Thread: 98 Stx 1100

Yeah, I've had the same issue. I can't tell u exactly but my ZXi 900 had 90psi stock @ the 70hr mark. The reason they don't give a specified PSI reading for 2 strokes is that they make their peak compression at high RPM, at least a lot higher RPM than any starter could make it do. It doesn't matter too much what the compression is, as long as it's not OBVIOUSLY low & as long as there is less than 20PSI difference between cylinders.

I'm pretty sure the 1100's had the same compression as the 900's or maybe a tad less but it wouldn't be much.

Compression on a 2 stroke can only be done dry, as when u pour oil into the cylinders, then crank, it'll go straight thru the ports.

Actually, I'm not sure that reading of 90PSI I got is accurate, coz we used Slashers guage which is damaged.

90 is still acceptable, but lowish. 150 is too high for a stock motor. 120 would be the max. unless u have a mod'd head. 100-110 is about right but as I said, they don't read accurately with the starter motor. U need to get em cranking pretty fast to get accurate peak compresion, unless u have a rotax motor or u seal the ports.

my 900zxi just had a full rebuild from main dealer when i got it. while it was still in the dealers showroom i did a comp test before i bought it, and i got 115psi across all cylinders. thats a good figure. a good motor should be 100 - 120 for a stocker. yours is just under, so its a little worn, but still usable never the less. depending on how much you use it you may be looking at a rebuild in about a year or so. hope this helps

Not anymore , that was before I rebuilt it. The head was shaved amongst other things, but the ports were shoe-horned a bit so compression may be same as it was. I haven't put a guage that I trust on it yet to see what it reads off the starter.

I have a way of making the start motor produce enough engine spin. Not necessary safe for engine though, but gets the RPM up.

1. Wait until the battery is too flat to kick over to start (or not, but this was the cond. I started with).
2. Park large engine vehicle next to Jet Ski, and open hoods and seats to expose batteries on both.
3. Start vehicle
4. Connect jumper cables to Jet Ski (pos then neg)
5. Connect jumper cables to Vehicle (pos then neg)
6. Rev vehicle to about 2000 rpm to ensure vehicle producing excess power to cause the JetSki battery to be charged.
7. Keep up Revs for 5 mins or more.
8. Hop out of car, and for a shits and giggles, Check the engine will turn over by trying to start it
9. Wonder what the difference in Jet Ski engine sound is..
10. Crank again..
11. Finally figure out the jet ski is doing 3000 rpm.
12. Sh*t yourself, and stop cranking.
13. Disconnect leads, and shut vehicle off.
14. Start Jet Ski.
15. Drop in Water and go for ride, thanking every god under the sun for not fudging the engine.

Or Short Version: Hook a second battery in parallel to give more AMPS to the starter.

Guys, it is very dangerous (to the health of your ski) to jump start it in that manner. If you are wanting to charge your battery from another vehicle, disconnect the +Ve wire from your jetski to isolate your ski's electronics from the "action". Then do the jumper charging as above. Once it is charged, detach the jumper cables, reconnect the +ve cable and try to start your ski again.
I don't want to bore you with the technical details as to why (unless you insist) except to say that solid-state components do not like spikes and surges!
If you do need that extra current boost - jump start your battery as described above, then switch your car off. Reconnect the +ve on the jetski. With the jumper cables still connected, start the ski. Get the ski motor warmed up and cleared of fogging/flooding or whatever. then switch the ski off. Disconnect the jumper cables and try to start the ski again (which should take less effort now that the motor is warmed/cleared).
If your battery is still giving problems by now you should seriously consider replacing it. Trickle charging the battery while the ski is not in use is best.
This concludes my 2 cents worth.