OK, here we go, just a rough up for now ... but XR1200 rocker covers on an Evo Big Twin.

I'll admit the originals still have a kind of slim elegance about them but, apart from their two piece nature, improved sealing and positioning but I think they are going to work. Just need to strip and blast them now.

The XR1200 rocker covers fit perfectly, the internals, e.g. rockers and shafts etc, are all the same. Height wise, I think they are actually slightly lower at around 2.300" rough measurement.

Their shape is quite similar to Vulcanwork's Xzotic rocker covers. The big difference is, of course, the breather system.

They do away with breathing excess out through the heads and in through the air filter cover, carb and dribbling over the cone completely. Instead they re-route the oil/air mix and have a single PCV valve in the middle, breathing out the top of their heads.

The 'work in theory' is to see if I can run a tube back to the oil sump somewhere and add another one way valve and mini-filter along it -- but it'll be a while before I get to that point.

If anyone knows for sure if I am headed towards disaster, let me know. The only concern I have is the unknown of what capacity they have to breath in comparison to stock OEM or v.2 Sportster covers.

(Pushrods aren't really that red, it's just a weird out on my camera. They've been stripped of chrome waiting for me to decide what to do to them, or work out which bits would look good black).

There's a comparison with the stock 3 piece at the end.

 

I say again to each their own.

 

There's a really helpful site about XR1200 innards, and how to tweak them. It helped a lot, and I am indebted to the author (if it all works!).

You can see the reduced size of the air passage ways, in comparison to the "out of the head/carb" version, below. I'm thinking at worse it might whistle.





In true Harley habit, the XR1200 actually uses the same green umbrella valve as the Evos do and so my guess is it has the same capabilities/capacity. This valve is 50% cheaper than the ones for the older/standard Sportsters that use the same 'thru the head' exit point as the later Evo Big Twins.

The covers themselves were used spares from some dealership that raced XR1200s. New they are about $300+ for a set. Given they are higher revving and sportier, I'm gambling on them coping with the 80ci.



They've also got this cool little knee protector for the rear pot (19). I don't remember even knocking mine against it or having hold on that tight, but I'll probably rig it up just for the heck of it. The seals are definitely better, sitting vertically in grooves rather than just sandwiched between flats.

 

Being one of the other evo motor guys with sporty covers on it, do you have the room for that nipple on top for the breather to work without it hitting the frame?

I'm not sure it would clear on my 94 dresser and the 96" motor in it, although mine are not XR covers and just stock sporty ones.

Good job working it out.

Griz

 

Thanks.

I don't know yet is the honest answer. It's a concern. My frame is away being worked on right now so it will be a few weeks before I can tell.

I'm hoping the off centre nature of the positioning will clear them, otherwise I need a Plan B; either some other kind of screw in attachment, or falling back to the two part Sportster covers. I tried them out and they are certainly less of a risk, using the same airways exiting via the heads and carb.

I'd like to size these up against the two part Twin Cam covers. I've got a feeling that they would actually fit too. Some other member mentioned fitting them but also blowing the centre piece out ... they don't have the hole through the top that I think has to help with cooling.

Do you know which models/engines use the heat sensors in the heads? Is that for FLHTC with gauges in the fairing?

 

If I had to GUESS, I would GUESS that the heat sensor in the head was for EFI bikes. You need a cylinder temp sensor when you EFI something aircooled. I don't recall seeing a factory bike with a gauge for a cylinder head temp.

 

The temp gauge on Ultras etc are oil temperature, which is taken from a sensor on the engine, down by the cam chest. I suspect Dr H has answered that query!

 

I think I confused some folks with those TC "style" covers that I had an issue with the center piece coming out. They are look-a-likes for TC's but won't fit a TC.

Griz

 

They kinda have an industrial motor look to them. I'd chrome 'em if they were going on one of my motors.

 

Or paint them? I quite like the idea of painting my outer covers, including primary and timing side, although I must confess that I haven't done anything about it. I saw a stunning custom Sporty many years ago painted like that in powder blue, matching the other painted parts including the frame.