RVF 400 3-6k Flat spot

[Grigo1]

Hello all, I have been reading the forums on past flat spot issues but I was wondering if I could get some specific advice on the situation I am in before I go changing bits here there and everywhere and going wrong as they are at a basic state with new parts.

So the bike RVF400 NC35 has been sat around for about 5 years or so and when my friend had bought it, it had never run right since he had it.

Recently took apart the carbs and they were in a horrible state and the bike wasn’t running.

Now:
New pilot jets #35 all round
New main jets #115 as advised by RickO (kept older emulsion tubes as they cleaned up ok.
The exhaust is a slip on can so upped jetting from the original 108’s all round.
Reset the float heights to 12.5mm
New float needles all round (cleaned the seats as best as poss)
Air screws have been turned out to 1 5/8 (the best I could judge anyway)
HRC replica slide springs fitted
1mm shim on standard needles (the 0.5mm shim that was on originally I removed)
New gaskets fitted
Oil and oil filter change
New NGK ER10 plugs all round (it will be a race bike after a few months of good runs on the road)
Air filter has not been replaced but does not look in bad condition (but is old)and is a standard Honda one I believe.
Free flow fuel tap mod

Right so the bike is now starting and sounding really good compared to what was however:
The bike is not needing any choke at all to start and if it is on then it kills it.
Doesn’t tick over on its own when cold but when warm I’ve managed to get it at a nice steady 1 1/2 thou revs.
The initial pull away from idle is ok but when accelerating from anywhere within the 3-6-7ish range it is very laggy and boggy, I believe it’s rich but would appreciate advice on where I should fiddling first before I make it a puzzle.
7k revs all the way through to red line it pulls like a truck and seems to run really well.

Any advice appreciated I will be taking the carbs off this week to play.
Thank you
Grig.

[Suzuki416]

did you synch the carbs?

[Grigo1]

That is something I haven’t done. Not too sure on how, anyone have a link to a guide? I will start searching... is this relatively easy to carry out?

[Suzuki416]

It helps to have the correct tool.. I, like many, use a carb tool from:

http://www.carbtune.co.uk/

Works perfectly.

However even if you only 'bench synch' your carbs you will be in a better place.

Hundreds of you tube videos on this subject

[Grigo1]

May be easier for me to bench balance sync then. Trying to find a guide but can’t seem to find a detailed enough one for the rvf at the moment. If anyone has a link or can explain, would be much appreciated

[micpec]

Did you clean carbs thoroughly (e.g. Ultrasonic cleaner) and sync’d after a 5 yrs stand still?
Why #115 mains plus 1mm washers under the needle, with just a slip on can fitted?
And do you use genuine standard NC35 needles or something else?

I think it is now too rich. Go back to standard factory setup and go from there in small steps up.

[Grigo1]

It didn’t have a ultrasonic clean but I did a pretty good job at cleaning it up and replacing jets, float needles etc.
Will be syncing the carbs this weekend. Will go to 0.5mm shim on standard needle instead of the 1mm that’s now on it.
I was recommended getting #115 main jets and I was under the impression the the needle shims to 1mm would help the mid range flat spot.
It’s definitely rich. Going to try this weekend. I’ll check the air screws, sync carbs and go down on the needle shim and see if that helps and report back.
If it’s still bad I’ll look at putting the 108 main jets back.
Will keep the HRC slide springs though.
Thanks for the reply mic

[Flip998FE]

Did you ever get your bike running correctly?