Rvf tuning

[indy-joe]

I am going to jet my Rvf.

I have a strait through pipe only, HRC cdi, Tyga carbon aribox with stock filter with snorkel.

It has the usual flat spot at 5-7k, I done a search and found I will have to shim the kneedles with .5mm washers for the mid range. Found I could use 112 mains, though this is with the stock airbox not the tyga carboon one.

What do you guys think?

[Cammo]

112's all round and 0.5mm washers would be a good start.

The increased volume of the airbox shouldn't change the jetting requirements significantly.

[indy-joe]

Thanks Stickshift,

Thought as much, but just wasn't sure about the volume increase in the airbox.

Will give that a try.

[RVFJE]

112's all round and 0.5mm washers would be a good start.

The increased volume of the airbox shouldn't change the jetting requirements significantly.

Stickshift - what would you suggest then for NC35 with full tyga exhaust system,carbon airbox and HRC CDI and Pipercross foam filter?
And then secondly with Honda filter and front snorkel weith the top part removed?

[indy-joe]

Well went looking for jets today, you would think it would be an easy process..

I haven't taken them out so I don't have a sample to show the local shops if there either hex or round.. long or short type. These are the questions they asked me.

So what are they...? least I can call on the ph and see what is available.

Thanks
Jay

[superlite]

They're long and round.

http://www.showandgo.com.au" onclick="window.open(this.href);return false; are the Aus distributor for Keihin carbs. They'll sort you out cheaply and fast. You want these: 99101-393

Have a look on their website under Keihin carbs - second main jet down.

[Cammo]

Stickshift - what would you suggest then for NC35 with full tyga exhaust system,carbon airbox and HRC CDI and Pipercross foam filter?
And then secondly with Honda filter and front snorkel weith the top part removed?

Jetting requirements for nc30/35's are heavily dependant on induction mods. Small changes to induction can require big changes to jetting. Change of exhaust systems generally require only minor adjustments to jetting, all types of exhaust (full, half, muffler only, etc) need changes to jetting only over a small range. For these reasons it's easiest to set the bike up using only a standard paper air filter, as most jetting requirements for these are relatively well known.

If using aftermarket filters (pipercross, hrc foam, etc) it can be very time consuming to jet them properly, and I believe that they actually give you a decrease in engine characteristics as the fuelling transition from the needle to large main jets (needed for the filters) is hesitant at best. Don't be fooled into thinking that more air needs to get into the carbs for an increase in performance (at street bike level at least). This isn't the case with these bikes, as many have found out through trial and error. You may gain 0.5hp, but you'll lose some upper midrange and the engine will lose some of its linear power characteristics making it unpleasant at times.

Stick with a standard air filter would be my first recommendation.

In the first setup, if you replaced the pipercross filter with a standard filter (highly recommended!) then I would go with 112 front, and 115 rear main jets which would be near enough to being spot on. See superlites post for where to get these jets in Aus, from memory they're about $10 each from Show and Go. If you stuck with the pipercross filter, the jets would need to be 130+ depending on how well it flows, a dyno is the only way to tell if it's safe or not and it can run into big $ if the carbs need to come off a few times.

In the second setup above it's difficult to recommend jets, I don't recommend modifying the airbox at all for all of the above reasons.

[RVFJE]

Stickshift thanks for the feedback however I think you overlooked the fact that I have a NC35.
Generally the main jets are the same front and rear or are you saying for NC35 that different as per NC30 is ok?
With a Pipercross filter I had 112 Mains but 130 would be far too big for a 35 surely? But I had also removed the rubber flap and installed the carbon fibre HRC copy air tray. On your previous advice I have removed the air tray and reinstalled the rubber flap and put back the Honda paper filter.
As it always seemed to be running lean and not pulling up top (due to the removal of the flap) I have gone up to 116 mains and higher octane fuel with a HRC CDI. Quick test on the road last week and it was better than before
This is a track bike BTW.
Track day coming up on Saturday so will test it out. Unfortunately I'm never inclined to spend hours at the track removing the carbs to change the main jets. I'd rather ride and then come home and play again but getting the mains right first is critical so at least I know where to go after Saturday.

[Cammo]

I realise it's an rvf. Yes it's fine to mix jet sizes, the rear cylinders will run hotter than the front requiring larger jets. Lots of people run this setup in rvf's (although this size difference becomes more necessary as larger jets are used, hrc nc35 setup uses 148/152 as a starting point for instance [this is with no filter]). Contact me with your email address if you want a copy of the hrc manual.

112's will be far too small for a pipercross filter, it will be running dangerously lean at high revs.

If it were mine? 112f/115r, standard airbox, standard filter, flap in place. This would work well with a full system and hrc cdi.

Your setup could work well, only track time will tell, certainly a move in the right direction.


Yeah it can be a pain to change the carbs at the track, I think we set a new personal best of 12 minutes the other week at the track though...

[indy-joe]

Well I got mine sorted.

I removed the carbs, checked the jets that were in there. And 115's all round. I kept these in.

I then checked the kneedles to see of they had been shimmed. They had been with a .5mm washer. So I decided to try a .8mm washer which is all I had.

I noticed that the mixtures were way out as well like 1.5turns and 2 and just all over the place. I went to 2.5 turns on the mixtures.

The mid range flat spot, the torque is there now 4-7k as I apply the throttle.

The only gripe is, when it's warm it does splutter ever so little, bugger all to tell really.

Think it might be the mixtures, gonna go .25 of a turn less.

And then check the plugs.