717 confused

[k1llua]

Hello all,

Been a bit since I posted about my 2001 gs. I had it running ok for a while there, then it started having trouble with ignition. I was getting weak spark so I got a new ignition coil and it started up on the trailer real nice. After riding for a bit this year it just died, then hard to start. It would idle but then bog down hard with any throttle.

I pulled the carb and rebuilt it with mikuni parts, followed the guide, no leaks, pop off is at about 40 psi. Accelerator pump seems fine according to what I read here.

I put the carb back on, got it all sorted and now I can't get it to fire again. Battery holds 12.67 after a charge, though after a couple rounds of trying to start it im down to 12.25. Voltage at start is 10.6 when the battery is fresh, but drops down to 9ish after it loses a bit of juice.

Both cylinders compression 130-135. I had the cylinders bored out and rebuilt the top about 2 yrs ago.

It's almost like its flooding but then as it starts to get ignition it isn't getting enough fuel.

Not sure where to go next..

Could I have a check valve issue somewhere that I need to find?

Should I take the carb out and recheck the rotary valve?

 

[lavasioux]

40 psi may be too high for pop off? Interested in hearing what others say.

 

[hingstin]

Maybe 40 is high, but that is so individually / craft/engine, You cant say what is ok or not ok, but it seems to be at higher sida.

BUT, the "pop-off" do not make the engine go bad at Idle or half throttle or full throttle.
the pop-off just covers the lower part of rpm.s a bit over idle ...

Try to put gas direct into cylinders through sparkplug hole and see if it fires up.

If not, You maybe have an ignition issue (even if You have spark) Check the resistance at Pickup coil (CPS).
also do Yo have Fresh Spark plugs ALL 2-stroke engine "eats" sparkpolugs if something with fuel/air mix is wrong or Ignition.
even if You have somkind of spark "outside cylinders" it can be, that under compression it do NOT spark.
sparkplugs are so Cheap, it is a must to have spares when you are trying to solve problems, to be sure.

the readings of volt, is pretty normal. so thats OK

here a short explanation of how the Mikunis work

 

[mikidymac]

Your battery voltage is low.
Under about 11 volts you will not get spart and 9 volts that is terrible.
Time for a new battery.

135 compression after a rebuild is bad, you should be at 150, I would check with a different gauge.

That aftermarket coil is suspect, did you verify you have good spark still?

Your pop-off is within spec but I would verify jets and needle and seat size.

 

[k1llua]

I'll start with new plugs and battery. That's the 3rd agm in 4 yrs of having this ski, battery eater or just crap batteries I guess..

Thanks everyone

 

[k1llua]

All the parts in the carb are original as far as I know, the needle and seat seemed to be doing fine during tests.

Had my battery checked out and it's fine under load.

New plugs and a bit of gas in the cylinders and it ignites. I double checked the fuel filter cup, and took the lines off the ski and made sure I was getting gas out of them. I got the ski to start regularly now, I can get it to fire up without adding extra gas.

It seems to be a little boggy when I try to get it to wot. so I've been reading about adjusting the idle and the low and high speed screws.

They are at the book values right now, low 1 turn out, high 0. Should I start by opening the high speed screw a turn? It seems like a trial and error kind of thing from what im reading.

 

[burtshaver2021]

I would leave the carbs at the factory settings. Sounds like you need a fuel system rebuild refresh. Have you had the carb apart to clean?

 

[k1llua]

Just took the carb apart and cleaned it all out, fuel lines are new from the top end rebuild all black. I did what I could to clean the gas tank then as well, siphoned it all out and rinsed it with new gas.

 

[burtshaver2021]

Did you verify that you have the correct jets in when you cleaned? I don’t think it should be a permanent fix but yea, your right try opening the high speed a 1/8 turn and see what happens. Can’t hurt it being to rich.

 

[k1llua]

I didn't take out the calipers and measure them, no. I just assumed lol.

If I can't sort it out I'll pull it apart again and check. Is there meant to be a jet between the main body of the carb and the accelerator pump?

 

[burtshaver2021]

I didn't take out the calipers and measure them, no. I just assumed lol.

If I can't sort it out I'll pull it apart again and check. Is there meant to be a jet between the main body of the carb and the accelerator pump?

I’ve never measured the jets, but it’s written on them what size they are, may need a magnifying glass though

 

[burtshaver2021]

I didn't take out the calipers and measure them, no. I just assumed lol.

If I can't sort it out I'll pull it apart again and check. Is there meant to be a jet between the main body of the carb and the accelerator pump?

I believe a lot of them do have a restrictor in one of the lines for the accelerator pump. Never had one out but I hear they are similar to a pilot jet

 

[lavasioux]

I'll start with new plugs and battery. That's the 3rd agm in 4 yrs of having this ski, battery eater or just crap batteries I guess..

Thanks everyone

Yep unless they are on a tender during winter, they often dont last more than a year. But with a tender they can last longer.

 

[Grim]

Something I would try, you said you had the battery tested and it was good. Charge it up with a battery charger, don't do it while connected to ski, take it out or at least take cables off. After a good full day charge see if it cranks and rides nice. You could be having an issue with your rectifier. If it rides nice put a meter on the battery and tell us the voltage at idle and then rev up to 4500 RPM and tell us those voltages. It should be in low 13V at idle and rev into the low 14V to mid 14V range at 4500.

It sounds to me if the ski is not charging the battery and its getting low, causing low spark.