Xj750 drilled out jets catastrophe

So i was told my main jets on my seca 750 were 126's but when i took the bowls off and all 4 mains where previously screwed up and i could not make out any of the last digits but the all looked like 0's or 2's not 6's. So i drilled them out to like something in between a 120 and a 140 my guess is like a 135. But the chart i had was super unclear to go off of. i don't have a metric drill bit set, cuz i life here in America, and the list didn't give me a conversion. So i made a uneducated guess and failed. But the first time i took it around the block it idled fine rode fine but at half throttle it would sputter and pop and jolt. So i brought it home and guessed i went to big and now the main was to big for the pilot. So i did the dumbest thing i drilled out the pilots which were clearly a #40. and i used 1/16 or a 3/64 i don't remember which looked way to big after i drilled em. So wouldn't u no it i cant get it to idle now and it barely rides pops jugs backfires u name it it does it. So what do u guys think.

 

I think you better find a 1500 to hook that carb rack to!

Time for new jets!

Ghost

 

Drilling jets rarely works out the way you hoped. Order up a set of the proper sizes for your mods, intake and/or exhaust.

 

The largest jets you will need for a Seca 750 is 126 Mains, 41 Pilots.

I looked thru some of your posts and didn't see any info on exhaust or airbox mods. (let us know, add to your sig line)

If stock jets produced a "lean" condition for you - then either you didn't finish your tune-up, or your carbs weren't absolutely clean (Main nozzle, Pilot passages)

 

well i put individual pods on and a Vance and hines 4-1.And yes i did have a lean condition and a hard starting problem, lack of fuel. My guess would be to do a main jet size of 128 if u use the formula of:

+4 for pods

+4for 4-1

At 888ft so i wouldn't subtarct any

im not sure on the pilot jet

 

The problem is not limited to FUEL Jet sizes.

Pods allow air flow OVER the Atmosphere Vent.

Reducing Pressure --
Subtracting available AIR to feed the Pilot AIR Jet, Main AIR Jet, and reducing pressure in the Open Space beneath the Rubber Diaphragm ... making the Diaphragm resist collapsing upon Pressure Deviation when the Intake Stream passes-by the Hole in the Bottom of the Piston.

 

HUH?

so what are you saying rickomatic,im a tad confused

 

These might help too...

http://jetsrus.com/FAQs/FAQ_rejetting_1 ... _rejet.htm

http://jetsrus.com/a_jets_by_carburetor ... ction.html

 

okay well thanks the second link with the prices was helpful. But i was slightly insulted by the jetting info page. I have re jetted many a dirtbike and a few street bikes in my short 21 years. So i know what a lean and rich condition look like. But this freaking seca is whooping my arse. Idk if its the weird yics design but this has been a nightmare to tune.But the whole jet drilling is my fault, i screwed that up So basically what i would like to know is, If you had a seca 750 and put 4 individuL pods on it, and a V&hH 4into 1 exhaust system on it and you lived in the midwest at 888ft above sea level. What jet combo would you use?

 

What Rick was trying to tell you is that re-jetting will probably not be 100% of your solution to pod filters.

You also need to re-read the "re-jetting for your particular mod" recommendations here: http://xjbikes.com/Forums/viewtopic/t=14692.html You missed a lot.

MAINS are not your entire issue by a long shot. It's not responding as you expect because your experiences prior have apparently not been with CV carbs.

YICS will only mess with you if you're trying to sync and don't have it correctly blocked.

 

Okay i will be a grandpa by the time i finish reading this


xjbikes.com/Forums/vie...14692.html



. So i guess since nobody wants to give me a ball park jet combo then i will guess. I learn best by doing any how not reading. So to be clear i do not want to rebuild my whole carb system . and i definitely do/will not separate them from the rail. I am not syncing these things f-that. But before some one says anything the the carbs are spotless clean. So all i want to to do right now is swap the mains and pilots if need be. Then what ever else, well we will cross that bridge when we come to it.

 

Well, let me tell you. If you DON'T "sync them" then the bike will not run right, if at all.

You don't need to read the whole article. (Although it wouldn't hurt.)

