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29 smoothies on GS750 questions

dardoonk

dardoonk

Forum Mentor
I landed a set of 29mm Smoothbores for my 77- 750.
Standard jetting per Sudco for the 750 & 1000 is:

115main
25 pilot
5DL31-3 jet needle
.9 air jet
.6 needle jet

I have a Jardine 4-1 & pods - will I need a 130 main jet & the same pilot, or since this carb flows much better will the changes be even greater?

I am just looking for a baseline to get me started as I rebuild them.

Maybe these will just be overkill too, so if you think I won't see any benefit for the headaches I am about to endure then tell me that too.

Thanks,
Kurt
 
I dont have any info now, but I have a set of vm29's coming in the mail from ebay for my 79 gs750 with pods and v&h header with yoshi pipe. I will be doing some jetting to so I will keep posted.
 
Yeah, got them for $350. The week before I was bidding on a set for $425 and got outbid. So I saved a few bucks.
 
do you have stock cams in that bike?

115 might be a touch lean.

small increases up to or about 126 mains might be the fattest you'll need to go

maybe depending on humidity (those carbs are effected by humidity more than temperature) it'll fluxuate a little
 
Well Im running 115 mains in my 26mm's now and 20 pilots. I think I will start with 125 mains and 22.5 pilot on my 29mm's.
 
I got my carbs today and decided to take them apart and take a look. There pretty clean buts theres just a few pieces I wanted to replace. Bowl screws, gaskets, jets, etc. After about a half hour on www.z1enterprises.com, I managed to rack up a $190 bill of parts including a new pingel petcock. I got the carbs soaking downstairs. So hopefully I can get these back together this weekend.
 
I'll get mine torn apart next week. I already have misc jets, new jet needles & new floats, but have to order new gaskets, o-rings, etc..
 
I have them on my bike now, I have started tuning them last night. The problem is I have 22.5 pilot jets and on idle, The air screws have to be all the way in to get the highest idle. So does this mean I need to go up in size on pilots?
 
yes that is good for the next step. but there is another tuning factor to consider before spending money on a set of pilots.

just in case the bigger pilot does not help.

next I'd check the synchronization for how high the vacuum level is.

equalizing all 4 carbs is one thing and it is all you need to do on CV carbs, however mechanical slides can be adjusted for a specific vacuum pressures

just remember no less than 15 cm at idle!!

some bikes run good at 20~23 cm and others need to be set a little higher at 24~28cm at idle

this is where the slide cutaway has an active part of the pilot circuit mixture.

the mercury gauges are easy to read but dials work good to. cm is the height in centimeters. Hg is another way they measure it

tuning is science good luck bro
 
Well, I'm about 3 weeks behind on this now, but I have almost everything to rebuild these. Unfortunately, the PO managed to monkey up one of the pilot jets and strip the head trying to remove it....... BAD, but we'll manage to extract it.

I need one more gasket & can't find it though. There is a gasket (#88 on the Sudco exploded view) that fits under the Jet Block (#87 on the Sudco exploded view). Mine are totally disinegrated & Sudco does not show them as available. I can't even tell what they were made of.

Hopefully, someone knows of a source for these. Or, if anyone knows what these were originally made of, please tell, because I am probably going to have to make these myself.
 
i thought sudco still had them, you might just have to call. i think thats where i got mine. i still haven't installed them, i ended up just using a peice of newspaper, was the same thickness and just cut out gaskets with a exacto knife to fit in there. i used a red hot peice of wire to burn the little hole that was needed thats in front of the needle hole. I have run the bike atleast 3000 miles so far and runs and starts quick.
 
dardoonk said:
Well, I'm about 3 weeks behind on this now, but I have almost everything to rebuild these. Unfortunately, the PO managed to monkey up one of the pilot jets and strip the head trying to remove it....... BAD, but we'll manage to extract it.

I need one more gasket & can't find it though. There is a gasket (#88 on the Sudco exploded view) that fits under the Jet Block (#87 on the Sudco exploded view). Mine are totally disinegrated & Sudco does not show them as available. I can't even tell what they were made of.

Hopefully, someone knows of a source for these. Or, if anyone knows what these were originally made of, please tell, because I am probably going to have to make these myself.
Click to expand...

Part #002-535 $3.71 ea. They are still available, I think. I bought some about 6 months ago. They are made of paper from what I can tell. I'll find them and post a pic.
 
Wheww, I was worried after the Berryman's didn't break her loose, but after soaking the carb with the stuck pilot in some S-100 for a day, the pilot came right out.:-D....

Reno, you say these gasket things are paper? And $3.71? This must be some kind of paper! Are they something I can make myself?
 
dardoonk said:
Wheww, I was worried after the Berryman's didn't break her loose, but after soaking the carb with the stuck pilot in some S-100 for a day, the pilot came right out.:-D....

Reno, you say these gasket things are paper? And $3.71? This must be some kind of paper! Are they something I can make myself?
Click to expand...

Well, they sure look like paper! But they must be made of something special.... you would think normal paper would deteriorate after a short time. I'd bite the bullet and buy them instead of worrying if your homemade ones will hold up.

100_0617.jpg
 
Reno, any idea why these things are even in there? The main jet screws into the bottom of the block and I can't figure out what they even "gasket". Seems like something to keep grunge from building up in there, but I guess that begs the question " how does the grunge get in there to begin with?"

Thanks for the pic
 
dardoonk said:
Reno, any idea why these things are even in there? The main jet screws into the bottom of the block and I can't figure out what they even "gasket". Seems like something to keep grunge from building up in there, but I guess that begs the question " how does the grunge get in there to begin with?"

Thanks for the pic
Click to expand...

I have no idea what they are for. All I can assume is they are just there as a barrier between the block and carb body to prevent metal to metal contact? I know the original ones that were in my set were still there even after dipping... I had to gently scrape them out with a piece of wood.
 
Okay, the Smoothies are rebuilt and on the bike.. My initial jetting is 25 pilots and 130 mains with air screws 1 turn out. Turning the air screws from 1/2 to 2 turns doesn't do anything, so I don't know if that means I am spot on or need to go down to 22.5 pilots.. I suspect I am a bit rich, but it starts well with full choke and after less than a minute I can press the choke off and it holds a real steady idle at 1000rpm. When warm or after sitting for 1/2 hour it starts perfectly.

I think my main jet is too large as it bogs down under full throttle. No, I am not just cracking the throttle-- - it bogs when running about 2500 rpm and quickly, but smoothly going WFO.

I spoke to Z1 yesterday (thank you for the advice).. he thought I might need the smaller pilots, but not to worry if the 25's are working well.

I do notice the throttle hanging a bit at times.. I am sure I have no air leak and my boots and o-rings are brand new. I would think this indicates lean, but that is doubtful. Any thoughts??
 
Do some plug chops at min. throttle, 1/3, and WOT. Your plugs should tell all. If you have pods, make sure you don't over oil them... that could cause a bog down at WOT (ask me how I know).
 
Im running 22.5 pilot now and 117.5 main on my gs750 with pods and 4-1 exhaust. The main jet is perfect but the 22.5 pilots seem a bit to rich. The lower rpm range is running a bit rich but once you get to wot open throttle above 5,000 rpm The bike takes off and I start to slide off my seat.

If you throttle is hanging, take the return spring from a set of vm26 carbs and put it on the 29's. Mine was at first because the 29's spring was softer than the spring on the 26's.
 
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