'83 XJ750 jet kit

Can someone please clue me in on where I can get a jet kit for the 750? I can't find one anywhere. I see the 650 listed for all years and one for the 750, but only for '81-82. HELP.... This is the last thing I need to buy for the bike for awhile. Then I'll be set until I need to put the finishing touches on the project like tail light/license plate bracket and gauges

 

What is different about the 83? I have an 82 what is different? What carbs do you have?

 

750 uses bigger jets then the 650.

same carb. but only 2 jets and the needle are the same. the rest are bigger. according to the book i have.

 

I know the 750 uses bigger jets than the 650. That wasn't really the question. You can tell that just by comparing the 650 and 750 jet kits. I was just wondering if there was a difference between the jet kit made for the '81-'82 750 and what I would need to use for the Hitachi's on my '83. Brawler answered me in another thread and said the carbs should all be the same through '84, so think I'm just going to order the '81-82 750 kit.

 

Dynojet?? Go stage one.. Tell them what bike you have and let them figure it out.

 

why stage one? I sent dynojet a message a few weeks ago and never heard back from them.

 

Cos with stage 1 you don't need to mess about with individual air intake etc and you'll get a small power boost. Go stage 3 if you want.

If you look on the Dynojet website there's a list of authorised dealers, pick the one nearest to you and ring them or call round.

 

thanks jon

 

Has anyone tried out a jet kit from these guys on ebay?

http://cgi.ebay.com/ebaymotors/ws/eBayI ... OTORS:1123

When I asked them if they had a kit for me this is the response I got....


Yes we do make a kit for your '83. We custom build each kit to the bike. Each kit is different, based on the bike, modifications, and operating altitude. Based off of your description, it would be a stage 3.5.
Kit Includes: Main Jets, Needle Adjusters, Nylon Spacers, Drill Bits, Slide Hole mod (with CV carb), Idle Mixture mod, Slide Spring Mod (with CV carb), Carb Schematic, Bike Specs, Carb Sync Tool build, and step by step instructions with photos.

....... what do you guys think???

 

I think that isn't a lot of money compared to Dynojet. Worth a try, but they talk about modding your carbs. Once you've done that there's no going back. You happy with that?

Personally, if all I wanted was to getmy bike on the road, I'd do a bit more searching. If you can't find anything before this auction ends, buy them.

 

I don't have to go with the auction. They build the kit for your bike. I'm waiting on an invoice right now.

 

Did you get this? Did it work? I'm thinking of buying a set myself.

While I was messing about cleaning my carbs the other day I realised it would be a cinch to pull out the airbox and attach individual air filters to the air intakes, I love the look, so if this worked for you, I'm gonna have a look.. The K&N individual pods look superb but I'm going to have to tidy up my carbs.. Black I think.

http://www.knfilters.com/search/product ... od=RC-1824

 

I got the kit, but didn't install it yet.

 

Post a photo of the contents if you can please. I want to see what I'd get for my money.

Are you going individual pods or sticking with the standard airbox?

 

pods

 

Cool look man. Photos!

 

i can get photos later tonight or tomorrow

 

No dood.. I meant photos of your bike with the pods..

Of course the jets too though

 

ooooooohhhhhhhhh..... that might not happen for awhile. I have the jet kit to install, airbox to remove, pods to throw on, screamin eagle pipes to put on, and then tuning to do. Not to mention I have the apes sitting on there right now and need to measure and order new cables to fit it.....and forward controls to put on. I have a lot to do I think I'm holding off on the hardtail though and going to make the sportster seat I just got work, so I can ride 2 up for now. If I ever get more work done I'll toss up pics in my build thread (the koolaid project)

 

Ah... That sounds fun.. I think I might have my pods on before you!

My bikes slowly going down a mordern twist on a cafe racer style..

I'm going to jack the back end up, give it a set of clip ons, and try to get that classic Cafe Racer flat rear end in there somehow..

