97 GTX low on RPM

[cloudmaster_321]

Last year, final test run before winter lay up, ran 7k rpm, approximately 52mph indicated @ 50 degrees out.

This spring, after working some bugs and changing some parts, not getting the same results. I was indicating 6,600 rpm's 52mph indicated @ 75 degrees.

Things I changed this spring:

1. Removed beach house sponsons and installed new OE sponsons
2. Replaced stator with a new OE, and connector replaced (fixed charging issue)
3. Replaced Oil tank with new (fixed oil leak)
4. Unbolted carbs, reset my needles after futzing with them last year to try and figure out my large under rpm issue (turned out to be exhaust hose)

- Low needles set to 1 turn out​

-High needle 0 out on mag, 1/2 turn out on pto (1997 service manual says 0 out for both high needles)​

5. Rerouted pisser to front starboard side so i can see it when running vs out the back. Used 1/4" line and fitting. The route is twice as long as OE. The outlet is 1/4" vs the small 1/8" hole or less out the back. (possibly less backpressure?)

Seems I was approximately 300 rpm's short yesterday. Indicated speed seemed about right though.

​

 

[cloudmaster_321]

Had the ski out last night. Started good cold with choke. Idled around 1,500-1,600 in the water. Initially had decent response from idle. After running the ski for awhile, i'd get an interittent hesitation when pinning it from idle. I tried some choke, i think it helped the low end if i held it out about 1/4", but hard to tell. Seemed if i just came down to idle, and then pinned it, it was fine. Just if i sat at idle for awhile. I'd say it's loading up, but it doesn't feel like a rich hesitation. Also, top rpm's are still around 6,500. A little boggy getting there too. The other thing i noticed, is after getting run for awhile, and having the engine shut off, it would take some throttle to get the engine to fire back off. I couldn't just hit the start button, it wouldn't fire enough to stay running without some throttle. Once it starts, idles like normal. I did some plug checks last night at half throttle and full throttle. I'll attach the pictures. The picture of the plugs together are from the 1/2 throttle test. The pictures of them separately are from the full throttle test. I feel the mag side is slightly lighter than the pto. Currently 1 turn out on the low speed needles, and 0 mag, 1/2 pto high speed needle. I'm considering opening the low speed needles up a bit too. Texted with 2stroke smoke, and his suggestion was to go to 1.5 turns out on the low speed needle, and opening the high speed needles 1/2 turn. I think that concensus is partially due to the fact my compressions are high for some reason. 170/175. Don't know the reason for that, as my Matco gauge seems to read correct on everything else i own. Not sure what the PO did with this engine.

Thoughts?

 

[mikidymac]

You can't hurt anything going richer.
Open the screws and see if it gets better or worse.

 

[cloudmaster_321]

You can't hurt anything going richer.
Open the screws and see if it gets better or worse.

agreed, i'll give it a shot and see what happens

 

[DaddyLoafin]

If you trust your gauge and the compression is higher, are you running higher octane fuel?

 

[cloudmaster_321]

If you trust your gauge and the compression is higher, are you running higher octane fuel?

I've been running 91 no ethanol

 

[DaddyLoafin]

I've been running 91 no ethanol

was just checking. i rebuilt my 787 over winter and had the head cut so it was on my mind lol

 

[cloudmaster_321]

was just checking. i rebuilt my 787 over winter and had the head cut so it was on my mind lol

what are your compression numbers after your rebuild with cut head?

 

[DaddyLoafin]

I haven't checked yet. I've been busy and am still breaking in the engine. Hopefully I can get it done this weekend and ill let you know.

 

[DaddyLoafin]

what are your compression numbers after your rebuild with cut head?

172ish in both holes

 

[cloudmaster_321]

172ish in both holes

that's about what i have. How much did you take off, and how do you plan to compensate on the carbs?

 

[cloudmaster_321]

A little feedback from my adjustments made of low speed needles at 1.5 out/ea; and high speed needles pto 1 out, mag 1/2 out.

Low end throttle response was pretty respectable. I'm going to leave that alone. Problem, I could only get 3500-4000 rpms at WOT. Way too rich. I milked it until i could get to a sand bar and make an adjustment to at least the pto high speed needle. I took the PTO from 1 turn out to 1/2 turn out. The mag i can't get to unless i take the airbox off; so didn't do that adjustment. Tried with just the pto adjustment, and it was close. Revs up to 5,500-6,000 and then slowely makes it way up to 6,400. So still rich; but i noticed more power at the 3/4 throttle mark when doing tight maneuvers.

