Carb Jets?

[6KJR]

Just wondering at what point in time you should get new carb jets. (high speed) I noticed my screws are out quite a bit. The machine runs well so I dont plan on changing things for now or maybe ever. But if I was to order new jets, is there somewhere that you can see what size might work with engine setups, ect?

 

[kustomkarl]

The High speed adjustment should be set to "0". If you have to adjust the high speed I would look into cleaning your carbs first, and do a compression test before you jump to conclusions.

Karl

 

[6KJR]

Someone asked me once how fuel can flow through a jet set at zero (all the way in?) The carbs were redone not that long ago before I bought the machine and I have them off now for inspection, fuel filter cleaning, fuel line replacement. While they are off I figured I would get a carb kit to do the fuel pump but noticed the jets are out pretty good. I cant find info anywhere on jets, sizes, ect. aftermarket flame arrestors and oil injection delete probably calls for some different settings.

 

[kustomkarl]

The way the carbs are set up from seadoo, is that Mikuni carbs are used on a lot of different craft. On seadoos, the engine is set up to use the fuel supplied with the needle all the way in...so no extra fuel is necessary to run at hi speed...no adjustment is needed. It is cheaper for seadoo to go that route than have a new carb built just for their engines, that didn't have a HI speed adjustment. You would only need to change jets if you modify the engine. In stock form just adjust accordingly.

Karl

 

[seadoosnipe]

Fuel flow?.......

The high speed jet adjustment is not actually adjusting fuel in the path of the fuel for intermediate or wide open throttle operation. It's a by-pass around the high speed jet. If you have your high speed by-pass opened, then you either have a dirty jet or mods have been made in the flame arrestor that have required it to need more fuel.

Your jet sizes are determined by your horsepower. The carb is set up for each engine configuration. You could find the same carb on a bigger or smaller engine but running different size jets. Your model SPX is using a 142.5 main and a 70 pilot size set of jets with a 80 gram spring set on your lever and needle valve. :cheers:

 

[6KJR]

Thanks for the info. What do you think the adjustments might possibly be with aftermarket flame arrestors and oil injection delete? Does the injection delete even make a need for a carb adjustment? I thought youd want a little more fuel for the top end?

 

[seadoosnipe]

oil injection?.......

Blocking off your oil injection should make no difference to top end. When you pre-mix, your ratio is set for WOT. You'll notice at WOT, there is little or no smoke from pre-mix. You may notice a little smoking at idle though.

As for your carb adjustments. That is totally dictated by your plug condition (click on my "Snipes Korner" for a complete guide to reading your plug, including pix) and vacuum of your carb (manifold pressure). The venturi will create the vacuum on your carb to pull in all it needs. If it needs more, you'll know. That's when you can open your high speed by-pass a little. Do not attempt to adjust your high speed screw at idle. Fuel should be from your low speed jets at idle, both jets in transition to high speed, then high speed jet at WOT.:cheers:

 

[6KJR]

Alright, well when it gets all back together next spring I am gonna have to do a couple chops and see whats goin internally.