New member with some drivetrain questions

[49er]

Thanks to all for the replies. I think (guess?) the secondary drive must be sheared at the thread. If so, can this repair be done with the engine in place, or do I REALLY have something messy to do this winter?

How high is the mileage on this bike? If it's over 150,000 mls, you'll probably want to pull the engine and do a rebuild at the same time.
If mileage is low, you can leave the engine in place and remove the torque tube/swing arm assy to get at it.

To remove the drive assy, loosen a few of the case bolts around it to lessen the crush effect. Once you have removed the 4 assy mount bolts, you should then be able to pry it out. Take care not to damage the mating surfaces.

One of our Aussie members recently detailed a repair for one of these. He tapped a thread and then fitted a cap screw with loctite. I did similar when I repaired my diff pinion, but loctited a piece of HT threaded stud so that I could still torque up the stock nut. I ground a flat on the stud end so that the nut could be lock tabbed to prevent it from working loose. You don't have that option if you use a cap screw.

[TitanNeil]

Thanks, 49er. The mileage on the bike is 92,000kms. I have not heard it run yet, so I don't know if it has any problems. One thing I was considering was to remove the engine and paint it silver (its black now). I don't know if the silver-engined ones had painted top ends, or if it was the natural metal finish from casting. Does this sound like a bad idea?

It may come down to the repairs. If I had to pull the engine - I'd paint. If not - just clean it up. I'm at the point where I would repaint the frame as well - but now that I don't really have to...to heck with it. I'll pull the swingarm, pull out the gear, fix (or replace -can I? Or are they a matched set?) gear, touch up frame and swingarm paint, put the whole mess back together, paint the brown bodywork in black with gold pinstripe, and be very, very happy with the result.

Oh, and put the Velorex sidecar on it. Only if the new law they are passing here in Ontario comes into effect. They are outlawing any child under 14 from being a passenger on a motorcycle.

[BassCliff]

One of our Aussie members recently detailed a repair for one of these. He tapped a thread and then fitted a cap screw with loctite. I did similar when I repaired my diff pinion, but loctited a piece of HT threaded stud so that I could still torque up the stock nut. I ground a flat on the stud end so that the nut could be lock tabbed to prevent it from working loose. You don't have that option if you use a cap screw.

Check this out:
Bevel Gear Shaft Repair
(by Mr. Zooks)

Thank you for your indulgence,

BassCliff

[49er]

Neil - Before pulling the engine out, check the condition of the spark plugs. You can tell a lot about the health and state of tune of an engine just by reading the plugs and looking at the piston crowns through the spark plug holes.

I just had another look at my 1100G engine. It has been silver painted all over. I haven't run mine either, but I know the internals are sound by the colour of both the spark plugs and the exhaust ports. It has only done 50,000 kms. I have lubed up the top end (bore) and spin it over, when I remember.

The secondary gears are lapped in at the factory. You need to replace them both as a set. If you repair yours, it shouldn't be too much hassle re-checking the tooth contact and backlash. I found the bearing preload was quite low on the diff, as it will be on your secondary drive pinion too.

[TitanNeil]

Thanks to you both, BassCliff and 49er, you basically told me everything I needed to know!
I just pulled the plugs out, and it appears to have been in a perfect state of tune when last running as all the plugs were uniform in colour, not too sooty and not too clean. I'll pull the carbs and clean them out anyways, they did sit for 1 or 2 years.
I still have to decide whether to paint the engine or not - the swingarm had lots of surface rust on top (battery overflow, i'll assume) so while its out i'll redo the paint on it. I've already blasted and painted the battery box.
I guess that little Vespa restoration will be taking a backseat this winter!

[TitanNeil]

Back at it...

O.k, I took the advice of some knowledgeable members and figured that the threaded end of the bevel gear had sheared off, thus giving no drive. I have just pulled the swingarm off, but left the driveshaft in place. Should this have happened if the threaded end had sheared off? The driveshaft WILL NOT come off the back of the transmission unless I unbolt it from the bevel gear assembly. I think it should just fall off now, right? Or (God, no...) something has sheared in the transmission...

