05-31-2012, 01:28 PM #1
New SL780 vs Old SLT750... first impressions... sound normal?
I've gotten my once-basket-case (literally) '96 SL 780 finally rebuilt and reassembled and out on the lake. It is running awesome! I'm very excited. (Yes, I'm keeping a very watchful eye on piston wash, temps, etc.)
So, how a ski "feels" is all relative. Up till this point... I've only had significant seat time on my rebuilt SLT 750 ski. It's a fun ski... not too fast... but is great for turning and sliding and spinning. Large flat seat. Very stable on the water.
Now... I'm learning my new beast. '96 SL 780... w/ ext pump, ext ride plate, R&D intake grate, 6 vane SS stator, 5 deg wedge, cone extension... and my first ski with trim on it. My first impressions are... HOLY COW... this thing is fast! It's all relative, I know... coming from my slow 750.
I'm also noticing it's more tipsy in the water... but I'm guessing this is because the SL is smaller/shorter than my 3 seater SLT.
It also has the hump in the seat... guess that'll help me from flying off the back... although I think I'd like it a few more inches rearward so I can better stretch my long legs. It should also help rear passengers sit a tad higher so they can see better.
I've yet to push the SL hard in the turns/slides... the lake was a tad cold for swimming... but it's definitely way more planted than the SLT. Is this due to the sponsons and/or the extended ride plate and pump? My SLT has none of these and seems a lot more "tossable". Riding it like I do my SLT, I felt like the SL was either gonna throw me off or tip over.
The steering on the SL is different too. At slow speeds, it's as free and easy to turn left/right as my SLT... but on plane and at speed the steering gets very tight. Is this normal? Perhaps a safety thing so you can't easily throw yourself sideways at speed? What causes this... the sponsons? ext ride plate/pump? the trim? The trim does work and I can feel the nose come up/down depending how I set it.
Sorry for the newbie questions about the SL... just looking to hear everything is as it should be with my 2 seater.
05-31-2012, 10:05 PM #2
- Join Date
- Jun 2010
- Milwaukee WI
The better handling is from the sponsons and extended pump/plate. A much more fun ride in my opinion. Everything sounds normal. The bars are a little harder to turn at high speeds, and especially with the trim down.
06-01-2012, 10:07 AM #3
Thanks BryanP for the confirmation. I was thinking that was probably the case.
After another fun evening of shakedown... I'm very pleased with how the SL780 is running. I checked plugs/wash 3 times... one time being a long WOT run across the lake where I killed the engine at WOT and paddled in to the beach to pull plugs and read wash. Readings were pretty good overall on the edge of lean so I richened up the high and low mixture screws just a tad... and finally got nice slightly rich readings I was looking for. I'm okay sacrificing a few mph/hp's for the added safety of running just a tad rich.
Compression readings were good for stock pistons/cylinders with just new rings: 120#M-115#C-120#P... so I'm pleased with that. My well worn SLT750 could only muster 112#'s after new rings (yeah, it's due for an overbore and pistons/rings... but it's running great anyways). Had my Garmin GPS with me... confirmed flat out 52mph at 6420rpms. Man, is that a rush! This little 2 seater really jumps out of the hole.
As for the steering... I'm also thinking the cone extension plays a role too. The pressure out the back through the steering nozzle is higher with a cone extension (like putting your finger over the end of a hose) so it resists redirection more. I also noticed I have a little slope in the steering. Gonna have to check both ends of the steering cable to remove as much excess play as I can.
So here's another issue I'm wondering about: "coming on the pipe". When this 780 hits 4000 rpms... it gets this thrust... this boost... even the exhaust sound changes as it surges up to 5000 rpms. I kept trying to get the engine to settle between 4k and 5k but could not. It would either surge from 4k to 5k... which is a sweet rush... or if I held it at 5k and let off throttle just a hair... it would sorta step down right to 4k... the rush would stop... exhaust note even would change. Is this what folks refer to as "coming on the pipe"? I've not experienced it on my 750... must not be as noticeable.
06-01-2012, 11:27 AM #4
Absolutely what is happening when you are getting on the pipe. My SL780 does this as well. The Pro 785 is even worse....more like a light switch; either WOT or not.
06-01-2012, 12:25 PM #5
- Join Date
- Jun 2010
- Milwaukee WI
06-01-2012, 02:47 PM #6
06-01-2012, 02:48 PM #7
[QUOTE=LaveyT;1950782]My SLX (95 780) does this but my SL 780 does not. My SLX will not run 4400 rpm, 4100 then jumps to 5000, I figured it was a Rich spot in the fuel curve?
06-01-2012, 02:49 PM #8
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