no 5th gear under load

[gogo]

My GS(X)1100 racer has decided to not select 5th under race load.
All is well in all gears pootling thru the pits but at 9000rpm it will not go into top. All other gears and neutrals AOK.
The counter shaft length low to 2nd is 0.5mm
(111mm instead of 111.5mm) less then the manual suggests, and I would think that would not be enough to cause this problem?
Any clues folks?

 

[focus frenzy]

shift sooner! you run any bike that hard and things will bend and or break. it is the way it has always been. may need a new set of under cut gears.

 

[Steve]

All other gears and neutrals AOK.

Just how many neutrals do you have?

I pretty much agree with Focus on this one. Yeah, it probably ought to be able to shift at 9,000 rpm, but unless you are racing on a track, there is not much need to be running up to 9,000 on the street.

Couple of questions, out of curiosity:
1. Will it shift at 8,000 rpm?
2. Just how fast are you going when it's doing 9,000 rpm in fourth and won't shift into fifth?

.

 

[hampshirehog]

Well, as a bit of an idiot and a thrasher I'm going to disagree about the high revving. The GS boxes (and other Zook boxes of that era) were great and could stand pretty much any abuse. I've always viewed the red line as 'advisory' and never regretted it.

Does it refuse to go in with both clutch and clutchless shifts? If it works on clutch and not clutchless I'd be guessing worn / bent selector fork or something else internal.

First checks are drain the oil, flush and replace plus check the gear selector arm / lifter plate / pawls / springs etc and give the thing a dang good clean.

 

[Guest]

I would have to say that either the shifter drum has gunk built up in the tracks or fifth gear is trashed. If the shifter forks were bent I'd say that he'd have trouble with more than fifth.
Probably the dogs and ears aren't mating.

 

[gogo]

gears

gears

Thanks folks. It is a racebike and I have wound DOWN the rev limiter coz the motor is fresh. I usually hit 9500 on the back straight before I hit top.........
The mtr is clean and has been "inspected for anything obvious" etc etc.
The gearbox is not modified in any way, and I have successfully run other motors thru the box at those revs.
Never had this happen before, and the usual fix is to weld the low gear into place, but I was thinking a drift of 0.5mm from specs as I have found was minimal and therefore not the cause of my problem. I stand corrected if it is.
Keep the suggestions coming, might have to do em all eh!
And, yep it gets along at a fair clip.
cheers

 

[rapidray]

The 16 valve GS transmissions are notorious for being strong, smooth, & able to take LOTS of abuse! You need to look at the dogs & slots on BOTH gears & the shift fork for 5th gear. I shift mine at 10,000 rpm EVERY shift & have NO issues when I start with a CORRECTLY race prepped trans. If your trans is stock, have it RACE prepped! Fast By Gast, MRE, Robinson, Orient Express, R&D Transmissions, along with others can do what you want & do a GOOD job at it. Ray.