What did you do today? Cobba's rebuild

[cobbadiggabuddyblooo]

And again the advantages of ceramic coating with the exhaust ports coated to deal with that extra heat contained within the combustion chamber once expelled allowing for the heat to travel straight out though to the exhaust headers and onwards keeping things cooler around the chamber and limiting absorption by the head itself


.

All was flowed with the intake manifolds inplace and matched to the FCR41's






Next on the hit list is to take the barrels to be bored and drop the head back to have all the valve springs and Kent Cams fitted back in place.
In the mean time I'm off to get some copper head gaskets produced for the TRX850 so if ever the bike needs to have the head removed, it's just a matter of re annealing the gasket and reusing it once again so eliminating extra costs.
I figured I can get them manufactured for around the same price as a OEM Yamaha gasket.
Other obvious advantages with the copper head gasket being it's strength.

[sanddune51]

Crikey Brian, You're really going to town on your motor.

I thought I was obsessive about mine. I did everything I was able to do myself to allow my engine to produce torque and power at the lowest revs I could.

You've taken yours to another level with all the processes you've employed. Hat's off to you mate

Is yours intended for track work only or is it dual purpose road and track ?

Keep up the good work, I can't wait to hear about this when it's up and running



Mark.

[M.V.]

Looking good mate!

Are you ceramic coating the exhaust too?

[cobbadiggabuddyblooo]

Thanks lads,
Primarily for the track but I can see I won't be able to contain myself so the road use will only grow..
I'm toying with some lightweight forged aluminum wheels too if I end up traveling on the road too much.
But I really cant afford to loose my license again just for the inconvenience sake plus the fine can go towards some decent track tyres..
I'll get a couple of extra head gaskets made up in std bore also so others can take advantage of this too if either just doing maintenance or top end rebuild plus they can be bored out to what ever size you need to suit your purpose..
I was thinking on having some at 0.7mm as per std and a couple a little thinner to just bump the compression back up to accommodate for any fly cuts to valve reliefs.
I'm just in the process of haggling out a formula and manufacturing for some cush drives rubbers for the Dymag wheel at present as another little side project along with the copper head gaskets.

It's obsessive and where do you stop exhaust has entered my mind.. but a cheap, easy mod for later if need be..
Anyone had experience in Lectron carbies on a 4 stroke motor .. TPS set up may be an issue tho????

[davamb]

Norton has a Copper head gasket Cobba, but I've found annealing it to be a difficult process to get right. Due to the size it's very hard to get the whole thing glowing bright cherry red and then immediately quench. Might be a goer to do in the kitchen over the gas range, but no town gas where I live, so I'm trying to do it with a poxy little gas bottle normally used for blow (torch) jobs.

[Rod.s]

Thanks lads,
Primarily for the track but I can see I won't be able to contain myself so the road use will only grow..
I'm toying with some lightweight forged aluminum wheels too if I end up traveling on the road too much.
But I really cant afford to loose my license again just for the inconvenience sake plus the fine can go towards some decent track tyres..
I'll get a couple of extra head gaskets made up in std bore also so others can take advantage of this too if either just doing maintenance or top end rebuild plus they can be bored out to what ever size you need to suit your purpose..
I was thinking on having some at 0.7mm as per std and a couple a little thinner to just bump the compression back up to accommodate for any fly cuts to valve reliefs.
I'm just in the process of haggling out a formula and manufacturing for some cush drives rubbers for the Dymag wheel at present as another little side project along with the copper head gaskets.

It's obsessive and where do you stop exhaust has entered my mind.. but a cheap, easy mod for later if need be..
Anyone had experience in Lectron carbies on a 4 stroke motor .. TPS set up may be an issue tho????

You don't need the TPS with the ignition unit we're using

[sanddune51]

You don't need the TPS with the ignition unit we're using

TPS isn't strictly essential with the Ignitech ignition, agreed, but gives the option of full 3D mapping of the ignition . This uses percentage throttle opening (10 set points) as well as rpm (10 set points) giving 100 different advance possibilities as opposed to just 10 without TPS.


Mark.

[cobbadiggabuddyblooo]

You nailed it Mark.
Perfect example to see this is on killers hi comp tornado cam profile program he pasted up earlier.

[Rod.s]

You nailed it Mark.
Perfect example to see this is on killers hi comp tornado cam profile program he pasted up earlier.

Then why ask about the Lecron carburettors that DON'T have any capacity for a TPS, if you have no intention in using them!

[cobbadiggabuddyblooo]

I've read of some a couple of weeks ago with a TPS mod on snow mobiles

[Rod.s]

I've read of some a couple of weeks ago with a TPS mod on snow mobiles

Yes, they (TPS) have been tried on 2 stroke (race) engines and they don't work well. They need to be incorporated into the throttle cable which stretches over time, is susceptible to fluctuations in temperature and needs constant adjustment. On any road engine they need a more accurate governance with little if any impedance, hence the use of the throttle butterfly shaft!

[Con Rod]

love this thread

[Rod.s]

You don't need the TPS with the ignition unit we're using

TPS isn't strictly essential with the Ignitech ignition, agreed, but gives the option of full 3D mapping of the ignition . This uses percentage throttle opening (10 set points) as well as rpm (10 set points) giving 100 different advance possibilities as opposed to just 10 without TPS.


Mark.

100 points of reference is great if you know and understand what you're doing, useless for someone that doesn't even understand why a TPS is even fitted

[cobbadiggabuddyblooo]

options ,options,options,
MMMMM I'll have to remember the age of entitlement is no longer with us and an ever tightening budget..

But
TPS values can easily be re calibrated via the ignition program if stretch becomes an issue on a cable set up for a TPS.

[cobbadiggabuddyblooo]

Busy day yesterday, cleaning all the bolts that hold the upper and lower crank cases together.
Wire brush and kero bath and quickly run the die over them so all nice and clean, just like the threads in the case themselves which I had run a tap through a couple of weeks ago.
All clean, new main bearings and time to place the crank into the upturned top half and then place another 3 pieces of plastiguage on the crank before bolting it all together.
The 6 main m10 bolts torqued up around the crank then started on the other 20 odd bolts around the outer edges of the case .
Started on one of the smaller m8 bolts and thought to myself this doesn't feel right but lets just give it a touch more and CRACK
Straight away I took the torque wrench off the bolt and put the ratchet on to loosen it off.
and to my surprise it loosened off and screwed out.
Thank god I had cleaned all the threads out as any gunk in there and things would have easily gotten stuck and just sheared the bolt right in half.

So now I will not take any chances and I'll replace all the bolts..
I can only surmise after seeing all the silicone used between the cases on a previous rebuild by someone,there may be a good chance all the smaller M8 where just done up with a socket as the torque spec is 4nm under most torque wrench ranges and you need a smaller nm/ inch pound torque wrench which not every joe blow has.
The smaller m6 bolts are even down at the lower end of the inch pound range on my torque wrench but it just drives home the fact these torque specs are placed there for a reason.
The young fellow who bouht a head off me a couple of months ago had suffered a similar fate by over tightening the cam caps. and again the trx I looked at last week locally here on gumtree had done exactly the same thing with the cams locking up in the head.
Well least the engine number is still original on the bike as not much else is now

Crank came up ok 0.035-0.040 gauging in at the upper desired limit (0.026-0.038) with a service limit at 0.1mm
So thats a blessing