YZ Blues, well it is blue afterall

Thanks Robo, I reckon I pulled it down just at the right time, was tempted to leave it as it only had 40 hrs on the entire engine, but that mongrel little rainforest S/T Craig and I tried cutting in last weekend I reckon did it, as it lost all lowend power for a while and never really came good again.

I’m felin’ better, sons almost over it, daughters just starting into the bad bit and the Mrs is a crook as, but she didn’t have many flus as a kid so this is an old one doing the rounds again so I reckon I had the anti-bodies lying dormant in me already.

Cylinders looking good now bit of a wash and clean up and she’ll be right to go.

BC

white rocket wrote:

No air leaks, the jettings a little fat down low so I’m pretty sure it is the aforementioned “hotspots” that we’ve been yapping about elsewhere on here. I’ve had other 2T watercoolers do this over the years in similar areas. I’m ptting a close tolerance piston in today/this week so I’m probably going to run engine ice in the cooling system as well.

I knew something had gone wrong and better safe than sorry.

bc

i’ve gone back on the engine ice, as while it has a far higher boil point as someone pointed out it doesn’t transfer heat as well as water. Axel the reason I am going along the hotspots is that all engines have them, ask TB, and some worse than others they have flow “deadzones” and bypass areas, sandcasting the barrels has engineering limitations and as well know everything is made to a market driven pricing system. Now usually if you run stock jetting/carburettion systems they run phat on the mixture which will help hide these issues, lean out the mixture to around the correct stoichometric ratio ato rerelease some ponies and they start to rear their ugly little heads. Mine runs about 4 pilot sizes beneath factory setup and the needle has a completely different taper (tri-tapered JD) which gives it unbelieveable boogie of idle, but also because it is burning more efficently and I run a very close tolerance skirt/bore ratio there is far more heat to be carried away, and any (notice I didn’t say “if”) deadspots in the cooling systems will be overtaxed and localised “steam pockets” can result, steam doesn’t do anything for heat transfer in this situation and so that area expands exponentially until something gets hurt.
This is why some of the old 24hr le-mans rotaries (which they outlawed in that race) had liquid cooled exhausts, to help get heat away from the exhaust ports where there were problems at high speed running.
Now a well tuned 2T has a fresh charge running back into and back from the pipe so the upper/large section of the port should be getting some incoming charge cooling, but the auxilary ports- (like the katos screw type) two sub-ports maynot benefit from this backwash of fresh mixture and it becomes superheated….easy fix= richer jetting, downside poorer performance.

These are some of the problems as i understand them, the fix is what rat and Bull have been working on, and from memory the GM silver and gold series screamers had similar issues back in the day.

BC

You’re right T/B I was just explaining to Axel why I believe it is so, anyway the bore is on it’s last piston change now, so next time I’ll go back to an “A” sized slug and start all over again or maybe go to a forged unit, because it ain’t an F1 engine, but I do like it to be right, anyway no matter what still better to be liquid cooled than not, I remember my old seizures from the air-cooled smokers, not good fun.
Was thinking a fan, but what the hell just something else I can wreck on it then :blush:, I’ll just ride faster instead, and put the fan on me .

BC

Sounds like a good idea, I’ve got a pair of ACD radiator braces coming from the UK that allow full flow through my poor old mangled radiators, the beauty i=of these braces is by the looks I can mount a fan with no obstructions.

Got quite a few dead computers at work too, so fans should be a cinch.

BC