs in the sachs forks aren't great quality. if there's a metallic clunk every time the forks top out, stop riding and get them fixed before the broken springs start to wreck your shims. apparently the 2016 top out springs are better quality. don't stress though, seems to be a very small percentage that fail.

the forks on my 2015 RR300 did this after the last ride where they copped a bit of a flogging across rocky terrain at speed, going from heavily compressed to fully extended rapidly every second or two on some nasty terrain.

took it to the suspension shop and the little springs designed to soften the forks topping out had both disintegrated, damaging the rods and the valves. i hunted around and this doesn't seem to be a known issue, but just letting everyone know if you start to get a clunking when the forks top out it's probably best to stop riding and pull the forks apart before causing too much grief in case your return springs have broken.

out of interest, the suspension tuner i went to, full force racing http://ffracing.com.au/ is fully equipped with a $30,000 dyno as they design custom valving to supply other suspension shops with. they asked if they could test the rear shock and were surprised that the sach rear shock is actually quite good.

they said the needle tapers off too quickly so that if you soften the damping settings from default then very little happens but increasing the damping works well. they felt it easily outperformed the ktm rear shock and was light years ahead of the showa shocks they work on with hondas etc.

their opinion on the sachs forks was they aren't bad but not yet up to the standard of the WP forks on the katos so still room for improvement there (and of course they are being tweaked yet again for 2016 so might match the WP now?). i had their custom valves put in to replace the damaged stock ones so should be interesting to see how it goes on the next ride.

[Johnny Depp]

Upon tear down of my Sachs I found one side of the base valve with the spring to be loose. I have never heard of anything like what you describe?

Interesting feedback on the shock. I have found the Sachs forks to be superior to every KTM WP I've tried, 4cs and CC both.

[GMP]

I found no loctite and no peen on the base valve taps, and one nut loose. Perhaps you lost damping first and that destroyed the springs? Other than that fork is made very well.

[betajuice]

I found no loctite and no peen on the base valve taps, and one nut loose. Perhaps you lost damping first and that destroyed the springs? Other than that fork is made very well.

i'm not sure glenn, i had the most experienced guy in the shop doing the work and he couldn't find any reason. he said it's normally only something you might see from supercross riding where the forks are taking a constant battering, and even then it would be rare.

out of interest, he did say he was surprised at the weight of the forks, he reckons the outer case is probably still a bit beefier than it needs to be. and the internal rod (not sure on the right term) is made of steel and he says it should be alloy.

if true i guess it's still a hangover from the early models which weighed quite a bit but apparently the original aim was to make the bikes unbreakable... so i read in a review somewhere.

[betajuice]

shit, it's happened again i think! the same sound has started after about a dozen rides on the rebuilt forks and i've lost my damping again.

taking it to the suspension shop again to get it fixed again and i'll report back. the guys there did say the return springs or whatever they are called were pitted and looked to be quite poor quality. i trying to contact a guy in another state who said he had the same issue, and knows of a few other local riders on betas who've had this happen too.

i can't find cases reported online anywhere so it will be interesting to see if it was just a quality control issue with a batch of betas that came to australia, or if it's a widespread problem.

[Marty Moose]

Same as in another forum similar issue. These were an updated part in 2016 made mention in the bikes blurb as one of the improvements. If I had a 15 I'd be buying the 16 top out springs.

[Mark Donovan]

My daughters 13 300 did the same thing. The plastic spring holder broke on both forks. Kevin at Stillwel Performance found the problem. He said he had seen it before with light fast riders. I think he was just being nice.

[betajuice]

Same as in another forum similar issue. These were an updated part in 2016 made mention in the bikes blurb as one of the improvements. If I had a 15 I'd be buying the 16 top out springs.

thanks marty, i'll check that out.

[GMP]

Is your fork revalved, rebound slowed down? I had a couple sets of WP43s years back that broke top out springs. They also had cupped and cracked midvalve shims, causing lack of rebound control and abuse of the top out spring. The stock Sachs valving is way too fast and in the set I have the midvalve face shims are cupped badly in 70 hrs., due to the stack design I suspect. Fork felt like a pogo stick but top out springs were fine. Just a thought.

[Marty Moose]

Is your fork revalved, rebound slowed down? I had a couple sets of WP43s years back that broke top out springs. They also had cupped and cracked midvalve shims, causing lack of rebound control and abuse of the top out spring. The stock Sachs valving is way too fast and in the set I have the midvalve face shims are cupped badly in 70 hrs., due to the stack design I suspect. Fork felt like a pogo stick but top out springs were fine. Just a thought.

Your making me want to pull my forks now and check the mid I guess it would be nice to see the changes made to the 2016 if any at all. The mid I posted out of the 2015 390 was shim cupping territory for sure.

MM