Jet kits
- Thread starter fen0men
- Start date
Roadghost
Well-known member
I have what's called a Dynojet Stage 1 kit on my Harley. Basically it includes a slightly different set of jets (you choose jets for straight pipes and intake, or semi-straight baffled pipes) a slightly larger needle, a different diaphragm spring, and drilling out the needle hole with a supplied bit. I was recommended the kit by a friend who was a Harley mechanic. Paired with semi-straight pipes it really woke the bike up, without biting into fuel mileage much. Here's the kit for your bike:
www.dynojet.com
Pair the kit with your exhaust and intake. You won't be sorry.
Jet Kit for 1999-2000 Honda CBR600F4
Take your performance to new heights with a Jet Kit for your motorcycle. Increase power and improve performance throughout the entire RPM range, while improving throttle response and smoothness. These Jet Kits take the guesswork out of tuning your bike. Whether you’re rolling with a stock bike...
www.dynojet.com
Pair the kit with your exhaust and intake. You won't be sorry.
I have what's called a Dynojet Stage 1 kit on my Harley. Basically it includes a slightly different set of jets (you choose jets for straight pipes and intake, or semi-straight baffled pipes) a slightly larger needle, a different diaphragm spring, and drilling out the needle hole with a supplied bit. I was recommended the kit by a friend who was a Harley mechanic. Paired with semi-straight pipes it really woke the bike up, without biting into fuel mileage much. Here's the kit for your bike:
Jet Kit for 1999-2000 Honda CBR600F4
Take your performance to new heights with a Jet Kit for your motorcycle. Increase power and improve performance throughout the entire RPM range, while improving throttle response and smoothness. These Jet Kits take the guesswork out of tuning your bike. Whether you’re rolling with a stock bike...
Pair the kit with your exhaust and intake. You won't be sorry.
I was looking at 6 sigma because they have more different stages instead of dyno jet
Mad Mike
Well-known member
You could do it, but why? What are you expecting from an exhaust and carb upgrade? You can expect 3 to 4HP gain with a really good Stage 1 tune $150 for Jets + $500 for install and tune) and decent exhaust ($500-700)-- that's less than 5% -- do you think that's worth the cost of the upgrade?
If I owned a Hornet, I'd be looking at upgrading the cheepie suspension and brakes first. Upgrading the rear shock ($300) and front springs ($200) is a start will give you more riding performance than a a few HP at the wheel. The squishy brakes on a Hornet can get a lot crisper just by changing to steel braided lines. I'm guessing you can do any of these upgrades (maybe all) for less than a good can, jet kit and tune.
If I owned a Hornet, I'd be looking at upgrading the cheepie suspension and brakes first. Upgrading the rear shock ($300) and front springs ($200) is a start will give you more riding performance than a a few HP at the wheel. The squishy brakes on a Hornet can get a lot crisper just by changing to steel braided lines. I'm guessing you can do any of these upgrades (maybe all) for less than a good can, jet kit and tune.
Mad Mike
Well-known member
Hornet is the naked, Hurricane the faired. I think you are right, doesn’t make a difference from a performance perspective.
The ugly a Hornet was a sleeper, the could move!
I second the "What are you hoping to gain" comment.
If it's stock at the moment, you have a somewhat-classic older sport bike in original condition. That is A Good Thing as long as everything is in proper working order. Suspension and brakes are likely to need attention on something this age. Give them that attention. If something's broken, it needs to be fixed, and that's fair enough. But otherwise ...
Making the bike noisier doesn't make it better.
Installing different bits inside the carburetors doesn't make it better unless you're replacing something that's worn out or broken, or fixing some sort of issue with the bike. Not broke ... don't fix.
Making the bike lighter is arguably making it better but it's still going to be no match for a newer bike, so why bother.
