Possible trans problem

Hi, I noticed when i go fast in first gear it seem like it slips into neutral what is the problem????? :?

Although some will argue this, I changed the detent plunger and spring( see Item 15 and 14 http://www.oldbritts.com/1972_g6.html ) and solved that issue. The gearbox oil will drain when checking this. These are reasonable in cost.

I also purchase a first gear lay (still on the shelf) thinking that the paul from the second gear lay were wearing at the point where they come together. When they are engaged, it's in first. If the detent spring loses its gumption, they don't fully engage to each other and can disengage under load or high rpm. This is the highest point of leverage require by the camplate due to the torque in first gear.

Order these from Old Britts tomorrow and you will have them Thursday. This is absolutely worth the effort (or lack of effort) because it is a simple fix requiring no dismantling if the gearbox. The worse that can happen is that you will have a fresh spring and detent for around $25. If the detent is in good condition with a good bullet shape, the spring is only $2.50.

After that you can start listening to people talking about the layshaft bearing. That situation is a totally differant set of symptoms.

It is certainly worth testing the detent plunger theory, if only because it's such a quick and easy procedure. If it works, count yourself blessed.

My own theory would be worn out dogs on the relevant gearsets, but you won't confirm or deny that without a teardown (which, without more, would not require you to remove the box from the bike).

Good luck.

When I had 1st into N issues it only occurred when loads cut, like to just coast easy or back off to shift up in lazy dazy state. It took me down twice going as slow and safe as possible 20 mph then 12 mph and injured/fractured lumbar spine on the 12 mph smack down when rear grip let go in leaned surprise. Turned out to be thin 1st gear bush let cog unlock to darn easy. Just a thought to keep in mind.

Greetings,
I hope you do find something simple (like the detent spring), but what you describe is classic bent/worn shift fork. Typically what happens is that the bike gets dumped on the shifter side which forces the shift lever to move. If the dogs on the sides of the gears are lined up at that moment no problem, if not, it may bend the shift fork. When the shift fork is bent the gear dogs/holes will no longer engage to the proper depth. After that when you accellerate hard (high load condition) the gears may force themselves apart (IE jumps out of gear). Each time that happens the edge of the gear dogs/holes get more rounded off making it jump out gear more easily. Fortunately, the Norton transmission is easily accessed and repaired.

GB

Ludwig, you need to put together a photo/text compilation of improvements you've made to Nortons over the years.

britbike220 said:

Ludwig, you need to put together a photo/text compilation of improvements you've made to Nortons over the years.

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Pretty sure that would fill up the internet.

I have cured my gearbox of jumping out of first gear under acceleration by replacing the first gear bushing. I've done that twice in 35 years.

I had the same issue on my '73 850...was ready to tear into the gearbox, but thought to check the clutch adjustment first. Turns out the clutch rod lever, where the clutch cable attaches, was in the wrong position. Did a proper adjustment, as per the shop manual, except did the rod's screw turnback a 1/2 turn as Hemmings suggestion, rather than the full turn back as per the manual. Also, switched to Redline Heavy ShockProof gear oil for smoother shifting. Solved the first gear slipping out, and problem never returned.

Wind the detent plunger in a couple of turns.

When riding uphill in a tight turn ( hairpin ) , jumping out of 1st can have unpleasant consequences .

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AMEN Ludwig, I can testify it can jump out of 1st for all the listed reasons above, also in down hill coasting as well as up hill with some lean. If does jump out in these
conditions you will come to same conclusions I have the HARD way > that rear tire grip rules the roost for staying up right and aimed right. SPLAT! Lucky my 2 events on same day were w/o traffic to run over me as bike slide right out from under leaveing me running a bit to stay standing in middle of lane as bike slide downhil into gard rail. 2nd jump out was 12 mph coasting turn into driveway that dump bike on top of me on top of 3 ft brem which broke pelvis and L5 vertebrae. Took months to walk like a man again, but was happy I protected my new paint job. I found worn bush as reason this time. Later found slack in cogs also caused dog ears wear that took a bit more use before shifting was fouled again and total gear box refresh. Will attend to the cam plate as shown thanks.

If your kickstart stub has more than minimal end float (in and out travel) I would concur with previous replies that end float is likely to be the culprit. A rear Isolastic shim is placed between the stub and the inner gearbox cover to positively locate the pawl end of the stub inward toward the clutch, deeper inside the layshaft first gear. Old Britts has a comprehensive writeup on the procedure.


Tim Kraakevik
kraakevik@voyager.net
Three Commandos