Replaced Engine - Carb Tuning?
So I replaced my old 'blade lump (893) with a newer one (919) after my gearbox went pop. Been for a blat today and seems to be running well,
except for lots of popping on the overrun (sounds good  but not ideal!). This is usually leaks in the exhaust (used to have one), so checked and
could see no evidence. So next I adjusted the idle screws assuming it was lean at 0% throttle. It used to be 2.5 turns out (got set at rolling road
a few years ago). I've backed it out to 4 turns and that's pretty much cured the popping but I believe 4 turns is too much for risk of
the screws coming out.
Would it be reasonable to assume that the slightly larger engine desires slightly more fuel, and although it feels to run OK it's probably
slightly lean(er) throughout the range? In which case I'm probably best not "spanking" it until I confirm that on a rolling
road?
I think I'm also correct in assuming that the main jet doesn't affect 0% throttle, and so any tuning would be a combination of main jet
and slow jet (and needle jet/height) replacement? Would the slow/needle jet on carbs on a 918 be larger than the 893 (I'm using 893 carbs on
the 918) and explain the symptoms?
I had intended to get a new exhaust made (current one is restrictive and starting to vibrate itself to pieces) so was going to rolling road it after
that anyway, so thinking I should expedite the replacement and get them properly tuned sooner rather than later. I could probably t1t about doing
plug chops etc but if multiple things need changing then back to Holeshot seems the best bet.
I know the main jets are 128 at the moment, and the needle clip is at the top (leanest setting) as tuned by Holeshot last time.
Does any of the above logic make sense or not?
Ta
|
