Hey Guys,

I've been building up my track bike from a non runner. And it's running(but not very well) so I took it to the dyno for a run just to see what it's doing. this is the graph. And before anyone says it, no, it's not my RGV, that actually has a more linear power curve!



Could a few of you post your dyno graphs for a GK76 if you have any. It would be nice to see what it should actually look like, as I'm a little worried and confused about mine.

The spec of mine should be stock, engine wise, as far as I've been told, but everything else on the bike had been messed with, so I couldn't guarantee it.

The spec is(just in case you're wondering);

Stock air filter
Standard idle/choke and main jets (not sure about needles/emulsion tubes)
Litetek o-ring kit
Sandy Bike stainless headers
Johnson carbon end can
new plug caps and leads and cr8eix plugs
Custom loom removing most of the road bits
88deg SVthou thermostat

Cheers,
Martin

They are usually very linier when running well and can fell gutless because of this so yes it looks off.
What year is it, 55 hp is about there for the age.
Take a look at the needles and needle jets as they wear and give poor midrange running.
I'm not very good with dyno reading but you weak then rich so could be needle wear, fix that rich spot and it should fill in the hole.

Thanks vvs. It's a 1990 so 55hp on the top was what I was expecting and a/f ratio looks good at the top, so reasonably happy main jet is right.

It's that very lean bit at the bottom I wanted to compare with others. I'm assuming it's very odd.

Hopefully needles and needle jets will sort that rich bit in the mid.

Does anyone know what influences the 3.5k to 5.5k region on these carbs?

Cheers,
Martin

You will never be below 10000 on track!

Things to try are - give it extra fuel it the bottom by adjusting the float height smaller (from the gasket surface) and then see if you fix the rich spot by dropping the needle.
If its being caused by wear you may find dropping the needle weakens it too much and it will run worse,
Only one way to see!
Think the float should help the lean spot though, remember more fuel in the float bowl, less height from the gasket as the carbs are upside-down.

True! It's just one of those annoying things now.

Thanks vvs, that makes sense. I'll give it a try. I'll post my results when I manage some time for dyno.

Cheers,
Martin

Nothing worse than F'ing about with carbs, my bandit is rich at the bottom and I can't be arsed fix it.

Make sure the air box is sealing well as these bikes are touchy.

Variablevalves suck wrote:Nothing worse than F'ing about with carbs, my bandit is rich at the bottom and I can't be arsed fix it.

I hear ya. My other bike has EFI, what a great invention! I'm not into dicking around with something more than once.

mines a similar spec, but mines had head work etc and im up to 64 but it needs more time on a dyno to perfect.

Hey Guys,

KiwiBiker; I think EFI might be a bit out of the budget for this year, but you never know, sometime it could be a go-er. Especially if the carbs play me up enough times.

morris147; Could you post a graph if you have one? It would be nice to have a benchmark of how another one looks(even if it's had a bit of work done). Mine's been in having the carbs sorted by a shop this week. I didn't fancy all the messing around in the end, thought it would be easier for them to try and fix. I'll be posting the afterward graph when I get it back.

Cheers,
Martin

I think it's ok and not too far out at all. The 14 A/f mixture is the ideal figure if you're going for minimum hydrocarbons. You need to aim a little richer to increase engine response and lower engine temperatures, and maybe hp figures.
For 4t's I aim for 13/1 flat out, and 14 on cruise, and 12/1 on 2t's flat out.
The gsxr is a little wheezy in std form, and seems to suffer form a weak 'signal' at the carbs making them tricky to tune as you want them.
I've gone pod filters on mine, and mine goes super rich at 12-14000rpm but makes 55 at 12000 on the same dyno.