Lean on top 300 2010

[kiwia]

Halo all:
I come from Spain and I am new in this forum, i wonder the information you have here.
I Have tried many options with some diferents needles but i always get A grey colour of plug on top always on top. I have even tried with 185 main but still lean on top with N3CJ, N2ZG, NOZG.
Could anyone suggest me a good needle rich on top like N1EF but lean on low?
Thanks

 

[Jakobi]

On top like WOT? Or 3//4 throttle? What clip positions have you tried running in conjunction with the large mains? Is the bike feeling starved for fuel or just giving a poor/lean plug reading? Have you triple checked the float heights? Is the carb breathing? All breathers unblocked, including the tank. Nothing inhibiting the flow of fuel from the tank? Hows the bike run through the rest of the range? Temp, elevation, relative humidity?? Mechanical condition? What model carb? What year bike?

 

[kiwia]

Halo, thanks for your help. (Sorry for my English)
My gas gas is a 2010 model 300. I normally ride from 900m to 1.500m, my carburator is the new one.
The float lever is ok since I change it like 1?5 mm and there is no fuel going out.
I have checked 3? and 4? position for the clip but no way to get a good colour plug on top always coming grey. The bike has a good run all ranges without strange things like N1EF.
The bike is only 1 year and a half almost new, the condition is really good.
I repeat that all ranges going well, it is only a bad plug colour.
You say that porcelain is not important? It is more important circle?

 

[Jakobi]

So its the ASII carb with the shallow bowl and flat metal cap? It does like to be jetted leaner.

Other than the plug does the bike show any signs or symptoms of running lean? Cutting out, running hot, pinging, surging as you back the throttle off? Its very possible its just a combination of your fuels and or premix that are giving grey readings.

What happens if you go really rich? Does the power get softer and fluffier as expected? If you put a 185 in it will it start to break up in the higher rpm? This will be more evident in lower gears under little load.

I found my 2010 model when stock didn't give very good plug readings due to an exceptionally large squish clearance. Once bringing it in tight and having the fuel ignite under the spark where it should be the colour is much better.

To top it off see if you can get a used and dirty old plug and run a plug chop. If its truly lean it will indeed burn any existing colouring off the plug and leave it looking very white again.

 

[kiwia]

Thanks.
I a wondering that I can find a Gas Gas in Australia, we are proud that this bike is coming from our contry but many people here specially magazines prefer to say that Ktm is the best.
I am going to check the breathers of carburator but I did not know that it can have an influence on regulations.
I mean Top from 3/4 to 4/4.
I used to motorex but now I have been using GRO, maybe that is the problem?
I have tried N3CJ, NOZG, N1EG, N2ZJ with jetting from 35 to 48 and from 172 to 185. Used Plugs no news.
After checkings some posibilities, the one I like is 48 180 N0ZG ON 3? POSITION, speacially on low and medium but still lean on top.
When I put the 180 or 185 the top is sweeter, I mean smooth, the sound changes, with 175 sound was more metal.
So Jakobi wich needle you think is rich on top out of N1 series. Note that N1 series is the only one that I get good read plug on top but rich on low.

 

[Jakobi]

The oil should not make a difference. I used GRO with no issues at all. It didn't colour the plugs as well as the Amsoil but lubed well and burnt clean.

They look like rather rich settings but without knowing your conditions or fuels they could be right. I'd be double checking mechanicals for no air leaks including intake manifold and flywheel side seal.

The N3/NZ needles both lean out from 3/4 to WOT and require a larger main than the NO/N1 needles. This should only be a size or two. Really from 3/4 to WOT you are dealing with the main jet so if going richer is resulting in better results thats the direction you need to go. If you are jetting a lot richer than anyone else in your area for same conditions and same/similar bikes then imo that is highlighting that something else is going on (probably mechanically).

 

[kiwia]

I am going to do another check this weekend and I will back to you soon.
I do not think that have a mechanical problem. Maybe some air is goign in trough intake but something outside the engine since I bought it brand new.
Thanks for your help.

 

[kiwia]

Halo Jakobi, what did you do to briging in tight squish clearance? Just to tighten cilinder screws?
I think that maybe is that the problem, do you use 2 or 3 ciliender gasket, some people here use only 2.

 

[Jakobi]

The squish clearance is the distance between the piston and the head. Removing base gaskets will reduce this distance, but also changes some other things such as port timing and compression ratio. If you have the head machined to reduce the squish, this will keep the port timing the same, but increase compression. If you want to keep the same compression ratio you also need to have the machinst remove some material from the combustion chamber to correct it.

The exact figures need to be calculated, and first up you need to take a squish measurement before you get any work done. Usually best combined with a complete top end teardown.

I have set my 250 up to use a single 0.5mm gasket which leaves the piston above the exhaust ports a bit at bottom dead center. This is just to compensate for the porting on my cylinder being orientated towards top end, so allows the power delivery to remain closer to stock with a little top end bonus. I basically configured for the most useful spread of power over max hp.

 

[kiwia]

I have already found the problem, it was that plug was black and when I tried to
have a good plug reading, it coming similar than grey.
What I did is to start with a new plug and now plug reading is ok.

Thanks a lot Jakobi for for help.
After triying many posibilities the one I prefer is 48 178 NOZG 3? and screw 2,5.
i am going to add it in database.