monster 620 bore increase

[Duck-Stew]

What compression ratio would I attain if I used the FBF 12:1 750 pistons with 800 cylinders and  620 heads ? The reason I ask is FBF are currently out of 88mm 11:1 pistons that would give me 12:1 in a 620.

Due to the longer stroke 800 crank, the piston pins are located closer to the tops of the pistons than 750 pistons.  Therefore, if you were to attempt this, you'd have to space up your barrels away from the engine case which may cause the intake manifolds and exhaust header not to fit right.  Even if it did fit right with barrel spacers, I'm w/DP on this one: too much CR yields the need for racing fuel or additives and that's always a pain.

[DarkMonster620]

I was gonna say that same thing Duck-Stew

[POCO LOCO]

What OEM ducati pistons could I use in place of the Ferraccis

[DarkMonster620]

bore is 80mm in the 620 . . . 750/695/969/796 are 88mm . . so you would need to bore and re-nickasil the cylinders . . .

best bet, get an 695/800 engine and ECU or reflash your ECU to 695/800 DP Map . . . as someone said, since these ECUs are Magneti Marelli and most compatible with your actual wiring harness

http://www.ebay.com/itm/Engine-motor-17-k-miles-Ducati-Monster-800-03-F6-/111986593492?hash=item1a12ebced4:g:HCUAAOSw~OVWxmdl&vxp=mtr

http://www.ebay.com/itm/Ducati-Monster-S2R800-06-08-Engine-Motor-Video-Only-1-615-Miles-22521821A-/272275475387?hash=item3f64e20bbb:g:~GMAAOSwvg9XYcXX&vxp=mtr

http://www.ebay.com/itm/07-Ducati-Monster-S2R-800-ENGINE-MOTOR-11K-MILES-VIDEOS-INSIDE-/381221328527?hash=item58c28fd68f:g:UM0AAOSwBahU9f5m&vxp=mtr

http://www.ebay.com/itm/2005-DUCATI-800-DESMODUE-ENGINE-/401023127335?hash=item5d5ed74f27:g:Jx0AAOSw~bFWPADu&vxp=mtr

http://www.ebay.com/itm/06-DUCATI-MONSTER-S2R-800-Motor-Engine-/201653207459?hash=item2ef377c1a3:g:upsAAOSw9NdXvds8&vxp=mtr

[POCO LOCO]

bore is 80mm in the 620 . . . 750/695/969/796 are 88mm . . so you would need to bore and re-nickasil the cylinders . . .

best bet, get an 695/800 engine and ECU or reflash your ECU to 695/800 DP Map . . . as someone said, since these ECUs are Magneti Marelli and most compatible with your actual wiring harness

http://www.ebay.com/itm/Engine-motor-17-k-miles-Ducati-Monster-800-03-F6-/111986593492?hash=item1a12ebced4:g:HCUAAOSw~OVWxmdl&vxp=mtr

http://www.ebay.com/itm/Ducati-Monster-S2R800-06-08-Engine-Motor-Video-Only-1-615-Miles-22521821A-/272275475387?hash=item3f64e20bbb:g:~GMAAOSwvg9XYcXX&vxp=mtr

http://www.ebay.com/itm/07-Ducati-Monster-S2R-800-ENGINE-MOTOR-11K-MILES-VIDEOS-INSIDE-/381221328527?hash=item58c28fd68f:g:UM0AAOSwBahU9f5m&vxp=mtr

http://www.ebay.com/itm/2005-DUCATI-800-DESMODUE-ENGINE-/401023127335?hash=item5d5ed74f27:g:Jx0AAOSw~bFWPADu&vxp=mtr

http://www.ebay.com/itm/06-DUCATI-MONSTER-S2R-800-Motor-Engine-/201653207459?hash=item2ef377c1a3:g:upsAAOSw9NdXvds8&vxp=mtr

That is not the path I want to take. I already own a set of 03 800 cylinders. All I would need is a set of pistons. The FBF 88mm 11:1 sets are suddenly unavailable, so I am looking for the right size Ducati pistons that would work.

[DarkMonster620]

if you have the cylinders you would need to "add" a head gasket in order to lower the comp and be streetable . . .

