Gearbox oil

After riding my 750 S for half hour or so the gear changes get harder and clunkier (if thats a word). is it an oil problem or should i look further

If all starts out ok and gets worse as the oil gets hot then changing the oil is a good first check. How long since you last changed the oil?
I change mine when the gear change no longer feels silky smooth, which typically is a bit shorter distance than the manual says.

Rockyrob,

What oil type and grade are you using in the box?

Bad gear changing can also be caused by clutch drag?
Possibly too much oil in the primary? What oil is in there? Don't be tempted to overfill the primary case.

Maybe the clutch could do with an inspection?

I am a bit embarressed to say i dont know what types or grades of oil are in the box. . The guy i bought the bike off told me that it was serviced just prior to delivery so i havent bothered to look further into itI seem to remember him telling me it runs ATF in the primary?would that be right or am i imagining things? I did clean out the oil tank /filter and replace the engine oil tho. I will change the gear/primary oil before looking into the clutch.( altho now you mention it, it does seem to get a bit harder to pull in the longer i ride it) I just asumed that was my hand geting tired. Any reccomended oils. or should i just go with a good brand at the manuals recomended type/rates

I don't know which brands of oil are available in Queensland, but ATF should be fine for the primary drive and EP90 for the gearbox.

Thanks LAB , we have all the good stuff Penzoil etc I will change it and see if it helps

I've had good luck with Redline MTL (manual transmission lube) in the primary and Shockproof Heavy (GL-5, but hasn't seemed to hurt anything) in the gearbox. Completing the trilogy, I use Redline 20W-50 motorcycle oil in the crankcase. Not affiliated with Redline, and I pay full price for their products (and "full" is the word! - spendy indeed!) but have been very happy and have all my bikes, and one car, on them now.

FWIW.

Rockyrob said:

After riding my 750 S for half hour or so the gear changes get harder and clunkier (if thats a word). is it an oil problem or should i look further

Click to expand...

Could also be that you have a bit too much endfloat in the layshaft causing the gears to lock up a bit. Any idea if a layshaft roller bearing conversion was done on your gearbox? Shimming the layshaft inside the inner primary may help. Old Britts has a nice article online describing how to check layshaft endfloat. My impression is that it sometimes takes a bit of shimming and fiddling to get the AMC gearbox just right. Once you get it right, it is a very nice gearbox. The box on my Commando is smooth as silk from cold to completely warmed up while my Matchless G12 box (identical to the Commando) gets a little sticky after it heats up. Both have layshaft rollers. The G12 gets stuck in first and it is difficult to find neutral sometimes. It may just take some running in but I suspect the only major difference between the boxes is the amount of endfloat.

Something that's happened to me with those symptoms was a loose gearbox. After a while, the gearbox gets pulled back a bit and the primary chain gets tight, causing harder shifts. You might also notice more vibration in the lower gears if that happens. Anyway, might be worth checking...

BrianK said:

I've had good luck with Redline MTL (manual transmission lube) in the primary and Shockproof Heavy (GL-5, but hasn't seemed to hurt anything) in the gearbox. Completing the trilogy, I use Redline 20W-50 motorcycle oil in the crankcase. Not affiliated with Redline, and I pay full price for their products (and "full" is the word! - spendy indeed!) but have been very happy and have all my bikes, and one car, on them now.

FWIW.

Click to expand...

I use Red Line MT-90 (GL-4 rated) gear oil in the gearbox. I've read that GL-5 rated oils can damage the gearbox bushings. The stuff is hard to find around here, so I order it online direct from Red Line. Just ordered a couple of quarts yesterday!

For the primary, I used to use 20/50 engine oil, but switched recently to ATF. I'm noticing less clutch drag and smoother shifting with the ATF.

Debby

Debby, hi. I've heard the same thing about GL-5 lubes, but also others say it doesn't matter. Anyone have any good information on this subject? I would like if possible to stay with the "140-weight protection in a 90-weight viscosity" that Redline Shockproof Heavy provides.

Back to original question.

Is it hard to get the clutch to break when you start it cold? If so, could be the old tranny oil in the clutch plate thing. Mine used to get a bit stiff in shifting if the plates didn't separate cause they were sticky with tranny oil. Constant adjusting of the clutch cable , underway, to get the plates to separate. Bad for the clutch pushrod. Long running might present a time and place for the oil to creep into the primary. Problem solved by Dyno Daves' main shaft seal install. Easy to break clutch now, and it shifts much better.

Just a thought.

Where can I get the Dyno Dave clutch seal?

Hi

Have a look here http://atlanticgreen.com/store.htm

List several dealers or just order directly from Dave

B.R.
Henrik

P.S. It works great I made my own.

I posted a definitive answer on the GL-5 issue some months ago but can't find it. I was from a bronze bush manufacturer who recommended GL-5.

Just been on google to try and find it but no joy, but confusion rules OK, one post said GL4 and 5 were no good for bronze bushes.

I have always used GL5 in my bikes for the last 28 years and never had an issue.

Thanks kommando - it may have been your post I was thinking of in saying I'd heard somewhere that GL-5s were okay.

Joe's Secret Gearbox Lube formula:
50% BMW 90 Gear lube
25% Lucas Oil
25% Slik-50 manual trans additive

I have been using this in my Norton gearboxes for a long-long time without any problems. Sweet shifting --no sign of any wear "ie. metal ; on the magnetic drain plug when changing---while "HOT". and, I change at least once per season here in Colorado.

Of course the tranny has to be in good running order--the clutch has to be adjusted properly---primary chain slack--lever and cable lubed- clutch actuating arm set in the correct position--cable run in the correct route so as no sharp bends--pollished ramps on the selector plate help also. And for good measure perhaps straight selector forks in the tranny.

Did I mention flat steel plates in the clutch and deburring the lands & grooves on the clutch friction plates and shimming the clutch pack to optimun thickness, fabricating a 3-piece unbendable clutch push rod and perfect alignment of the engine drive sprocket and the clutch drive basket teeth, rear wheel drive sprocket and countershaft sprocket alignment and of course drive chain freeplay.

I could probably add at least a dozen more ailments to this list that I have remedied on my bikes but why whip a dead horse. Just use a good 90 wt gear lube and change at least once a year if riding less than 5000 miles a year, twice if you ride more than 5000 miles.