Tuning IDA`s

[Berger]

Need som advice tuning my IDA`s.

Here`s the engine spec:

2276ccm
Super Flo 1 heads
11,5:1 comp
FK87
Joe Hunt Magneto, 10degrees advance, set to max 30 degrees
48 IDA ,Main jets: 165fuel/190air F7 tubes(?)
Runns on 98 oct pump gas.

The engine runns greate when cold, means oil temp below 80 deg. celcius.
When the engine is hot, the power is less and the engine seems to "schoke" at high rpm (above 6000 rpm).
Also the response in the engine is less when it is hot (at full trottle).

My first thought is to change the main jets, but how? Any suggestions or experience to share with me?

Thanx!
Øyvind

[Roman]

What size are the venturis? The rule of thumb is venturi X 4.
If it runs better when its cold it is usually lean.

[Berger]

The venturis are 42mm. Following Your rule of thumb means I should step up to 170 on fuel jet? What about air jet?

Thanx 

[Roman]

The air jets are making big difference in 4000 rpm's and up, so if it is lean at the top, go DOWN one jet size.
180 airs is normally the starting point for tuning so I would give that a try.

I have bought all my jets from alfa1750 at E-bay. He ships instantly from Italy and pricewise he is very hard to beat. The jets are 1,75 US$ each and in Sweden they cost 90 SEK. That is about six times as high!

Link to the main jets:
http://cgi.ebay.com/ebaymotors/WEBER-DCOE-DCOM-IDF-IDA-MAIN-JETS-NOS_W0QQitemZ8074198478QQihZ019QQcategoryZ33551QQssPageNameZWD1VQQrdZ1QQcmdZViewItem

[SOB/RFH]

65 or 70 lowspeed jet (no stumble at 3000 rpm and 1/2 to 3/4 turn on the idles is the goal.....move inward till stumble and then out untill it is clean, takes a good ear but time spent is rewarded with a smoth working engine)

170 main jet

200 air is the one to go for as a baseline on an aircooled engine with F7 E-tubes

[Petter Carlberg]

If it runs better when cold, it is to rich, probably you just neeed to change your lowspeed jet like SOB said. Your main jetting seems close to what it shuld be. Insall a A/F gauge and find out, a very useful tool if you ask me!

[Berger]

I run 70 on lowspeed jets. Runs nice at idle. No stumble at 3000 when I hit the floor.

What fuel pressure do You run in on the IDA`s?

Thanx again

[Petter Carlberg]

If you are running stock needle and seat, 0,2bar. Try a smaller idle jet, 60-65.

[Roman]

If it runs better when its cold it is usually lean.

What was I thinking... it should of course be rich...
Just think what you do when you start a cold motor - you choke it to get it richer so it runs better.

[SOB/RFH]

3.0 needle and seats is the way to go. 35 PSI and a Holley blue or equal and at least 8 mm lines. Normaly a SF head with your cam should run fine with a 70 jet. Check the number of turns on the adjustable idle correction as I described erlier...they are a good sign if your jetting is good or not on the low speed part of the carb.

[Berger]

I use stock fuel line with a 4-8 PSI pump up front. I used to run 4 PSI after regulator, but have now turned down to 2 PSI.
SOB/DBR; I hope You mean 3,5 PSI??
Again , when cold it runs nice, no problem with fuel flow racing 1/4mile.

I think I have located another problem yesterday. After running the egine hot, I stopped and there was a "gurgling" sound for one of the carburators. And then it was hard to start up again. Seem like one of the carburators are flowing over when engine is hot. Does this make any sens to my original problem?

[Fastbrit]

I use stock fuel line with a 4-8 PSI pump up front. I used to run 4 PSI after regulator, but have now turned down to 2 PSI.
SOB/DBR; I hope You mean 3,5 PSI??
Again , when cold it runs nice, no problem with fuel flow racing 1/4mile.

I think I have located another problem yesterday. After running the egine hot, I stopped and there was a "gurgling" sound for one of the carburators. And then it was hard to start up again. Seem like one of the carburators are flowing over when engine is hot. Does this make any sens to my original problem?

That sound is almost certainly fuel boiling in the float chambers. You can buy thicker insulated carb gaskets to help prevent heat transfer to the carbs at  t he arburetto throats. Turn th efuel pressure up until fuel starts to drip out of the pump jet nozzles, then back off the pressure slightly. I'd recommend using a larger diameter fuel line (-6) and add a breather to the tank which is at least the same size as the main fuel line. I'd guesstimate 42mm venturis with 165–170 mains, 200 air, F7 emulsions and 65–70 idles.

[Berger]

Thanx agian. This is very helpful
Fuel boiling in the float chambers sounds logical.
Where can I buy insulated gaskets for superflo/IDA48?

[Berger]

Your description of Your engine problem fits my (old, engine now sold) engine perfect! But as I changed to 170/200 jets, the problem was almost gone. I think the engine runs to lean in the mid range, causing the boiling in the float chambers.

[Peter Roberts]

Are these new IDA's , if they are , check that a float isn't porous by the solder join and sinking . I have had this problem with a couple of sets of New IDA's , it was baffling at first , but a new float sorted it out .

[Diederick/DVK]

i saw someone (i think one of the guys from that scc video) having 48 IDAs on a 1600.

is this possible? what would this mean performance-wise? is it a screamer and no bottom end, or does it give you a nice powerband?

[Lee.C]

Yeah I remember a feature in volksworld a few years ago with a black looker running a 1641 on ida's! I always wondered what it would be like 

[Zach Gomulka]

They will work- you just have to jet them down. Start with 32mm venturies. Also, having a 3rd progression hole drilled makes a big difference in stock stroke motors- makes them much smoother through the transition since stock stroke doesnt have much torque.