After hearing my own start rattle and the suspect sound of another high miles K bike i am determined to find a reasonable and not too expensive fix. (I could not get my rivets to move with thte unit out of the bike) I have read around our forum and there a a few threads on this topic. So far apart from the german guys with a machien shop at their disposal no one has done this. (that i can find). Replacing with a 12 rivet unit is ideal butt it IS expensive..EBay..AUD 450.00 ++ Motobins AUD 400+++.

Recently I bought a later model engine for spares and mainly the output shaft. getting home and open it was a 6 rivet unit with bolt inserts!! Someone beat me to it What has been done is this. removed the rivets. Turned the absorber 30 deg to position new alloy above the gear rivet holes. Drilled new bolt holes and macheind the surface beneath the the nuts flat for them to be pulled down securely. Can any one see where this might go bad?? I think it shall be a cheap fix. I am going to follow through on this so we all have some idea on how it pans out.
I have a picture somewhere of the gear side..somewhere...


I have another spare that I pulled down and spoke to local machenist who thinks it will be a fairly easy fix to mill a bit of the alloy away for the nuts to seat properly and a lil bit of the hardend gear to countersink the hex heads. This will be the hardest part as it will be hard steel. here is pic for those who have not seen one open.

Any thoughts or suggestion guys??? I will be going back to the shop in about 4 weeks.

Ask machinist about balance of shaft? Its probably factory balanced, but when you put six screws with hexheads, what it means four shaft balance?

No suggestions but will be interested to see how it goes. Mine is getting noisy when the engine is cold here in Guyra winter mornings. Haven't seen one apart before either, so that was good. Thanks for posting.

nino wrote:Ask machinist about balance of shaft? Its probably factory balanced, but when you put six screws with hex heads, what it means four shaft balance?

I had thought about this. Jeff did not seem to think it would be a problem. There are no noticeable factory balance marks as with the clutch where you can see they have drilled metal out to achieve balance.

The rivets moving and flogging the holes out does not seem to cause a problem other than noise or catastrophic failure when they fail.. If all components are the same weight and centered properly and the milling is exactly the same for each piece it should not be a problem.

Albyalbatross1 wrote:

nino wrote:Ask machinist about balance of shaft? Its probably factory balanced, but when you put six screws with hex heads, what it means four shaft balance?

I had thought about this. Jeff did not seem to think it would be a problem. There are no noticeable factory balance marks as with the clutch where you can see they have drilled metal out to achieve balance.

The rivets moving and flogging the holes out does not seem to cause a problem other than noise or catastrophic failure when they fail.. If all components are the same weight and centered properly and the milling is exactly the same for each piece it should not be a problem.

Probably doesnt matter, because diameter isnt so big as on the clutch

Ask your mate what he thinks of using shoulder bolts in a grade 5 steel they would be the best to use as the shoulder needs to be lightly pressed into the hole and then the torque on the bolt only holds it in and doesn't do the job of preventing any lateral movement.
Probably pay to make the bolts fron a larger bolt and turn the dia to suit and cut a new thread.

What's about knurling screws and nuts?
I believe that you can find them in grade 5.
You would not have to machine a recess for the heads. Their is enough space on the aluminum side to put the nuts.

[quote="Crazy Frog"]What's about knurling screws and nuts?
I believe that you can find them in grade 5.
You would not have to machine a recess for the heads. Their is enough space on the aluminum side to put the nuts./quote]

I think they'll work as long as they don't have the longitudinal grooves and are of the proper grade. Torque will be important as these seems to be friction joints and preload is neccesary to avoid displacements and subsecuent deformations.

Best regards

JAP

I like Rick's idea to press the bolts into the steel section.

How about turning some threaded 'rivets' with heads to match the originals and an interference fit in the holes. That would avoid having to machine the hardened steel.

Paul.

The knurling is there to prevent the bolt turning when tightening the nut . I dont believe the knurled section would last very long with the lateral stress it would get. The best of all solutions is hot riveting but a bit impractical for a limited production run.

You said "Lets get serious" ?
It took me some time to find it among my archives, but I knew that I had it.
(I have a lot of archives that I should make available )

Somebody was serious and documented the repair. This is professionally done.
I believe that the original was posted on the old Flying Brick forum and it's in German.
You can download a copy of the full PDF HERE

Here is a preview of the repair:


This is an outstanding repair!

