Anyone done a 695 conversion on a 620?

[v290rider]

Just curious if anyone's done a 695 conversion on a 620 Monster...

I wondered how complicated it was and if the end result was worth it...

Thanks!

[Speeddog]

We put a set of 695 heads on MetalDuc's 750 and it rocked. 

[v290rider]

We put a set of 695 heads on MetalDuc's 750 and it rocked. 

Sweet...   

So, can you "easily" get the parts (big-bore pistons, cylinders & heads) to make a 620 a 695?  What other considerations are there?

Thanks!

[Speeddog]

Sweet...   

So, can you "easily" get the parts (big-bore pistons, cylinders & heads) to make a 620 a 695?  What other considerations are there?

Thanks!

620 and 750 are 80mm and 88mm bore, respectively, with the same stroke, 61.5mm.
695 is 88mm bore and 57.2mm stroke, so you could think of it as a de-stroked 750.

I *think* 750 barrels will fit 620 cases.
I don't think 695 barrels are a direct swap onto 620 cases, IIRC there's an issue with alignment dowels.
<edit> 695 heads may be better than 620 heads, but are way better than 750 heads.

Not sure of the availability of 695 heads, it was kind of a coincidence thing when we did MetalDuc's bike.
But if you're interested, I can check with my source.

[madmatt]

what are the real world gains from such an extensive project?

[Speeddog]

Probably 10-15 HP.

As a reference, here's some info from Brad Black...
620 Sport, 59 HP: http://www.bikeboy.org/620sport.html
Warmed-over 750, 76 HP: http://www.bikeboy.org/brads750m.html
I wouldn't expect the 695 heads to be far off from his modded 750 heads.

And I've corrected my previous post, 695 barrels will fit 620 cases.

[The Bacon Junkie]

We put a set of 695 heads on MetalDuc's 750 and it rocked. 

OOH!!!

Do tell... want to know more.

Clicked on those ^^^ links, but all the colors and wavey lines confused me.

[Duck-Stew]

OOH!!!

Do tell... want to know more.

Clicked on those ^^^ links, but all the colors and wavey lines confused me.

The 750 is a good engine making respectable power.  With the addition of 11:1 Ferracci pistons *and* the 695 heads it made a LOT more power.  Definately a much more fun engine.  Definately.  I would say by my not-so-calculated seat-of-the-pants dynomometer, we did pick up 10-15hp.  No shit.

[MetalDuc]

I have the 750 heads available if you want to go that route. They are complete including a fresh 12k valve adjustment by nick and stu. Not sure how much it gets you over the 620 but you could definitely rework them.

If you are simply after more power it is cheaper to buy a bigger bike. If you are after a project it costs but can be worth it. For me it was and I lucked out on the 695 heads.

Work:
695 heads and cams
High compression pistons
Yoyodine fly wheel
Jet kit
Pod filters
Exhuast

Result:
80 hpish according to stu's butt dyno
"it feels like a stock 900 but it revs crazy high and keeps pulling the whole way" - stu
It does pull hard though 10k all the way to the end of the tach before you start feeling the power level off.

[sbrguy]

so you are saying it has the power of a 900 but the fun of a 600.. cool

[erkishhorde]

So you're saying it's got the power of a 900 but more torque than the 900? So if I've already got the 900 how do I get the more torque part? 

[Speeddog]

No, it doesn't have the torque of the 900, it just revs higher to make the power with less torque.

I may have misremembered which heads I was comparing the 695 heads to.
They're definitely better than the 750 heads.
They may be the same as the 620 heads, unfortunately I have neither 695 or 620 heads in my shop now.