[ace.cafe]

Stainless header with O2 bung and Ace spec reducer.

Looks good!

[gizzo]

Looks good!

Thanks 

[gizzo]

I finally had a chance to go for a roll around the hills on the GT today. I don't know what made the difference, whether it's the little porting job, the new exhaust valve or the big header,  maybe a combination of all three but Wow! It pulls like a train when the revs are up!
It feels like maybe it's lost a bit of it's bottom end plonk off the line but makes up for it when the rpms build.  It'd be interesting to see how much power and torque it actually has but the butt dyno says it's good.
Also has a different exhaust note now, more of a bark than before. The thick wall stock pipe must have been soaking up a bit of the racket.

Happy days.

Oh yer,  and the sweet handling is back again with the new fork oil and tapered steering bearings. That was an expensive mod but worth it.

[Arschloch]

Nice, I could imagine the loss of the bottom plong is maybe just subjective feeling that comes as a result of the improved bang at higher revs.

What oil did you use in the forks?  The recommended 2W is bit too watery isn't it?

[gizzo]

Nice, I could imagine the loss of the bottom plong is maybe just subjective feeling that comes as a result of the improved bang at higher revs.

What oil did you use in the forks?  The recommended 2W is bit too watery isn't it?

You could be right about the missing plonk. I have 12.5w oil in the fork. Because I had a half bottle each of 10 and 15, mixed them together instead of going to buy a fresh 15w. It seems to work fine. I'm pretty interested in trying the YSS emulators now I've seen them. They're only $150.

[ace.cafe]

The big diameter header loses low rpm torque and adds high rpm power.
The inner sleeve that you added per my suggestion helps to alleviate the symptom to some degree by keeping exhaust gas exit speeds high for the few extra inches down the header, and helping to reduce exhaust reversion.

[gizzo]

The big diameter header loses low rpm torque and adds high rpm power.
The inner sleeve that you added per my suggestion helps to alleviate the symptom to some degree by keeping exhaust gas exit speeds high for the few extra inches down the header, and helping to reduce exhaust reversion.

I remember that conversation when the Carpy's header was a thing going around. Remember it had the small tube for about the first 12 or 16 inches? Funny thing, I had ordered some mandrel bends to make my own pipe per those specs and then they never showed up. Meanwhile I needed to order a bunch of stuff from H and thought I may as well have the header thrown in. The day after the parcel from UK arrived, my mandrel bends from the next state over showed up too! I'll still make that pipe, but there's no hurry anymore. I'll get onto it some other time.

[Arschloch]

You could take the HMC header, cut it after the first bend and weld in just one bow of the smaller diameter.

[gizzo]

No way, it's too pretty for that.

[ace.cafe]

I remember that conversation when the Carpy's header was a thing going around. Remember it had the small tube for about the first 12 or 16 inches? Funny thing, I had ordered some mandrel bends to make my own pipe per those specs and then they never showed up. Meanwhile I needed to order a bunch of stuff from H and thought I may as well have the header thrown in. The day after the parcel from UK arrived, my mandrel bends from the next state over showed up too! I'll still make that pipe, but there's no hurry anymore. I'll get onto it some other time.

The length to the step in the header is somewhat related to rpm for the reflected wave. I figured 16" was a pretty good approximation, and that is also what Carpy's had.

Putting the sleeve in the H pipe created a stepped header too, but a much shorter distance for the reflected wave. It is probably tuned too high in rpm for the reflected wave in our machines, but it still does the job of keeping exhaust gas speeds up for better extraction and less reversion.

To go from 34mm to 38mm in one jump right at the head joint causes the exhaust gas to take a very early and rapid slowdown, and trades that velocity off for higher pipe pressure, and that is a recipe for reversion.
Not so bad at full tilt, but not desireable at lower rpms.

[Arschloch]

No way, it's too pretty for that.

  , you may have to weld on a bigger size lambda bung anyway should you want to take it to the dyno.

[gizzo]

Already done it. It has the autotune module.

[Arschloch]

Did an complete engine overhaul. Big end bearing was toast, piston sized and bit tight on the wrist pin. What caused what is hard to say, however since the piston was non stock forged with a flat top it might have gone first and caused the other symptoms.

The good news is after 20tkm the rest of the engine is totally unimpressed, main bearings show hardly any signs of wear, gearbox is as good as new.

Back together with a new crank and stock piston the engine is back to life. I was a bit surprised that they apparently stopped using a bronze bush in the small end. Accordingly to HMC this is the new practice.

Other than that the rebuilt is about as straight forward as it gets, no special tools required and no fancy assy methodologies required. Very happy with that.

Back to the road.

[gizzo]

Nice! You must have needed one special tool though, the flywheel puller? And maybe a clutch holder?

[Arschloch]

Yes, a magneto puller and an  kitchen oven for the assembly of the needle bearing race at the timing side of the crank.