SV cam timings?

Im wondering what the stock cam timings are on the SV's? How common is it for them to be off of the factory intended settings?

Just wondering as its interesting to see what they are setup for and if changing the timing could improve power much?

(Also found out that the Rotax's in the aprilia's have been known to be quite soe distance off ).

Apparently for the rotax 106intake 109exhaust is the best setting for them.

Cheers for any insite... Danger Dave might be able to show off his know how here...

[jambo]

The timing on the cams is in the Haynes manual I believe, you can certainly buy new cams with a slightly different profile to alter the power characteristics from people such as JHS. My understanding of changing the timing on stock cams as in, intentionally putting them in in a position ahead or behind that stated in the manual, is that this leads to less power because you've bent a valve

Jambo

Originally Posted by jambo

The timing on the cams is in the Haynes manual I believe, you can certainly buy new cams with a slightly different profile to alter the power characteristics from people such as JHS. My understanding of changing the timing on stock cams as in, intentionally putting them in in a position ahead or behind that stated in the manual, is that this leads to less power because you've bent a valve

Jambo

Well now that depends on how far you move them. I mean you arnt going to move them far enough to cause the valves to impact the Cylinder that would be silly.

Reprofiling does help yes, or can, longer duration and/or higher lift will help the air flow.

Altering the valve timing can result in higher compression ratio's, infact someone playing with a V990 managed to get it to knock he got the comp so high. He had to alter the ignition at tickover to compensate. But he did gain about 10bhp in the mid range and 7BHP up top by doing this!!!

Its easy to do (in theory) slot the cam gears and move them to the desired position. Though it takes some special kit and know how to do this well.

[jambo]

Originally Posted by ThEGr33k

Well now that depends on how far you move them. I mean you arnt going to move them far enough to cause the valves to impact the Cylinder that would be silly.

My point was that as far as I'm aware, the minimum increment you can move the cams by without modifying them is one tooth. This is apparently enough of a change to cause interference between piston and valve. I'm not sure anyone has modified the cams so that they can be advanced by smaller increments than this, as those taking these things that seriously tend to just shell out for more aggressive cams anyway.

Jambo

Originally Posted by jambo

My point was that as far as I'm aware, the minimum increment you can move the cams by without modifying them is one tooth. This is apparently enough of a change to cause interference between piston and valve. I'm not sure anyone has modified the cams so that they can be advanced by smaller increments than this, as those taking these things that seriously tend to just shell out for more aggressive cams anyway.

Jambo

Aye but that costs monies. This is free if you have the money and know how...

Moving in one tooth increments is a bad idea that is true! You need to slot the cam sprockets to get the small increments I mean. Im wondering if Danger Dave has done this... his bike is about as modded as they come... So id guess he has.

http://www.apriliaforum.com/forums/s...=141972&page=3

You can see what I mean at the bottom of this thread. There are better examples of people doing it BUT I cant see many of the pics on the net bacasue im in work...

[jambo]

Ah, the camshafts are mounted to the sprocket by bolts on that design, where as I believe on the SV they are pressed on with an interference fit or similar. I don't think there is an easy way to remove the sprocket, machine some material away and refit, turning slightly from true, you'd need to get the sprocket off the camshaft some way in the first place.

I think that's the case anyway, and would explain why the idea's a go-er for the aprillia, but no one's done it on the SV.

There seem to be some different sprockets you can fit to the SV cams here, but they don't explain how to remove the sprocket.

Jambo

Ahhh fair enough. Still though id like to know the standard timings for the SV... see what sort of power its tuned for (or not).

it is easy,you press off sprockets and press on adapters on which you bolt sprockets.
timing is not same on curvy and pointy.curvy is apart more than pointy.
mid 100's is good starting point.

would an ignition advancer not acheive the same thing and be far simpler to do?

[yorkie_chris]

Nope. Ignition advance changes the ignition timing, valve timing changes the valve timing

More advance can give you more power up to a point, after that it's dangerous.

Cam profiles can turn a torquey engine into a peaky one and vice versa, again there's only so much difference can be made in any layout, there's a lot of factors at work as a lot of it depends on the momentum of gas flowing in and out of the cylinder.

I have no idea whether 1 tooth will cause interference, or whether less of a change than this will give any benefit.