Tuning CV40 using AEM30-0300

[1340evo]

Hi All

Following advise on here I've now got my new build up and running with a sensor in the front pipe.
Its getting late here so just took the bike for a quick run and according to the gauge I'm running lean?

I'm seeing 16 to 16.5's under load.. really open the throttle and it jumps back into the green but soon returns to 16's as I equal out

It is however 13.5 on tickover but anything above that it lean.
So where to start?
Its a 1340 CC'd heads, about .015" off the heads to make them equal
CV40 with V&H pipes (with some limited baffel in there)

In the carb I have 45 / 180 right now with a N65c needle 2.5 turns on the air screw....

If I pull the choke 1/4" it improves but still not in the green range?

Plugs look spot on so I'm questioning if its correct a bit.

What you think? 

[rigidthumper]

Add shims under the needle, 1 at a time, and retest.

[1340evo]

I don't think so, I have one or two so will give it a go tomorrow 

[1340evo]

ok, so fitted a 0.030" shim and its improved a lot
Tickover 13 now, Constant running 13.5 low to mid range, high range 14.5 ish,
Where it does go lean is on acceleration from bottom to top into the 16's and accelerate at the top end I saw a 17. you only have to open the throtle a tad and it leans out straight away...
how many shims can you put in?
What to change to stop it leaning out on acceleration?

[turboprop]

'High range 14.5 ish'


Have you considered going up a size on the main? This may require a reduction to thickness of the shim(s) under the needle.

[1340evo]

Yes, I have all the jets, needles, shims, but unfortunatley not a lot of time so did hope someone could help me fast track this a bit by knowing exactly what to do.
Its the acceleration thats the issue more than anything. Do you think going up on a jet size will address that? by reducing the shim you hopefully keep the jet / needle relationship, but just let out a tad more fuel when needed I guess...

[Hossamania]

Yes, I have all the jets, needles, shims, but unfortunatley not a lot of time so did hope someone could help me fast track this a bit by knowing exactly what to do.

Would that it were that easy.
One change at a time, measure results, one more change, another measure, rinse and repeat.

[1340evo]

I know, there aint no quick way on tuning....
So, the next logical step is the next size up main jet.. That will be tomorrow now   

[turboprop]

I know, there aint no quick way on tuning....
So, the next logical step is the next size up main jet.. That will be tomorrow now   

Dont do that. That extreme lean condition is bad. Go up a couple sizes. Get rich, and then come back down. The engine will thank you.

[hrdtail78]

I have the best luck tuning big twins with CV carbs with stock needle, slide and spring.  I always do a float level check. I start with idle, and then WOT for my main.  I then do all the in-between. 

The XL needle is sometimes used to help a possible lean spot during transition but as you have reported.  It goes rich during transition and then leans out.  You are also needing to raise the needle that is compounding the issue by being raise to a skinnier portion of the needle quicker during transitions before the slide settles a bit.  Somewhere on this site.  There is great write up on different needles and their sizes.

[1340evo]

I have the old needle, but there is no marking on it at all? guess its stock but who knows?
I'll try a larger main to try help WOT and acceleration.
I did read to drill the slide hole bigger to make it resond quicker, any thoughts on this?

[Hossamania]

Do not drill the slide.

[1340evo]

OK no drilling, 190 fittef last night, so will see how it goes a bit later on today when it cools off a bit and I can clearly see the gauge

[1340evo]

Results in

so now I have

45 slow jet
190 main
.030" shim
2 1/2 turns
N65C needle

12.7 / 13 on tickover
WOT acceleration bobs around 14 all the way through the range
But mid range and lets say 1/10 turn on the trottle, im seeing a lot of 15.3's

[turboprop]

Results in

so now I have

45 slow jet
190 main
.030" shim
2 1/2 turns
N65C needle

12.7 / 13 on tickover
WOT acceleration bobs around 14 all the way through the range
But mid range and lets say 1/10 turn on the trottle, im seeing a lot of 15.3's

So what change do you think you should make next?

[1340evo]

Sounds like the slow running as that impacts in a CV all the way through??

[1340evo]

Do you agree or should I be going another way?

[dynabagger]

Make sure the accelerator pump is working properly.