Cleaning my Carbs & Jetting

[SRV540]

I was up North this weekend to install a new windsheild and skid plate on my 800, and decided to clean the carbs before the cold weather and snow hit, as last time I was up north the sled seem to have dirty carbs as it would not rev past 6000rpm, so I drained the fuel from it wich was really bad and installed new fuel wich made a difference a bit of one anyhow, will now rev to 7000rpm. So this weekend Itook the carbs off for the first time, and cleaned and inspected. They were pretty clean and no clogged jets. But what I find interesting is that it has 157.5 main jets installed on all carbs, could this be why its not running like it should be???? the Carbs are supossed to be bored 3mm and it has bender quads and trail porting and reeds.....but 157.5 seem way high. Bender says to run 145's with there quads on stock porting and carbs???? Can anyone recomend jetting for me????? I am pretty much at sealevel here in southern ontario.....should I try 147.5's???? [I] dont know alot about jetting, I have a spare set of stock carbs with stock mainjets, But I was affraid to try those as I might have leaned it out to much......but does this sound why it seems to be running sluggish......to rich? and by the way the plugs are kinda black and wet, compression is 120lbs across the board.

http://tinypic.com/fodc2a

http://tinypic.com/fodc83

[SRV540]

and where is a good palce to buy jets?? right from yamaha or is there a cheaper place?

[SRV540]

well looks like Royal Distributing here in Canada has them for $3.79 each, I was thinking of getting 4 145's and 4 147.5's any input on this???

[vmax4rules]

I can't help you on jetting, however with 157.5's you better carry an extra backpack of fuel.
I have found that you can get most jet's except for the in between sizes EX:138.8's from most A/M suppliers - the tweaners are Yamaha only.

[SRV540]

Thanks vmax4rules, yeah the stock carbs I have have 143.8 in them, I really dont know why this big of jet was installed, the guy I bought this sled from had just put in this 96 motor which he bought complete with carbs,pipes and clutch. he said he just rode it around the yard and then, I bought it.

[vmax4rules]

Here is my jetting specs (which is too fat and will be leaned out shortly)

96' 800
Thin head gasket mod
Dial a jets set at #3
PSI quads
135 mains
Needle clip at #3

[SRV540]

What elevation are you at? I am just going from benders set up say go for 145's for 0-2000ft. I am at sealevel here in Ontario.




Here is my jetting specs (which is too fat and will be leaned out shortly)

96' 800
Thin head gasket mod
Dial a jets set at #3
PSI quads
135 mains
Needle clip at #3

[vmax4rules]

What elevation are you at? I am just going from benders set up say go for 145's for 0-2000ft. I am at sealevel here in Ontario.

500-2000' in elevation here in Michigan.

[Mtnmax]

Stock sled comes with 143.8 mains. Quad pipes may need to be a little fatter. Other things to check would be the clip position on the jet needle(should be in the 3rd position), the float height( 13.3mm maybe a little less for quad pipes),and the idle mixture screw( 1.5 turns out for starters.) For your info the stock pilot jet is a 47.5. I do have Yamahas tuning and service data for the 800 if your interested. Other than that I cant really help. I ride at 8000-10000ft, and run 125 mains accross the board. You should get 8300 to 8500 rpm. Good luck!

[Reimond]

You have to make that WOT 'spark plug' run to verify your A/F ratio.
Maybe these main jets was used with power filtters before ???

[vmax4rules]

I think with Bender quads you should be spinning 8800-9000 rpm's.

[SRV540]

Yeah I guess so, but would you say it would be a good start to get some 145's and 147.5 main jets



You have to make that WOT 'spark plug' run to verify your A/F ratio.
Maybe these main jets was used with power filtters before ???

[fastmax]

Did the sled run good last season with this jetting and just crapped out the last time you rode it? If it did, then jetting is not your problem. I have seen sleds with a weak sparkplug or sparkplug cap haveing the same symptoms as yours.

[SRV540]

I just bought the sled in September, and the guy I bought it from threw a piston and rod in the original motor, right at the end of the season, so he bought a 96 motor with fresh topend,trail porting,3mm bored carbs, reeds and bender quads, it cam with carbs and clutch, so he really did not ride it much (just around the yard). I have changed the plugs, but not the caps, will do that though. It start on the first pull and has even compression. Well I just ordered a few sets of jets today....so I am going to lern how to jet my sled!!! As I really dont like taking any of my toys to the shop unless I really have to!