Introducing ANY aftermarket bits and pieces introduces the risk that not only do you not solve a problem that wasn't there to begin with, but you also introduce new problems that potentially you don't have the knowledge and experience to solve. Can you tell the difference between an engine that is running rich and running lean? How rich? How lean? High revs or low? Part-throttle or full throttle? Do you know what needs adjusting under which different circumstances? No? -> DON'T MESS WITH IT
The F4 is new enough that the stock stuff that the bike came with, is decent, which means that further gains require you to actually know what you are doing, and it's easier to lose (by doing the wrong thing) than gain. It's nothing like the bad old days of strangled and/or horribly-designed intake and exhaust systems that anyone could de-restrict.
If it's stock at the moment, you have a somewhat-classic older sport bike in original condition. That is A Good Thing as long as everything is in proper working order. Suspension and brakes are likely to need attention on something this age. Give them that attention. If something's broken, it needs to be fixed, and that's fair enough. But otherwise ...
Making the bike noisier doesn't make it better.
Installing different bits inside the carburetors doesn't make it better unless you're replacing something that's worn out or broken, or fixing some sort of issue with the bike. Not broke ... don't fix.
Making the bike lighter is arguably making it better but it's still going to be no match for a newer bike, so why bother.
Introducing ANY aftermarket bits and pieces introduces the risk that not only do you not solve a problem that wasn't there to begin with, but you also introduce new problems that potentially you don't have the knowledge and experience to solve. Can you tell the difference between an engine that is running rich and running lean? How rich? How lean? High revs or low? Part-throttle or full throttle? Do you know what needs adjusting under which different circumstances? No? -> DON'T MESS WITH IT
The F4 is new enough that the stock stuff that the bike came with, is decent, which means that further gains require you to actually know what you are doing, and it's easier to lose (by doing the wrong thing) than gain. It's nothing like the bad old days of strangled and/or horribly-designed intake and exhaust systems that anyone could de-restrict.
Guy I jump in that for one reason I want better performance. And by the way I’m mechanic and I know when one engine running rich or lean how much I know to I already have the tool to check how lean is and more specific on which cylinder I just looking for review if someone in here is done that type of updates on the carbs about the bike is everything is fine with the engine coz I rebuilt it from the ground up and I already put 5K since rebuilt about the suspension is already upgraded to the breaks are from 1000cc bike and are awesome I just like to squeeze a bit more power from the engine so again I looking for reviews and comments from guy who did that mood
Trials
Well-known member
Isn't the best performance upgrade that can be done to a CV carburetor,
to replace it with a non-CV carburetor?
I don't think that has changed in 20 years.
Unless somebody makes aftermarket fuel injection that would be very cool.
If you know what you say you know, then surely you could establish whether the engine, as it stands right now, is running rich or lean (a) at wide open throttle and high revs, and (b) at wide open throttle and moderate revs, and (c) at part-throttle cruise, and (d) at starting and idling. And surely you could establish whether there would be anything to be gained by changing that air-fuel ratio ... and perhaps even identify how to address that without actually buying that moderately-expensive jetting kit and just changing specific jets (cheap) instead.
A jetting kit isn't magic. All it does is allow the air-fuel ratio to be changed under certain operating conditions by changing the amount of fuel delivered. Whether that's going to be a constructive exercise ... you tell us.
I will grant that I have never worked on specifically a Honda CBR600F4. I have worked on and raced motorcycles with carburetors. In fact, I have one - a Yamaha FZR400. Know what's in the carbs? Stock main jets and needles! One size bigger slow jets to solve the notorious hard-starting issue that those bikes have. Stock airbox with the stock snorkel in place, too ... because although you can gain possibly 1 horsepower at the very top of the RPM range by using individual filters, it isn't worth the loss in mid-range and driveability, which are important when accelerating out of a corner.
YES, you can get a bigger power increase by completely replacing the stock Mikuni BDS CV carburetors with a set of Keihin FCR flat-slides. You'll be rewarded with having to fiddle with jetting every time the weather changes or you travel to a track at a different altitude. I never bothered.
