SGX 91RS

[dwilfong]

I am having trouble with my new to me rigger. Can't get the eng to clear out. Try to lean it down and it just shuts down. Doesn't take the plug just stops. Running 55% nitro 7.8 comp at .014 clearance with a .95cc head and dish volume. MAC13cc muffled pipe tried 12" to 11.5" on length. Bob Austin H50 6.3 cup. Seams to clear out in the corner then sputter in the straits. The carb is a modified 9B with a .100 spray nipple. The bore is oval shaped 12mm and 13.5mm and a BV neddle.

Dose not seam to be able to burn the fuel. Could the compression be to low or the carb nipple to large?

David

 

[Andy Brown]

I am having trouble with my new to me rigger. Can't get the eng to clear out. Try to lean it down and it just shuts down. Doesn't take the plug just stops. Running 55% nitro 7.8 comp at .014 clearance with a .24cc head and dish volume. MAC13cc muffled pipe tried 12" to 11.5" on length. Bob Austin H50 6.3 cup. Seams to clear out in the corner then sputter in the straits. The carb is a modified 9B with a .100 spray nipple. The bore is oval shaped 12mm and 13.5mm and a BV neddle.

Dose not seam to be able to burn the fuel. Could the compression be to low or the carb nipple to large?

David

Yes the spray bar may be too big. But first I would bore out the stinger in the pipe. Go to .470" Then you can work with the spraybar.

It won't hurt to pull the head down to .010" either. And don't be afraid to shorten the Pipe.

 

[dwilfong]

I am having trouble with my new to me rigger. Can't get the eng to clear out. Try to lean it down and it just shuts down. Doesn't take the plug just stops. Running 55% nitro 7.8 comp at .014 clearance with a .24cc head and dish volume. MAC13cc muffled pipe tried 12" to 11.5" on length. Bob Austin H50 6.3 cup. Seams to clear out in the corner then sputter in the straits. The carb is a modified 9B with a .100 spray nipple. The bore is oval shaped 12mm and 13.5mm and a BV needle.

Dose not seam to be able to burn the fuel. Could the compression be to low or the carb nipple to large?

David

Yes the spray bar may be too big. But first I would bore out the stinger in the pipe. Go to .470" Then you can work with the spraybar.

It won't hurt to pull the head down to .010" either. And don't be afraid to shorten the Pipe.

First it is great to have some one like you on Intlwaters to help out us new boaters.

It dose seam that the eng is choking. This was the first run and I was real surprised when it took right off. I will try opening up the stinger makes sense now that you said it. Have lots of nipples to mess with can just press them out and press a new one in. will squeeze it down some to.

Thanks Andy

David

P.S. the boat handles like a dream

 

[Tom Foley]

Sounds like you have your zeros in the wrong place for the head volume . Are you sure you mean .24 CC ?? Even 2.4 CC would be large for a .91 CUI engine . IE the RS 1.01 CU I uses a 1.0 CC head button volume with reasonable success . Andy is the expert but sounds like the head button is off to me ?? h34r:

 

[dwilfong]

Sounds like you have your zeros in the wrong place for the head volume . Are you sure you mean .24 CC ?? Even 2.4 CC would be large for a .91 CUI engine . IE the RS 1.01 CU I uses a 1.0 CC head button volume with reasonable success . Andy is the expert but sounds like the head button is off to me ?? h34r:

YA YA YA Got it confused with my MAC21. I changed it .95cc.

David

 

[Tom Foley]

I would also bolt on a 15 CC pipe at 11.5 " and see what happens ...what plug ?? Try a MC - 9 or KB HP ..you probably did all this stuff already though:lol:

 

[Ray Sametz]

Am I missing something, are we talking .010 head clearance on a ninty motor???? :huh:

 

[dwilfong]

I would also bolt on a 15 CC pipe at 11.5 " and see what happens ...what plug ?? Try a MC - 9 or KB HP ..you probably did all this stuff already though:lol:

I only use K&B HP plugs. I don't Have a 15cc got this 13cc muffled new for for $58 at the LHS. Still waiting for the 15cc to arrive. How about one of those fancy headers you make. Got one to sell. Using Octura hose right on the eng flange right now. Must say it works pretty good though.

This was the first run to check things out. Must say it handles real good. The set up is nice didn't touch a thing.

