Carb problems

[kizersoze]

I have a 97 GS with a stock 717 engine and single mikuni carb. I recently replaced the original fuel lines and did a carb rebuild at the same time. After putting it back together, the throttle action is not smooth. As I give it more throttle from start it does not increase the rpm smoothly. I pulled the carb to check it out thinking that maybe the pop off was out of specs. It reads 40 psi, which is within the 23-43 spec range for a 1.5 needle valve and I used the 95 gm spring (dull silver?) which looked like what was in there originally. I set the low and high speed adjusters to the minimum adjustments (1 turn low and 1.5 turns high) after rebuild. My guess is that these need to be fine tuned. Any ideas? Thanks

 

[Dr Honda]

Does it idle? will it go to full throttle if you just pop it wide open?


Unlike most manufactuers... I've noticed the SeaDoo does a good job of tuneing at the factory. It should be running at the factory specs.

 

[kizersoze]

yeah, it idles ok. As I throttle up it doesn't increase the rpm smoothly but will jump to a higher rpm. Doesn't seem to have a problem running wide open.

 

[Dr Honda]

Sounds like the little check valve in the high speed circuit is leaking back... OR (more likely) the bypass holes in the carb are plugged.


1) If the check valve is leaking back... it will draw the fuel from the high speed jet, and it will take a little time to refill. Anything from a unstable idle, to a bad mid miss will result.

2) The bypass holes are the small holes in the body section that are directly across from the butterfly (throttle) valve. As you open the throttle, they add fuel in small steps, as they are uncovered by the butterfly. If one or 2 of these are plugged, you will have to rely on the low needle to feed enough fuel, until there is enough air velocity to activate the high fuel system. This is probably why you feel a lag, and then a jump. (poor mid, and then a hit from the high fuel)

 

[kizersoze]

I'll check it out tonight. I saw those in the schematic but didn't think about checking them. Thanks!

 

[kizersoze]

Holy cow, how can you tell if the bypass holes are open? I took the carb apart and tried carb cleaner and compressed air on these holes and cannot tell if they are clean or not. I even tried a thin piece of copper wire in each direction but there is not a straight through opening that you can put the wire through.

 

[seadooya]

while carbs apart, install the oem n/s springs. Also, use carb cleaner, then compressed air to clear out the fittings and passages

 

[Dr Honda]

Holy cow, how can you tell if the bypass holes are open? I even tried a thin piece of copper wire in each direction but there is not a straight through opening that you can put the wire through.

If you cant get a thin piece of wire into the hole, then that's your prob. Although, it's not recommended to use wire, since you don't want to change the orifice size... but I've been known to use it on stubborn clogs.


You will have to take the plate with the check valve out of the carb, and then have a helper hold the throttle valve open. Then, shoot carb cleaner into the pilot jet, while looking in at the bypass holes. There should be enough volume and pressure to see it coming out those holes.

You may have to go back and forth with carb cleaner, compressed air, and a wire to break though a tough clog. Once though... keep going back and forth with cleaner, and compressed air. (got to melt out all the junk)

 

[kizersoze]

OK. Been at Lake Martin on and off for the last couple of weeks and have some updated info. GS is still running the same, OK but not right. Still sluggish at take off but runs OK at higher speeds. Pulled the plugs that had been in the engine for several months and both looked like I expected with a brown colored insulator. I installed a new set of plugs and ran it at 1/4 to 1/3 throttle for about ten minutes. Pulled the plugs and the back plug had a nice chocolate colored insulator, pulled the front plug and it was still white. I just pulled the plugs and there is a difference between the front and rear plugs. Rear is dark brown and the front is tan colored. Is it not pulling fuel into the front cylinder. Obviously it is firing as there is some color on the insulator but maybe not getting fuel at low speeds. Is my engine toast? How can I check it? Compression test?

 

[Johnson8537]

OK. Been at Lake Martin on and off for the last couple of weeks and have some updated info. GS is still running the same, OK but not right. Still sluggish at take off but runs OK at higher speeds. Pulled the plugs that had been in the engine for several months and both looked like I expected with a brown colored insulator. I installed a new set of plugs and ran it at 1/4 to 1/3 throttle for about ten minutes. Pulled the plugs and the back plug had a nice chocolate colored insulator, pulled the front plug and it was still white. I just pulled the plugs and there is a difference between the front and rear plugs. Rear is dark brown and the front is tan colored. Is it not pulling fuel into the front cylinder. Obviously it is firing as there is some color on the insulator but maybe not getting fuel at low speeds. Is my engine toast? How can I check it? Compression test?

A COMPRESSION TEST is always a good idea after every few rides IMHO
You want an EVEN number above 125 if you are getting lower number 100-115 (or uneven off by more than a few lbs) start thinking about a top end rebuild.