Super Jet exhaust blocking diaphragm vents / carb tuning problems

Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
I've seen many instances where people have advised folks to ensure that the exhaust tube is not blocking the diphragm hole on the carbs.

I've been having a very difficult time tuning my new carbs. I can't believe they were setup incorrectly so I'm on the hunt of other sources of error. Performance was complete crap out of the hole. It would rev up quickly, but with any load in the water it would break up and have about half of the bottom end hit it has now. Mid and top were pretty close to spot on. Throttle response was not bad. I can grab a handful of throttle and it would not fall on it's face, but it wasn't crisp at all.

Carbs are set with:
2.0 NS
95g spring
130 low (3/4 to 7/8 turn out)
110 high (1 turn out)
Dual 44's on an R&D intake with new Vforce 2 reeds with reed spacer

I'm in central Ga with elevation not much above 500-600ft over sea level.

Engine:
760 BB flat top (Riva pistons/dominator sleeves)
Dasa porting cylinder/cases
26cc domes (195 compression)
Bpipe limited
mated to OEM blue printed pump w/ 9/15 hooker, bored 85mm nozzle

Take a look at the pics and see my rub marks. So evidently my exhaust is rubbing and possibly blocking my diaphragm vents.

1. What tuning problems would be expected as a result of blocked vents?
2. Does anyone run reed stuffers with V-force reeds?
3. Why use reed stuffers?
3. Does a reed spacer make a hill of beans difference (with OEM or A/M reeds)?
 

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W

waxhead

wannabe backflipper
Location
gold coast
The engine will go very rich If you block the vent holes.

You use reed stuffers if you want to lose a large amount of hp
 
Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
No kidding wax? I'm asking cuz I don't know chit. So forgive me. Why make those things then? I thought the idea with those things was to increase air intake velocity by tighteneing up the incoming air fuel mix.
 
Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
my point to the original ramble:
1. Would a blocked vent be enough to make tuning the low speed jet a nightmare?
2. What r the symptoms of blocked vents?
 
easyrhino

easyrhino

needs more cowbell.
Location
The river
The ad says it move the reeds away from the crankshaft turbulence.

And I saw one thread or hit that says it hurts port charge because there is more volume to pressurize. However, it makes up the loss of air/fuel by giving the tune pipe more volume to SUX.
 
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Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
wax,

my bad if it came off smart-azz like. I didn't mean it like that. I'm really stumped as to how much a dramatic improvement there was between my two sets of carbs and if the blocked vents could be the sole culprit of the whole thing. Funny how things come across in print vs. saying them in person.

waxhead said:
I'm not sure if your being sarcastic or not. So instead of getting smart I will let other people answer this thread
Click to expand...
 
Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
Easy,

I've heard that same thing about moving reeds away from the turbulence and therefore increasing reed life, but not heard of any real performance gains by using a spacer.
\
easyrhino said:
The ad says it move the reeds away from the crankshaft turbulence.

And I saw one thread or hit that says it hurts port charge because there is more volume to pressurize. However, it makes up the loss of air/fuel by giving the tune pipe more volume to SUX.
Click to expand...
 
W

waxhead

wannabe backflipper
Location
gold coast
ok all good.
When you block the holes liek that the carbs will go rich very rich as the diaphram will push down and open the needle and seat.
It will not work, drilling a hole will fix the issue.

And reed stuffers as good as they sound do actually take away from the engine, major losses with them.

The reed spacer does make it easier on the reeds and will make them last longer , however modern reeds are pretty good on life so its not an issue.
The angled r&d one aims the flow up and over the crank and it works well with my case porting I do. other people may find different results
 
Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
No BJ's on till I get the engine out and ship my hull. Gonna rock the oem's until I put it all in the new hull. got it running too good to change back now.
 
Crab

Crab

thanks darin...noswad!
Location
Seattle
Im wondering about the 130 low, my 718 non ported 61x limited setup is using 120 low 115 high with vf2's with the low adjusters at 1-1/8, high adj. at about 1/2 and runs almost perfect. Popoff set about 20psi, same needle/seat. It may have lost a tiny bit of crispness just off idle but seems to make up for it with a much stronger pull in the midrange and top end, have not had it in the surf yet but so far I like it. BTW I removed the covers I had with 2 holes, they seemed to let water in to the diaphram area more on occasion.
 
Pablo

Pablo

sqeez bth levrs & lean bk
Site Supporter
Location
georgia
good question BK. I've had two engines that have been built by "builder" peeps and both came with reed stuffers??

Big Kahuna said:
Randy, what are your thoughts on the reed stuffers. I have ran them for years and they have run good.
Click to expand...
 
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