Now i have manage to have a real „shakedown“ with my P150X.
Due to the fine weather here in Sweden.
But i have encounter a minor setup problem.
The engine run a little rich in 0%—20% throttle range
and a little rich in 75%—100% throttle range. This is not a big problem, the problem is in between those at aprox 20%—>75% throttle, its the place you are in when youre cruising around.
And there it is too lean. The engine pick up very well in the lean range but when you let go of throttle the engine will hang on to same rev for a sec or two in a way that is not normal.If i pull the choke in the lean range the rev will come down in a normal way.
I have tried too change the main jet but if i go with a bigger the rich range is going even richer, but then the lean range is ok.
If i go with a smaler main jet it would be the opposite.
Anyone have an idea what to do next.
I currently have this setup:
Welded and ported P150X engine halves.
Polini 177cc cylinder kit.
Dellorto 28mm with 122 main jet, X2 needle.(Malossi kit)
Maccucelli race crank.
Leovince exhaust.
Champion sparkplug L82c = B9HS
you should lower the needle clip 1 - 2 position from where it is now.
The range where you are experiencing a lean condition is most effected by the needle clip positon that adjust the lenght of the needle making it shorter to make the mixture richer or longer to make it leaner.
yes rise the needle one or two step ( it means you lower the clip one or two step).
The main jet seams rich, but if when you are at high rpm it seams fine it is OK… just try to see what happens at full throttle if you fit a smaller main, if it’s not any better it means you are fine with what you have… but first you have to fix the middle range since as you have noticed it is the most used range.
I ordered the spark with my cylinderkit, and the recomended is W4AC plug, but i got L82C. So i thougt this was the right one…
Well i will throw that plug as far as i can [:@]
And i will get a genuine NGK plug this lunchbrake.
Well that could have been a disaster…
Thank you very much Brian.
There are some things to think about when you rebuild and
tweak an engine for sure ;D
Well even the „big“ guys seems to have problems with sparks and there crossreference.
NGK website is saying that a W3AC=B8HS and Bosch website
is saying that a W3AC=B9HCS ??
Anyway if Curare is recomending an W3AC i will buy one of those. And hope i can avoid a hole in my piston, that will not do any good to my fine compression… [:D]
Well its not the first time i have got something else than that i have ordered from Sip.
I think i have naild it today, raised the needle one step
and went down to a 118 main.Now it fells like she is pulling
even harder.Tried to raise the needle two step but then
she just spit and run to rich in the middle. [:(]
I wil run her like that until summer is here and see
how she react to the warmer weather.
By the way, its realy nice to do a wheelie with an old scoot… [H]
In full throttle it is a little too rich, i think i could try 120 or even 118 main, i will do a new „shakedown“ tomorrow before the Formula 1 race [:D]
How much on the throttle is the mixture screw involved.
Is it bypassed directly when you start to throttle,or does
it affect the mixture in a wider range of throtteling ?
Yeah…just by coincidence I was checking spark plugs, I have opted for the Bosch W3AC also since I am ordering parts from SIP and they sell bosch as preffered choice.
…Bosch as a wider grade, so its W3 includes the NGK 9 and 8 grades, though I personally feel NGK 9 is slightly colder then Bosch 3 and NGK 8 is slightly hotter then Bosch W3.
Hope this would help.
Pallla, if your time is correct you are not going to make a hole in your piston even if you have a hotter spark. (untill a certain limit).
But the detonation with a too advanced timing could never be corrected by a colder spark grade.
