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.

 

Just my .02, you got to clean them (carbs), sync them to run together, with your mods, it will be a journey to get them exactly right....the above members have told you what you NEED TO DO, there is no "This jet setup will work", its trial by error....

My case was, I went pods, 4 into 1, I was going to start with 118mains, 40 pilots, shop didnt have 118, so just for shits n giggles I ordered them but bought 122's they had, installed....BIG Difference!!! through out rmp range still a little bit of a hicup at lower end.

Plugs look good, choclate colored when I plug chop them, but want a little richer just my prefernce, so Im going to install 41pilots hoping it takes care of lowend, and shim my needles and see what I get from that...

To get running "good enough" is not getting it running the way "I want it"...trial and error, time, patience....or just buy you a new ride. Just take your time, do it right, its trial by error when it comes to modding, what works for others may not work for you....

 

Di it run perfectly before you changed the exhaust and went to pods?

If yes, then play with the jets. If it had other problems, you will chase you tail playing with jets alone.

As for drills, jet drills are small increments and not your normal drill set. It is possible to solder closed a too big jet and redrill it correctly, but I would advise doing some size research and check the drill bits with a micrometer.

Measure twice, drill once. Think three times about what you are measuring.

 

Ric,

Do the clock mean something like.... It's a new day, get up, clean yourself up, eat breakfast, grab a cup of coffee and left click the self "refresh" icon. Good, now go forward and have a good day?

Gary

 

I did not install the pipe just the pods. The guy i bought the bike from said that he had the bike jetted for the pipe but he obviously didn't. I am 100% sure i am not going to screw with anything that doesn't need it. Iam not going to tear apart my dd to do some stupid dealer suggested maintenance.

 

you got that right, you da man

 

Like adjusting the valves? Setting the float levels?

The DEALER doesn't "suggest" anything other than what the manufacturer did.

You ignore all the critical maintenance you want to; the bike will just die eventually.

 

The reason why so many forum members have acquired a Yamaha XJ-Bike for short money is because the Previous Owner ignored Perscribed Scheduled Maintenance, the bike wouldn't run, could no longer be ridden until repaired, and the parts and labor costs to rehab the bike to roadworthy condition became astronomical.

Those who could wrench took the sitting messes off the hands of those who neglected their bikes or failed when modifying them, and took care of doing what the others wouldn't do or regrettably undid.

What you should have done with your bike is to have used the Prescribed Maintenance Schedule as a check-list.
Returned the bike to a state of all its component parts functioning properly and within the specs of well maintained and finely tuned machine.

Once you had the bike returned to a condition where it was running quite well and had a base to return to, should mods present known difficulties, should you have begun your situation complicating experimentation.

Go back to START.
Do not pass GO.
Do not collect $200.

 

I'd like to add.....listen to the advice that's been given. Everyone who is telling you to do it the right way have all made the mistakes that you are making now. Chasing your own tail will just waste your time and make you even more frustrated than you currently are.

 

Come on guys, obviously this fellow knows what he is doing. He does not need extra advise nor the stupid stuff that the dealer suggests.

He clearly understands his bike and is on his way to build the world's fastest xj ever.

 

Worlds Fastest:
I didn't research what carb is put on your bike but if it is a Mikuni your available jet sizes increase 2.5 between available jets.
Your bike came from the factory slightly lean but not so lean that going up 2.5 will make it better, usually. If you can go up by 1 it may be better but I don't think you will find the jet.
Now if you add pods or different exhaust often one jet size will perform better. If you do both maybe two jet sizes.
As other have said, this is only if the other things are right.
So if you want a quick stab at it, buy the next two jets richer and do a "Trial & Error". Since you have to pull the carbs to do this I would recomend wet setting the floats. That will elininate one possible problem and is easy to do with the carbs off.

Good Luck

 

I am confused as to why you guys think that i have time to tear apart my motor and check valve clearances, fiddle with carb syncing, and float levels. I WORK and i use my xj to get me to work rain snow sleeet or hail my seca will prevail. I needed to re jet it, due to a super lean condition, due to the pods and after market 4-1 pipe. I rekon i am going to put 126 mains in and im still not sure if i should go 40 or 41 pilots. Thats where you people can help. Not by giving me a bunch of stupidly obvious advise on things that one would need to do if he wanted the worlds fastest xj.

 

This thread is a lost cause.

 

You know it it wouldn't be a damn lost cause if you old coots would just answer the stinking question. I asked numerous times. WHAT COMBO WOULD YOU PEOPLE USE. a 126 and 40 or a 41 THAT IS ALL. Nothing else don't give me any other info. All i want to know is what you personally would do. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Go with the bigger pilot jet.

We're not suggesting you "tear your motor apart." The things you need to do are MAINTENANCE ITEMS, simply that. Valve clearances, every 5000 miles. Ignore long enough, bad things happen.

We're trying to tell you that there is more to solving your issues than just re-jetting. And it WILL require you get the float levels right and re-sync the carbs, or it won't idle properly nor respond to throttle correctly until you do.

And until everything else is right, your re-jetting efforts will be very frustrating.

So ignore us. And fight with it for a really long time. Have fun with that.

 

Ok i appreciate the answer finally, that's all i was asking this whole time. And i understand that it is regular maintenance but what i still fail to see is why i would have to reset float levels when i did not remove the floats or needle ? And why synce them wheen they dont leak and i didnt seperate them?

 

If you take them far enough apart to change the jets, they'll need to be re-synced. Period.

