Drilling jets bigger?

keith1 wrote:

otakar wrote:

polkat wrote:

110 is stock? Okay, does anyone know the actual diameter of 110 jets?

The bike is a 1982 KZ750H3 four. It is bone stock, although I am doing a few bobber mods. I want to go to pods as I want the space that the airbox uses for something else, and because frankly, I like the pod look. I will also drill the stock mufflers with 6-1/2" holes around the main outlets. That is all the mods the engine will receive.

I've drilled lots of auto carb jets without problems and have lots of drill sizes. I figure why bother to go through the hassel of ordering jets when I can easily open up what I have. I just don't know what size to open them up to.

What would be a good ballpark pilot/main jet size for this (or leave the pilots alone as mentioned?)?

They are not measured in size. They are measured in flow rate. size 100 = 100cc/min. That is on the Mikunis. Iam not kidding when I say that no one knows how the Kaihins are numbered. It is not just the size of the hole because three or four sizes might have the same hole but the length of the hole is different and the taper on each side is different. That is how the jets are fine tuned. On the average the difference between sizes is approximately .001" To give you a perspective, a #58 (.042") bit would be a 110 jet but the length of the hole now is the other variable, and that is if you ignore the tapers at each end.

knowing this, it escapes me how someone can do a bike build and try to cheese out at every corner....no offense,
but ya got to cut loose with some cash if you are going to be successfull....if the cash isnt there, wait till it is.....

Aw Come-On haven't you ever fixed a flat tire with some Duct tape? Or put a candle inside your headlight when your light-bulb burned out. What kind of meknik are you.

otakar wrote:

keith1 wrote:

otakar wrote:

polkat wrote:

110 is stock? Okay, does anyone know the actual diameter of 110 jets?

The bike is a 1982 KZ750H3 four. It is bone stock, although I am doing a few bobber mods. I want to go to pods as I want the space that the airbox uses for something else, and because frankly, I like the pod look. I will also drill the stock mufflers with 6-1/2" holes around the main outlets. That is all the mods the engine will receive.

I've drilled lots of auto carb jets without problems and have lots of drill sizes. I figure why bother to go through the hassel of ordering jets when I can easily open up what I have. I just don't know what size to open them up to.

What would be a good ballpark pilot/main jet size for this (or leave the pilots alone as mentioned?)?

They are not measured in size. They are measured in flow rate. size 100 = 100cc/min. That is on the Mikunis. Iam not kidding when I say that no one knows how the Kaihins are numbered. It is not just the size of the hole because three or four sizes might have the same hole but the length of the hole is different and the taper on each side is different. That is how the jets are fine tuned. On the average the difference between sizes is approximately .001" To give you a perspective, a #58 (.042") bit would be a 110 jet but the length of the hole now is the other variable, and that is if you ignore the tapers at each end.

knowing this, it escapes me how someone can do a bike build and try to cheese out at every corner....no offense,
but ya got to cut loose with some cash if you are going to be successfull....if the cash isnt there, wait till it is.....

Aw Come-On haven't you ever fixed a flat tire with some Duct tape? Or put a candle inside your headlight when your light-bulb burned out. What kind of meknik are you.

:laugh: ...:laugh: ..:laugh:
i m no meknik....i m still trying to find out why when i replaced the multi function switch in my marauder, it blows the fuse when i turn on the wipers...guess i ll just
yank on a shoelace through the drivers window and call it done......yup...i m tired....

MARAUDER????? You mean the only cool car that mercury ever made?? ( I am not a FROD guy) :lol: Would look nice sitting next to a period Impala SS. :woohoo:

otakar wrote:

loudhvx wrote:

Z1 sells the Dynojet kit. It's expensive, but you pay for the research. It includes 4 adjustable needles for easier tuning.
www.z1enterprises.com/detail.aspx?ID=4038

If this guy wants to drill jets, he dose not want to spend the $8 on the four jets. How do you expect him to spend $100 on a Dynojet kit. :ohmy:

I've got no problem with him drilling jets. I assumed the CV34 jets are available, but I don't see them at Z1. Maybe Dennis Kirk, but he's gonna have to do some research on what he has. (Just use drill shanks as gauges to see what size you have.)

I only gave him the link in case he wanted the needles too, but it does come with Keihin-compatible Dynojet jets.

I agree, that if he can get the jets, he should, but if not then drill away.

Mikuni jets work fine as long as you know the cross-reference between Mikuni and Keihin. I gave him those #s
www.z1enterprises.com/detail.aspx?ID=57



Mikuni Large Round Main Jet #115
KL18-4378-1

---

Round jet with slotted head

$1.60


Qty:

otakar wrote:

Mikuni jets work fine as long as you know the cross-reference between Mikuni and Keihin. I gave him those #s

Do you happen to know what the actual thread difference is between the two types of jets? Is it a pitch difference or a diameter difference?

It is only a tiny (and I MEAN TINY)pitch difference.

I put Mikuni Jets in these Keihin 34s

I did forget to mention that Dinojet dose the same thing. Their threads are same as Mikuni but they give you the same jets for Keihin.

Well I can't comment on the old Keihin's but the newer CR Specials, please..... :laugh: Let's not even go there for they freaking ROCK! :woohoo:

But since we're on the subject, yeah, those Mikuni BS 34's (Bull SHiza) carbs are just magnificent.... :S :laugh:

OMR

I'm the OP.

Well, I'm older, unemployed and quite poor (although not yet homeless), and that won't change any time soon. $8 is a meal for me, and I'd rather drill then go hungry. lol

But wether I buy or drill, my question went unanswered. The CV34's have two main jets, a primary and a secondary. I checked my jets today and mine are stock at #125 and #62 (in agreement with the book). It also has #35 pilot jets.

I'm going to pods (which I already have) and will drill some holes in the muffler. Can anyone suggest a ballpark jet idea? A friend told me not to swap the pilot jets but just to open the screws a turn. But what should I use for the two main jets?

Rejetting CV carbs for pods and exhaust modifications will be no small task. It will require a lot of trials.

You can find charts online that compare jets sizes among different brands, but that's because the diameter is not the only factor in determining the jet's flow rate. The jets height, the length of the bore, the shape od the head etc, affect the flow. Once you start jetting, you will want to stick with one type of jet for consistency.

The problem is that when you go bigger on the main jet, you may want to go smaller on the secondary jet to compensate at partial throttle. You can't do that with drilling, obviously.

You need to find someone with the exact same bike and exact same setup that is jetted right on, to get a one-try, final jetting answer. But engine condition, environment, etc will afffect the final sizes.

Dynojet theoretically did the research and that's what you pay for with them. You will probably save money and a whole lot of time if you can save up for awhile and get their kit. If not, then you'll have to search and se if someone is running the same setup you want to run.