popping out of first gear, need advice

[Bill__Woods]

I got a 1882 xj1100 that pops out of first gear. I have read all the transmission repair articles in the forum, but still have some questions. I removed the engine from the bike and removed the oil pan. The teeth on 1st and 2nd gears look galled. I was wondering if anyone had any advice on the first gear popping out of gear (I don't see any bent shift forks), before it tear into it. any help or insight would be great!

it is a nice bike, i want to fix it!

[uk1.1s]

Gears popping out

Bill,

Sounds like a similar problem to the famous 2nd gear trouble. What it can be caused by is worn dogs on the gears which don't hold when the power is applied. There may be some pearls of wisdom to come specifically on first gear trouble - but here is my stab at what (in my experience) causes bike transmissions to jump out of gear.

So - Gear Dogs ? (just in case the terms are different with you)

When the gears (on the same shaft) move towards each other during a gear shift (operated by the shift fork) - they fit together with sturdy looking curved 'prongs' which are on the side on the gear wheel. These are the dogs. The side-wall of the gear which they meet with has webs. They maybe even mate with adjacent 'dogs' but not too sure on that - haven't studied the different shift processes. When they are up close they have to turn together because of this 'meshing'.

So - the problem:

When the edges of the dogs begin to wear they become curved slighly at the ends. The force of one driving the other is in this web / dog interface, (or maybe dog / dog interface too - somebody please correct me if this is bull) and the curved surfaces can allow the meshed gears to jump away from each other under load.

A cure:

A friend of mine fixed the problem from me by machining (cheap small grinder or even a Dremmel will to) the webs and dogs slightly so that they key together. I think he even went as far as undercutting the profiles of both so that they were slightly triangular in shape (imagine the dogs wider in section at the top than at the gear wall). This has stopped them repelling each other under load.

If I had any spares I would try and add a picture here - but all my gears are in the bike! Hope all that is not too hard to wade through and understand. Of course, someone may know a better reason first gear on the XS11 to mis-behave.

[TopCatGr58]

Diagrams for 1st and second gear fix.

Hey there Bill,
Here's a rather large diagram that may help to explain and help you understand what is wrong and what will need to be done to fix it. Apologies for the large viewing size of the image file, was created with MS Paint.!!

[uk1.1s]

Getting the message across

Now that's easier to understand than all my 'cack-hander' attempt at describing it!

[Bill__Woods]

Hello again,
Thanks for the help uk1.1s and TC. The pictures are really nice Top Cat. I got the engine out of the bike, i am going to disassemble it this week to inspect it. i will post again when i know more, maybe with some pictures.

[ACE]

Hello,
I just read this post since i bought a 79xs110 f mainly for parts and the price was right.
She has alot of miles but runs good.
The only major problem is in first gear under acceleration.
It seems to be skipping, for loss of better words.
It doesn't pop out but seems to skip a few teeth and back in again.
Can anyone tell us if this problem is basicly the same as popping out of first, or what others refer to as the second gear problem??????????
thanks
Mark

[Mike Hart]

Originally posted by ACE
Can anyone tell us if this problem is basicly the same as popping out of first, or what others refer to as the second gear problem??????????
thanks
Mark

Same deal, can happen in any gear, actually. If it 'skips', you got the prob. Funny how some do and some don't. Might have been an assembly issue.

[uk1.1s]

...and fifth gear too

Just to add to the knowledge - in case anyone hasn't has the same problem - or is having it and, like me, can't work out at first what the cause is.

My intimate knowledge of the inside of my '82 XS1.1s sport started when I lost fifth gear completely half way back home on a long run away from home.

In fifth the power started to 'skip' and I began to think...fuel...noooo...errr...carbs getting blocked ....hmmm, maybeee...then I lost fifth all together apart from a nasty graunching sound.

I pulled over and the engine idled well, no oil was coming out - so started off again. Could easily shift all the gears but fifth just made an unhealthy sound and gave no drive.

I quickly decided to ride home (about 150miles) without 5th gear - and still kept up a pretty good average speed

When I came to pull the engine apart I found no obvious problems apart from some marks on the inside of the crank case. The gears were all in place and nothing seemed to be able to contact the marked surface. I was pretty puzzled and threw it all back together again. Got 34 miles before the trouble returned

Finally traced it - on the second rebuild.

The problem in the gear box was that fifth is kept on from moving too far on the shaft by a conventional circlip. Mine had worn the groove it fitted into, letting the circlip finally move out and the fifth gear pinion could move further down the shaft than it should - grinding the inside of the cases as it did At the first investigation the damn thing had move back again and the weakly held in circlip had 'pinged' back in the groove!

Cured by reshaping the groove and a new circlip that I wired for good measure.

No trouble with the gearbox since - thank goodness, as I had the gear dogs recut at the same time to avoid second / first gear trouble.

[skids]

Re: ...and fifth gear too

Xcellent diagnosis! This one is a keeper.

Originally posted by uk1.1s
Just to add to the knowledge - in case anyone hasn't has the same problem - or is having it and, like me, can't work out at first what the cause is.(snip)Finally traced it - on the second rebuild.

[ACE]

Well Everyboby,
I've had plenty of mechanical experiance but still don't know alot about the XS transmissions.
this explanation and the diagram make it easy to understand now.
AS old as these bikes are getting there are sure to be others will similar problems showing up.
I'm feeling like that many mornings anymore, does anyone have a fix for this?
Thanks for the info.

[Bill__Woods]

Update

I got the time to finally there down the XJ1100. It need 1st gear 2nd gear and the #3 shift fork. My business partner decided to make it a rider, and is going to sell his 1979 XS750SF. He will be joining the new forum soon, i imagine. He has not yet, but it is still in my garage in pieces. It is going to be nice. If anyone is around ohio and looking for a nice XS750 check this link out

Thanks for all the advice on the trans, I will post more of an update when we fix it. No cutting, we are replacing the damaged gears with new ones.
Does anyone know what can damage the #3 shift fork?

Is Anyone around ohio lookingfor a nice XS750?
It is a nice bike i have ridden it several times.
check this link out

1979 XS 750SF Special

[Bill__Woods]

The parts are on order for the XJ1100J. We are putting 1,2,4 gears and all 3 shift forks in it, straight from Zanotti's. Paitently awaiting them to be delivered.
I will post my results.
thansk again everyone!