SGX 91RS

[Terry Keeley]

What kind of carb are you using?

Put on a turbo head at 0,45 mm squish band, fill up with 25% nitro and you will make it a lot easier for your self

Joern

The carb is a modified OS 8AA. There is a pic of it in the thread.

I am very interested in your set up. What plug do you run. Also what carb do you run. I know that the sound level needs to be low at your races what pipe are you running.

I am always open to new Ideas.

David

Been looking for a big bore OS for my 80, Tower says the I/D is:

Inner Diameter of Air Inlet (narrowest point): 11.85mm (0.47")

(widest point): 15.75mm (0.62")

Is it really oval shaped?

Terry

The 8AA that I have was not oval bore when I got it. This carb has the same part # for the barrel as the 9B. The body is bigger with a wider spacing on the bolt pattern. It also dose not have the idle stop screw.

I modified it to make it oval bore. The measurement are referring to the tapper of the inlet Ventura. With the body being larger you have room to grind the body and barrel on the low speed needle side of the bore.

It is much less expensive also.

David

Saw that it took the same barrel, thanks for the reply.

 

[dwilfong]

Had the boat out to day and ran a gallon of 40% thew the new P/S. Ran real nice. Love this boat handles like nothing I have ever drove. Eng revs real nice, even nice and rich and gurgling. Throttle response is spot on from a crawl. Ross and Wayne were very impressed with the way it runs. No nitro boat smack talking about this boat.

Should be a good race with Dick Jones and Brett English next weekend at Melbourne.

David

 

[Andy Brown]

Had the boat out to day and ran a gallon of 40% thew the new P/S. Ran real nice. Love this boat handles like nothing I have ever drove. Eng revs real nice, even nice and rich and gurgling. Throttle response is spot on from a crawl. Ross and Wayne were very impressed with the way it runs. No nitro boat smack talking about this boat.

Should be a good race with Dick Jones and Brett English next weekend at Melbourne.

David

Great to hear you like the 90 SGX David!

Is the race in Melbourne next weekend a 2 day race?

 

[dwilfong]

Had the boat out to day and ran a gallon of 40% thew the new P/S. Ran real nice. Love this boat handles like nothing I have ever drove. Eng revs real nice, even nice and rich and gurgling. Throttle response is spot on from a crawl. Ross and Wayne were very impressed with the way it runs. No nitro boat smack talking about this boat.

Should be a good race with Dick Jones and Brett English next weekend at Melbourne.

David

Great to hear you like the 90 SGX David!

Is the race in Melbourne next weekend a 2 day race?

Andy

Yes it is a two day race. I will be there Friday to run some more fuel thew it before I wind it up. Dick's SG80 with the small narrow sponsons is a very good running boat Hope I can hang with him and Brett's Twin 91VAC RR is very fast. Should be a good 3 boat race.

Got the MACS 80 pipe at 11 1/2" How short can you go. I know it depends on many things but still have to ask.

David

 

[Andy Brown]

Had the boat out to day and ran a gallon of 40% thew the new P/S. Ran real nice. Love this boat handles like nothing I have ever drove. Eng revs real nice, even nice and rich and gurgling. Throttle response is spot on from a crawl. Ross and Wayne were very impressed with the way it runs. No nitro boat smack talking about this boat.

Should be a good race with Dick Jones and Brett English next weekend at Melbourne.

David

Great to hear you like the 90 SGX David!

Is the race in Melbourne next weekend a 2 day race?

Andy

Yes it is a two day race. I will be there Friday to run some more fuel thew it before I wind it up. Dick's SG80 with the small narrow sponsons is a very good running boat Hope I can hang with him and Brett's Twin 91VAC RR is very fast. Should be a good 3 boat race.

Got the MACS 80 pipe at 11 1/2" How short can you go. I know it depends on many things but still have to ask.

David

David, I'm sure you'll do well in the race. Remember that finishing every heat is first and foremost.

You could probable squeeze it to 11", but don't do it right away. The p/l fit has to be right to handle the extra rpm.

BTW- Maybe you could change the subtitle on this thread to "Running Great"!

 

[dwilfong]

Had the boat out to day and ran a gallon of 40% thew the new P/S. Ran real nice. Love this boat handles like nothing I have ever drove. Eng revs real nice, even nice and rich and gurgling. Throttle response is spot on from a crawl. Ross and Wayne were very impressed with the way it runs. No nitro boat smack talking about this boat.

Should be a good race with Dick Jones and Brett English next weekend at Melbourne.

David

Great to hear you like the 90 SGX David!

Is the race in Melbourne next weekend a 2 day race?

Andy

Yes it is a two day race. I will be there Friday to run some more fuel thew it before I wind it up. Dick's SG80 with the small narrow sponsons is a very good running boat Hope I can hang with him and Brett's Twin 91VAC RR is very fast. Should be a good 3 boat race.

Got the MACS 80 pipe at 11 1/2" How short can you go. I know it depends on many things but still have to ask.

David

David, I'm sure you'll do well in the race. Remember that finishing every heat is first and foremost.

You could probable squeeze it to 11", but don't do it right away. The p/l fit has to be right to handle the extra rpm.