CF

A lot of work went into that but I will have to dissagree with you Bert.
If the pictured bolts were the ones used then you have the top edge of the threads taking all the stress and that will wear out much quicker than the rivets did. The idea is very good but as I have said before shoulder bolts are what is needed and to be pressed in with about 1/1000in interference and 12 of them would last the life of the drive.

I agree with rick. A lot of work in there for the repair...It is a solid repair. The hard part is milling the hardend steel..
I pulled down the repaired output shaft today for a look see.

here are the nuts used. Very little machining to be done. just enough for the nuts.

And when i showed a friend of mine for a third eye.. he simply said.."HUH! There just threaded rivets..!! get some more the same diameter and a bit longer and thread em bolt em up!!""

Who new it would be that simple...Now who do we know with a mini lathe to mill out a bit of alloy and hold a rivet in the chuck to thread it??? This repair should last .

Alby,
Rivets are generally soft, so I would go for HT Allen screws with the heads turned down. If the gear wheel can be drilled I would be inclined to go to 8 mm with an interference fit. If you stick to 6mm then you could bolt it / loctite it together and then machine or file the heads down to get enough clearence




Food for thought.
Paul.

sidecar paul wrote:Alby,
...I would go for HT Allen screws with the heads turned down... bolt it / loctite it together and then machine or file the heads down to get enough clearence




Food for thought.
Paul.

Hi there, I think that Paul´s option is the best, a bolt is a much better fastener than a cut threaded rivet.
Youll use the head to reach the proper torque and develop all the bolt´s grip capacity and then get rid of it to allow the required clearance. Final head heigth no less than 1/4 of the original, if possible 1/3. Avoid overheating the bolt while grinding/cutting the head. Interference fitting and 8mm diameter will grant more lifetime.
Best regards
JAP

i agree jap, paul and rick

the whole thing depends on "sheer" strength of the fixings ...the tightening process just stops any movement obliquely ....

i seem to recall that soft things wear out hard things ......well the result is that the soft things give way enough to start some movement and then the hard things just flog themselves to death .

a good solve for not much money alby ....it would really be great if there were a way to retrofit some steel sleaves into the old damper housing assembly (over sized ) with standard size bolts with lowered heads and get back to a 12 fixing solution ..

congrats on the process alby ...hope she comes together soon

I have just opend up another 89 K engine to find another old 6 rivet shaft. That is two engines now that should have been 12 rivet units. I also noted the history of Both engines having work done on them previously. I am wondering if someone has swapped the output shafts out and sold on the 12 rivets??

I am also going to see a fitter/turner today about the iterference fit idea. Turnng the heads doen on the bolts is a good option I agree. i will see waht he has to say.

I once used some bolts that had heads like washers absolutly flat with 4 holes in it for a 4 pinned spanner to fit. the thing was they screwed together one inside the other one a bolt the other a blind nut. both looked the same except for the thread on one of corse, but I have no idea what they were called. I believe it was a stainless boat fixture they went into. they may be ideal for this type of repair

Those type of bolt are often used for a fitting that has to be fitted to the hull of a sandwich foam fibreglass construction

Yes too light for this application. but knowing them they do seem to be the right type of shouldered bolt and nut for this task although a tougher unit would be needed as in higher tonnage material

That type of bolt would do the job well.

I caught up with the fitter today and he had a look . he suggested the same as Paul. Use high tensile bolts and machien the heads down.

He is going to do this-
Turn the ABSORBER GEAR WHEEL 30 deg and drill new holes in the aluminium using the gear as a guide.
Mill just enough alloy off the inside edge so the nut and washer will sit flush
Turn the Bolt heads down to fit with just enough clearence under the idler gear

Does anyone have some idea to what torque these bolts should be done up to? I was thinking between 5 and 8 flbs going buy their size.

What is the thread size on them, that is what you go by.

i would suggest a bolt with a shoulder right up to almost the nut fitting before the thread starts , nylock nuts ...a thin flat washer before the nut .

might have to cut a bolt to get the shoulder length correct

looking at the clearances an 8mm would be best ....but more machining will be required into the casting of the damper ...unless you can manage the 12 x fitting , then 6mm would be fine i guess ,

as you suggest alby the tightness wont need to be extreeme as its sheer strength of the bolt that is the determining factor ....might pay to research some metalurgy regarding the bolts and the aluminium damper housing though ..

hope it goes well mate ...many of us are awaiting the outcome ...

btw ...have a great break ..

Rick G you were right. I have found a page of recomended torques for bolts and it uses the thread pitch/size/diameter and steel type.

Charlie... I had not given the galvonic reaction much thought. Oxides loose in the engine!!!! NOT GOOD me thinks now .. I will ask hi about what grade of stainless perhaps and i will get him to use your shoulder length idea as well. there is plenty of room on the outside for a bit of thread and using a spring washer will allow a bit more shoulder to come right through almost. Not too sure about nylocs in the harsh environment heat/oil.

You are far better off using high tensile steel that stainless. Stainless and aluminium don't get on at all.
There are other factors about using stainless that are far too involved to get into here but it is not the right metal to be using in that application.
You are best to use a washer that will allow the shoulder to come all the way through.

+1 ..stainless looks good ...but its just a show pony with aluminium

Thanks...I will go with the high tensile and a washer/spacer that will bring the shoulder right through.

Alby if your using a machine shop they should be able to make you some fitted bolts, but the holes will have to be reamed to suit. Maybe look into getting some clutch plate bolts from a speed shop or Rocket Industries or VPW they are both online. You should be able to get them in the size you need if they are 8mm i think nissan skyline or such would suit. ARP make them from memory.
The reason i suggest this is the clutch plate bolts on most cars are hi tensile and are a shouldered bolt so that the clutch aligns and doesn't move.
You might even be able to scrounge some from a local wrecker up there. Most of these bolts wont really have seen any undue stresses.
Just my 2 cents worth. I agree with Rick in that i wouldn't use stainless in a sheer application, Stainless is not designed for this as it work hardens and is likely to shear under stress loads. Not something you want in the bottom of your engine.

Bert you're comment is worth more than 2cents it more like gold in them thar posts

I picked up my parts today and there were six shiny new holes with a lil bit machined off for a washer to fit nicely. You can see where the old rivets were. There were also 12 new bolts...Might as well do the spare as well hey!!


i then fitted the bolts for a look see and they needed an extra turn or two of thread to be sure the nut pulled up tight on the washer.


next I have to cut the bolts back to length. Clean up all the parts and get all burs off every edge. Order some new rubbers/seals/o-rings and a replacement big end bearing.
Wait untill i have the engine out for the rings and head rebuild and then road test!!!!

One thing to be aware of is that rivets expand when they are fitted which changes the whole deal.When you use a bolt and nut you are depending on friction to keep everything from moving at all.The slightest movement starts the rot. With a rivet when driven it changes this to predominately shear which is more effective in stopping the movement starting. I have had some experience with solid rivets in a homebuilt aircraft I built some years ago.The alternative was pop rivets which rely on friction and unless you use very expensive structural pops they are not as good. In saying this it is probably not practical in this application however I would caution you to have a look at some info on bolts and thread lengths drilling sizes etc as used in the Aviation field. Aircraft bolts are very good quality and are available in a great variety of sizes with low profile heads and nyloc nuts if required.If you have an airfield somewhere in reach see if you can have a talk with a LAME.(Licenced Aero Mech Eng.) about it . they will have a wealth of knowledge on the subject. On the other hand what you are doing will probably be perfectly satisfactory.
Regards Dennis.

Hi Albyalbatross1 , Have been following your post on the rivet repair / replacement with great expectations and was wondering how far you have got with it ? I am sure it is going to be a big success as i can see that you have put a lot of thought into it, and with the added ideas of the other forum members I dont think that it can go wrong ! I can hear the telltale sounds that my 1984 RT (121000Km) is going to need attention sooner or later . I am planning to look at it early in the new year and try and follow the same method you have used. HAVE YOU FINISHED THE PROJECT AND HOW IS IT WORKING ?? Looking forward to some good news.

Lazyboy.