But that's a slow project to do over the next few months, I've got to get it through the road worthyness test here first, next month.. Then I'm going to have a mess around with the airbox and pods and a stage three.. I've got stage one on my XJR, if these are any good, I'll stick stage three there too maybe, but fitting pods on the XJR is a pain in the butt because of lack of room.

Anyhoo.. I've been reading your Koolaid project.. looks like a good project..

 

i know this is an old post, but any word on what jet kit worked? I have an 84 750 and supposed to have the same carbs as the 83. were the 81-82 kit compatible with your 83?

 

As far as I know they should be. Mine was specifically for a Seca while I have a maxim and it worked great.

 

I'm interested too, I've got an '84, going a aftermarket open pipe system and I want to put pods on, so I'm looking at a stage 3, but every one I find listed for the XJ750 is 81-82.

Would love to know if they would fit an 84.

I'm making a Cafe Racer myself.

 

This thread in ancient, but I'm knocking the dust off of the bike and actually gping to try and get her roadworthy before the end of the riding season.

So, that carb kit didn't work for me. They sent me the wrong jets. They didn't for and then the company never returned and of my emails.

I just pulled my carbs a few days ago to clean them. I need a rebuild kit and might as well address the jets while I'm at it. I contacted dynojet and the guy told me they don't have a kit for an '83.

I'm still searching, but figured I'd jump this back to the top and see if anyone had any suggestions for me.

 

An '83 XJ750 will use the same jets as the 1981-82 XJ750 models. The guys at Dynojet are confused, or perhaps something else.

That being said, unless you LOVE to tinker with carbs, I would stay away from the kits that require you to cut the vac piston springs, and ESPECIALLY stay away from the ones that require you to drill out the vac piston air bleed holes. Replacement diaphragm springs are available (so you can "go back" to stock if the tinkering gets too tiresome, or just plain doesn't work), but replacement vac pistons/diaphragm units in usable condition are getting scarce and expensive.

 

I don't really want to "tinker" at all. I want someone to tell me what jets to Use, also them in, sync the carbs, and call it a day.

 

Stock jets with the factory airbox. The man just above your last post knows what they are and has them to sell.

From his catalog: http://www.xjbikes.com/forums/threads/xj-parts-catalog-section-c-fuel-system.44642/
Scroll about 1/8 the way down for Hitachi jets.

 

Nope..... No airbox. I am well aware that it would make life easier, but I'll be fine with pods......

......eventually.

 

In that case: Note that Len uses the XJ750 as the example.

- WHAT ABOUT PODS?:

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!

And some pod filters make a difficult situation even worse.........read all about it:

http://www.caferacer.net/forum/technical/19639-pod-filter-thread-geeto.html


MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)


Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)


Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.



PILOT FUEL JET SIZES CHANGES NEEDED PER TYPICAL MODIFICATION:

Pilot fuel jet size changes are related only to the change in main fuel jet sizes according to the main fuel jet size formula described above. Note that this pilot fuel jet rule is for the main fuel jet size change BEFORE any main fuel jet altitude compensation is factored in:

Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

Additional changes:

- Decrease pilot fuel jet size by 1 for every 6000' above sea level.



PRECAUTIONS:

- Make sure your carbs are in perfect working order before making ANY jet changes....meaning fully cleaned internally and rebuilt, operating properly in their stock configuration, proper sized air jets and needles, etc. Otherwise, you'll like find that all of your efforts are going to be a HUGE waste of time.

- Check plug color often and adjust as needed, 2 main fuel jet sizes at a time and 1 pilot fuel jet size at a time. Bright white plug insulators are a sign of an overly lean fuel mixture condition and WILL cause damage to your engine over time, up to and including engine seizure!

- Synch the carbs after each jet change.

- Make sure the floats are set correctly

- Seriously consider purchasing a Colortune Plug Tuning kit.

- You may find it necessary to make changes to the size or shimming of the main jet needle. There are no guidelines on what or how to do these changes, this is true trial-and-error tuning!



