Race Engine Forum UK

You cannot really compare two different carbs, even they are the same type.

Thanks urbancamo. