1999 GSX750 X/Y (RETRO) (INAZUMA) jetting

[Jimbo90]

1999 GSX750 X/Y (RETRO) (INAZUMA) or whatever people decide to call it.

Issues with it running Lean after installing Delkevic stubby race can. I have adjusted mixture screw out as far as possible and wanted to install stock replacement K&N air filter for better perfomance.

There is little info online for this bike as there were only 2 years made of this model. The only jet kit I can find is DynoJet Stage 1 or Sigma. Looked at buying jets seperately but the only parts I can find for the Keihin CVK32 carbs are cheap chinese crap imported from china.

Has anyone rejetted this bike before? if so what did you use? what size jets? and was it successful? Dont want to just bite the bullet buy a DynoJet kit and find it didnt make much difference.

Any advice I would be grateful.

[banoffee]

Personally I’ve found that going up two sizes on main jets to be a good starting point when fitting a slip on can and a k&n element on CV carb bikes. Not sure if the needles are adjustable on those or if you’d need to consider raising them a tad with suitable washers.

No experience of those carbs or bikes however that’s served me well for a base setting on various bikes. A dyno run would help.

[Jimbo90]

Thanks, the needles I have shimmed so have been raised slightly. I have been in touch with DynoJet who have a stage 1 kit so have gone and purchased that.

The needle they have is an adjustable C-clip one and it comes with 4 sizes of Jets and instructions on which one to use based on my set up.

Was a little confused that the Stock Jet in the Manual sais its 105 however the Stage 1 upgrade is slightly less. I was assured by a  DynoJet retailer that the DynoJets have been machined differently and allow more fuel pass through and there sizes dont necessarily match up with stock sizes.

Does this sound about right or have they spun me a yarn??

[banoffee]

Yes they are different numbering compared to OEM.

[Jimbo90]

Thats filled me with a little more confidence.

It arrives in the next 2 days so will keep the thread posted with how I got on and the overall performance after.

[Jimbo90]

**UPDATE** Stage 1 installed feels alot better through out the rev ranges with no power loss at all now. Colourtune looks as if it is furing as it should.

I am getting Rev Hang after a throttlw blip where it takes some time to drop back to idle. Also once it was warm I noticed the idle was a little unstable, dropping up and down every so often.

Now that would suggest its running Lean however the clourtune looked good and its running alot better now. I hqve also tried restricting airflow on the filter to see if it runs smoother but it just makes it run like dog shit.

Could it just be as simple as balancing carbs?? I havent done that yet (naughty me) but didnt want to do it yet incase it was something else and had to take them out again.

[Inazuma750]

Any update on this Jimbo? I realise this is a couple years old.

[Blubber]

Doubtful ..  last log in was March 2019. 

We can try an use the mention function @username .....@Jimbo90 maybe he has email notification selected

[banoffee]

I'd still start with what I suggested above, always do with a new bike with CV carbs running aftermarket exhaust and a K&N airbox element. Not blown one up... yet  

[Rsk_141]

I fitted a 6 Sigma jet kit to my 1200 its fine, sent info on pipe and air filter style, sent through pilots and mains and washers to lift the needles so far all good.