EXAMPLE:

A 1982 XJ750RJ Seca using an aftermarket Supertrapp 4-into-1 exhaust and a single K&N air filter in the stock, unmodified airbox. Bike is primarily operated at an altitude of 2600 feet above sea level.

XJ750 Seca Stock Hitachi HSC32 Carb Jetting:

#120 Main Fuel Jet
#40 Pilot Fuel Jet
#50 Main Air Jet
#225 Pilot Air Jet
Y-13 Needle


MAIN FUEL JET SIZE CALCULATIONS:

Changes made:

Exhaust:
4 into 1 with Supertrapp = +4 Sizes Main Fuel Jet

Intake:
K&N Pod Filters = +4 sizes Main Fuel Jet
----------------------------
Equals: +8 main fuel jet sizes above baseline
Subtract: -2 main fuel jet size per formula above
----------------------------
Equals: +6 main fuel jet sizes due to modifications, thus:

Stock main fuel jet size is: #120
+ 6 additional sizes
= a #126 main fuel jet size
---------------------------
Subtract: -2 main fuel jet sizes for Altitude of 2500' Average

= #126 calculated from above
-2 jet sizes for altitude adjustment

= a #124 main fuel jet size.


PILOT FUEL JET SIZE CALCULATIONS:

The formula is: +1 pilot jet size increase for every +3 main jet sizes increased.

Stock pilot fuel jet size is: #40
+ 2 additional jet sizes (since we went up +6 main fuel jet sizes before the altitude compensation was factored in):

= a #42 pilot fuel jet size.

Note that no altitude compensation is needed on the pilot fuel jet since our elevation is less than 6000' a-s-l.


------------------------------

RESULT:

A #124 Main and #42 Pilot is A GOOD STARTING POINT.

******************************************************

Note that the above calculations do NOT take into account any possible changes in the sizes of the main or pilot air jets, the main needle or main needle jet size, and thus are additional variables and opportunities for tuning excellence. These are areas which are largely unexplored by most tuners, but logically should allow for additional fine tuning or additional rage and frustration.........


Normally, changing to an aftermarket exhaust does NOT require re-jetting, (or minimal re-jetting) as almost ALL of the airflow restriction in the airflow path thru the engine (meaning: ATMOSPHERE > AIRBOX > FILTER > AIRBOX BOOTS > CARBS > INTAKE MANIFOLDS > CYLINDER HEAD PASSAGES > EXHAUST SYSTEM > BACK OUT INTO THE ATMOSPHERE) is within the intake side of this air flow path, and primarily within the stock airbox/air filter. Your stock EXHAUST system can already flow more air volume than the stock INTAKE system allows.

Thus changing only the stock EXHAUST system, with no changes to the intake side of the heads, normally makes NO DIFFERENCE IN TOTAL AIRFLOW, and "no difference in total airflow" means "no difference in TOTAL FUEL FLOW" either, and thus bigger jets are not needed.


But once you start freeing up the INTAKE side of the entire system, you will produce more system airflow, even with a stock exhaust system (because, the stock exhaust system has the capability to flow more air through it than what the stock intake system allows).

This is why re-jetting is usually needed even if you keep the stock airbox and the stock exhaust, but use a K&N low-restriction filter, or even if you drill holes in the stock airbox, or leave the filter lid off.

All such actions free up the intake side airflow restrictions; the stock exhaust will move this additional airflow, and without providing addition FUEL flow to match the increased airflow (within limits, an engine will gobble up the maximum amount of airflow that it can; an internal combustion engine is actually just a self-powered AIR PUMP) then the engine will run "lean"---meaning not enough fuel to match the amount of airflow that the engine can (and now will) gulp.

Most pod type filters allow for vastly increased airflow, and thus require fuel re-jetting, and although no one really talks much about it, probably also require AIR JET changes to match the additional fuel flow, but since no one likes to deal with two parameters at once, it becomes a "tuning nightmare".