I too have opened up a '89 motor expecting to find a 12 rivet shaft and only finding a 6. What i believe is that the 12 rivet was used first in the 16V motor of 1990, in place of the 6 rivet shaft which was then obsoleted and replaced by the 12 rivet. This new shaft was supplied as a direct replacement for the 6 rivet shaft from '86 on, which of course is different to the '83-'85 shaft. So any 8V motor '86-'89 ,that has not had a new shaft fitted at some stage will still have the 6 rivet shaft, but if it has been replaced then it would be the 12 rivet shaft.
I know the parts books show the 12 rivet shaft from '86 on, but that is because the 6 rivet was superseded by the 12 rivet in 1990,and any parts books printed from that date would only show the 12 rivet shaft because the 6 rivet shaft was then obsolete. I bet if you could dig up an original 1986-89 parts book, it would list the 6 rivet shaft only.

good thoughts robin

[quote="robinm"]I too have opened up a '89 motor expecting to find a 12 rivet shaft and only finding a 6. What i believe is that the 12 rivet was used first in the 16V motor of 1990, in place of the 6 rivet shaft which was then obsoleted and replaced by the 12 rivet. This new shaft was supplied as a direct replacement for the 6 rivet shaft from '86 on, which of course is different to the '83-'85 shaft. So any 8V motor '86-'89 ,that has not had a new shaft fitted at some stage will still have the 6 rivet shaft, but if it has been replaced then it would be the 12 rivet shaft.
I know the parts books show the 12 rivet shaft from '86 on, but that is because the 6 rivet was superseded by the 12 rivet in 1990,and any parts books printed from that date would only show the 12 rivet shaft because the 6 rivet shaft was then obsolete. I bet if you could dig up an original 1986-89 parts book, it would list the 6 rivet shaft only.[/quote]



I put a 12 rivet shaft into an otherwise stock 1984 vintage K-100 with no difficulties, other than getting the thing out of the bike. There is no difference in fittment. I have done this twice.

I am also of the opinion that even six stout bolts is not enough. I wouldn't waste the time and money. Buy the 12 rivet unit and you won't ride around chewing arse crackers worrying about your modified output shaft letting go at an inconvenient time!

Btw, since you are in there, ditch the spring loaded half of the split gear. The absolute only time it does anything is at idle and even then I have ridden engines with the spring loaded gear deleted and there is no excess backlash to worry about. You also completely eliminate the infamous K bike whine. It has more of a growl at idle. Eliminating the spring loaded half of the gear lightens the output shaft and slightly improves throttle response.

While you have the intermediate housing off, don't forget to update the starter sprague with the newer part that has oil drain holes in it.

When the 12 rivet shaft was introduced, also the anti backlash mechanism was revised.
4V models have a far less pronounced typical K whine.

Its been a busy weekend here in our old shed.   I have finished repairing the output shafts failed rivets. 

Not sure what these actually do but put em back as they came out.(somebody tell me please?)


They are nice and clean and seated in just so.


Now is also a good time to replace the pin that holds the tension on your absourber gear wheel and the spring itself.
This little pin can pressed out and new one pressed in with permanent lock tite.
Front view.
Rear view
Then you can place your absorber gear wheel back into place and fit the new bolts through the new holes.

Then you can see how much you need to take off the bolts. They were just easier to machien the bolt heads down this long.

Then you can cut them to length. and press them in again. I went with a nice snug interference  fit.

I then used lock-tite..for transmissions permenant. then torqued them all up to 65 inch/lbs. I decided on this as 60 was about right for the 6mm bold and thread and just to be sure in my mind.

Then replaced the backlash spring and idler gear.  You can see the bolt heads have just enough clearence for things to move as they should.

Now I have two of these. One out of a working engine and my damaged one now a spare.

It is a fairly simple operation if you have access to a small lathe or local shop. We lost all our local fitters to the gas fields west of here and our last engineering works is selling off their gear. the only remaining works are only doing mine/gas contract work..

great job alby
this should demystify the whole thing big time.
well done !

that centre pack ...looks to be similar to a clutch pack of sorts ...I wonder if its to allow a little slippage between the central output shaft and the rubber vane carrier - thrust washer ...and driven gear assembly ..whilst still maintaining a close up fit when the clutch assembly is correctly installed with the thrust washer between the clutch basket assembly and the damper assembly. (that's a mouthful )

(you know that little bit of movement you spied before) and I recon is most of our low idle output shaft -clutch type noise if the rivets are ok ))

 

well done - old prob
we had a few guys here that took a different way
but usually: change to new version es easier

Description

CAD Drawing 1

CAD Drawing 2

zonenfeile

I had looked into those drawings a while back. being in a smallish country town none of our local machienists were able (willing) to work with hardend steel. 


As of the weekend just passed we have a bike out there with the repaired Output shaft rivets. Charlie has fitted them up in Gerty.  Charlies Easter weekend effort!  The improvement in sound at start up is amazng. No more rivet rattle just the cushening rubbers leaving a little slap.