07-11-2009, 01:23 PM #1
which parts to use 750/780 conversion
Finally brought the cylinders to the machine shop and had them bored for my new pistons (using 780 jugs .5mm over). Also planed the heads down .030" to make it flush with the bottom of the domes. Have the new crank waiting to be installed but I'm wondering which set of cases to use. Have both 780 and 750 cases, the 750 still has the oil pump and a better paint job. Would rather use the 750 with the oil pump since I don't really want to mix gas all the time. 750 also has primer lines on the intake manifold but I can always mix and match intake manifolds. Also I think the CDI on the left is the pro cdi, but need someone to verify. I think I have a pro stator too but I can't tell the difference between the two if there is any. Lastly the reeds, which the picture turned out crappy but the red reeds are the V force the other ones are stock 750 reeds. Wondering if the V-force will even work.. so need some input have a lot of different parts including pipes (longs short and medium) and water boxes just need to find the best combo. pipe selection I think will be dependant on what will fit into the 94 SL750 hull.
07-11-2009, 01:32 PM #2
What yr are the 780 cases? If 97, then that would be the one to use. They were ported a little differently than the prior yrs. Gave a few more horse power. The oil pump can be installed in the 780 case.
Absolutly use the v-force reeds. Much better than stock!
The left cdi is a 785. Lets see some high res pics of it and the stators. I should be able to tell what yr and model if I see the part #s.
The stator pt #s are on the back.
07-11-2009, 01:37 PM #3
Note the # on the back in this pic. 78 is 780, and the last 2 digits are the yr 96.
07-11-2009, 01:37 PM #4
high res? oh boy that means I have to borrow the wifey's camera.. and bring it into the shop.. do we have to go there? ha jk I can get them but its going to take a few days. She is at the beach while I stay home and work, I mean play, err, work thats not really work.. who needs the beach when you have an engine that needs to be built
07-11-2009, 01:38 PM #5
07-11-2009, 01:45 PM #6
The pro cdi should have a number like 78Z97. the Z indicates 785 and again, the last 2 digits are the yr. The stator pt # will be the same.
07-11-2009, 10:49 PM #7
- Join Date
- Oct 2006
- Cleveland OH
What are you ultimately after? Top speed or accel?
The 750 porting will out accel a 780, but the 780 will catch it and walk on bye...
Always use V Force if that's what they are. The red is confusing me.
Use the 785 CDI, and that is what is on the left.
750, 780 and 785 stator reallt shouldn't matter. Ohm test the 2 and install the better one according to specs.
Pipes will fit regardless of what you use, slight rubbing on hull may happen, but a little rubber padding will stop any damage.
Short dry pipe for top speed and wet pipe for accel.
03-19-2014, 09:48 PM #8
iam in the same boat cant decide what parts to use I have a 650 and a 750 also a slx 780 . was thinking boring the 750 to 777 ,porting and milling the heads . would this work better than the 780 ported and head milled . what about using bored 750 cylinders on the 780 case .there has to something about the 750 or group k would have liked the 780 better ? help me figure this out please.
03-22-2014, 01:41 PM #9
I did this conversion a couple years ago & was dissapointed with the results, gained 2 mph at the most, acceleration is better though, no difference using 750 or 780 CDI's, didn't try a 785, V-force reeds offer no improvement on the 750-780, if you have them you can use them, just don't spend the money to buy them. I used 750 cases which is what I had, the 780 case was 'tunnel ported' for better flow which may be holding my coversion back a bit. I am currently fitting a long dry pipe on it to see if I can gain some rpms, I have yet to find anyone on this site who has tried this & posted results, this summer I will post results weather is works or not. You will also need a 780 exhaust manifold to do a 750-780 conversion.
Last edited by RLACEMAN; 03-22-2014 at 02:33 PM. Reason: more info
03-22-2014, 03:16 PM #10
- Join Date
- Jun 2010
- Milwaukee WI
Get a set of psi triples
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