David

 

[dwilfong]

I am having trouble with my new to me rigger. Can't get the eng to clear out. Try to lean it down and it just shuts down. Doesn't take the plug just stops. Running 55% nitro 7.8 comp at .014 clearance with a .24cc head and dish volume. MAC13cc muffled pipe tried 12" to 11.5" on length. Bob Austin H50 6.3 cup. Seams to clear out in the corner then sputter in the straits. The carb is a modified 9B with a .100 spray nipple. The bore is oval shaped 12mm and 13.5mm and a BV neddle.

Dose not seam to be able to burn the fuel. Could the compression be to low or the carb nipple to large?

David

Yes the spray bar may be too big. But first I would bore out the stinger in the pipe. Go to .470" Then you can work with the spraybar.

It won't hurt to pull the head down to .010" either. And don't be afraid to shorten the Pipe.

Andy

I opened up the stinger on the out side muffled end what about the internal. Need to open up that one to.

David

 

[dwilfong]

Am I missing something, are we talking .010 head clearance on a ninty motor???? :huh:

Ray

Dick Jones runs his SG 80 with a 91RS and I think he said he runs it at .008 with a stock head and his boat runs real good.

David

 

[Andy Brown]

Yes Ray .010" is fine on a 91. Tom, I knew his head volume must have been a communication error.

Yes the pipe needs to be .470" all the way David. As I recall the 80 stinger is s only about .420" I would stick with the 80 pipe. The 90 pipe will only give you more torque that you don't need.

6.3 cup is too much for a 90 SGX unless your looking to go 100 mph. 5.8" cup on that H-50 will put you in the low 90's and the boat will handle better. Just shorten the pipe and let it breath (stinger) and you will go fast with little effort.

 

[dwilfong]

Yes Ray .010" is fine on a 91. Tom, I knew his head volume must have been a communication error.

Yes the pipe needs to be .470" all the way David. As I recall the 80 stinger is s only about .420" I would stick with the 80 pipe. The 90 pipe will only give you more torque that you don't need.

6.3 cup is too much for a 90 SGX unless your looking to go 100 mph. 5.8" cup on that H-50 will put you in the low 90's and the boat will handle better. Just shorten the pipe and let it breath (stinger) and you will go fast with little effort.

Thanks Andy. Will be fun trying to open up the inner stinger. Your memory is real good .420 it is. Got to scratch my head a little on this one.

Ya I did bend it a little to much at the pond. But it sure did go. Think I will hold off on propping it up till I get the hang of it.

The fancy button and all the whittling on the P/S it sure seams to like the cup. the stock 1667 made it jump out of the water at launch.

Just want to keep up with the new twins. :lol:

David

 

[Michael Costanzo]

Am I missing something, are we talking .010 head clearance on a ninty motor???? :huh:

hey bro, yes sir, I HAVE RAN THEM DOWN TO .008 with .O9 head and 50% nitro with no problems. mikie.

 

[henry velasco]

David

The spray bar drilled to .100 is good but the fuel inlet nipple is only .070 approx. --if you have not changed the inlet side I dont thinke your getting the volume of fuel you think are

The older Mac 67,s we had to drill the bar,s out the get enoughf fuel in -- it sounds to me that,s what,s going on

Something to think about

Henry

 

[dwilfong]

David

The spray bar drilled to .100 is good but the fuel inlet nipple is only .070 approx. --if you have not changed the inlet side I dont thinke your getting the volume of fuel you think are

The older Mac 67,s we had to drill the bar,s out the get enoughf fuel in -- it sounds to me that,s what,s going on

Something to think about

Henry

I tough of that from the start and made a reducer out of a glow plug and taped it 10-32 . Then I installed a K&B 90deg fitting in to that. The whole assembly fits in where the needle would go. Then plugged the original hole for the fuel fitting. The K&B fitting is a little bigger than .100.

Here is a pic of Frankincarb.

David

 

[dwilfong]

Yes Ray .010" is fine on a 91. Tom, I knew his head volume must have been a communication error.

Yes the pipe needs to be .470" all the way David. As I recall the 80 stinger is s only about .420" I would stick with the 80 pipe. The 90 pipe will only give you more torque that you don't need.

6.3 cup is too much for a 90 SGX unless your looking to go 100 mph. 5.8" cup on that H-50 will put you in the low 90's and the boat will handle better. Just shorten the pipe and let it breath (stinger) and you will go fast with little effort.

Thanks Andy. Will be fun trying to open up the inner stinger. Your memory is real good .420 it is. Got to scratch my head a little on this one.

