Re-Jetted carbs, now no start

[mcibmw533]

I put a 760 from a WBII in my SN last winter and have been working on getting everything to cooperate this summer. As far as I know, the motor is stock with aftermarket flame arrestors and a Pro-Tech Mach 1 Pipe.

I re-jetted the carbs based off the specs I got from Pro-Tech but now I can't get the ski to start. (It ran fine, but slow, with the stock carb settings.)

How long does it take to get the fuel flowing back through the carbs after re-jetting? I have checked and double checked all the lines and they are all hooked up as they were before removal of the carbs.

The ski fires and runs fine when using starter fluid or dribbling gas down the carb, but once it burns off, the motor dies. :banghead: Is there any way to check to see that I'm actually getting fuel through the carbs?

If the original 650 wasn't totally shot I'd put that back in, at least it ran. I'm just about done messing with this 760 but have been told it will be worth the hassle once everything gets tuned in.

Thanks for any advice.

 

[u887266]

If you take the return line loose and spray some gas in the carbs., you should have gas run out the return line. Thats a good way to tell if you are getting gas in the carbs, or not.

 

[mcibmw533]

Thanks, I pulled the return line, it does dribble out gas when starting, but the engine still dies after a few seconds.

I am following Watcon's testing/tuning techniques. Currently the high speeds are 1/4 closed and the lows 1 turn open.

I tried opening first the lows and then the highs 1/2 turn more, but still no work.:banghead:

Any ideas?

 

[Matt_E]

Gas should do more than "dribble out" of the return nipple on the carb when you crank the engine.
It should literally spurt out.

Do you have the fuel supply line going to the bottom nipple?

Do you have the short pulse line going from the case nipple to the middle carb nipple?

 

[jeepinxj]

What jetting did you put in the carbs?

 

[mcibmw533]

Per Pro-Techs recommendation:

140 main
115 pilot jet
1.5 needle & seat
115 gram pop-off pressure spring

I tried using Watcon's tuning techniques - Lows 1 turn out and Highs 1/4 turn out from closed.

How "tight" is fully closed? I didn't torque on the high & low screws but turned them enough to know they were fully closed.

They are now each 1/2 turn out past Watcon's starting point, as referenced above. The ski will now start without starter fluid but dies in less than 1 min. I can run it slightly above idle but then the ski revs up slightly (on its own) and plateaus, then suddenly stops as if all fuel was cut off (no sputtering).

Pro-Tech also recommended that the low speed screws be 1.5 turns out and high speed screws 2 turns out. Should I try this to see if it will at least run consistently and then fine tune from there?

All the hoses appear to be hooked up properly, I did some more testing with the fuel return hose removed while starting/running and get about 1 cup for every 45 seconds-1 min running @ low rpm - it's basically a steady stream with low to no real pressure.

Thanks

 

[SUPERTUNE]

Per Pro-Techs recommendation:

140 main
115 pilot jet
1.5 needle & seat
115 gram pop-off pressure spring

I tried using Watcon's tuning techniques - Lows 1 turn out and Highs 1/4 turn out from closed.

How "tight" is fully closed? I didn't torque on the high & low screws but turned them enough to know they were fully closed.

They are now each 1/2 turn out past Watcon's starting point, as referenced above. The ski will now start without starter fluid but dies in less than 1 min. I can run it slightly above idle but then the ski revs up slightly (on its own) and plateaus, then suddenly stops as if all fuel was cut off (no sputtering).

Pro-Tech also recommended that the low speed screws be 1.5 turns out and high speed screws 2 turns out. Should I try this to see if it will at least run consistently and then fine tune from there?

All the hoses appear to be hooked up properly, I did some more testing with the fuel return hose removed while starting/running and get about 1 cup for every 45 seconds-1 min running @ low rpm - it's basically a steady stream with low to no real pressure.

Thanks

I say yes!
Your way to lean trying to run the screws too far in...
Change the spring to a 95 gram spring too, give the carbs some fuel pressure or put in a much bigger low jet like a 125.

 

[jeepinxj]

I put a 132.5 and a 135 main jet. 95 gram spring would be perfect. Just did mine and runs like a champ.

 

[Woody]

seems like a stupid question...but are you positive you put everything back together on the carb properly? i made that mistake on my 650 and it ran when i threw gas down the carb but as soon as that burned off she shut down

 

[mcibmw533]

Thanks for the help so far.

I made sure to mark all the lines very clearly. I'm fairly certain everything went back together as it came out.

My rebuild kits just arrived, so I plan on cleaning & rebuilding this week. Hopefully that will do the trick - the carbs were amazingly gunked up inside.

If I use the Yamaha Carb Cleaner Dip is there any component I can't/shouldn't put in it? It seems like all should be OK since it's non-caustic & I'm putting in all new gaskets, seals, etc. in anyways.

Updates to come once rebuild is complete.

 

[Tanman]

check the return line plumbing on the carbs. There is a restrictor on one of the carbs that keeps pressure in the carbs but still lets unused fuel out. I had a problem where mine were plugged. do a good clean on the back side of your carbs where your return lines are. if still weak fuel pumpin out while runnin your pulse or fuel pump might be bad. Just my 2 cents : )

 

[mcibmw533]

Thanks for all the input.
It Runs!:bananajump: (140 main jet, 115 pilot jet, 1.5 needle & seat, 95? gram spring)

I was running the ski on the flush kit and I currently have the low speed turned out 1.75 turns and the high speed turned out 2.75 turns.

I'm thinking I need to go to the next bigger main jet (142.5 right)?

It iddles OK with a "hick-up" (not a backfire) every 5-10 seconds when idling, I've tried turning out the low speed which decreases the frequency of this problem, but hasn't eliminated it. Any ideas on what to do next?

It has slight hesitation when hammering the throttle from iddle but has become almost non-existent with 2.75 turns out on the high speed.

At what point do I need to worry about changing the spring and/or needle & seat?

I think I used the 95 gram spring (my rebuild kit came with two springs & I didn't use the 115 gram)? It has 1.5 needle and seat.

Will performance change when there is actally load on the motor when in the water as opposed to running on the flush kit? I probably won't be able to perform water trials until this weekend, but am hoping to get really close with the correct parts this week.

Thanks for all the help.