Rejetting the VF500F

Hey guys, I've got a Factory Pro jet kit for the 86 VF500F and I'm wondering if anyone had recommendations for mixture screw and needle height settings. I'm running F1 slipons and what appears to be an aftermarket air filter, though it's not K&N. I'm at sea level.

Thanks!

 

Best bet may be to ask Factory Pro. I am surprised that there was no instruction about these settings. I am not familiar with this kit, but if you can't get any answers a good starting point may be to compare the needle with the stock needle and drop the clip one notch richer than the stock needle, as if you were shimming the stock needle (but you already thought of that I bet...).

Curious, what are the jet sizes with this kit?

 

Well, there ARE directions with the kit, but they are about as cryptic as all their other kits. Generally speaking, the best setup is found from information on forums like this one. I just find it hard to believe that there isn't anyone here who has installed one.

The kit comes with 4 needles, (7) clips, (2) 98 mains, (2) 100 mains, and a set of allen screws. Oh, and of course (2) Factory Pro stickers! Those add another 5 hp each.:smile:

 

I posted jetting questions for the 500 a few times with no response. I don't know that a lot of people here have gone away from stock, based on responses. It might even be tougher go with the 86. I wonder if Matt changed his jetting?

 

An excellent jetting tutorial (link to Factory Pro's website)

CV Carb Tuning Procedures

 

Yeah guys, I get it! - jetting, that is. I've been tuning carbs for over 10 years. I am looking for a good baseline so I don't have to pull the carbs multiple times to swap jets, adjust mixture screws, and fiddle with the needles.

I'd also rather not have to pay for dyno time.

 

Bump to the top. Anyone got any experience with this?

 

Keep the main jets stock, that's the first piece of advice I'd give you. You'll need to dial in the needles but there really isn't much anyone can do to help you with that. The pilot screws are simple as it just takes a screwdriver and they are easy to get to. I'd run the recommended needle height in the instructions and start there.

 

Thanks for the advice, Jamie. Time to start tearing into it. UPS says the carb boots are "Out for delivery"! Hmmm, should I check the valves while I'm at it.....?

 

Out of curiosity, why not bump up the main jets?

 

With slip ons and what appears to be an Uni (? Aluminum endcap, non-oiled foam, with an aluminum mesh backing) filter I think I just might bump them.

Next question: Why do we jet leaner on the rear than the front? It seems bass-ackwards to me. I thought since the rear ran hotter (less airflow across the heads) then you'd want it a step richer to keep combustion temps down. The VTR1000F is that way. Hmmm.... FYI, I just verified 92r/95f.

 

I was corrected awhile back on this misconception too - the front and rear heads run at about the same temp, as this is a water cooled engine. The difference in jetting has to to with the orientation of the carburetors and not the cylinder temp, from what I have read.

 

A good point...my question on the bump though was more related to the fact that the '84 had 102/105 mains. Honda went to 90's front and back per the later years and also per a hot start service bulletin from back in the day.

If the bike can handle larger mains why not go for it? After all using the largest main jet that you can use, without causing a performance loss, is step number 1 on Factory Pro's tech guide...

 

Yes on the first and 32mm vs 30mm on the second.

Honda went to 90/90 on the '85 model (w/ a 32mm bore). On a side note, I do know that the emulsion tubes are different on the '84 compared to the '85.

I would think though that you would want to install the largest mains that will work as the first step.

This could very well be 90/90 but I'm guessing that Factory Pro includes the 98/100 combination for a reason - after all I've read that their kits are the bees knees.

 

I moved the 95's from the front to the rear and installed the 98's in the front. I figure with my bike and my conditions I should have no problem going one size larger. The needles however got me a little stumped. They are significantly smaller at the tip and about the same near the top (clip end). They are also significantly shorter, so short in fact that I was hesitant to install the clips in the (recommended) middle position for fear it would be too rich. The overall length of the Factory Pro needles is 47.265mm. Additionally, subtract the distance between the clip and the top of the needle. Stock is 49.01mm.

I drilled and removed the mixture screw caps and adjusted the screws to 2.25 turns out. They were initally all over the place, from 1.5 to 2.5 turns.

I put the clips 2nd from the top and hoping it won't be too rich.

Still waiting on the UPS guy...

 

Interesting note about the needle length, please keep up posted on this.

You mentioned that you have set the mains up as #98F/#95R.

I know you have an '86 but, if I could ask, what is your reasoning here?

As an example, the '84 was initially setup with #102F/#105R main jets - Honda has the larger jets installed on the rear cylinders (no. 1 and no. 3).