madzx2
Member
I installed my Mr viper 780 top end today and my question is how do the power valves come apart. I need top change them but I can't find any info on how the come apart. I have them out of the cylinders but still connected right now.thanks in advance for any help.
super1c
Super Moderator
I just open up the servo motor and with a pair of channel locks wraped in a wrag turn the motor so the cables unwrap from the servo. Then just gently pull on the valves and it shuld come out of the housing enough to unhook the cable.
madzx2
Member
Thanks, maybe I'll get to fire the beast up tomorrow.
madzx2
Member
Worked like a charm, fired up the beast today. It sounds like its pissed off, must be having withdrawls from no snow ! Thanks again super!
madzx2,
I was thinking about building up a 780. I was wondering what you need to do to pull that off. I don't know if my memory is correct but are the power valves the same or are they larger? And aside from that is the only difference just bore and jetting?
I was thinking about building up a 780. I was wondering what you need to do to pull that off. I don't know if my memory is correct but are the power valves the same or are they larger? And aside from that is the only difference just bore and jetting?
staggs65
Moderator
cyls bored, and should be ported, renik'd, heads need to be machined, powervales cut to match the overbore
staggs,
Are the heads cut for the bore? Or are you just talking about grabbing some more compression for performance? And does anyone use stock heads on that or do you need to go aftermarket to make it work?
Just wondering
Are the heads cut for the bore? Or are you just talking about grabbing some more compression for performance? And does anyone use stock heads on that or do you need to go aftermarket to make it work?
Just wondering
staggs65
Moderator
stock heads are fine, they need to be machined for the bore and to correct the compression from the overbore/porting
show a video of the beast
madzx2
Member
I'll get some video tomorrow. Best part is looks stock underhood now. I have mega power heads for my 700, eventually if like to find some mega big bore inserts.
What do you think it is puttin out for Hp ?
Madzx2,
Sounds like a sweet machine. I apologize for the hijacking. I was just interested in what's needed to do the big bore. People probably really scratch their head hard when their eating the white stuff behind you and their 800 isn't gaining on you.
Sounds like a sweet machine. I apologize for the hijacking. I was just interested in what's needed to do the big bore. People probably really scratch their head hard when their eating the white stuff behind you and their 800 isn't gaining on you.
madzx2
Member
I haven't ridden it yet, bought the top end this spring. It should be fun, I have 38mm mach z carbs on it too. My 700 made 150HP i'm guessing 160ish for the 780. I'm dynoing before it snows so I'll let you know what it makes.
madzx2
Member
https://www.youtube.com/watch?v=uK4_LLiPa4c&feature=youtube_gdata_player
Not the best video.
Not the best video.
staggs65
Moderator
Madzx2, just send your mega inserts to Don and he can cut them for your 780. thats what I did with mine.
It will sound better at WOT.
mrviper700
VIP Lifetime Member
make sure you adjust the powervalves to 2.5mm clearance!
Nice sound! Sounds crisp. I'll be interested to see what it does on the dyne.
madzx2
Member
I still have to adjust the valves and get my clutching together, but the hard part its done. Id like to have a set of domes for my 700 and a set for the 780 for the mega power heads.for now I'll just use the stock cut heads.