Gen 1 gearbox issue

[Rodster]

Hi,

I had my first hard ride out on the bike at the weekend, when I’m on full throttle in first or second and the front end is …. Well going up, when I bring the front down the bike pops into neutral off throttle , it also does it going over a hump back bridge and letting off the throttle. Never had a bike do this, I know the answer is stop being an idiot but..anyway.

the bike has been babied by the old owner for 8 years and he got it with 7k on the clock, and now it has 11200 miles 

Bike has had plenty of services and I have just done another with Motul oil etc.

The shift linkages are free and working
It does have a R6 shift arm (same as Richard Marks) 
Clutch has free play and doesn’t slip
I can’t replicate it on demand only in certain situations.

Has anyone had this or can you offer any advice aside stop being stupid ?

Regards
Rodster

Hi Rod.

Welcome to the forum.

Gearbox may well have been abused by previous owners, mileage means nothing.
Bikes got a ton of grunt, achieves nowt nailing it thru lower gears, these old Yamaha motors have what I'd describe as an agricultural gearbox.
Many of us have an early R1 shift arm fitted, shorter throw, needs a tad more lever effort imho, R6 may use exact same arm?


A few quick things to check:
1) Any stiffness in the rose joints on shift lever & shift arm?
2) Gear lever free & pivot greased?
3) Shift rod dragging on inside of frame tunnel? (common issue with shorter throw shift arms as offset is different causing shift rod to frame contact, R1 shift arm requires a mod to shift rod, bend a slight kink to clear any frame contact) 
4) Upper shift arm correctly orientated 90 degrees to shift rod? (pics will be useful)

First place I'd be looking before dropping the motor & stripping the box is inside the upper selector shaft casing, shift shaft runs thru a needle bearing & oil seal, bearing could be worn, shaft could be mullered / bent & dragging in the bearing, return spring may be weak/bent/cracked, order a new spring & gasket from Yamaha in advance, most of us use "Fowlers" for obvious reasons.

This is where you'd be accessing the selector drum to fit the "Factory Pro shift star kit" they'll probly be available to fit this motor, but listed as 1998/1999 R1 fitment, basically same motor.
Shift star kits are spensive, defo won't solve a jumping out of gear issue,  it'll make things worse, wear of damage is the most likely cause of jumping outta gear.

Let us know how you get on?

Thankyou for your reply, tonight I did the following -
Checked the rose joints, they move freely
Checked, cleaned and greased the gear pivot, it was free but thought it was worth doing. 
Checked it wasn’t hitting the tunnel, it has good clearance 
The shift feels solid (good) and returns to the center. I think the springs etc are good, but I may remove and replace them this winter just as a precaution 
Added more free play to the clutch 
Checked the chain tension, in spec 

Other than that maybe I just didn’t select the gear right but I have a feeling I’m being hopeful. 

Oh and get this ! I took my lightly resorted GPZ 500 out for its first ride tonight, and low and behold that actually has a proper gearbox issue, they are renowned for the gen 1 having bad boxes that pop out of gear so that’s getting a Gen 2 transmission over winter. 

Maybe it’s me ?

Hay Rod.

As the bike tends to drop outta gear off throttle after hard acceleration, my money's on either worn dogs or shift forks or bent shift forks, or worst still all of the above.
You can sort of figure out if it's worn dogs by accelerating thru 1st & 2nd & keep upwards foot pressure on gear lever after selecting 2nd cog, come off the gas, is she stays in gear, it's highly likely drive dogs are shagged on lower gears.

Gear cogs are only a 3 dog drive, it's a weak gearbox for a big motor, not uncommon for drive dogs to be worn out, might be possible to get em re-machined (undercut), will need doings as pairs.
Since they wear in pairs 1st gear cog meshes with 5th gear cog (no longer available)  2nd gear @(£126.50) meshes with 6th gear (£148.48) to order @ Fowlers. 
You might find a 1st & 5th if ya lucky trawling the tinterweb.
Or it's 2nd hand motor time, or a used gearbox assembly & cherry pick all the good parts outta that & yours to build a usable box.
It's gunna be a pricey repair which ever option, plus you might find a load more wear when stripped.

Joys of buying a used bike eh (Fakoolaka).

Thankyou for the reply mate, I can’t get it to do it when off the throttle or on. It seems to happen when landing a wheelie or landing the front off a hump back bridge off throttle.

I have done some work to the bike and I’ll adjust the lever tomorrow to make sure it’s right, I’m off out Sunday for a ride so I will see how it goes, I really hope it’s me, however non of my other bikes ever did it ?

Fingers crossed the bike is good ! I’ll update the post on Sunday ?