RGV250 Race bike jetting

[Billy]

Thanks for that, My biggest issue at the moment is probably more lack of test time on the track. Only time will tell but it would've been nice to have it nearly sorted in time for the weekend

Contact Chris Osborne (Ozzy 27) hes got a dyno set up in Palmy now and is very experienced at 2 stroke tuning.As an example I ran RGVs for a number of years and assuming you bought that bike from Lyttleton it has Sagaya chambers and factory kit spec cylinders with 34mm carbs and a 22d20 control unit which is similar to a set up we tried and we ended up using 320 mains with 55/65 powerjets but we had bored carbs so thats probably only a guide and I wouldnt be suggesting you try that without testing although it does sound like its rich according too your description.Get it too a dyno and jet it properly

[The Pastor]

you can never get 100% smooth throttle with open carbs btw.

a carb balance (a propper one - many crap gauges out there that dont work) goes a long way (mainly for idle, but improvement overall is there)

[phillip]

hi iv got a very similar bike, vj22 double base gasket flowed cylenders sp 1mm head gasket took 0.3mm off the head ( despite what everyone says about fucking with the squish) 32mm carbs and tyga full exhaust system with no top on the airbox

It used to bog down at 8kish, so nana it up to 9k then all hell breaks loose. took it to tripple zee cycles in manurewa and they dyno tuned the carb and abra cadabra no more flat spot and good mid range.

My 2cents worth, get it running good and take it to an expert for the carbs

[7mmWSM]

Bit of confusion with the main jetting sizes so hope some can help.
Some info I've found says for example L = 280 R = 270 and other figures are back to front. I know I need to run one cylinder slightly richer but which one?

As for the test over the weekend... still massive mid range bog so plan b is going back to standard and process of elimination after that.

[SS90]

You run the rear cylinder richer than the front.

It is impossible to say over the "tinternet", but, just for shit's and giggles, let's have a stab at it.

You say "mid range bogging", I can only surmise that in most likely hood it is too rich.

Note-------- One mans "bogging" is another mans "missing", so be warned on that one eh!

One common thing I have seen over the years when people "race tune" their 2 strokes, is they (mistakingly) believe that (after somewhat dubious levels of "porting" (ahem) that they have done "such a good job" that nothing short of biblical levels of fuel (hence bigger jets) are now required..........

More often than not, it is only a 10% increase in main jet is required from standard (RGV250's are quite rich standard anyway).

From your description, I feel there is a good chance that you are simply too rich on your main jets.

Possibly your needle position as well, but only time will tell.

I suggest fitting the original air box (with filter..... don't laugh) and the original carb settings, and go for a test run, see how it feels.

I am of the (experienced) opinion that even with the different expansion chambers, the reintroduction of the OEM airbox and jetting will makes things easier as far as jetting goes.

The likelyhood of running too lean when doing a test run in this set up is very very small.

Then, simply "do one thing at a time"

Remove the air filter, and put the lid back on, go for a short run, and see how it feels/read the plugs, most likely it will NOW be too lean...... increase the main jet my 2 sizes, and test again..............

when everything is ok, repeat the procedure until you can run the engine with the airbox set up you want.

You may well find you have an easier riding bike if you run an air box top, never forget that a two stroke SOUNDS more powerful with no air box, but that is not always the case.

[7mmWSM]

You run the rear cylinder richer than the front.

It is impossible to say over the "tinternet", but, just for shit's and giggles, let's have a stab at it.

You say "mid range bogging", I can only surmise that in most likely hood it is too rich.

Note-------- One mans "bogging" is another mans "missing", so be warned on that one eh!

One common thing I have seen over the years when people "race tune" their 2 strokes, is they (mistakingly) believe that (after somewhat dubious levels of "porting" (ahem) that they have done "such a good job" that nothing short of biblical levels of fuel (hence bigger jets) are now required..........

More often than not, it is only a 10% increase in main jet is required from standard (RGV250's are quite rich standard anyway).

From your description, I feel there is a good chance that you are simply too rich on your main jets.

Possibly your needle position as well, but only time will tell.

I suggest fitting the original air box (with filter..... don't laugh) and the original carb settings, and go for a test run, see how it feels.

I am of the (experienced) opinion that even with the different expansion chambers, the reintroduction of the OEM airbox and jetting will makes things easier as far as jetting goes.

The likelyhood of running too lean when doing a test run in this set up is very very small.

Then, simply "do one thing at a time"

Remove the air filter, and put the lid back on, go for a short run, and see how it feels/read the plugs, most likely it will NOW be too lean...... increase the main jet my 2 sizes, and test again..............

when everything is ok, repeat the procedure until you can run the engine with the airbox set up you want.

You may well find you have an easier riding bike if you run an air box top, never forget that a two stroke SOUNDS more powerful with no air box, but that is not always the case.

Thanks. Thats pretty much my plan.