loss of compression?

[the_adam]

A little while ago I upgraded the air filter, and at what seemed like the same time I lost a lot of engine braking and the bike didn't run quite as smoothly as before. So I'd just assumed it was somehow caused by the change of filter and thought nothing of it. Just been thinking about it this morning and wonder if it could be a coincidence - isn't that much better explained by a loss of compression, which would suggest I should probably get the valves looked at?

Bike should have had its 15000mile service earlier this year - instead of doing that I got the parts and did most of it myself, but I think there's meant to be a valve check in there which I've missed?

Adam

[Rally]

Burn't or badly adjusted valves will certainly let the compression drop. Valves normally loosen off with wear, rather than tighten up though. If they loosen, they will not let compression past. Maybe they have tightened up instead, but in my experience this is unusual.

Have you changed your jets since fitting the filter, as it may be running lean now and burn't a valve out.

[the_adam]

It's not carbed so not that simple unfortunately, I was getting a new exhaust a month or two ago and was planning to have a power commander set up with that to hopefully sort it out. Things haven't gone to plan and I'm still waiting for it though! Will definitely check the plugs to see what sort of state they're in

[rac3r]

Take to a Ducati dealer and get it hooked up to the computer thingy and they should be able to adjust the fueling slightly

[gary tompkins]

The desmo shims run almost zero clearance on the closing side. As the valve seats wear especially on the exhaust, this clearance will increase and valves get held open. Eventually the valve and seat will get burnt out needing expensive repairs. At the other extreme the valve can snap and drop into cylinder if there no clearance, because the valve head gets forced into the seat. This is why shim adjustment shouldn't be neglected.

I think the interval for checking/adjustment is 6000 miles

[the_adam]

Thanks Gary, this is what had me a bit worried. It's definitely overdue a check anyway, I'll take it down to them tonight and see when it can be done...