My 69 Bonneville jumps out of 3rd gear. Typically it happens when first opening the throttle then easing of and then opening the throttle again. If I after this put it back in gear it usually stays there. It also helps being "firm" with the foot when first putting it in 3rd gear.

I suppose this is due to wear? Is the only remedy to buy new parts or is there anything else I can do? The new parts being kinda expensive. Do you usually need to buy for both main and layshaft?
I guess It will be easier to tell once the gearbox is apart and I can post some pictures of it but any info on what I have ahead of me would be much appreciated.

/simon

It is always due to wear, but the more usual gear is 2nd. Additionally, extra damage is done by the act of "jumping" so you do NOT want to ride again until some type action is taken.

On the 650/750 twin you can try a short cut, quickie fix of replacing the 5 coil springs. This since gearboxes are prone to collecting water that attacks the coil springs, and general spring collapsing arising from 30 years of being under compression.

The camplate plunger spring is inside the dome-shaped nut on the bottom of the gearbox. (Next to #3, below.)



Then there are 4 shifter springs inside the outer cover.

This is a very inexpensive repair, and one you'll end up doing anyway. Now the modern springs will not be exact copies of the ones you take out. This is due to wear (as mentioned) and newer sping manufacturing methods. Not to worry, just replace them.

:bigt

What would the "extra damage" be?

The thing is the bike is newly rebuilt. But due to budget at the time (and always...) I put the gearbox together thinking "I'll se what works and what not". I think I did replace those springs though but I am actually not quite certain. I will have to check the paperwork when I get home.
My filosofi being that the gearbox is easier to fix later on then say crankbearings.
I did not save a penny on internal parts of the engine though. New 750 cylinder as well.

Thanx for reply!

/simon

p.s. for a few seconds I got quite confused by the arrows in the picture you submitted. I then realised they where more likely pointing at things associated with oilchange rather than the gearbox.

/s

If the camplate spring is new, then you can shim it up by dropping a ball bearing into the dome nut cup before adding the spring. Triumph doesn't make these springs, so none of the 3rd party spring manufacturers is quite sure of the exact pressure it was designed to have.

When the gear "jumps" out it eagerly applies all 40 HP of engine output to the shifter fork and camplate guide grove. This as well as round off the "dogs" on BOTH mating gears.

It can get expensive VERY fast.

Best of luck. :bigt

OK, thanks again!

Is it the pinions that gets worn or something else?
Guess my gearbox soon will be looking like this again

DSCN2224 by Bohuslän i mitt hjärta, on Flickr

And my wallet slightly more emty than before. I'll probably get back here with a picture or two of the worn gears before I order new ones. Just for RF or anyone to comment on the looks of them.

/simon

What are you calling "pinions" ??

Gear perhaps...? The round things with various numbers of teeth on them placed on the main and layshaft inside the gearbox. The ones that makes the bike go at different speeds. Internal parts of a motorcycle was never in my englishbooks at school. A flaw in the swedish education system no doubt

I have learned a lot of technincal words but sometimes get them confused. Partly because sometimes different parts might have the same names i swedish and three different names in english. And sometimes there are three different names i swedish and just one collective name in english.

/s

Your English is better than mine - I have no trouble understanding your posts.
Then there is British English, American English, Australian English, etc. etc..

Rarely will a 4 speed transmission jump out of gear without some visual clues on the related parts. Look at the parts closely. Look for abnormal or heavy wear patterns and signs of over heating.

Then you need to look beyond the camplate, shift forks and gears. As Richard said above, some shifting problems are related to problems with the shifting mechanism in the outer transmission cover. It is important for the two springs that centralize the shift lever to be balanced, or equal tension. These springs lead a tough life as they are often exposed to a lot of condensed water.

I also see from your flickr account you have bought a lot of new parts for this engine. If you have bought new index plungers (little fingers) for the shift quadrant. Current production has created a problem... There are people making five speed plungers that are not marked (identifying groove around diameter) as they were at the factory. A lot of parts vendors are unaware of this and get the 4 and 5 speed ones mixed up.

Thank you John,

I'll start by looking into the parts in the outer transmission cover. I seem to remember checking the plungers and thinking "they look just about new". They might just as well be new but wrong from previous owner. I bought the bike in baskets from a person who in turn bought it in baskets and quite quickly gave up on re-building. Realizeing he was in over his head.
As was I by the way -I just didn't give up...