BTW- Maybe you could change the subtitle on this thread to "Running Great"!

Thanks Andy for the help. I think I got the cc and the clearance at a good place. Marty gave me his new eng soft were to play with and it has worked very well in making some good choices.

I think this set up will run good and stay alive.

David

 

[dwilfong]

Good day at open water. The H50 was too much would not come out of the corners strait. needed to slow it down some my first time running it. Ended up with a pitched up 1667. With a little help from my buddy Dick Jones got it on the buoys and running strait.

Broke the throttle arm on the carb stuck wide open strait in to the reeds full bore. Not a scratch on the boat. What a tank. This is one killer boat.

David

 

[Tom Foley]

Good luck at the races today , say hello to the guys for me .

 

[dwilfong]

Good luck at the races today , say hello to the guys for me .

Got 2nd out of 4 boats. Throttle arm on carb broke two times wide open Got two starts and finished both with throttle stuck wide open. Last heat every one scratched. Did not run the heat.

Good test run.

David

 

[Tom Foley]

Post pics of your linkage setup , never had a CMB throttle arm break .

 

[dwilfong]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

 

[brett english]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

your boat runs great david, and thanks for the safe driving..im glad you took the step into the x-hydro class..

I only hope to see more people join us, once you run a big block or twin rigger, theres no turning back!!

 

[Tom Foley]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

You might try a 2 -56 rod or a supported Ny - Rod as they will absorb lots of vibration . Also adding a third motor mount bolt in the center of the other two really helps in that hull .

 

[RaceCraftBearings]

David if you can come up with a control arm I have a solution for you and it will not break again!

 

[dwilfong]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

your boat runs great david, and thanks for the safe driving..im glad you took the step into the x-hydro class..

I only hope to see more people join us, once you run a big block or twin rigger, theres no turning back!!

Thanks Brett. Had a blast running it. Can't wait till the next run.

The thrill of running that fast can not be explained you have to try it to under stand.

It is amazing how your mind speeds up to keep up with the boat. Felt good makes you know you are alive.

David

 

[dwilfong]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

You might try a 2 -56 rod or a supported Ny - Rod as they will absorb lots of vibration . Also adding a third motor mount bolt in the center of the other two really helps in that hull .

Tom I have flex push rod that I used on my first boat. The tube with the rod in side. Think I will try it on this boat,

David

 

[Tom Foley]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

You might try a 2 -56 rod or a supported Ny - Rod as they will absorb lots of vibration . Also adding a third motor mount bolt in the center of the other two really helps in that hull .

Tom I have flex push rod that I used on my first boat. The tube with the rod in side. Think I will try it on this boat,

David

David , just to clarify that third bolt (Nylon ) goes in the hull with another grommet . On the nyrod deal form a "U " shaped support out of some thin 1/2 " brass or other stock that supports the outer nyrod properly about where it passes the engine .

 

[dwilfong]

Post pics of your linkage setup , never had a CMB throttle arm break .

Thats the problem it's a OS carb. Made a new one out of a K&B arm after the original one broke and broke that one to.

Will make one out of aluminum stock next. Also broke the arm on the BV needle. To much vibration I guess. Did not realize how much vibration one of these eng can produce at high RPM.

David

You might try a 2 -56 rod or a supported Ny - Rod as they will absorb lots of vibration . Also adding a third motor mount bolt in the center of the other two really helps in that hull .

Tom I have flex push rod that I used on my first boat. The tube with the rod in side. Think I will try it on this boat,

David

David , just to clarify that third bolt (Nylon ) goes in the hull with another grommet . On the nyrod deal form a "U " shaped support out of some thin 1/2 " brass or other stock that supports the outer nyrod properly about where it passes the engine .

Thanks for the tip. Yes it dose like to bend easy. can make a support to fit on the mount bolt. Used grommets to go thew the box.

 

[dwilfong]

Did some testing today and tried 55% nitro. I think I got the numbers right and the new button design worked great. No miss haps and no detonation.

Now I just need to get the prop right. Lots of revs with the pipe at 11" and good throttle response with a H30. tried a 1967 and it pulled it good just lost some throttle.

going to step it up on the nitro and see where it goes.

What props work good on a SGX. Could use some input

David

 

[allenrichards1]

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.

Just did the same thing today!!! Recently Andy Brown modded running 1667 @ 6.5" Macs 15cc at 11-1/2" with 65%. I knew it was lean from the last time out and I had to go to the manual adjustment on the needle. I backed it out 1/2-3/4 turn but I guess with the cool weather and the added pitch on the prop it wasn't enough. Yes, I am frustrated but I guess it happens. I will tell you this, I have never had to be so "gentle" with a motor when it comes to rich/lean as I do with the CMB 101. I remember my 2 AB modded Mac 45's as well as a 67 and I could run on the edge every run (take a plug every time even) and never put a hole in the piston or chipped up the edge of the piston and head button like I have seen on the CMB!!!! This is my second piston/sleeve in this motor. First, stuck. Second, hole in piston!!! On a side note, boy was it fast!!!!!!

Allen