Float levels need to be VERIFIED; if they're fine then don't fiddle with them. If they're NOT fine, you'll never get the bike in tune. Period.

You cannot do a good accurate running vacuum sync unless the valves are in spec. Period.

The work you are doing WILL require a re-sync. Period.

End of discussion. Fitz out.

 

Last year I started getting AARP letters in the mail. Now I am officially an old Coot. I guess altziemers is next...

 

okay so still getting a tude so i still dont know why i will have to tear the carbs arpart to replace two jets in the bottom of the carbs?

 

I totally understand were you are at. Yes, you can change a jet without breaking the rack. It would still be worth the time to check your float settings (wet) and do a bench sync before you re-install the rack. In the last 20 years I have had mine off about 4 times for basic cleaning and those settings were always off a bit. It just takes some of
the guess work out of the final tune if you know these are squared away.
And as always +1 to all the wisdom the Wizards said above its all important
good luck to you...

 

i told ya once dude
"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"
what part of that don't you understand?

 

Actually . . . you don't have to break the rack to replace jets, adjust floats, "clunk" the slider piston ( a polishing term here) or service the Pilot jet & "O" ring.

You must break the rack to replace (8) throttle shaft seals and (6) fuel rail seals. You must re-sync a re-assembled rack. You should bench-sync anyway, in my opinion, as you never know what the previous person did.

And +1 on the valve lash check/adjust. You can make it step 3 or step 23 - - you decide.

 

Listen to the Old Coots! I did everything they told me and are telling you and it worked perfectly. I'm probably older than the Coots but have learned over the years to take advice from those who have first hand experience with the problem at hand.

 

I'm still trying to figure out why anyone still responds.

My brief XJ ownership has been a learning exp for me. When I ask what may or may not be a simple question, I listen to EVERYTHING someone that know s more about the subjec than me has to say about it. In may do it differently, I may take the advice verbatim, but nonetheless I accept whatever help comes my way respectfully, not because they are old coots but because they are willing to help.

 

Agreed. That kid is clearly being a negitive nançy. And I recync my carbs quite often on my bikes and tell my customers to have them checked often. I check them for free for my usuall customers. I love working on bikez so this stuff doesn't bother me. But having the right attitude has alot to do with it...

General on time/routine maintenance = A. A healthy happy bike. B. Prevents big problems down the road. Yamaha recommends its maintenance for a damn good reason, they built them! U should be happy you own a Yamaha and not a Honda, valves are to be checked around every 2500 miles. IV owned and worked on alot of bikes (American and Japan) and Yamaha makes the best son.

Btw the old timers always know best when it comes to mechanics so don't be bashing them for their expreience. U may get old one day to...if your bike doesn't fall apart while riding it and you die...

 

Ordered my jets 4 #126's and 4 #41's. Iinstalled them and they work just fine. No more lean condition,super crisp throttle response , no flat spotts or dieseling. TOLD you guys, at the end of the day the man who owns/rides the machine knows it the best.

 

From Bob Pirsig's "Zen and the Art of Motorcycle Maintenance" on the subject of "gumption traps" or those things that sap the enthusiasm:

"The next one is important. It's the internal gumption trap of ego. Ego isn't entirely separate from value rigidity but one of the many causes of it. If you have a high evaluation of yourself then your ability to recognise new facts is weakened.

Your ego isolates you from the Quality reality. When the facts show that you’ve just goofed, you’re not as likely to admit it. When false information makes you look good, you’re likely to believe it.

On any mechanical repair job ego comes in for rough treatment. You’re always being fooled, you’re always making mistakes, and a mechanic who has a big ego to defend is at a terrific disadvantage. If you know enough mechanics to think of them as a group, and your observations coincide with mine, I think you’ll agree that mechanics tend to be rather modest and quiet. There are exceptions but generally if they’re not quiet and modest at first, the work seems to make them that way.

And sceptical. Attentive, but sceptical. But not egotistic. There's no way to bullsh1t your way into looking good on a mechanical repair job, except with someone who doesn't know what you're doing.

.... I was going to say that the machine doesn't respond to your personality, but it DOES respond to your personality. It's just that the personality that it responds to is your real personality, the one that genuinely feels and reasons and acts, rather than any false, blown-up personality images your ego may conjure up. These false images are deflated so rapidly and completely you're bound to be very discouraged very soon if you've derived your gumption from ego rather than Quality.”

I have my money on the bike

 

Now that he's solved this problem, I'm assuming he won't be asking for any more help on carbs. - oh, and can one of the mods change his status to "master wizard"?

 

WIZARD? That must be why nobody answered any of my questions. Bexause they saw into the future and foretold that i would indeed fix it with out their help. :lol: :wink: Hope that doesn't look smug>

 

Oh, hands down. I'm not even betting. It's not a matter of if, it's just when. Wanna start a pool? Miles or months?

Excellent quote, by the way. You should happen by more often.

 

How sure are you that it's running perfectly? My bike ran perfectly when I got it. The PO had just gotten the carbs cleaned and the valves adjusted. I rode it for months with a huge grin on my face every time I grabbed a handful of throttle. This winter I decided that I was close enough to the next valve check that I should go ahead and do it before the next riding season. Cylinders 3 and 4 are both running lean, and the exhaust valves are 0.05 too tight on #3 and 0.10 tight on #4. That's with just over 2k miles since the last "service" that PO did. So......how well is your bike really running?