Suntour Accushift doing my head in - mechanic?

[smithcorp]

I have an old Genesis from 1991 or so, with 7-speed Accushift downtube shifters and Suntour SL rear derailleur.

I stopped riding it about 10 years ago after I busted my elbow and couldn't straighten my arm any more - I had to adjust my position on the bike a lot (saddle down, stem up and shorter) but still couldn't stay comfortable. However, I determined to drag it out of the garage and get it back on the road. Mission accomplished, sort of.

When I was riding it years ago, the Accushift system drove me mad. It would shift smoothly for a while but then after some kms, would jump down the cluster under load, not sit properly on a cog etc.

In the meantime, I had discovered some scans of a Suntour mechanic's troubleshooting guide and using that I worked out the problem was probably related to cable tension at the RD. I fiddled with it, backing off the tension and I got it shifting perfectly. Nice, positive clicks at the shifter and positive shifts at the RD. A short ride around my local streets and it was shifting beautifully.

I then ride for about 8kms to the park my wife and kids are at - the bike performed beautifully. Leaned it against a tree for 40 minutes or so while the kids played, but when I got back on, it was a mechanical nightmare. Back to uncommanded shifts (particularly from big/big to the next gear down) and then no positive position on big/gear 3 or 4. Off the bike trying to fix it, the cable tension now feels so tight it doesn't want to shift up from the smallest cog! By adjusting tension at the RD I was able to get it shifting well enough to get home, but I had difficulties if on the big ring. These are the exact problems that led me to stop riding the damn thing back in the dim past.

I am going to work my way through the trouble-shooting guide again but does anyone have some suggestions as to what the hell might be going on; and any recommendations for Sydney-based bike mechanics who might know their way around Suntour gear to help me solve this?

Thanks in advance for any help from the brains trust,




smith

[ldrcycles]

First thing i would try is replacing the gear cable, both inner and outer. I have used a SunTour GPX groupset with Accushift indexing and never had a problem at all, but the system has a bit of a bad rep, maybe from early production?

[rkelsen]

As above. Sticky/bent or frayed cables can cause all sorts of grief.

Next thing to look for would be a broken spring in the derailleur.

[baabaa]

Smith! Please delete this thread.
If it is Suntour you are only allowed to ooow and ahh.





Have you tried them in friction? Also undo the cables at the rear and the see/ feel if the cables flow thru the housing with out binding if so yes try new cables and maybe housings.

[ldrcycles]

If it is Suntour you are only allowed to ooow and ahh.

+1 . My love for SunTour took a slight blow after the tension spring in my Cyclone RD snapped on the weekend.

[greyhoundtom]

Definitely, as has been mentioned, new cables may certainly help the situation.

However, from what I have been told the Suntour derailleur system simply does not handle cross chaining real well unlike the more modern indexed systems.
Being careful not to cross chain may make the system work better.

Big/big will cause problems in shifting out of those gears by jumping sprockets on the rear under load.

[smithcorp]

Definitely, as has been mentioned, new cables may certainly help the situation.

However, from what I have been told the Suntour derailleur system simply does not handle cross chaining real well unlike the more modern indexed systems.
Being careful not to cross chain may make the system work better.

Big/big will cause problems in shifting out of those gears by jumping sprockets on the rear under load.

Thanks all - this makes sense greyhoundtom.

[Wal42]

It could be the spring inside the RD has lost tension (most are getting quite old), if you're set up is ok then cross chain shouldn't be too many issues, my Verty (is friction only) handles cross chain no stress, the Malvern commuter (indexed) does jump around quite a bit.

Even in indexed you can trim a little, try that. But most likely is that the cassette is worn, if you can't sort it out with a little trimming then maybe look at replacing the cassette (sometimes trimming the FD will help). Is it on the middle gears, if so the very likely cassette, they're the most used ones.

If you want totally silent running, get the RD checked, fit new cables, cassette, give everything a really good lube, you have to remember, your drivetrain is 20 years old, you have to expect some creaky bones to be showing themselves.


Oh & it'll still be running long after most modern bikes & running gear have gone to bike heaven, so you beat them by having a longer life

[smithcorp]

Quick update - after quite a bit of faffing about with trial and error adjusting, my LBS checked the RD hanger and it was slightly bent. They corrected it and the bike's been shifting beautifully since.

smith

[munga]

palm, meet face.

[ldrcycles]

Ah i love a happy ending .

[smithcorp]

palm, meet face.

That's how I felt. It did not look bent at all and was out by a mill or less. Seems to have made a big difference.

[elantra]

...................................................

smith

By the way, very nice looking bike

[smithcorp]

Thanks - I'm quite fond of it!