Ya I did bend it a little to much at the pond. But it sure did go. Think I will hold off on propping it up till I get the hang of it.

The fancy button and all the whittling on the P/S it sure seams to like the cup. the stock 1667 made it jump out of the water at launch.

Just want to keep up with the new twins. :lol:

David

It worked!!!

The RPM's were over the top. Way over the top blew the guts out of the plug seal and all. Could not catch up with the needle and burn a pin hole in the piston. :angry:

Time to start over.

 

[Andy Brown]

Yes Ray .010" is fine on a 91. Tom, I knew his head volume must have been a communication error.

Yes the pipe needs to be .470" all the way David. As I recall the 80 stinger is s only about .420" I would stick with the 80 pipe. The 90 pipe will only give you more torque that you don't need.

6.3 cup is too much for a 90 SGX unless your looking to go 100 mph. 5.8" cup on that H-50 will put you in the low 90's and the boat will handle better. Just shorten the pipe and let it breath (stinger) and you will go fast with little effort.

Thanks Andy. Will be fun trying to open up the inner stinger. Your memory is real good .420 it is. Got to scratch my head a little on this one.

Ya I did bend it a little to much at the pond. But it sure did go. Think I will hold off on propping it up till I get the hang of it.

The fancy button and all the whittling on the P/S it sure seams to like the cup. the stock 1667 made it jump out of the water at launch.

Just want to keep up with the new twins. :lol:

David

It worked!!!

The RPM's were over the top. Way over the top blew the guts out of the plug seal and all. Could not catch up with the needle and burn a pin hole in the piston. :angry:

Time to start over.

I guess I should have mentioned to be sure to start with a richer needle setting....always a good idea when making changes to the engine/pipe.

 

[dwilfong]

Yes Ray .010" is fine on a 91. Tom, I knew his head volume must have been a communication error.

Yes the pipe needs to be .470" all the way David. As I recall the 80 stinger is s only about .420" I would stick with the 80 pipe. The 90 pipe will only give you more torque that you don't need.

6.3 cup is too much for a 90 SGX unless your looking to go 100 mph. 5.8" cup on that H-50 will put you in the low 90's and the boat will handle better. Just shorten the pipe and let it breath (stinger) and you will go fast with little effort.

Thanks Andy. Will be fun trying to open up the inner stinger. Your memory is real good .420 it is. Got to scratch my head a little on this one.

Ya I did bend it a little to much at the pond. But it sure did go. Think I will hold off on propping it up till I get the hang of it.

The fancy button and all the whittling on the P/S it sure seams to like the cup. the stock 1667 made it jump out of the water at launch.

Just want to keep up with the new twins. :lol:

David

It worked!!!

The RPM's were over the top. Way over the top blew the guts out of the plug seal and all. Could not catch up with the needle and burn a pin hole in the piston. :angry:

Time to start over.

I guess I should have mentioned to be sure to start with a richer needle setting....always a good idea when making changes to the engine/pipe.

I put the Boris flow meter on it and started at 40. Just got away from me. The link on the needle fell off and that was all see wrote. It wants to rev to the moon though. I just have to learn better needle management. I am very bad at it when it starts to sing and my heart starts pumping. Didn't stick the piston any way. The mods work on the 91 the same as on my 45. I'll get it next time. Maybe?

Got a 1.00 EVO P/S to use just need the button. Think I'll wait till I get the hang of it before I go there.

Hope Stu gives me the volume discount. :lol:

Andy you have any headers for a 91RS in the SGX?

David

 

[BigChuck]

David

If the 1.0 P/s has not been milled to fit yet...............don't. They are one of and it would hurt to lose it before you can see what you have. Put a 101 P/s & head in and go to the race.

 

[dwilfong]

David

If the 1.0 P/s has not been milled to fit yet...............don't. They are one of and it would hurt to lose it before you can see what you have. Put a 101 P/s & head in and go to the race.

Chuck

Yes I am going to hold off till I see how it runs first. I think I am going to run the 91 P/S I already have the button customized for it and the pipe. The power is there with this set up. Pulled the H50 5.9 cup like it was not there. Just need time to get it tuned. The P/S and head modes work real good. Rev's its a$$ off. Used the dump bottle of fuel to run it. John Otto's 55% should be a whole new ball game. Don't think I will need more till I get some time behind the wheel.

I am still shaking form the run. :blink:

I think the .21 just got shelved for a wile.

David