/simon

If it jumps out of 3rd,you can increase the dog engagement.
Loosen the mainshaft nut at the kickstart ratchet.Select 3rd gear.See how far you can push the mainshaft in,before it bottoms on the 3rd gear drive dogs.

You can fit a shim,slightly less than that,between the timing-side mainshaft bearing and the gear on the mainshaft.This works,if there is still some clearance left (not bottomed out hard).

After that,you need to shim the crankshaft sprocket an equal amount,to keep primary chain alignment.Check the chain alignment.

Thanks,
I'll look into this whenever I get around to work on the bike. No spare time what so ever at the moment.

/simon

Sounds a lot like the problem I had with my TR6C. Third gear was not staying engaged. Solved it by shimming the mainshaft. Here is the thread:

http://www.britbike.com/forums/ubbt...;Main=43805&Number=396860#Post396860

Aah! Great stuff.
Does anybody know why this occurs? Assuming that Triumphowners back in -69 didn't have to do this on their newly bought bikes I'm guessing there is something causing the problem.

/s

Not sure I can generalize but in my case there appeared to be too much endplay in the mainshaft. The dogs on the gears that engage for 3rd gear (I think it is the middle two??) were not engaging far enough or rather they were engaging but then slipping out. I had exactly the same symptoms as you describe, falling out of gear once I let off the throttle. Under load it seemed OK. I put a 0.065" shim between the inner case and the mainshaft and it solved the problem. As was pointed out by a few folks on my original thread, it is essential to also check primary chain alignment if you shim the right side of the mainshaft. Interestingly, when I checked my primary chain alignment, it wasn't very far off at all with the 0.065" shim on it. So the primary alignment must have been quite a ways off inboard in the original configuration but I never checked so will never know for sure!

The amount of endplay in the mainshaft will also depend on whether you are using a gasket on the inner gearbox cover, how thick it is etc.

Regarding your question about whether there was significant slop in these gearboxes when they were new, I can't answer that. Maybe someone else on here can though! My guess is that there was probably a fair bit of variation in the tolerances in these gearboxes from bike to bike straight from the factory and wear over the years has pushed some of them out of alignment enough to cause problems. If you look at the photos I posted, I could only detect minimal wear on the shifter forks and gears themselves which could also cause the symptoms you describe. When I pulled the gearbox apart, it seemed to me like the components were in pretty good shape and most of the respondents to my post on this forum seemed to agree. This got me thinking about other potential causes.

Have a look here this might solve your problem. Sorry the copy is a bit poor.

https://picasaweb.google.com/109840758061372490709/18May2012#slideshow/5743760370507334482

Jomo service note 01

The link doesn't seem to work.

/s

Okay sorry try this one, it worked okay when I clicked on it.

https://picasaweb.google.com/109840758061372490709/18May2012#

Or this one

https://picasaweb.google.com/109840758061372490709/18May2012#5743760370507334482

Still no go

ARE YOU THE ONLY ONE THAT IS NOT SEING THE SERVICE BULLITIN?

If it was easier to post pictures here I would do it, but this is the only forum that I struggle with, surely there must be a better way - THE SAME AS ALL OTHER FORUMS!!!!!!!!!!!!! I.E. UPLOAD FROM YOUR COMPUTOR, ETC.

Okay let’s try again else where

http://s801.photobucket.com/albums/yy298/bushyberster/?action=view&current=JomoServNotes01.jpg

None of the Picasa links worked for me either.

The Photobucket ones are ok.

Hi. I hope I will not be clouding the issue but many years ago I had a similar issue with my '68 trophy when I first put it together.
In a similar situation, i.e. changing into third and then backing off to change into top, the gearbox would "auto shift" into top.
After talking to my brother about he suggested that he would re-set the gear quadrant engagement, he did it "his" way, set the box in first and set it up like that, the same way a lot of other people have suggested here on the forum. I had tried to set it by the manual. The box shifted fine after my brother re-set it, and has done so for over 10.000 miles. By the way, looking at the picture of your gear cluster, it all looks to be in good condition.

Thank you sir, this one works great. No reason to get testy!

Okay lets try this one:-

[img:center]https://plus.google.com/photos/1098...0507334482&oid=109840758061372490709[/img]

Try this