looking for a good 860gt/900ss recipe

Cragar · Post by **Cragar** » Sun Nov 15, 2009 11:38 pm

I am building a 900ss type cafe racer with an 860gt spring valve engine. just wondering if anyone out there could advise me on some good standard upgrades to help me get some 900ss type performance from my 860. a good basic recipe would be nice, carbs, valves, pistons, Cam?
nothing extreme.
Thanks

BEVEL DAVE · Post by **BEVEL DAVE** » Mon Nov 16, 2009 3:53 am

36mm carbs & 88mm pistons.
Keep all the low end performance, its nice to use instead of more top end.

Dave.

abmartin · Post by **abmartin** » Mon Nov 16, 2009 4:02 pm

A less restrictive exhaust helped the driveability of my old 860GT. After I sold it to a friend he threw lots of money at it and still ended up with a slower bike than my SS.

My advice is to appreciate what you have and get it working as well as possible rather than trying to make it into something its not.

Bruce

wdietz186 · Post by **wdietz186** » Mon Nov 16, 2009 4:34 pm

A good, fairly inexpensive up grade is a set of the 87mm Wiseco pistons.While the heads are off make sure the valve guides are good and the valves are sealing properly.A pair of Contis or the Keihan mufflers and pod style filters will give a few hp over the stock setup,The 32mm carbs are fine unless they are worn out.I think Megacycle can make a springer cam with the SS timings but it might be a tad hard on the valve train.Of more concern is if your stock Ducati Elettrotecnica ign. unit is still in working order as they aren't the paragon of reliability.

Cragar · Post by **Cragar** » Mon Nov 16, 2009 8:50 pm

forgive me if I'm wrong but isn't the 900ss just an 860 with some performance upgrades? what are the true differences in the engines other than the desmo heads, billet crank, and bigger carbs? It doesn't seem like it should be that difficult to squeeze some 900ss type performance out of these things with a good combination of upgrades. I am worried about that ignition buisiness though. what's the best alternative and where do I find it?

wdietz186 · Post by **wdietz186** » Thu Nov 19, 2009 4:33 pm

The differences between the two engines were compression and cam timing. The SS cranks weren't billet but the connecting rods were a bit stronger in theory.The weak part was the rod bearings were sort of fragile and sustained high loads and revs would kill them.Read Kevin Brackens article on building a bevel racebike for more insight.

Cragar · Post by **Cragar** » Fri Nov 20, 2009 12:39 am

Thank you for that update, and I will read that article, and oops I did mean rods. I'm just trying to learn as much as I can here and I appreciate all the contributions.