Persistent Jetting Problems

Hello, so i was trying to solve the jetting problem i was telling you about before. Something strange is going on. Let me start from the beginning. For those of you who don't know, i'm running a Sport Pro MKII kit, C16 and a dellorto 21, on a minarelli LC engine. So at first i was running a 72 main jet with the stock air box. Everything seemed fine, good acceleration and no bogging. Then i decided to go with an open air filter, in particular the Malossi Red Filter. So i installed the filter but kept the same main jet ( 72 ) . Bike wasn't running well, needed a lot of throttle to accelerate, misfired and just wouldn't accelerate. I guess these are symptoms of running lean, right? Anyway, today i tinkered a bit with it. Changed the spark to a racing, the one with the iridium or whatever it's called and also installed a 100 Main jet. The bike literally wouldn't move and go until 5 KM/H or something. Logic says it was rich, so then i changed to a 80. When i tried it it still was a little sluggish and boggy at acceleration, but after 30 KM/H it flew off. I think it was the C16 entering the power band but still IMO it does not explain the sluggish/boggy acceleration. Note that the bike was at a warm-hot temperature when we made the tests. Anyway me and the mechanic thought it was the correct size so closed everything up. Also, the mechanic told me that the acceleration might be like this because of the excessive amount of oil i add into the gas. Moreover, afterwards when i had went home and let it cool off for about 3-4 hours i thought i would take it for a spin. The symptoms were mixed between the 72 and 100 jet. It was very hard to pull off and with opening a full throttle if moved very slow with a top speed of 60 KM/H . I thought maybe if i removed the air filter and switched to the stock air box it would help but it was even worse. It's driving me crazy!
How can i actually tell if it's running lean or rich?
Any suggestions for solving the problem?
P.S sorry for the long story

 

As I said in the other post:
Why jump back straight to an 80? You should start with a jet you KNOW its rich and work your way down from there, 1, 2, max 5 sizes at a time (and 5 sizes only if you know its still way too rich).

Me, honestly, I'd ditch the open filter and go back to the airbox, altho I'm not sure it is enough to completely feed the 21mm.

 

Well i thought if i solved the problem with the air box i would return to it. The strange thing is that before it was running much better with the 72 jet and the airbox but now when i put it back on even with the 80 jet it's running poorly.

 

Have you tried putting the airbox back in with the 72 jet? 80 should be way too rich, since it was running good with a 72

 

Yes i did and it was misfiring a lot, like cutting the fuel supply for a second and the continuing.

 

Is the spark plug in good condition? It might have got fouled from being used in a too rich or too poor condition. Try swapping it with a new one

 

have the standard airbox with a 72 jet and put your original spark plug back in, then see what happens

 

Well i have now installed the new one as i said above. The old one seemed like it had burned carbon deposits or whatever they're called. It was covered in a black, dry substance.

 

I think i'll try a 90 main jet and see what happens. Then 85 maybe and if nothing works i'll try 75 with the air box

 

Hve you tried it after installing the new one? With the airbox and the 72 jet that is

 

Well no. The thing is i prefer to have the filter installed rather than the air box, but if the problem persists then i'll have to go back to the air box unfortunately.

 

those open filters are dog shite no offense but they more trouble then there worth

 

Could you elaborate please?

 

nasically they are hard to get the engine to work around and many people such as yourself end up with these un-predictable problems thats why i have upgraded nearly eveything on my bike (upgrades to increase speed) except the air box, becuase it is perfect.

 

Open filters are really not needed till you reach quite a high level of tune and they have many downsides: fuel consumption and lack of backpressure being some of them. Altho im not sure if thw airbox is enough to feed the 21.
If you want to keep it, gets yourself some jets ranging from 100 to 80 and get testing, going down from 100 2 to 5 sizes ata time. Also get a new spark plug before doing so, asa fouled spark plug will make it impossible to tune it corrwctly

 

Logically the 90 will be somewhat correct, right?

 

No way to tell but to try it. Open filters make it really hard to guess an ok jet.
I was running a streetrace with a gianneli next and an open filter with a 17.5 dellorto and it needed a 112

 

Hmm, i'll try then. Is there a chance that the pilot or needle need changing?

 

Main jet first, then when you find the right onr mess with the needle and air screw, and possibly pilot jet (usually not needed). Thats the way i think at least.

 

Isn't it really strange that mine needs a 'small' jet compared to other set-ups with open-air filters?