There is also this option, http://www.pistalracing.it/  and check the 796 option . . .

[Duck-Stew]

That is not the path I want to take. I already own a set of 03 800 cylinders. All I would need is a set of pistons. The FBF 88mm 11:1 sets are suddenly unavailable, so I am looking for the right size Ducati pistons that would work.

Wait. 

Hold the phone and all that. 

I thought somewhere in this thread you swapped the entire engine for an 800.  Am I wrong?  Do you still have a 620 which will be receiving the 88mm barrels?

If so, then yes.  Ferracci 750 pistons will work for you.  As far as the CR goes, I think the combustion chambers are roughly identical between the 750, 620, 695 and 800.  I could be wrong.  I've never measured.  I did, however, put a set of 11:1 pistons into an '01 M750 and topped it with 695 heads for a customer. 

THAT was a fun bike to ride!  Ran on premium pump fuel w/o issue from what I remember if that's any indication of compression ratio.

[Duck-Stew]

Another tid-bit:  The Ferracci 12:1 pistons can be machined into 11:1 pistons by having a shop cut the tops off of them.  I'm not sure if you want to do that or not, just thought I'd throw that into the mix as it were.

[koko64]

And while they are at it they may need to smooth the edges of the valve reliefs. A recent set of 12:1's I handled had very sharp edges on the valve cut outs that could cut your hand (literally). The blade like protrusions could make for great hot spots/glow plugs.

[POCO LOCO]

if you have the cylinders you would need to "add" a head gasket in order to lower the comp and be streetable . . .

There is also this option, http://www.pistalracing.it/  and check the 796 option . . .

Would I be able to use 800 Ducati pistons that came with the 800 cylinders?

[DarkMonster620]

Would I be able to use 800 Ducati pistons that came with the 800 cylinders?

yes and you would have an 800 engine . .  just reflash the ECU to DP map . . .

[POCO LOCO]

yes and you would have an 800 engine . .  just reflash the ECU to DP map . . .

Now you have me confused. I thought the 800 pistons have the same part # as the 750s. The stroke on a 620 is the same as a 750.

[Speeddog]

There's a bit of confusion about exactly what Poco has.
My understanding is it's a 620 motor he's starting with.

800 pistons will come up way short if they're used with a 620 crank.

695 pistons are tall.
750 pistons are medium, same height as 620.
800 pistons are short.

695 pistons and 800 pistons could likely be made to work with a 620 crank.
But at a minimum, there's quite a bit of fabrication and/or machine and/or special assembly work that would need to be done.

For example, 695 pistons could be made to fit with a base gasket/shim ~2.25mm thick.
That introduces possible issues with throttle body and exhaust fitment.
Requires re-indexing the cam to provide proper timing.
And may well not work at all due to the length of the cam belt.

[POCO LOCO]

There's a bit of confusion about exactly what Poco has.
My understanding is it's a 620 motor he's starting with.

800 pistons will come up way short if they're used with a 620 crank.

695 pistons are tall.
750 pistons are medium, same height as 620.
800 pistons are short.

695 pistons and 800 pistons could likely be made to work with a 620 crank.
But at a minimum, there's quite a bit of fabrication and/or machine and/or special assembly work that would need to be done.

For example, 695 pistons could be made to fit with a base gasket/shim ~2.25mm thick.
That introduces possible issues with throttle body and exhaust fitment.
Requires re-indexing the cam to provide proper timing.
And may well not work at all due to the length of the cam belt.

Don't 750 and 800s both have the same part number? Therefore how can one piston be medium and the other short?

[DarkMonster620]

Now you have me confused. I thought the 800 pistons have the same part # as the 750s. The stroke on a 620 is the same as a 750.

I personally went the way of getting an 800 engine and reflashing my ECU . . . project on hold since I need some legal documents in order to send the parts of my engine that have the engine # . . . but, indeed I am installing some mild HC pistons . . .

Now, as Speeddog says, could you tell us exactly what you have and what you want This way we could help you better and easiest way is to get the 800 engine and if you want HC pistons then the link I gave you could be your best bet or any of the "Gurus" here might give you pointers of other choices