Scroll down about 7/8 of the way, until you find the section that begins:

"WHAT ABOUT RE-JETTING FOR PODS, ETC?:

It's a question we get asked often and unfortunately, one that we cannot answer honestly about your specific bike besides with "it depends".

Which is a nice way of saying "you're about to enter the seventh circle of hell......."!

Carb jet tuning required by aftermarket modifications is somewhat of a black art, part science, part skill, part luck. It depends on the current state of tune of your engine, your altitude, the mix of aftermarket parts on your bike, etc........a lot of variables.

The best advice we can offer is: Just Say No. Don't do it! Leave everything stock!

But, since most people---with good reason, I might add---don't always listen to our well-intentioned advice, then the next best recommendation we can offer is: "if you want more power get a bigger bike!".

And since that doesn't cut it with many owners, either, for the remaining stalwarts out there who insist on "experimenting" with aftermarket intake and exhaust systems, here's the best information that we've come across to give you some GUIDANCE, which you should take as just that, and not as ANSWERS, because it isn't!

MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:

That is where you'll find the jetting recommendations for mods.

And let me give you one more piece of advice: You won't be able to "guess" or "fiddle" your way to success. You need to get serious, learn about the carbs and how they work, and be careful, methodical and precise or it simply will NOT WORK. And whether you like it or not, unless you get all 4 carbs doing the same thing at the same time (SYNCHRONIZATION) then it won't run right if at all.

So yeah; you'll be synchronizing them if you ever want to actually ride the bike. But that step is a long way off.

 

well if your not going to break the rack apart or sync you may as well quit right now and save the aggravation of failure.
if you were to buy a jet kit you'd get some jets, a adjustable needle and a drill bit to make another hole in the bottom of the slide.
also consider that you may need to make some rpm ranges richer and some leaner.
FYI, you can solder a rich jet shut and redrill it................ if your good

 

WAIT!! just 1 minuets here please tell me why on earth i would have to separate the carbs or synce them when i am just changing the jets????????? You guys need to understand you cant just make crazy claims and keep skirting around the questions being asked. I asked you guys once before what combination would you use. That being said i understand its a BLACKART and its hard to tune it perfect. But yet once again i am reminded why i really do not like taking time to post in this forum. Frankly you guys are all a bit grouchy. And i still don't know why you all seem very reluctant to answer any questions.

 

If you want to know what jets are recommended for your mods, READ the bloody article I posted the link to. Do I seriously need to go through the article and tell you what it says to do for your particular mod?

Reeaaallly?

Carburetor synchronization is necessary after valve adjustment or PROPER carb service. And certainly will be if you want the bike to run right. It's simply part of the tuning process, the bike has 4 carbs. You think we just make this stuff up? Seriously?

About those "crazy claims."

10K miles since the recommissioning, with nothing but a scheduled valve adjustment (with carb sync touch-up) and a new rear tire.




Put about 9K on this one too, since resurrected (which included synchronizing the carbs



Crazy claims indeed. I RIDE my XJs. You need to get serious about this if you actually want results.

 

Well said Fitz.
Your tag line says "Worlds Fastest XJ 750" listen and learn from the oldtimers and your bike may have a chance to be just that...

 

you want to break the rack apart to put in new throttle shaft seals, if they leak it'll seem like all kinds of things, they can leak at low rpm's or high rpm's and you can't really tell by looking at them.
sync will give you a bad idle and low speed throttle response, you might think it's idle jets or screw adjustment, it'll be the sync. big throttle openings it won't matter much.
here's what i got after a whole bunch of farting around, uni foam filter in stock box with mac4/1 pipe and super trapp muffler with 4 plates.
main 126, low jet 41. started with 8 plates then 6, settled on 4 in the super trapp
wish i had some pretty pictures

 

So like i thought you don't need to do all these extra things to get the mainjets to pump the right amount of fuel. You just giving me the freaking fsctory tune up specs. I know what the gosh darn thread says i was asking if you guys had any luck with any otherr combination.

 

Here's your jets -

You need to stop beating up on the Wizards.