Going to need help setting up 780 srx

drew24

drew24

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I am going to be setting up a srx 780. What are people running for jetting in these? I know they are all different and I will have to test but I am curious. This was built by aaen and when I talked to him last spring he seemed like he didn't remember much about it. The jetting in the carbs from the sled it was in is 160 mains and 47.5 pilots. I do not know what the needle position was. I have done some searching and found a couple different jetting specs and this jetting seems fat to the others I saw. I also have a set of 156.3. Any ideas on which jets I should have on hand for when I test? Should I get the 158.8? Also my airbox is stock from a 2001. I know I wont know much until I get a chance to run it but I also don't know how many chances I will get to test. Also I have a mountain max rear cooler on this sled. Will that be enough for cooling? Any thoughts will be much appreciated. Thanks
 
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YAMMIEGOD3:16 said:
don,t touch that air box for starters. i would drop mains some and up pilots. did you say what size carbs ? 3:16x (yammie tony)
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I am definitely planning on leaving air box stock. I am wondering if the air box that was on the sled the kit was on was gutted and that is the reason for the 160's. I have the stock carbs. You thinking up the pilots from 47.5 to 50? Looking for a good place to start with the needles and mains and then I can make sure I have at least one size each way of where I start. I'm definitely going to start rich. This will be my first time jetting a sled so I want to make sure I do it right. Thanks.
 
In my 99 with a 600 box I ran 152.5 and needles at 4 with both washers over the clip. That was good to 0 ish here in MN with fresh 91 and torco accelerator to bump up the octane. Ran it that way for 4 years with 0 issues.
 
I will get the light mac posted. That would be handy. I will get a set of 50 pilots. Do you think I would be safe starting at the 156.3 mains or should I get the 158.8's? I will get some 155 and 153.8 and if I need to go lower I will order more later. If I remember correctly (been a while) all the settings I saw when searching had mains in between the 152.5 and 155. I didn't see many needle settings but when I did it was either set at 4 with both washers on top or at 3 with both under (which I believe is stock) so I will start at 4 with both on top and see what that looks like. Thanks guys, I appreciate the help.
 
You don't need 50 pilot jets with stock carbs and stock pipes. Stock pilot is 42.5, so if you go up to a 45 youd be plenty good. I always run the needles richer then stock slightly like ryan posted, 3.5 on needles setting will be good with todays lousy gas. The mains would be more then rich enough at 155,s if the airbox is stock and has the shelf in the center of it. If it has the bender cold air opening on top I would use 157.5 with stock center shelf in.
 
mrviper700 said:
You don't need 50 pilot jets with stock carbs and stock pipes. Stock pilot is 42.5, so if you go up to a 45 youd be plenty good. I always run the needles richer then stock slightly like ryan posted, 3.5 on needles setting will be good with todays lousy gas. The mains would be more then rich enough at 155,s if the airbox is stock and has the shelf in the center of it. If it has the bender cold air opening on top I would use 157.5 with stock center shelf in.
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Airbox is completely stock so I will setup initially with the 155 mains and needles at 3.5 and see what that looks like. The piston tops looks like it was pretty rich but I am not sure the conditions it was run in. They are all black and you can barely see the marks from the ports like I can on all my other pistons. Thanks for the input.
 
drew, i for sure would start at 50 pilots, you can always drop back in testing. it always safe to start rich and work back some. 3;16x (yammie tony)
 
I am also looking for ideas where I should start my clutching. I have 8bu-00 weights and what I think is an advant-edge G helix. Supposed to be a 50/40. I saw a setup that had a .8 gram in inner hole and a 4.5 in tip. It had a maximum performance white primary spring which isn't available anymore. I have a green-white-green Yamaha spring which is close to the same. I have a green secondary spring. It had 23/38 gearing and I have 23/40 right now. This will be a trail sled. Any suggestions or opinions on any of this. I realize its hard to figure this stuff out without testing so I am just trying to get as close as possible to start. There is no possible way I would have been able to do this last year with the weather so that's why I am trying to figure it as close as possible right now. Thanks again. I appreciate the info.
 
