What did you do today? Cobba's rebuild

[johno440]

Don't bother, I should've checked the downloads section first

[cobbadiggabuddyblooo]

Update on how things are going, Front end should be completed hopefully by next week and with a bit of luck I'll have the head back and then it's time to remove the valves again, bore out the barrels and have the bottom end balanced as the 878 pistons are heavier than std..
Then off to have the pistons,valves and combustion chambers and exhaust ports ceramic coated.
Over this period of late it has given me the chance to research so much information on how a combustion motor works and the advantages of tuning a motor for the optimum efficiency and output you require.
I've read and gained knoweage on the theories of why motors are engineered the way they are, and ways and means on how to harness the most effecient way to gain power. Harmonics, friction, heat to name a few and the list goes on.
Exhausts pulse and systems relative to diameter and length for the desired output and how to get the optimum from the fuel mixture and timing.

So I thought I'd share a some of this information I'd gained with you if interested.
http://www.gonefcon.com/whatifdyno/combustion.htm

Please check this link out...

[cobbadiggabuddyblooo]

And other good educational tools on just some basics to suspension
http://www.promecha.com.au/leverage_linkages.htm

http://bikearama.com/theory/motorcycle- ... explained/

http://www.gostar-racing.com/club/motor ... set-up.htm

http://biketrackdayshub.com/motorcycle-tyre-wear-guide

and I,ve found a weath of info on this link above ,giving a range of subjects when you go to the home page.

[rbaron25]

I'll just take the summary ) with a dash of lemon thanks

[cobbadiggabuddyblooo]

Off my butt once again now Rod is back from holidays and its time to attack the rear end and suspension. First thing I need to do is remove the pivot bearings and swing arm bearings. . Once I had the bike strapped in place it was just a matter of freeing up the rear caliper from the swingarm, then removing the dogbone and taking the linkage off for the suspension. Once I had that free the pivot bushes slid out then remove the seals and bearings. A little stubborn but a few minutes with a little heat from a propane torch and out they came.. I figured once looking at the bushes things would not be healthy and I was correct so once I had the swingarm removed, I new I was in for much the same just by inspection of the swingarm pivot axle.. So time for new pivot bolts, bushes , bearings and seals. And yes you guessed it, swingarm bush and bearings.

[cobbadiggabuddyblooo]

Damm photobucket via mobile phone. Pics didn't appear..

[cobbadiggabuddyblooo]

. . . . Obviously not my day

[cobbadiggabuddyblooo]

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[cobbadiggabuddyblooo]

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[cobbadiggabuddyblooo]

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[cobbadiggabuddyblooo]

I give up... Wait till I get to my laptop again

[cobbadiggabuddyblooo]

[cobbadiggabuddyblooo]

. Finally got it sussed as you can see some pretty extensive wear .. One of those things on the to do list that just never got around to doing until now at 125,000km's. So now looks like a new agenda after replacing all these bits.. Check , Repack or lube at regular intervals.. And a big thanks to Rod once again for allowing me to ride his trx for a few days. Funny even though his bike has my old forks set up but the first thing I noticed was the turn in with his running a 60 series front tyre compared to a 70 on my own front rim. That feeling when half way I to the corner of the front end dropping away under you like its about to slide away ..

[cobbadiggabuddyblooo]

Time to get off my butt and do a little more to the bike .so I went and picked up the front end and here is the axle mod that Dave from Dave Kellett engineering here is Brisbane (down at Slacks Ck).. He has managed to keep the R1 forks in std format without modifying them in any way. So if need be I just track down another fork.
He dug through his barrell of axles and came across another 17mm axle that is longer than the std TRX front axle.
It was a simple matter of welding a bush on the bolthead end of the axle ,then machined spacers for each side of the TRX front wheel, he then machined a bush for the other leg where the axle screws into.
He then machined the end of the axle so it fits through the fork without fouling the thread in the fork and the because of the extra length fitting all the way through both legs leaving enough thread to place a nut on the end of the axle.
So pretty well the same set up as your back wheel or swingarm pivot, a bolt (with nut) not a screw like the std front axle.








I had the option of machining a couple of mm off the inside face of the forkleg to mount the speedo drive and place a small lug on the leg but opted to just fit an electronic speedo.
The brake callipers only needed a 1mm washer between the mount and calliper to centre them over the disc.

Next job is to press all the bearings into the swingarm and suspension pivot points, replacing all the bushes and closing the sloppy std tollerence with new bolts to get a nice snug fit within the bushes.

[cobbadiggabuddyblooo]

Suspension pivots where a simple job of pressing them in using a vice with a socket to push them through to sit centrally inside as room is needed each end to allow for the seals.
I just marked on tyhe 11/16 socket that was used to press them into place so as to get the bearing sitting central .




You can see on the next photo how on the pivot point on the swingarm where the dogbones bolt upto, Yamaha machined it oliptically so when it comes to punching the old bearings out, this leaves a part of the end face of the bearing exposed so you may plave your punch onto it to aid removal. The swingarm bearing have the same set up to aid in removal of the bearing.

So be aware when pressing in the new bearings that the bearing goes in the right way as the ones supplied to me have a wider end face on one end.









And the swingarm bearings where pressed in using a long piece of threaded booker rod with the end cap on one end of the swingarm for the bolt to travel through and tightened on the other end with spacers and another socket to push it all the way home..