What did you do today? Cobba's rebuild

[cobbadiggabuddyblooo]

Spent a few hrs each day over Easter and finished dialing in the cams.
Inlet opening 13 / 53 closing. 2.3mm lift at TDC
Exhaust Opening 46 / 27 closing. 3.2mm lift at TDC

Static compression 12.5:1
Dynamic compression 9.4

Next fun and games will be to trim 0.5mm off from around the inside of an old MLS head gasket.
There is 0.25mm overlapping inside the bore.
Peter in at Comp. Coatings showed me how he trims his back with a dremmel and flapper to finish them off. I've got 3 old used MLS gaskets to practice on but if I cant manage it , I'll look at laser trimming the new gasket.
In the mean time I'll use the copper gasket again.

[Mincehead]

Mark it with permanent marker pen, CAREFULLY and yes, Dremel it with sanding rounds on the rubber arbors, like this one:

http://www.raygrahams.com/products/1162 ... 40732.aspx

A steady hand required mate.

[hendocdog]

Thanks Mince..
In hignsight I should have ran the bike with the TPS turned off while sorting the air/fuel and done my dyno runs with it off first. Advance curve was close but the TPS map was too advanced.

Tps values at 10% at 4-7,000rpm where as high as 45-47* and this is what I feel was causing the excess cylinder pressure and the copper head gasket to break its seal.
It wasn't until I began to ride it long and hard then it would leak.
Through those large sweeping corners in 3rd or fourth at 5-6000rpm riding the throttle till the exit may have been enough to cause mild detonation and excess pressure.
Wouldn't be surprised if the excess heat from advanced timing and tight piston/bore tollerence took the ceramic coating from the skirt.
Good testimony to the strength of the Arias forged Pistons and the sacrificial lamb being the ceramic coat on the skirt.
New rings, plateau hone and skirts recoated so I'm thinking I might try the copper head gasket once again. In theory the copper head gasket will cope with the higher compression..

Hellk there mate.
i am currently doing some bits and pieces to my yamaha trx and am looking to blue print the engine and raise the compression.i hav read all your posts but wondered if you have skimmed the head. If so how much did take off??
Regards kevin

[Mincehead]

Hahahaha, you FOUND IT!

[cobbadiggabuddyblooo]

Didnt skim the head at all.
I have Arias Pistons making pistons for me that I sell to suit the TRX and I raised the piston deck by 0.3 mm .
They are 12:1 and weigh in 5 grams lighter than standard OEM TRX PISTON, rings and pin so rebalancing the crank is not nessesary.
My own personal Arias Pistons had maximum weight removal so the are 25 grams lighter than std , plus the lighter Carrillo rods hence the rebalance on mine.
Plus they can accomidate oversize valves and i still have good piston/valve clearance with the cams I run (0.5 extra lift and 246/253 duration)
It makes more sense to remove material from the base of the barrels than to remove it from the head if you are looking at that option.

[Killerwhale]

Do Arias make a TDM900 set??

Didnt skim the head at all.
I have Arias Pistons making pistons for me that I sell to suit the TRX and I raised the piston deck by 0.3 mm .
They are 12:1 and weigh in 5 grams lighter than standard OEM TRX PISTON, rings and pin so rebalancing the crank is not nessesary.
My own personal Arias Pistons had maximum weight removal so the are 25 grams lighter than std , plus the lighter Carrillo rods hence the rebalance on mine.
Plus they can accomidate oversize valves and i still have good piston/valve clearance with the cams I run (0.5 extra lift and 246/253 duration)
It makes more sense to remove material from the base of the barrels than to remove it from the head if you are looking at that option.

[cobbadiggabuddyblooo]

Give me 24 hrs and i can find out for you Mathias.

[cobbadiggabuddyblooo]

Bit more tinkering over the weekend and have made a template for the tray I'm making for under the carbies to keep the hot air out that passes through the radiator so I can channel mostly the cool air coming in from under the front of the tank.





I've got some fuel line on the way that I'll slice along to dress the edges around the manifolds and once the motor is in the frame, I can tidy up the front with a little hinged flip top triangled piece to sit on the frame up to the head stock.
There is a cross member on the frame close to float bowls and have a couple of ideas on what to do.
1 being to roll a piece around the cross member with a small length to either lap over or see if I can find some plastic H panel type joiner and that should seal the back edge.
I left enough material on the side to fold and edge to attach the small side wings to tuck under the tank and I'll attach it using the H panel joiner too.

http://www.bunnings.com.au/james-hardie ... r_p0710220

[cobbadiggabuddyblooo]

Chance has I was just chatting to a guy with a gsxr 2001 model and now my rear caliper is finally sorted. They are slung under the swing arm like the trx and 220 mm.
I'll get Dave Kellett to machine it to fit and sleeve it to take a 20mm axle.
Found this light weight wavey disc from a YZ that will work too.

Head gasket is sorted and will fit that after Anzac weekend and get the motor back in the frame by the end of the month.

[cobbadiggabuddyblooo]

220mm Caliper mount and caliper arrived and just needs a top hat spacer made to reduce the axle from 28mm to 20mm .
Caliper axle mount width is correct but around 1.5 mm needs to be removed from the caliper mount to centre the disc to the caliper .
The 1.5mm removed will be then added as the thickness of the top hat peak section to give correct wheel spacing again.






I still have the top mount caliper which is a little lighter and tidier looking but it will mean welding the tee mount inside the swing arm. The DT 230 rear calliper comes with a sexy Yamaha stamped guard to neaten things up too.

[cobbadiggabuddyblooo]

Motor back together and resprayed black for a change.
Handy hint on how to fit the motor back in the frame, 1 man job and took me all of ten minutes.
First shuffle the motor under the frame and then screw in the engine mount bolts into the head and attach a ratchet strap to each bolt.




Attach the other ends of the ratchet straps to a common rigging point above the motor/frame.
Take up each strap a few clicks at a time until up into the frame at a working height.
Next use a jack at the rear of the motor, raise it and locate the bottom rear engine mount and bolt in place. You can then pivot the motor from here on in.


Chock the front of the motor and remove the ratchet straps and engine mount bolts in the head.
Move the jack forward and lift the motor and align the top rear engine mount and bolt in place.




Next remove the front engine chock and reposition the jack again and align the remaining front engine bolts.



With the motor back in place it allowed me to continue fitting up the heat tray I made up for under the FCR's.

[Mincehead]

[cobbadiggabuddyblooo]

Yahoo, cranked over for about 4-5 seconds then away she went purring like a kitten once again.
So ran it up to 107* then turned her off.
Tomorrow morning I'll dump the oil, check clearance then retention the head once again as I try the copper head gasket 1 more time.
Licenced to ride again next Tuesday so i've got to take it for a ride before Dave Kellett does the new mods planned.

[wreckage]

Yahoo, Licenced to ride again next Tuesday

Congratulations!

I'd like to see the grin on your face when you throw yer leg over.

[cobbadiggabuddyblooo]

Funny tho I put my helmet on today and I could still hear this wereing sound of a blue and white helicopter above me..
Bit like a built in limiter..