YAMMIEGOD3:16 said:
drew, i for sure would start at 50 pilots, you can always drop back in testing. it always safe to start rich and work back some. 3;16x (yammie tony)
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I will do that. From what I understand I should be able to get the pilots at least close without riding it so I should be able to push it out when its cold and tell if it is close right?
 
its just safer to start rich and work back. drew, i will tell ya if it wants those pilots, you will here it on the stand. 3:16x (yammie tony)
 
i got to tell ya, you posted this is gonna be a all around sled for riding, trails, lakes etc. don,t use 8bu-00. get your self a set of 8bu-10. way better for your setup. you can use the helix you posted, the maxx white spring and that green spring in secondary. also go to 23/38 gearing. 3;16x (yammie tony)
 
Thanks Tony. I have the bu-10s on my wish list but I will probably try the bu-00 first since I already have them. I was considering switching back to 23/38 gearing so I will do that. Anyone have any thoughts on my rear heat exchanger? I feel I need to do something different but I'm not sure. The mountain max one is pretty small and only 3/4" instead of 1". It seemed fine last year with it but would it need more with the 780? I am planning on installing a temp gauge.
 
8bu-10 put less power to the track then 8bu-00 do, so youd be going backwards for power gain to the track. In fact a 8bu-10 weight barely puts more power to the track then does a 8dn20. Solid info from a track dyno tells the truth on weights. If you want the most hp ability to go to the track the 2 top Yamaha brand weights to use are either 89a10 or 8bu-00, they apply the most power. There are aftermarket weights which out do these 2 but just for information sake I am keeping it to Yamaha weights. They are not necessarily the best trail riding weights tho. Backshift is diminished the heavier the weight and the more aggressive the profile is, but it can be tuned somewhat depending on the rear helix and spring used. Roller secondary clutchs also help overcome the backshift on these weights.
I would suggest putting the stock srx rear cooler back in the sled to handle the cooling, anytime you make more power you make heat. The 780 works fine with the stock srx cooling system, I would not take away from the stock srx system capacity with a 780 engine by using a smaller rear heat exchanger.

you will be having problems with running the sled down low and midrange so clutching and rpm will be moot as with 50 pilot jets, raised needles, it will belch fuel out the pipes and be low on rpm. it will certainly blubber quite a bit when trail riding it.

good luck!
 
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The 8bu-00 is what I will be using. I already have them plus I have been curious to try them. See how they will do this year and maybe next year try something else. I have a tunnel extension the srx rear cooler will fit in that I threw together when I extended the track so I will get another srx rear cooler and put it back in. I figured that would be pushing it but wasn't sure. Thanks for the info. It is greatly appreciated. I am sure I will have more questions when I get closer. Thanks again, Drew.
 
i would agree with mr.viper iv have had the 8bu's for a long time in my maxxium kit 780.with the pilots at 47.5 / 1 & 2 at 158.8 & 3 at 160.0 its a little rich.but i do have the nology hot wires.these are a big plus on the 98-99 srx's. from my set up really liked 8100 rpm's.so when you get it out keep a good look the RRR's.these are some FAST SLEDS.
 
8bu-10s , are the fastest weight yamaha ever made, their not the quickest e.t. but for mph they are the best , real world results, i can post my time slips. 10. 45 @ 120.98
mph stock 2000 srx on tar in the 1/4 15 in track. 8bu-10,s 110 mph on staker in 1000 f.t. with my 2002 srx on ice. drew, get your self a set of 8bu-10,s when your ready. for your riding style, they will work better than the 8bu-00. and start at 50 pilots, like i posted start safe, work back. 8bu-10s haul the mail 3:16 x (yammie tony)
 
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Thanks guys. I can't wait to get it together. I should have my water pump seals today so I should have everything pretty much cleaned up and ready to go back together soon. I got the needles set to 3.5 and waiting on some jets to come in. The crank should be delivered to the shop today. She's coming together. Will just need snow after that.
 
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