A jetting kit isn't magic. All it does is allow the air-fuel ratio to be changed under certain operating conditions by changing the amount of fuel delivered. Whether that's going to be a constructive exercise ... you tell us.
I will grant that I have never worked on specifically a Honda CBR600F4. I have worked on and raced motorcycles with carburetors. In fact, I have one - a Yamaha FZR400. Know what's in the carbs? Stock main jets and needles! One size bigger slow jets to solve the notorious hard-starting issue that those bikes have. Stock airbox with the stock snorkel in place, too ... because although you can gain possibly 1 horsepower at the very top of the RPM range by using individual filters, it isn't worth the loss in mid-range and driveability, which are important when accelerating out of a corner.
YES, you can get a bigger power increase by completely replacing the stock Mikuni BDS CV carburetors with a set of Keihin FCR flat-slides. You'll be rewarded with having to fiddle with jetting every time the weather changes or you travel to a track at a different altitude. I never bothered.
There's nothing wrong with the F4 exhaust, other than that BIG can, I would keep the pipe and replace the can with a Hindle slip on.
I don't know what you mean by "intake". If you mean you're going to put a K&N filter on it DON'T, the OEM filters are better.
With those changes I wouldn't expect to see any real performance increase, or any real changes in AFR.
As to "jet kit"... sorry. Jet kits are for people that don't understand carb tuning.
Honda didn't hide a bunch of HP that a "jet kit" will magically find. I find it hard to believe that Dynajet or Signa6 know more about the intake of a Honda F4 than Honda. Honda is pretty smart. Honda was building 20,000RPM four stroke motorcycles in the early '60s. They're quite competent.
If a "jet kit" improves your bikes performance, it means your bike is currently OUT OF TUNE.
Have you tuned the carb setup you have now? I didn't think so.
Ya wanna make the MOST power possible with your F4?
Find out what HRC did and copy that. IIRC it involves some VERY expensive spark plugs (I used to own an F4).
I don't know what you mean by "intake". If you mean you're going to put a K&N filter on it DON'T, the OEM filters are better.
With those changes I wouldn't expect to see any real performance increase, or any real changes in AFR.
As to "jet kit"... sorry. Jet kits are for people that don't understand carb tuning.
Honda didn't hide a bunch of HP that a "jet kit" will magically find. I find it hard to believe that Dynajet or Signa6 know more about the intake of a Honda F4 than Honda. Honda is pretty smart. Honda was building 20,000RPM four stroke motorcycles in the early '60s. They're quite competent.
If a "jet kit" improves your bikes performance, it means your bike is currently OUT OF TUNE.
Have you tuned the carb setup you have now? I didn't think so.
Ya wanna make the MOST power possible with your F4?
Find out what HRC did and copy that. IIRC it involves some VERY expensive spark plugs (I used to own an F4).
Trials
Well-known member
Yes you would, because right now your bike is fitted with the most complex carburetors ever designed to reduce fuel consumption and emissions.
It is obsolete technology, you are not going to squeeze more horses out of those vacuum operated carbs no matter what you do. You will be successful in making more noise, burning way more fuel and pumping out way more toxic emissions then federal law permits for that motorcycle.
Relax
Well-known member
OP - seriously, you are on the wrong forum if you're asking for advice on modifications to an F4. You probably want CBR 600F4 - CBR Forum - Enthusiast forums for Honda CBR Owners. Or something similar.
Trials
Well-known member
Absolutely Not intending to single out the op here, but why does a huge portion of the motorcycle public seem to think it is ok to ride a modern motorcycle that has all the pollution control equipment removed and is half way to being a race bike minus the safety wiring, specs and oil spill pan. I don't get that, and you are a mechanic so you know the law against emissions tampering? would you remove all the pollution control equipment on your family mini van or current model car and put a loud exhaust system on it? We know the cost, what's the gain if you don't intend to race the street bike.
