NC35 lumpy dyno chart, mild popping... main jets?

[thenewwazoo]

Hi all,

I recently had my bike dyno'd with no gas measurement (for free, so I got what I paid for). Here's the chart:



As you can see, the power curve is pretty lumpy. The bike feels pretty good on the street and the track, but on the dyno it popped and fussed a little bit, and popped considerably on overrev/engine braking. The bike has a full Tyga system, HRC slide springs, 112 main jets all around, stock spark plugs, and a stock airbox+filter.

I do intend to schedule a proper dyno session with gas measurement ASAP, but I'm looking for suggestions on where to start so can have any possible needed parts on hand. Any thoughts?

[thenewwazoo]

Oh! Also as a data point, it's got what I presume is an HRC CDI, since it revs cleanly up to 16,500 RPM.

[johnnie5]

i had an old bike put on the dyno and got a chart like that

start with all the obvious things

clean carbs
balanced
good chain and sprocket and tyres

[Malc]

Mild popping is usually a sign there's fuel in your exhaust, or to put it another way the bike is a bit rich. Don't instantly assume though the mains are the issue, as the needle and the number of washers fitted might play a part too.

[james66]

As malc has said dont assume mains, your main problem definitely looms like its starting on the needle but its pretty awful everywhere, what are your current carb settings? What carbs?

[Cammo]

Oh! Also as a data point, it's got what I presume is an HRC CDI, since it revs cleanly up to 16,500 RPM.

How were the revs measured? The genuine rvf hrc cdi's don't rev to anywhere near 16,500 revs, if yours was genuinely revving to this it might be a Chinese cdi and could be contributing to your issues - they don't have a good reputation i suggest replacing with a standard cdi.

Standard rvf cdi's start with the code MR8 printed on them, genuine hrc cdi's start with code NKA.

I don't know that this will be the cause of your issue but certainly might contribute.

[Drunkn Munky]

Hrc slides springs wont help matters either, bike sounds rich and the springs will only make things worse

[thenewwazoo]

Hi all, thanks for the input. The carbs are stock other than described in the first post, with stock slides, needles and (iirc) 0.5mm shims. They're spotlessly clean, having been gone over by a local Honda V4 carb guru, and the bike is otherwise well-sorted. The revs I "measured" using the tach (an MC19 unit, in fact), but they tend to be a bit optimistic, admittedly.

It really does sound like I need to get it on a sniffer ASAP. I was hoping someone had tried my specific setup before, but it doesn't sound like it! :)

[Drunkn Munky]

Id say theres 1000's running that particular setup although Ive never known a stock engined rvf need hrc slide springs

[CMSMJ1]

I ran HRC Springs in my RVF carbs..they worked lovely.

Just seems really skittish - not one thing causing an issue and so might be something other than fuelling. The tyre might have been slipping? The chain might be fucked?