Wrong jets. Now what?

I did the whole tear down of the carbs as described by RickCoMatic's post but I ran into a problem. The bike (82 xj650rj) has never run since I have had it and I think I now know why but I need some help. Below are a couple pictures of the jets that I pulled out of the #4 carb. Per the tech manual, I am supposed to have a #40 Pilot jet and a #110 Main jet. The #40 jet (left) was totaly mangled. The #110 jet (right) was pulled from one of the other carbs and looks good but I wanted to show a comparison with what I found in the main jet spot in the #4 carb. In the #4 carb I found a #118 jet (center) in the main jet spot.

Why would someone replace the #110 with a #118 jet in only one of the carbs? Also, the 118 jet does not even look like the same type of jet as its overall size is smaller then the original.

So where do I go from here? I went to the dealership today in hopes they had a box of old jet in a box somewhere but had no luck. The internet (bikebandit/bikebarn...) all say that these jets a discontinued so how do I go about getting the right jets in there?

On a more general note, do the "wings" of the jet really play that much of a role in the operation of the carbs? The hole in the middle is free of obstruction on the #40 but the wings and body are totally maimed.

Other then these discrepancies, the rest of the carbs look great so if anyone can help, I would really appreciate it.

 

Well, thats a wierd scenerio. Hope it didn't mess anything up. You can order replacement jets from either motorcyclecarbs.com or from sudco.com. Sudco is a better price so you can afford to replace that pilot jet as well.

 

You bump-up a Main Jet one size, across the board, to get a little-more "Pull" on the highway, if you do your clothes shopping at "Casual Male Big and Tall" ... and you ain't tall!

Just putting-in the wrong sized Jet in one Carb ... means the last guy dropped the one that belongs in there.

Dropped Main Jets vanish. You can drop a Main Jet through a little hole in the top of a small plexi-glass cube and it won't hit the bottom before it de-materializes and disappears.

It's a bitch; too ... because getting replacements for the ones that were supposed to last forever ... is getting tough.

"Say Goodnight; Gracie."

 

I could see if all the main jets were bumped up but its strange that only one was replaced. I think you are correct that someone probably dropped the original and replaced it with the best he could find. The #118 and #110 are very close in size with respect to the center hole but as you can see in the pictures, the bodies are different. Does this play make that much a difference in how the fuel will flow? Same with the #40, Does the shape of the body really matter or is it just the center hole that determineds the flow?

 

No. Your good if the metering hole isn't clogged. You can Doll-up the funky looking one with one of your wife's emery boards.

You can live with the one hotter jet ... but, I'm betting somebody has one they'll spot you.

You in a hurry to get it all together ... or, are we going to let the Post breathe and see if a Jet's out there?

 

Im going to keep checking around online and in the junk yards this weekend to see if I can find the parts I need. I have been having so many issues getting this bike to run that I want to make sure every variable I have control over is correct before I rule anything out. Better to be patient for now I think. I really dont think it can be anything else becase the bike runs really strong if I tweek it just right. Any variation though and the plugs soot up and stops running.

 

Looks like a Keihin jet. He probably buggered the original jet up worse than the pilot jet and stole one out of a Honda. Check the threads closely and if they are the same just order the right Hitachi jet. IF the threads are not the same then another Keihin or possibily Mikuni jet will have to go back in. Because if he forced the threads in then only the new threads may hold the jet in place.

 

Thanks for making me look bad. I really didn;t even think about it but I do still have my 110 jets at home. I'll check the condition of them when I get home and see it any are worth re-using. I might have a 40 in better shape than that one as well.

 

Thanks for all the help guys. This will all help a great deal while looking in the bone yard.

Updating a previous post, when I opened the carbs up I did not have the plate installed covering the two air jets under the diaphram. I did find a set of plates at the junk yard the other day but Im not sure if I should use them or not. I hear many do not use them but should I put them in anyways or just forget about them?

 

Forget. Yamaha did!

 

No, the hammer-fisted turd was in there before forgot them, along with the jets and other boogered bits.

Since you have the plates, go ahead and install them. I doubt Hitachi would have gone to the trouble of creating the covers without a good reason.
After all, you're trying to get your carbs back to stock...so why leave some parts out?.

 

Yamaha or perhaps hitachi, started shipping the XJ's without the plates in the carbs. My 83 did not have them. They don't matter.

 

Well ...

The plates do a good job hiding the two air jets that you might have put back-in --> backwards <-- if you go by the way Haynes says they go in there.

Other than that, I can't figure-out why the cover was necessary ... in the first place.

Mikuni's have a an Air Jet in that spot; too. Not covered.

 

This plate topic has been rehashed a few times. I have in my possession a set with and a set without the plates. I've not run the plate-less ones yet but, from what I hear, it will not have any effect on drivability. My belief, for the most part, is that if the factory put it in there, there is a reason to keep it there untill they supercede it with newer parts or a technical bulletin (and there are a few out there).

 

The buggered up jet can be fixed by filing off the rough spots and re-using it, I do it all the time. You may have to saw the screwdriver slot deeper in order to screw it in tightly but that won't hurt anything as long as the edge still seals properly so don't go too deep.
As for the #118 main jet that should be a #110, the numbers aren't always correct. To check them for the actual size get a set of small drills at a hobby store and a digital micrometer that reads in hundredths of a mm at Harbor Freight. Find the largest bit that will go through the hole easily and measure it with the mic. The jet sizes are found by measureing the diameter in hundredths of a mm. If you find a bit that will fit and it measures 1.10mm that's a 110 jet. To reduce the 118 to the correct size, use a small soldering iron with a pointed tip and solder up the hole in the jet, then drill it out with your 1.10 mm drill (or the closest one you can find) and you're all set. You may have to get a small chuck to hold the microscopic drill bit since most electric drills won't close down that small and it's best to use a battery drill that doesn't have much power or run too fast since an AC powered drill can break the bits easily.

 

Thanks everyone. I think I will try and put the plates in for now. I want to get the hats refinished soon, so when I take them off for that, I will also pull the plates out and see if there is any difference.

As for the jets, I found a guy on this site that was nice enough to part with a couple old ones he had laying around. Hopefully I will get them later this week. By eye, the center holes look the same but I think I may try the drill bit trick just for fun.

Thanks again for all the help everyone. I am learning a great deal about the carbs and the xjs in general.

Cheers!

 

You can get a set of main jets for 3 dollars each from cyclewareables.com The part number is 4H7-14925-10-00. I'm not sure if they have the pilot jets, you'll have to search for those yourself.

 

Great site. A little tough to navigate but lots of stuff there. I already got some help from a fellow xjer and should be receiving the jets any day now. But for future parts need, I will definitly give that site a look.