78 1000 carb specs

[OldVet66]

The Stage three jet kit is relatively expensive compared to Mikuni parts (they also have a different jet sizing system). They include the needles, two main jets, and some needle shims if I remember correctly. However, the smaller jet gets you right in the ball park for most motors and the needle is designed for the application. The Mikuni needle is not, so it may or may not be possible to get it to transition properly with some motors. Some have luck with it, but by the time you get it dialed in properly you might wish you had gotten the kit.

[Big T]

this bike does have the stock needle, and in the stock clip position. does that make sense for a bike that has 4-1 and pods?




i'm fairly certain this is the pilot jet, but it clearly says 17.5 on it. that's confusing given the manual says the stock is #15. is this just #17.5 or am i missing something




please correct me if i'm wrong here. i think this is the main air jet

it looks like it says 125, which i'm guessing is 1.25, which is smaller than stock. does that make sense for a bike with a 4-1 and pods?


thanks for all the help. trying to take stock of what i bought here and figure out what i should replace while it's apart, rather than possibly putting it back together with the wrong stuff

Okay, the bike was jetted up with 125 main and 17.5 pilot, that's fairly typical for pods ad a header.

Whether the needle gets raised depends on how well it runs when you put it back together

[shwaz]

pilot jet size + pointiness of pilot fuel screw

so two people, two contradicting opinions

4-1 header, pods - put back the stock 15 pilot jet, or leave in the 17.5's the PO had in?

i guess i'm inclined to leave it as is with 125 mains and 17.5 pilot and see how it runs unless someone tells me the bike will explode if i do that.




another question: pilot fuel screws == pointy || !pointy ?

all 4 of the ones coming out of this bank of carbs are flat on the end. they look smooth, no file marks, but some are a bit bent at the tip as well.
i have 4 pointy screws from a set of salvage carbs which i can use instead, but they're not cleaning up that nicely despite being dipped.
- are there different sizes for these screws, or can i just swap those pointy ones in?
- is there a (good) reason why the ones in this bike are all smooth at the end?

photo: carb 1, carb 2, and an example of one of the four pointy (but cruddy) ones

[Big T]

so two people, two contradicting opinions

4-1 header, pods - put back the stock 15 pilot jet, or leave in the 17.5's the PO had in?

i guess i'm inclined to leave it as is with 125 mains and 17.5 pilot and see how it runs unless someone tells me the bike will explode if i do that.




another question: pilot fuel screws == pointy || !pointy ?

all 4 of the ones coming out of this bank of carbs are flat on the end. they look smooth, no file marks, but some are a bit bent at the tip as well.
i have 4 pointy screws from a set of salvage carbs which i can use instead, but they're not cleaning up that nicely despite being dipped.
- are there different sizes for these screws, or can i just swap those pointy ones in?
- is there a (good) reason why the ones in this bike are all smooth at the end?

photo: carb 1, carb 2, and an example of one of the four pointy (but cruddy) ones

Broken fuel screws are common in VM carbs - just swap the pointy ones in, or order up a new set from Z1 today, they're longer and can be turned without pulling the carb rack. They can b cleaned with some reducer, like CLR (try it on a broken one 1st)

Be sure and check the carb bodies for the broken screw tips. There's a tutorial on this on BassClifff's site

As far as your carb jetting goes, starting out too rich is preferable to too lean, so you're OK with what you've got to test it out.

[OldVet66]

The broken needles are your biggest problem at the moment. The number 1 fuel screw really bothers me. Make sure that one has not enlarged the tiny hole in the carb body. As Big T said make sure the tips are not still stuck in the carb body and replace them. It will run with a # 17.5 pilot jet, but I'll bet they were changed to compensate for the broken fuel screws. It's never going to run right as it is. You will also need # 15 pilot jets in there to get the fuel needles dialed in properly ( between 1 to 3/4 turns out from lightly seated running low speed plug color tests). The DJ kit also recommends the # 15 pilot jets. I do know that setup works nicely on my GS1000, but all motors are a little different. I would start with a fairly well known quantity and then fine tune from there. If tips are still stuck in the carb bodies, they are going to require another dip, to clean those passages. http://www.z1enterprises.com/ItemDet...tem=SIK-1157SK

[shwaz]

Ordered 4 replacement fuel screws from Z1 but they're on back order so it will be a few more weeks before they got to me
Meanwhile I'm going to start putting them back together, will spray them again and do my best to compare the fuel screw holes between the two sets of carbs I have. Not sure what looking at them will reveal unless there's something really obvious .

Haven't done float height so that has to happen too.

Thanks both for the insights. Still not completely sure if I'll leave in the 17.5. Vet seemed to say I need 15 to get the fuel screws set right. Wouldn't pods also increase airflow to the pilot system requiring a larger pilot jet?

[OldVet66]

I'm no expert with carburetors. The experience I had was that I sent my Carburetors to Wired George to rebuild and jet for pods and 4-1 pipes. I was initially impressed with the 52 mpg I was getting after I got the carbs back after a full riding season of waiting and $408.00 until one 30 degree night in a traffic jam of stop and go traffic going up the mountain my, unknown to me, super lean carbs toasted my motor, it was smoking. It cooked off one and a half quarts of oil in the process. Needless to say I was totally clueless as to how the bike should have run. I changed the motor for a low mileage motor on my parts bike, and member KEITH KRAUSE came to the rescue walking me through rebuilding my carbs properly with a stage three jet kit and the proper O-rings. Another member sent me the #15 pilot jets recommended for this jetting setup because my carbs came back with #20 pilot jets, #117 main jets with needles in the third notch. Throughout the entire process with many members chiming in, I never once heard anyone suggest larger pilot jets for the VM carbs, and I have followed many similar threads since without mention. It was also recommended that I use the Dynojet stage three jet kit because I was told very few had satisfactory results using Mikuni needles. Something about the Mikuni needle shape not transitioning properly, where the DJ needle was designed to overcome this. I have my carbs working very well and have rebuilt several sets since with success, so I now know a good bit more about them than I did when I started, but I have never tried to jet for pipes and pods with the Mikuni needles, so you will have to draw your own conclusions. The Dynojet main jets shipped were 138 (Mikuni 129.4) and 142 (Mikuni 133.1) I used the 138's

[shwaz]

thanks vet
that's good info - i appreciate it! will definitely keep those numbers handy. think i'm a ways off from trying to get the bike running - certainly from having it legal and/or trip worthy

i did get my new fuel screws today unexpectedly, didn't think they'd show up for another week or more. props again to Z1. man are they pointy! even the old ones I thought were pointy don't compare.

one more spray and rub to get the greenish-white patina off all the small pieces and it'll be time to start putting the carbs back together.