[BassCliff]

Hi,

Does the driveshaft spin freely if the transmission is in gear? If so, there's a slim chance that there's a problem with #1 in this picture:



Let's hope not. Keep us informed.


Thank you for your indulgence,

BassCliff

[TitanNeil]

Hi BassCliff,

Unfortunately the clutch is out of the bike, and the springs are missing! When I grab the driveshaft and spin it, nothing in the engine seems to spin (I look in the cavity where the clutch basket was and the shaft there doesn't move). I can put the shift lever back on tomorrow and try to get it into gear.

[49er]

Sorry to hear that the secondary pinion was not the problem. It would have been an easier fix than going inside the engine.
Fit the gear shift lever and select a gear. Rotate the drive shaft and then see if the clutch shaft turns. If not select another gear and try again. If still no rotation at the clutch shaft, you could have a problem with damaged secondary bevels.

[TitanNeil]

Yup, problem is inside the cases. I put on the shift lever, shifted into a few gears but spinning the driveshaft produces no result, the clutch shaft doesn't move. It feels as if the driveshaft isn't connected just inside the case.
Is this a feasible fix without splitting the cases? I attempted to pull out the secondary gear from the side of the engine (after loosening a few crankcase bolts), but i'm reluctant to pry too much there. Ideas?

[SqDancerLynn1]

You need to pull the secondary gear set out. It can be done in the frame. Just take the bolts out/ they have thread sealer. It will be very stubborn & will take some effort so eat your Wheaties! After you take the bolts out, Use some screwdrivers/ small pry bar, claw hammer what ever you have as a lever between the case & the gear assembly BE CAREFULLY NOT TO DAMAGE THE CASE Move tools from side to side and work it out of the case. Prying on opposite sides at the same time
I would take the side part off first- behind the gear shift cover. If you need to ? use a lg pair of channel locks or pipe wrench to turn the gear assemble a little bit so that you can get under the edge to pry on it
DON'T loose the shims or mix them up !!!!!

[TitanNeil]

Problem solved!

O.k, I managed to pull the secondary bevel out of the side of the case - there was a case bolt that I had missed, once I loosened it, I could pry the gear out without damaging anything.
Not that the results were good. The gear was flopping around in the housing like a well-cooked piece of asparagus. The bearing assembly has totally destroyed itself and I can feel chunks of metal in the bottom of the transmission. The gear itself is only a little notched up, but since I think I should just pull the engine to clean out the bottom end I might as well use decent replacement parts.
The gear still attached to the driveshaft is firmly in place, but I guess these are a matched set and I should find a matched one to replace it.
I tyhink i'll be reading up in the manual on how to shim bevels...
Sad end to this tale, but at leat its figured out.
Thanks to all for the help!

[49er]

It's good that you now know what's up. If the bearing has collapsed, you need to establish if the stock ones are suspect or whether the damage has been caused through the secondary gear case running low on gear oil. If it's poor quality stock bearings, you may decide to upgrade with another make, if they are available from another source.
The bearing races will show discolouration if they have been running hot through lack of lubrication. The bevel gears and shaft will also show some heat colouring, if it has run low on oil.

[TitanNeil]

Next question: since the secondary gear bearing collapsed (O-ring was squished out of place, I think after 20 years it finally ran out of gear oil) I am going to need a set of bevels from a parts bike. Will the 850, or any other GS be o.k? If I put in a matched set from another bike (with shims), are the cases machined accurately enough that they will all fit without shimming again?

[49er]

I doubt that the machining will be identical on all GS1100G cases, so you should assemble with bearing blue and check the contact pattern at the bevels. Also important to set up a dial indicator to check the amount of backlash.
I don't believe that you can fit the 850 bevel sets to your 1100. The part numbers are definately different. Not sure what the physical differences are though.