550/650 conversion pipe question

S

Squiggleybeast

Location
Oregon
Working on a 550/650 conversion on an old race ski that had a 550 with a Goki Reed cage conversion. I already have one running but the hull is in REALLY bad shape. Right now it’s just a stocker 650. The plan was to put the guts into the older hull and put an Sbn44 and a pipe in with it. I can reuse the intake and the reeds from the Goki cage since they are 650 parts, but I am not sure about the exhaust and pipe. The 550 had a Westcoast pipe and Ex450 manifold. Is he pipe reusable on the 650 or should I be looking for a specific 650 pipe? If it won’t work does anyone have some suggestions, or a pipe they would be willing to sell?
 
smokeysevin

smokeysevin

one man with a couch
Location
Houston
I have a nice stock 650 pipe that will fit well that I will sell for cheap. The aftermarket 650 pipes are really tight in the hull.

Sean
 
S

Squiggleybeast

Location
Oregon
smokeysevin said:
I have a nice stock 650 pipe that will fit well that I will sell for cheap. The aftermarket 650 pipes are really tight in the hull.

Sean
Click to expand...
If it’s that tight is it just better to modify the stock pipe by lengthening it a few inches and moving the water line to the end of the stinger then? The stocker is already a pretty tight fit. I know I have some room to lengthen it but I know it’s already tight against the hull. I had to drill and tap a new mounting hole below the original and use a silicone coupler to get it low enough to fit as it is. That’s why I was hoping an aftermarket pipe might fit a little better.
 
smokeysevin

smokeysevin

one man with a couch
Location
Houston
Check my build thread, the pjs pipe is a super tight fit. Stock would be better but for a 750 its not enough flow.

Sean
 
fastgtfairlane

fastgtfairlane

Location
Charlotte, NC
i ran a 650 westcoast pipe on a 750 engine in my 550 hull. it fit easily even with a ocjs 5gal gas tank in the ski. i also cut the entire ribbed center section out and welded a 3 inch longer, 1/4 larger ID diameter pipe on to the stinger and headpipe to get more length and volume. it made a nice bump in especially bottom and midrange
 
jetskijockey

jetskijockey

Location
Eau Claire, WI
I have built a few and honestly just do a fresh 750 big pin with 180 psi, 44 or 46 mikuni SBN, timing advance, stock 650 pipe dried out, and maybe 18p if not 19 p impeller.

That is more power than that little hull and yourself could handle. I am being seroius! There is a reason why there is Superjets and 800/1500 SX-R’s!


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jetskijockey

jetskijockey

Location
Eau Claire, WI
And yes you have a 650 motor just dry that pipe right out to the point of burning couplers and just ride the b*tch! You can make a 550/650 real fun if you just freshen the motor up at 180psi, new seals, and dry out that pipe.


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S

Squiggleybeast

Location
Oregon
Sounds like that’s the plan. This one is going to be for my 15yr old son so I don’t want to get too crazy, but he’s pushed the limits of the 440 he was riding so we put a 650 in it last season. He likes it but I know there is more power to be had. Already have a new impeller to go in it, so I figure while we are changing hulls and tearing into it I might as well do it now. Waiting on front tubbies to get here before we do any wrenching though. Seems like everyone is on backorder. Thanks for the responses. Probably going to go with a lengthened and dried out stock pipe. Would putting one of the automatic water restrictors in before the water box worth it or am I just throwing money away at this point?
 
S

Squiggleybeast

Location
Oregon
Most of the reading I have been doing says that lengthening the pipe (increasing chamber volume) lowers the effective powerband. Lower rpm hit. Since I can’t get a larger diameter pipe to fit I’m pretty much stuck with lengthening it to get that increased volume.
 
kevbo

kevbo

Location
dfw
Get a long 4" silicone coupler and try different lengths. Long cones were popular in the days when people liked to lug their 650s down with 16 degree impellers. I think you will get better performance with a lighter pump load. Then you run into the limits of a stock 650 CDI. A complete 750sxi ignition will provide a good retard curve and high rev limiter.
 
O

oldschool1

Location
Michigan
jetskijockey said:
I have built a few and honestly just do a fresh 750 big pin with 180 psi, 44 or 46 mikuni SBN, timing advance, stock 650 pipe dried out, and maybe 18p if not 19 p impeller.

That is more power than that little hull and yourself could handle. I am being seroius! There is a reason why there is Superjets and 800/1500 SX-R’s!


Sent from my iPhone using Tapatalk
Click to expand...
What waterbox did you run with the dried out 650 pipe?
 
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