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I know and see many people have trouble with the stock carbs. I would like to know if anyone has tried a set of standard carbs, no power jets. I have a set of carbs off of a 92 Exciter (round slides) and was if anyone has tried them, what were the results. Brad

I see no reason why they won't work. Yamaha did go away from the P.J. carbs on the Exciters in 90 or 91 and there must be a reason for it. You will have to make sure that the total jetting numbers (main+pilot on Exciter carbs, main+power jet+pilot on Vmax carbs) is the same before you put them on and then start playing with it. The engines are similiar in the HP they produce and the RPM they produce it at so I would think you shouldn't be to far off with stock Exciter jetting but do be carfull and watch your plugs close until you get things sorted out. You could even hook up the Exciter carb heaters that can be turned on when it gets real cold. I would be interested in seeing how they work myself.

opsled

Dear Brad,

You should be able to interchage mikuni vm38's from an exciter to a vmax. You should be able to recalibrate to vmax requirements without any problems. First switch to vmax slides, needles and needle jets, this is important. Check your needle clip slot for wear, as I have come across this potentially deadly phenomenon before. Clips have worn the needle in half! Pilot jets, main jets, air srew settings, and whatever else I forgot. Calibrate your cable freeplay to synchronize your slides, and you should be good to go. Did I forget anything? Joe

Question on changing slides, needles, and needle jets. Now I havn't done this swap and maybe you have so I'm not saying I'm right. I just have these thoughts so I will ask.

Setting aside the fact that pilot jets do play into the equasion (as they both have them) power jet carbs don't pass all the fuel needed for WOT through the mains. Some of the fuel is also coming from the power jet. On non power jet carbs ALL the fuel passes through the mains at WOT. Wouldn't it stand to reason that the slide, needle and needle jet requirments for the two different types of carbs be "different" for the same engine? I would think (again I don't know for sure) that the needle and needle jet would need the ability to pass more fuel on a non PJ carb than a PJ carb to supply the same engine and because of that increased ability to supply fuel a different cut-a-way slide would be needed to keep the engine from loading up when transitioning from the pilot to the main circuit.

Does this make any sense or am I over thinking it?

opsled

Back in the early-mid eightys PSI performance out of Wisc. was having any yamaha guy using their performance tricks block off the pj circuit with a beebee in the pj supply line. They then spec'ed an increase of two steps in the size of the mj's. Like from 310's to 330's for the 569 Exciter (for example). Getting on with my letter I am not sure of there being a correllation between the needle-nozzle circuit and the pj circuit on pj carbs because the pj circuit comes into play only at much higher vaccuum, such as at full throttle. Lower down the needle overlaps the pilots then the nozzle overlaps the needle then onto the mains which briefly overlapped the nozzle. (Whatd I just say??) The pj circuit then follows, right? (or wrong). I believe opsled is right when he states that the pj circuit is intended to provide additional (not all) fuel to the engine at full throttle, but does it play a role down at lower engine rpm's? I'm not sure. As a rule I block the pj circuit, as was taught me by PSI, and back then they were in the know. Guys, on a different matter I cannot find my friggin yamaha-comet clutch puller, and it was brand new, arrrgh! Anybody got one fer sale or how can I pick one up? Mucho tanks! Joe

I forgot something, I must be getting old. About the powerjet blockoff: I remember now that after blocking the powerjet circuit PSI had me change the location of the main jet from (if I remember correctly) the bottom of the nozzle back into its spot in the base of the bowel. Or vice versa, it's only been 20 years! Maybe an email to Bruce Kahlhammer at PSI would be in order, hopefully he writes back. So, learn up, wise up, and be carefull while searching for more: POWER! MJD.

I was thinking about it after my last post on this issue and think I remember seeing some info on Dynotech about PJ block off in some of their old tests. I didn't get time to get on there and look it up but will try to do so tommorrow.

By the way the Dynotech subscription to me was well worth the money (around $25-$30 per year). Lots of VERY!!! interesting stuff.

opsled

I have a set of V-Max carbs that are blocked off with BBs. I couldn't understand why, but that spells it out for me. I also have a set of 38mm flat slide carbs (individual carbs), I was thinking of trying. Brad