mikestrikes wrote on 09/21/08 at 17:49:46:Yeah I dont want to do much at all to the intake side other than correct lean jetting and a better filter, I will want to smooth out the exhaust ports and raise the compression "to a point" but not so much as to worry about over heating and needing 90+ gas.
I may end up leaving the low comp and just get a bigger piston, it has a 94mm piston now so let me find out what the DR650 has.
I'll put on a diff exhaust but want it a dull thump thump sound
The trouble with the Savage is that it was built down to 30hp.
You can get a leeetle bit more power here and there, but to get significant gains you need to change just about everything – or somewhere along the line, something will be restricting the other mods you do.
- The standard exhaust header has a tiny diameter for a 650 cylinder, so that needs to be changed.
- Compression is very low. To raise it a lot you need a custom high-compression domed piston. More economically and practically, have 1mm/.040” shaved off the top of the barrel. That, along with the latest spec Suzuki dealer head gasket (a little thinner than original) will take compression from 8.5:1 to about 9.2:1. That amount of extra slack in the cam chain is manageable. Better still, re-dowel your cam gear but only if you have the right facilities(I’ve done it, photos are on here somewhere).
- Porting helps a lot. The inlet side is pretty good standard, just clean up the edges, while the exhaust port is awful – deliberate restriction designed by Suzuki. The valve seats are stepped on the underside, so blend those in too.
- The cam is part of the factory power restriction, but Lancer’s cams are superb and bring loads of midrange.
- The carb is designed for economy and emissions. A VM carb (again from Lancer) will work wonders.
- Air filter – original is poor, slot-in K%N doesn’t have much area because of the airbox design. Get a free flow cone filter (again, Lancer!).
All of the above should give you more like 50hp and a new project – upgrading the clutch!