Valve 'unshrouding' - worthwhile?

Has anybody tried this on the SV & are there any worthwhile gains?

[squirrel_hunter]

I've never heard of this, what is it?

It's where you remove a bit of the inside of the cyl head away around the valve area to unshroud the valve and thus improve gassflow.

I guess if that's the only thing you will do, you won't notice too many improvements. this kind of things are usually done in combination with lighter pistons and flywheel, full exhaust system, different air filter, remapping etc. ... with other words, full engine tuning.

try a more generous air filter before, it might improve the responsiveness of your bike a little bit.

[Red ones]

Why are they shrouded in the first place?

[Bibio]

Originally Posted by Red ones

Why are they shrouded in the first place?

its the excess material due to mass production that needs to be taken away. i think in the old days we used to call it gas flowing.

Not on a SV but on my 1200, exhaust & filter change brought rwhp up from a standard 108 to 128 (standard exhaust is extremely restrictive, a bit like tryin to running a marathon breathing through a straw!!). Further head work including unshroudind and skimming has brought this up to 135, not a massive increase top end but the area under the dyno curve midrange has increased quite considerably. I was just curious if anybody had tried it on an sv, it's not something you would take your head/s off for just to to do on it's own normally but i had mine off anyway i thought i may as well do something with it whilst it was sat there on the bench.

[squirrel_hunter]

If this is gas flowing or other tuning of the heads and your in a position to get it done then go for it. I've no direct experience of this, but understand that SuperTwin machines have it done. Though exactly what the changes that are to be made would be interesting to see as well as the process and research findings that have gone into it. Who would be doing the work?

[andrewsmith]

Sounds like a traditional blue printing job.
TBH unless your racing at Supertwin level, you can get more bang for you buck with a SV1000.

A supertwin spec motor is around £5k to build (rods and pistons are about £800 alone )

Apart from the head skim I did the work myself. I just pretty much copied what had been done & tested by our American counterparts, they seem to much more clued up on this kind of thing than we are. Removing metal from the combustion chamber will obviously lower your comp ratio but you can gain this back by skimming the head, obviously maintaining valve/piston clearance. Strictly speaking tho', there is no need to do this as compression ratio will have effectively increased as you are drawing more in because of the increased flow capability.