BUT, when you read all of the common symptoms of people who use pods, you quickly come to the conclusion that it's not possible to reproduce the stock "smooth in all rpm ranges" engine response. The reality is that you SHOULD be able to match it pretty darn closely, even with the increased airflow through the system, but ONLY changing the fuel jets isn't going to accomplish that. There are also air jets in the system, and they are there for a reason, as well as needle tapers and vacuum piston responsiveness issues.


For further insights and understanding, the Holy Grail (meaning: the whole miserable, un-varnished truth of what a real chore carb tuning is going to be, written by people who actually know what they're talking about, rather than by people who are trying to sell you something) can be found at:

www.factorypro.com

and then click on the "Product Support/Technical Support" link at the top of the page, then on the "Motorcycle Tuning Tech" link, and then the "CV Carb Tuning" link........and then read, weep, study, and do....if you still dare to! HINT: if reading through it makes you think to yourself "sheesh, this sounds like an incredible amount of effort!", well, you're right! That's just some of the joys (and pitfalls) of getting to play "tuning engineer", which is what you're going to be doing. Yamaha probably has 10 of those types of guys on staff, and millions of dollars of test equipment, both physical and computer-aided, that allowed them to get the mixture settings just right---from an overall drivability AND power output standpoint----and now, since you're changing the airflow parameters thru the engine, you'll have to figure it all out "from scratch", but WITHOUT the benefit of 10 trained engineers and all that test equipment and experience.

That's why we warn you that setting up a bike for pods can be quite a bit of trial-and-error procedure. You can make the calculations according to what is shown in that guideline and then order the jets that the "formula" recommends, and that should serve as a good STARTING POINT............you may (or may not!) have to do more tuning and trial-and-erroring substitution of different jet sizes, etc. to get it performing to you satisfaction, with the recognition that you may ALWAYS end up with a situation that has some kinds of trade-offs.....lazy at the lower end but runs well at mid/upper-ranges, or runs well at the lower end but a "flat-spot" at some other rpm range, etc. Unfortunately there is no magic formula........you might want to read through the factorypro.com article that I list at the end of that section, and you will get a better understanding of what is involved to get the carbs set-up properly in a non-stock configuration.

 

These statements DO NOT AGREE WITH EACH OTHER!
If you don't want to tinker, you are not fine with pods.
Here's a thread full of info on what others have used with their pods:
http://www.xjbikes.com/forums/threads/success-stories-of-pods-and-4-into-1-exhaust.29381/
Good luck!

 

Yeah, I know. I don't WANT to tinker, but that's in a perfect world. I will be fine if I have to though. I appreciate all the comments, information, and links.

I plan on ordering jets and bowl seals today.

 

Well, I guess it has REALLY been too long since I worked on the bike. Apparently I already bought new jets from you Len. I really don't remember actually getting them and if I did I have NO CLUE where the hell they would be.......

......................................................................................................................................
Hey Matt,

Okay, here you go:

HCP10608SET4 Aftermarket brass #124 MAIN FUEL JETS, set of 4:
$ 24.95

HCP6326SET4 Aftermarket brass #42 PILOT FUEL JETS, set of 4:
$ 24.95

all of the above items ARE in stock!

.......................................................................................................................................

 

Look in the bottom drawer...........

 

Or 1 of 3 footlockers full of jeep and bike parts. All crap I've stripped off, changed out, or ended up not using.

I came across the 6sigma jet kit that didn't fit, but I have no recollection of what yours would even be packaged in. I really don't remember getting them and I can't find a single mention about them in my email or are any forum. All I can find is our exchange deciding what jets to go with, the PayPal receipt, and then the notification that they were shipped.

 

Well, each set of 4 brass fuel jets come in their own little plastic bag with the part number / description on a white label stuck to the bag.

It appears that they were shipped to you via Priority Mail on 10/15/2010, should have gotten there by now!

 

Who knows what all I had going on at the time. You'd think I would have mentioned getting them or not getting them. It's like I ordered them and then forgot all about them.

Can I just place the order again?

 

Just today I found a box of tooling that I had begun to suspect was lost in the mail. I had set the box under another identical box without opening it to check the contents. Things, they happen.