sh2/22 trouble jetting

[HxPaul]

I've got a Casa 210 with a sh2/22 carb and I'm having trouble jetting it correctly.The bottom seems ok but it 4 strokes really badly mid range,but when I come down on the main jet to clean up the mid range the spark plug begins to turn white in colour.If I use a bigger main jet the colour of the plug begins to turn a nice colour of brown,but it begins to 4 stroke really badly in mid range.The main jets I have used are,130,stops the 4 stroking but turns the plug white.132,begins to 4 stroke but the plug seems a better colour.I havn't got a 135 main jet so I tried a 140,it 4 strokes really badly but the plug colour is a nice chocolate brown.I run the engine through the airbox with a normal filter,the exhaust is a Scootopia Ancillotti style clubman.

[ToBoldlyGo]

That doesn't sound right at all. I'm just a layman, but that seems awful large for a main jet. I run a 186 and a 123 main works for me. What size are your pilot jet and atomiser?

[HxPaul]

Thanks for the fast reply.The pilot jet is a 45 and the atomiser is a standard 5899-2.The carb is a Scootopia sh/2,but I've also tried a Jettex sh/2 with the same results.I also have a Casa 185 with an sh/2 and I have a 128 main jet in that and it runs great with a good plug colour through out the rev range.

[hullygully]

your airbox, is it drilled & swan kneck removed?
your air filter is it a breathe sweet one?
have you checked your bellows? is it the sh*tty Indian one that gets sucked towards the carb or Italian one?
pilot seams abit small
main jet & atomisor seam ok

[HxPaul]

Its a standard,undrilled airbox with the internal baffles removed and a standard Italian air filter element.The pilot jet is a 45 because I've tried it with a 48 and 50 and it 4 strokes really badly with them.The rubber bellows is a Casa one and it has no rips or tears.

[Wack]

Have you tried a different atomiser?

[hullygully]

you're still not getting enough air in there..........you've done half a job by taking the swan kneck out buddy

[HxPaul]

With more air it will surely make it even more lean at the top end.

[hullygully]

firstly, start with std jetting & slide for a GP200
get your tick over right next, if it races then up your pilot.
rev it with your choke on in various stages of open, to determine if main jet is weak,

[neil64]

hi ,

firstly yer mid range is not controlled by the main jet , forget that , i would look closely at yer atomiser,, that does control the mid range,. 5899-2 should suit, and check yer slide it should be 200 slide , .

[Adam_Winstone]

Don't hold me to it, as I've not used a Casa top end and you need to be responsible for correct testing to ensure that all is well, however, I've always found that the 5589-2 (200 and 175) standard atomiser is too rich too soon an most tuned barrels that need to run a larger main jet. I've changed atomisers to allow the bike to run cleaner through the mid range so that they can cope with the increase coming from the main at 3/4+. Typically for a SIL Factory IV 200 or similar spec 225 I've ended up using a 5899-4 (GP150 atomiser) with a 125-135 main, the main being heavily influenced by level of modification of airbox (range of standard with standard filter, baffle out with standard filter, etc.) and specification of clubman and ability to rev. Do note that this combo has always been used with a good quality and clean standard type filter and a GP spec airscoop and standard seat. Many of the slope back seats will greatly restrict flow to the scoop.

45 pilot (Dellorto) is typical as the 48 and 50 typically are too rich low down.

Remember.... try it and test it thoroughly as it is down to you to ensure that ANY/ALL jetting is appropriate to your engine, rather than simply relying on the suggestions of other.

Good luck with it.

Adam

[HxPaul]

Thanks for the reply Adam.I'll try your suggestion re. the atomiser,it would explain why the mid-range is so difficult to get right.When I Got the Scootopia carb it came with an extra slide and an extra atomiser,I'm sure thats a 5899-4,if it is I'll try it.