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This may sound like a foolish question, but when people talk about stage 1 vs. 2 or 3 jetting, what are they referring to? In other words, I know what a "jet kit" to go with an exhaust system includes, but what are the various stages referring to. What are the advantages. I'm, assuming that when you purchase a run of the mill jet kit to accompany a new exhaust, it is generally referring to stage one, unless you specifically install stage 3 or whatever? What's the deal?
 

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Quoted from Dynojet Website
Stage 1 Kits
Intended for motorcycles with a stock engine using the stock airbox, air filter and stock pipe. Stage 1 kits are fully adjustable to allow the use of a well designed aftermarket pipes and stock replacement air filters like K&N. Stage 1 kits are designed to improve throttle response and driveability and in most cases power increases of approximately 5% throughout the entire power range can be achieved.

Stage 2 Kits
Intended for motorcycles with a stock or mildly tuned engine using a well designed aftermarket pipe with a modified airbox and a stock replacement air filter. Stage 2 kits are designed for applications where individual filters cannot be installed and for applications where airbox modification improves the engine's performance. In most cases power increases of approximately 8% can be achieved.

Stage 3 Kits
Intended for motorcycles with stock or mildly tuned engines using a well designed aftermarket pipe and individual air filters. In most cases power increases of 10-15% can be achieved. However driveability may be compromised particularly with short stroke, high rpm motors. On some modern engine and airbox designs, individual filters and proper jetting offer no performance improvement yet compromise driveability, in such cases stage 3 kits are not available.

Stage 7 Kits
Intended for race only use or for special applications, like the Yamaha V Max complete induction kit. Stage 7 kits are designed to optimize jetting for a given tuning specification or racing conditions
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I think Jeff's right, check to see if the right kit for your bike and/or pipe was installed, then maybe lower your float level a bit. If that's all good go to valves/timing. My guess is that the float level is too high. If you're getting some backfiring, you might just need some new exhaust gaskets.
 

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Originally posted by SpeedJunkie:
This may sound like a foolish question, but when people talk about stage 1 vs. 2 or 3 jetting, what are they referring to? In other words, I know what a "jet kit" to go with an exhaust system includes, but what are the various stages referring to. What are the advantages. I'm, assuming that when you purchase a run of the mill jet kit to accompany a new exhaust, it is generally referring to stage one, unless you specifically install stage 3 or whatever? What's the deal?
<font size="2" face="Verdana, Arial">I'm no guru but I'm pretty sure that in most cases the only big differences are the sizes of the jets (3's are bigger than 1's) and the height of the needles + stock or aftermarket filters.Check out www.dynojet.com for real numbers. I think you kind of have to go with big jets sometimes to get smooth power through the whole power curve. For the most part what your doing is richening up the system to either make up for what OEM couldn't sell as stock (st1) or to match a new pipe that just made your system too lean (st3). I think a little rich is OK as long as you're not blowing smoke or fouling plugs.

[ 04-27-2002, 11:26 PM: Message edited by: 88/750 ]
 

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Ok before I get a new black box I was wandering if I could just go to a hotter plug. The manual calls for a ngk 9 or 10. I have been using the 9 and it is still really rich and back fires. I have tried to adjust the carbs but no matter what I keep fouling plugs. I changed ingnition now and still nothing. The guy at my local bike shop said that with that stage three kit I should go with a hotter plug does that sound correct to you? the bike was jetted when I got last year and has always backfired and ran rich. what do you gents think?
 

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no, you should not need to run a hotter plug with stage 3 jetting.

changing spark plug heat ranges is not the solution for jetting problems. if you're constantly fouling plugs, the source of the problem is not the heat range of the plugs (unless you're running plugs that are way too cold for engine operating conditions).

a hotter or colder plug does not 'spark' hotter or colder. a hotter plug is simply one that is designed to retain heat longer....a colder plug dissipates heat into the cylinder head quicker.

so bottom line is stick with the 9's and check jetting, air filter, exhaust, ignition wiring, coils, timing, etc.
 

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If you've gone really lean on the carbs (float height, needles, and mains as well as pilot-screws) and can't get `em jetted right to stop fouling the plugs, you *might* wanna check your compression... oil from worn rings and valve guide seals will foul plugs too y'know.
 

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Factory Pro's version of 1,2 and 3 is pretty much the same as Dynojet's.

However, Dynojet and Factory deliver quite different products to achieve more or less the same goals. Whereas Factory uses stock Mikuni parts (only different sizes) for jetting etc., Dynojet utilizes proprietary needles and emulsion tubes. Trying to compare Mikuni to Dynojet there is like apples and oranges. Also, Dynojet includes a drill bit in a lot of their kits for drilling out the slide to alter flow etc. Factory doesn't. Dynojet thinks that if you fuck with the pilot circuit in any way that your up the creek, since the engine will run on pilot without anything else.

Myself I like Factory. Don't like permanently fucking up the carbs or dealing with unknown quantities like the needles. Also, carbs are analogue, not digital, so you have a crossover period where the main circuit overrides the pilot circuit. This does not happen in zero time, and a slight enrichment of the circuit can both overcome stock leanness and kill off incipient bog.

That said, I'd take a jet kit made by Nabisco if it meant that a dyno was available to tune the install. I think they are all crap without the tools necessary to picture the before and after snapshots.

Loved having my Factory Pro kit tuned on a Dynojet dynamometer however
 
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