800
New member
The cyls between the srx and viper are different, so you'll have issues there.
Why don't you just let Justin fix it, realistically there's no way you're gonna fix that thing for $600, it needs more than a jug slid on it, you ate a reed cage so there are other issues in the case, the motor needs to come out I'm sure. You can make a 780 live, lots of guys out there running them every day, and like Valin said, the 780 will be stronger than the 700, even if you buy a 700 top end the motor still needs to come out so I would weigh things out in both directions before I jumped into anything. most 780's were built sloppy, but you can tighten the clearances on them and they are fine.
If you want it to be reliable, let Justin measure it up and figure out why it faile so fast, I'm sure it's something obvious.
Why don't you just let Justin fix it, realistically there's no way you're gonna fix that thing for $600, it needs more than a jug slid on it, you ate a reed cage so there are other issues in the case, the motor needs to come out I'm sure. You can make a 780 live, lots of guys out there running them every day, and like Valin said, the 780 will be stronger than the 700, even if you buy a 700 top end the motor still needs to come out so I would weigh things out in both directions before I jumped into anything. most 780's were built sloppy, but you can tighten the clearances on them and they are fine.
If you want it to be reliable, let Justin measure it up and figure out why it faile so fast, I'm sure it's something obvious.
blueblooded
Member
Justin is going to fix it i just was wondering the best way to go.The motor is out and Justin already tore it down.The bottom end looks good it just needs the top end rebuilt.I gotta call Justin tomorrow and figure out $$ to fix the BB.
Let us know how much it was.
blueracer
New member
if i was you i would check with mrviper700 before you start selling parts, im sure he can fix you up in a hurry.
blueblooded
Member
blueracer said:
Thanks,I sent him a pm and am waiting to hear from him.
motodave289
Member
I didn't have any luck with wiesco in mine. Had to change rings every 1k miles because of skirt clearence. Sounds like not doing work yourself, so this could start adding up if you ride many miles.
blueblooded
Member
motodave289 said:
What piston do you recommend?
motodave289
Member
Stock bore and OEM piston. Just my 2cents.
9801srx
Member
if you are going to keep it a 780 then wiesco is the only piston you can use. your engine most likely detonated from lean jetting or bad gas . if a 780 detonates it will break the ears off the bottom of the cyl from the piston rocking violently in the cyl . a 780 can be very reliable you just have to make sure it doesent detonate. mr viper is building me one now and i will be running a mixture of 91 pump gas and c-12 to hopfuly prevent the same problem you have. btw what gas were you running?
blueblooded
Member
Justin did tell me it was way lean by looking at my piston wash.I was running 91 octane.Ive decided to go back to the stock cylinders so im selling the big bore kit which i have listed in the classified section.
These 780 motors live just fine if they are set up correctly and you run good gas, basicly the wiseco piston is harder then the cylinder is, so if you start getting detonation it will wreck the engine. I would bet the needles burned it down, you cant run stock needles in a big bore, too lean in the midrange and BOOM, Squeeeeeek!
You can go what ever route fixing it as you choose but these can be trail reliable if they are set up right and you dont try and skimp on the gas, they also have to be completely warmed up when you ride, start the sled then go put on your gear and wait till you can feel some heat in the running boards.
the ported 700's like 150-155hp on pumpgas, unless you add bigbore pipes. 780's make a solid 160-165 with more torque.
You can go what ever route fixing it as you choose but these can be trail reliable if they are set up right and you dont try and skimp on the gas, they also have to be completely warmed up when you ride, start the sled then go put on your gear and wait till you can feel some heat in the running boards.
the ported 700's like 150-155hp on pumpgas, unless you add bigbore pipes. 780's make a solid 160-165 with more torque.
motodave289
Member
9801srx said:
C-12 & trail sled?????? Must have a lot better gas stations on trail in Canada then U.S.
blueblooded
Member
motodave289 said:
I was told 92-94 octane is fine to run with this kit.
valin
Active member
I used to run a 780 with no issues. I am in the process of setting another one up with alot more porting and low compression. I am still going to run stock pipes, and 38mm carbs from a MachZ that are bored to 40.5mm 
It should be good for an honest 170 hp, on pump fuel.
It should be good for an honest 170 hp, on pump fuel.YAMMIEGOD3:16
Active member
BLUEBLOODED, I SEE YOUR NOT THAT FARR FROM ME IN LOCKPORT NY. I AM BY ROCHESTER. ANYWAYS I KNOW THS GUYS FROM MAXXIMUM VERY WELL. RACED WITH AND AGINST THEM FOR YEARS. I REMEMBER WHEN THEY MADE THAT 780 KIT FOR THE SRX. SEEN AFEW EARLY ON THAT DID HAVE SOME PISTON ISSUES. I THINK THERE WERE TWO VERSIONS OF THAT KIT. THEY DID REVISE THE SECOND ONE WITH SOME FIXED ISSUES. TOO BAD THEY CLOSED. 3:16 (yammie tony)
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blueblooded
Member
Yes,this kit has the updated version.Mrviper 700 said he has the pistons and can either repair or replace the bad cylinder if anyone is intrested in the kit.
GS438
New member
- Joined
- Dec 28, 2004
- Messages
- 80
I also had this problem!! Twice with exactly 700 mile each time,took out the heads , pistons,cylinder ,reeds both times. First the mag side then the center. Im telling you if you need any advice LISTEN TO MR VIPER!!!!!!!!!. I'm at about 700 miles and keeping my fingers crossed. Mr Viper helped me correct my jetting ,and all seems okay so far.Whos BB kit are you running? Did you do any mods to the air box?If so put it back to stock!!blueblooded said:
L I S T E N T O MR V I P E R
9801srx
Member
no the gas were i live is 91 octane max so i bought a drum of c12 to mix about 70/30 ratio which should give me about 94-95 octane. also were i live there is no gas statoins on the trails, if you go on a long run you have to tow your gas or convince a buddy to tow it for you.lol.motodave289 said:
BIG bore 780
can anyone tell me the bore size of a 780 kit. don't know much about the 780 kit. I'm just wondering what all is invovled in a 780 kit, wouldn't putting one in my SXR.
can anyone tell me the bore size of a 780 kit. don't know much about the 780 kit. I'm just wondering what all is invovled in a 780 kit, wouldn't putting one in my SXR.
blueblooded
Member
GS438 said:
My failure was most likely caused by a lean condition.After pulling the motor apart it had very little piston wash.Mrviper said the 780 can be a very reliable motor if jetted correctly and given enough warm up time.I was also told an extra cooler would help.For the type of riding i do ive decided to go back to a stock cylinder and piston.The sled only has 1600 miles on it so to invest the money in a new rebuilt motor seems worth it to me.Hopefully i'll get it back before the end of the season.