The time has come to get the carbs on my RVF sorted (not much wrong with them as they are now, but...), so I need a few pointers from you fine carb-gurus on what to do to them.

The RVF has a 3/4 Yamamoto exaust paired with a Yamamoto can, it's running a modified airfilter with Pipercross foam (which I'm convinced it performs the same as standard ones), airbox and its snorkle are standard and the main jets are also standard 108's; pilot jet's also standard 35s, the needles have J8VA stamped on them (standard?) and if I understand it correctly (unlikely) the pilot screws were set at 1 5/8 out. Can anyone explain the incremental turns a bit please?



I had the bike on a dyno for a quick power check and the guy reckons it was fuelling well enough and that if it was running ok as it was (which it is), to leave the jets alone.
However, I'm going to give bike a well overdue full service, which will include carb clean up, etc so this is a good opportunity to get them as best as they can get for the road!

I've read Cammo's excellent carb guide for the NC30 and it did clear up a few carb-newbie questions however, the NC35 is a different bike with different carbs, etc!
It's my understanding that 112 main jets all around are a good starting point as is raising the needles by 0.5mm; but which main jets should I go for: standard or Dynojet? Once that's done, to what should I set the pilot screws to?
Have I forgotten anything?
Cheers.

Does your dyno sheet have a fuelling line on it too?

If it works..leave it! Simples!

The pic you posted is right - turn the screw in (count the turns) until it seats gently. Then back it out jsut under 2 turns.

Jets are jets, I'd use Keihin std ones to be honest.

It's showing 13.5 @ 7468rpm; what's the optimum supposed to be?

The main reason I'm considering upping the main jets is for reliability/peace of mind as well as getting it running as best as possible with the current exhaust.

Erm, what would be on the other 3 question marks?

Thanks.

13.5 is what you want...

To me, that looks rich already...so how old is your airfilter? If I get my ratios right anywyas - you want to hit 13.5 - 14 A/F across the range so it looks like your needles are nicely sorted but that it is starved of air at the top end and the air/fuel ratio drops losing you power and causing the fluffy action at 12000 revs.

Some of the other people can clairfy this or confirm whether I have got it arse about face. I am surprised as I would expect it to be leaner with a 3/4 system and aftermarkett filter...Shows that the Honda one is bloody good!

agree with that. You can see the trailing off of the HP corresponding to the drop in A/F. That is either air filter or main jets if the run was done with Full throttle

on the first drawing also, 5/8ths falls between 1/2 (4/8) and 3/4 (6/8th) I believe, not where you have it in the drawing.

How many km does the bike have on it? ive been told jets can open up with higher ks so the mains are likely bigger than they originally were depending on the kms

just to point out. turning clockwise 5/8 is the bottom left green question mark
anticlockwise 5/8 is bottom right red question mark

Whats with the big rich dip @5500 rpm ?

Old Painless wrote:Whats with the big rich dip @5500 rpm ?

That's probably typical of these engines, usually referred to as a midrange flatspot, felt as a loss of torque (compared to lower revs) on the road.

Not sure if it's built into the engine design (emissions and noise testing etc) or just a trade off of having a a fairly linear power curve from such a small high revving engine.

If it was ignition retardation it would still have the correct A/F ratio though ? Might be jetting issue ?