I have a 700 srx that runs grass and ice, it runs extremely well, only lost to 1 other 700 all year{in my class}. Does the 800 big bore kit really run that much better? or would I be disappointed for the money spent. If it were you would you do a full race port job on the 700 or put a big bore onit?
valin
Active member
A 700 improver can make in the 190's for hp. I have never done one, but I would expect a race 780 would be in the 200-205 range for hp.
For reference, my pump gas, ported 780 makes 181hp on the dyno, with Bender 835 trail pipes and 38mm carbs. With the porting in it, it should probably be 185-186ish, but there is too much blow down time in the porting, causing the motor to be a bit peaky. I am going to fix it this year, and port it slightly more to see if I can get into the 190's on pump fuel and low rpm.
As for being disappointed, it all depends on the port work done on the cylinders, pipes, carbs, compression, etc. There are alot of 780's out there with basically no porting, and they are probably only making 160hp at best.
For reference, my pump gas, ported 780 makes 181hp on the dyno, with Bender 835 trail pipes and 38mm carbs. With the porting in it, it should probably be 185-186ish, but there is too much blow down time in the porting, causing the motor to be a bit peaky. I am going to fix it this year, and port it slightly more to see if I can get into the 190's on pump fuel and low rpm.
As for being disappointed, it all depends on the port work done on the cylinders, pipes, carbs, compression, etc. There are alot of 780's out there with basically no porting, and they are probably only making 160hp at best.
YAMMIEGOD3:16
Active member
RYAN RIGHT ON HERE. SEEN SOME FAST 780 SRX,s. IF THEY ARE SLOW, THEY ARE EITHER WORN OUT OR NOT TUNED RIGHT. 3:16 (yammie tony)
mopar1rules
Active member
if you just bore your cylinders to make a 780 and not port it, it would be a dog, as the port timing gets reduced alot once bored. the boost port drops a ton and the secondary and main transfers drop a little too. don't forget the exhaust port roof height goes down some too. the 780 cylinders would need to be properly ported to get the full benefit of adding the extra displacement.
Mac
Member
I wouldnt purchase a brand new BB. I would wait and see what becomes available. Every year several kits show up on ebay and TY. I have seen 1/2 price or less and you get to keep your cylinders and pistons to resell or keep for re-use. They do run strong if setup correct.
