monster 620 bore increase

[POCO LOCO]

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

I own a 06 monster 620. I want to add a big bore kit to poke it out to 750. I so far aquirred a set of 03 800 cylinders of of Ebay, in the hopes I would be able to get FBF pistons item #F27510 11:1s. Therefore I would not have to rebore my stock 620 cylinders and replate. But guess what, Ferracci is all sold out of F27510s. Therefore I was trying to use a replacement ducati pistons as a replacement. I would love to know the piston part number of the ones included with the Ducati factory big bore kit that was intended for the 620.

[POCO LOCO]

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.

No I did not swap the engine for an 800. I just purchased the CYLINDERS to an 800 off of ebay, so I would not have to spend more money reboring stock 620 cylinders than replating.

[DarkMonster620]

I own a 06 monster 620. I want to add a big bore kit to poke it out to 750. I so far aquirred a set of 03 800 cylinders of of Ebay, in the hopes I would be able to get FBF pistons item #F27510 11:1s. Therefore I would not have to rebore my stock 620 cylinders and replate. But guess what, Ferracci is all sold out of F27510s. Therefore I was trying to use a replacement ducati pistons as a replacement. I would love to know the piston part number of the ones included with the Ducati factory big bore kit that was intended for the 620.

We own the same bike basically . . .   If I find my accesories catalog, I will send you the PN of the kit and a dealer might be able to get the PN you want/need . . .

For your cyls best bet now would be to get 800 heads . . . then down the road get the pistals or other brand hc pistons

[thorn14]

I looked at the link you posted Darkmonster, but couldn't see any pistons for the 800, so am I dense, or are there ones from another bike that work? I thought the only hicomps for 800's were the long gone run of Mahle pistons and getting them done custom.

[Speeddog]

I looked at the link you posted Darkmonster, but couldn't see any pistons for the 800, so am I dense, or are there ones from another bike that work? I thought the only hicomps for 800's were the long gone run of Mahle pistons and getting them done custom.

http://www.ducati-kaemna.com/catalog/ducati/88mm-pistal-hc-kolben-piston-796ccm-fuer-for-hyper-monster-scrambler.html

[ducpainter]

They list this one for 750 also... http://www.ducati-kaemna.com/catalog/ducati/88mm-pistal-hc-kolben-750-ccm-modelle.html

Don't know that it isn't the same set.

ETA...definitely a different piston. Skirt looks longer, and the pin looks like it's further from the piston crown.

[thorn14]

Wow, this is dangerous. Thanks.

[Speeddog]

800 piston would have a shorter deck height, and hopefully larger valve reliefs.

[DarkMonster620]

I wrote to piatal and the 796 are a fit for the 803 . . . the 696 are NOT

[ducpainter]

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.

It was thorn14 that made the swap.

So if Poco has a 620 bottom end, which pistons does he want?

[POCO LOCO]

It was thorn14 that made the swap.

So if Poco has a 620 bottom end, which pistons does he want?

I wanted the FBF item # F27510 88mm 11:1s that in a 620 head would give the bike 12:1, but ferracci has sold out of them,not expecting them maybe in spring. I was thinking of maybe the FBF item #F27511 these are 12:1 already, not knowing what ungodly compression ratio these would give in my 620 engine.So I am not sure that these would work.

[ducpainter]

I was asking the question regarding the Pistal product.

FBF pistons are J&E.

[koko64]

CCW had a contact for Mahle pistons iirc.

Maybe as a back up plan get the 12:1 FBF pistons and have them machined. The valve pockets will need a tidy up anyway. Having a pro set them up setting squish and machining them for piston to valve clearance is probably a good idea.
Some "drop in " pistons are not quite just a drop in propisition.

[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.

Then in that case I could get away using the stock 750 Ducati pistons in place of the FBF88mm 11:1s ?

[Duck-Stew]

           Then in that case I could get away using the stock 750 Ducati pistons in place of the FBF88mm 11:1s ?

FBF or otherwise, you'll need 750cc 2V drop-in high comp pistons to make this work.