monster 620 bore increase

[Speeddog]

Stu and I did a 695 heads + 11:1's on a customer's 750 carbie.

When I lit it off, Stu ran into the shop like his hair was on fire. 

Customer really dug it too.

[Duck-Stew]

Stu and I did a 695 heads + 11:1's on a customer's 750 carbie.

When I lit it off, Stu ran into the shop like his hair was on fire. 

Customer really dug it too.

Yup.  Sounded mean and ran awesome too...  It was a carbed '01 BTW.  We did not have to change the jetting much either.

[clubhousemotorsports]

If I get my hands on a set of stock 750 heads I will let you know.................. wait I might just have a set.

next up 750 cams in the 620 heads
or
750 stock heads
then
750 heads with 620 cams
750 heads with 900 carby cams
750 heads with 900ie cams
750 ported heads w/ 900 carby cams

620 heads and the 2 sets of 750 heads are different and it is a SS so i have to take the frame off every time I do a head swap so I am not sure how quickly I will get this done as it is bike season here and I need to get to work.

Okay I will add the 695 heads to the mix
695 heads with 695 cams
695 heads with 900ie cams

I need to find a set of ST2 cams, I have been building 800's (695 heads) and getting good hp

[caperix]

How much does the larger chamber of the 695/800 head effect the compression? I have a set of 695 cylinders & heads in my garage that I plan on putting on my 04 620. I just need to decide on what pistons.

[DarkMonster620]

Ok, so, I need to get:

695 heads or S2R800

750 FBF 11.1

750 cylinders or

MY 620 bottom end

Some $$$

New ECU to reflash/dyno tune

Right? Something else?

[Speeddog]

Ok, so, I need to get:

695 heads or S2R800

750 FBF 11.1
with 1 or 2 extra wrist-pin clips

a pair of base gaskets

695, 750, or 800 cylinders or

MY 620 bottom end

Some $$$

New ECU to reflash/dyno tune

Right? Something else?

[DarkMonster620]

Gotcha . . .

THANKS

[DarkMonster620]

Checking FBF website, I copy/pasted the following statement:

"PISTON KIT - 88mm 11:1 750 Ducatis

This fit the following model: This piston when used with the Big Bore application for a Ducati Monster/Multistrada/Hypermotard 620 will give a 12.0:1 compression."

Is this because of the 620 heads?

[koko64]

Combustion chamber size I guess. Havent seen inside one so the other blokes will know.

[clubhousemotorsports]

Just a heads up.

I finally got a 620 on my dyno. It is a 620 monster all stock but for a set of sil slip on megaphones and a light flywheel.
55hp and 37ftlbs torque

I compared my 620 to 750ss motor and the HP was only up about 5hp, not impressed with that but I think it is due to the differences in the head to piston shape match.
On the up side the torque of the 620/750 was just about 50 for about a 12ftlb gain. The SS runs the 750 mikuni carbs and long manifolds and is a pretty good match for the other 750's I have run, nothing special for a similar stock 750.  The torque gain from the 620 was huge though, most everywhere a good gain. It would be good to see what a injected short manifold 620/750 might do as the 620 made most of its power up high where the carby was done by 8000

[koko64]

Interesting.

[DarkMonster620]

 

[koko64]

I guess more capacity and long manifolds gave the grunt.

[clubhousemotorsports]

I would say yes it was displacement that boosted torque, I would like to see my carby rev out like the 620 did as the 620 made its power a good 1000 rpm further up. I have no plans on flat slides for this bike as it is not supposed to become a parts whore, simple and cheap mods are the goal. I hope to try pod filters in place of the airbox as I ran a 900 with hi comps and pods and it mimicked the short manifold bikes power curve. If it is possible to not use split single carbs it would be better for most.

This one 620 is not a trend so I do want to run a few more on my dyno to make sure this one is as standard as possible. Next I will need to build another 750/620 to make sure it was not just my 750.

[koko64]

Maybe open up the inlet manifolds cross section, so a bigger bore on the alloy manifold tapering down to the port? So trying to get the manifold closer to the 38mm diameter of the carb with a late taper. The IE manifolds aren't exactly short, just fat. What's your opinion?
I've been trying this to see if the bikes hold their power more from an inlet port/cylinder volume perspective, but don't have back to back data. I have the opinion (which I cant back up yet ) that the carby manifolds are not just too long for top end torque but too narrow. It may not be their length, just too skinny. I got thinking about port to cylinder volume ratio and the resonance stuff due to a Lofgren article and talking to a race car tuner buddy.
I don't know, I'm trying to get a grasp of this stuff.