Carb Tuning/Jetting Cynicism - An Investigation

when i sell a kit i find out home elevation exhaust type and mods and normal driving style

then jet the carbs sync and idle balance them then drain and ship

i test run all my carbs on the correct type engine

Sonreir said:

Saying it's simple doesn't make it so.

If I bought a pre-jetted kit for an extra 25 bucks and had to change only one jet, I'd be OK with that. Obviously, the preference would be that everything just worked out of the box.

But seriously... $25 and I only have to change one jet instead of four? That seems like a bargain. My time isn't free.

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well any decent tuner can pick the right jet the first time out if the jetting is already half way close . . the inexperienced people will likely spend more time and money on jets and when you have a bike witn 4 carbs and you just spent an extra 80.00 to 100.00 for pre jetted carbs that still need jetting, you can buy a lot of jets for that much money . . also hobbies like this are not free . . if someone does not have the knowledge to work on their own bike or the tkme or the money to pay someone else to do it for them they need to buy something that is a bit more fool proof and reliable like a hundai . . its that simple e 8448401030212461

Yeah, but then how do you learn?

$100 in jets is still cheaper than a college course.

cxman said:

when i sell a kit i find out home elevation exhaust type and mods and normal driving style

then jet the carbs sync and idle balance them then drain and ship

i test run all my carbs on the correct type engine

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Xlnt, then you do it as right as is practical and are a good person to know . . even if your carbs still needed one step bigger or smaller jet I would not cry about it because unlike some others, i know that pre jetting a carb is hard even when you know what you are doing plus the buyer might have forgotten to tell you that his engine is bored .200" over or his timing is way off or he only has 115 psi of compression because his engine is worn out etc.

Sonreir said:

Yeah, but then how do you learn?

$100 in jets is still cheaper than a college course.

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Well first you say that you want correctly pre jetted carbs but now you are promoting self learning by jetting your own carbs so I am confused as to exactly what point or points you are trying to make . . I am also a part time instructor so I like people that want to learn like this op, and I encourage learning, but its not always practical with a wife and a few kids and college tuition for them and house payment that requires one to work 6 days a week 10 hours a day etc. Plus you made. My point...why spend $100.00 on prejetted carbs when you can do it yourself . . you can't have your cake and eat it to in this cafeteria

Is there not room for both? A person needs to decide if they'd like to spend money to make time or spend time to learn something.

Sonreir said:

Is there not room for both? A person needs to decide if they'd like to spend money to make time or spend time to learn something.

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True 'dat.

Sonreir said:

Is there not room for both? A person needs to decide if they'd like to spend money to make time or spend time to learn something.

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Totally agree. There's plenty room to be a proponent of both.

As for the nature of this topic, I was more curious than anything else to see if it was indeed true that shops will look to generate more sales by claiming to jet the carbs as per your bike/setup/location, or whether the guy who told me that was just a mardy douchebag. The question was borne out of curiosity; personally I would like to learn as much as I can, but if someone can tell me they're going to jet my new carbs and it gets me on the road quicker, I'm doing that.

Safe.

Sonreir said:

Is there not room for both? A person needs to decide if they'd like to spend money to make time or spend time to learn something.

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I think that can be assumed, but this is getting far from the point . . basically do NOT under ANY circumstance buy a non custom jetted prejetted carb and expect it to be perfectly jetted for your bike . . it may or may not be . . again, it really is that simple . .

Anyone that thinks they can buy such a carb and have it be perfectly jetted for their particular setup or even close enough where it is still acceptable is either gullable, naieve or misinformed etc

My catalogs have quite a few pre-jetted carbs that are available based on size or application. The carbs will have jetting sizes already listed and we will compare them to their bike's optimal settings based on altitude and such. This is usually how it goes:

For the general public if we are selling a carb, pod style filter, exhaust, et cetera, we sell a jet kit as part of the deal or later when it isn't running right and they come back for it. God is in the details so I am usually directing them to forums or youtube videos so that they can learn.

For mechanics and experienced wrenchers they will usually already have their own jet sets and usually don't buy new carbs from me, they usually have a collection of carbs from ebay in a milk crate in the back of the shop anyway.

I have never seen an aftermarket Mikuni correctly pre-jetted for modified exhaust and intake.
On some bikes (older Triumph twins - 60's~70's) Mikuni's have been fitted for s many years there are set-up's which are very close as long as correct size carbs are ordered (usually 30mm~32mm on 650~750)
I modify quite a few CB360 CV carbs to run with K&N filters (cheap pods just don't work right)
Some work perfectly others not so much. I always tell people they may need to change secondary main jets and probably will need to tweak fuel screws.
The pilot/slow jets are usually very close and the primary main jet works pretty good (changing it is difficult as different sizes are not easily available when it needs to be smaller)
The secondary main jet is easily available if it needs changing.
Biggest issues I've come across are different exhaust systems and altitude settings.
Shorter than stock exhausts can need up to 20~25% larger secondary main jet.
Altitude to about 6,000ft with K&N filter, stock jetting seems to work just fine