Since, I've gained access to the mag high speed needle, and turned in 1/4 turn. So a total of 1/4 out on the mag high speed. Haven't tried that on the water yet.

With all these adjustments. If the motor is warm, or was just run and shut off; it does take a little throttle to refire; then it idles fine. I'm not too concerned about it. When the motor is coldish, it doesn't require that.

 

[DaddyLoafin]

that's about what i have. How much did you take off, and how do you plan to compensate on the carbs?

I didn't machine it myself. I sent my jugs to group k to have them bored out and there was enough room in the box to fit my spare head so I sent that with them to be cut. I asked group k if I needed to adjust the carbs at all and they told me I didn't, just to run higher octane fuel. I have a gp1800 svho to so I'm already stopping to fill my jerry cans up with 93 on the way over there, so it makes that part a tiny bit easier for me lol

 

[DaddyLoafin]

A little feedback from my adjustments made of low speed needles at 1.5 out/ea; and high speed needles pto 1 out, mag 1/2 out.

Low end throttle response was pretty respectable. I'm going to leave that alone. Problem, I could only get 3500-4000 rpms at WOT. Way too rich. I milked it until i could get to a sand bar and make an adjustment to at least the pto high speed needle. I took the PTO from 1 turn out to 1/2 turn out. The mag i can't get to unless i take the airbox off; so didn't do that adjustment. Tried with just the pto adjustment, and it was close. Revs up to 5,500-6,000 and then slowely makes it way up to 6,400. So still rich; but i noticed more power at the 3/4 throttle mark when doing tight maneuvers.

Since, I've gained access to the mag high speed needle, and turned in 1/4 turn. So a total of 1/4 out on the mag high speed. Haven't tried that on the water yet.

With all these adjustments. If the motor is warm, or was just run and shut off; it does take a little throttle to refire; then it idles fine. I'm not too concerned about it. When the motor is coldish, it doesn't require that.

so, I have an issue on mine where if I shut it off warm and let it sit for a few minutes it won't start unless I have the throttle wide open. It's because there's fuel getting past the needle valves and seats, but I've tried 3 sets of valves and seats and never go it to stop so i assume the carb bodies are the problem.

 

[mikidymac]

so, I have an issue on mine where if I shut it off warm and let it sit for a few minutes it won't start unless I have the throttle wide open. It's because there's fuel getting past the needle valves and seats, but I've tried 3 sets of valves and seats and never go it to stop so i assume the carb bodies are the problem.

A leakdown test on the carbs would tell you what is leaking. It is part of the Carb Rebuild Thread.

 

[DaddyLoafin]

A leakdown test on the carbs would tell you what is leaking. It is part of the Carb Rebuild Thread.

Its the seats. I never could get them to seal up perfectly. I just used the ones that sealed best. I'm convinced it's the carbs themselves that aren't allowing the seats to seal up perfectly. One of the previous owners did a lot of really shotty work on it at one point.

 

[RSteeves]

I too have fought with leaking needle/seats in these carbs.

Here's what has worked for me EVERY time on all 3 of my skis:

Take a Q-tip, cut off 1 end and stick it in a power drill. Dip the cotton end in metal polish and insert it into the seat with the needle removed and polish the seat surface until it is perfect using the rotating action from the power drill. Clean off residual metal polish with carb cleaner and compressed air.

Then, using WD40 to gently wet the needles upon reassembly - check your pop-off. Cleaned mine right up from leaking to a nice clean "pop". You could see shiny brass in the seat area where they were previously corroded looking.

Worked on my 787, 951, and Kawasaki 550 skis. I didn't come up with it - but it works well! And now my skis start right up without loading up with fuel.

Good luck!

 

[cloudmaster_321]

I too have fought with leaking needle/seats in these carbs.

Here's what has worked for me EVERY time on all 3 of my skis:

Take a Q-tip, cut off 1 end and stick it in a power drill. Dip the cotton end in metal polish and insert it into the seat with the needle removed and polish the seat surface until it is perfect using the rotating action from the power drill. Clean off residual metal polish with carb cleaner and compressed air.

Then, using WD40 to gently wet the needles upon reassembly - check your pop-off. Cleaned mine right up from leaking to a nice clean "pop". You could see shiny brass in the seat area where they were previously corroded looking.

Worked on my 787, 951, and Kawasaki 550 skis. I didn't come up with it - but it works well! And now my skis start right up without loading up with fuel.

Good luck!

Interesting. If i ever need to open my carbs back up i'll keep that in mind.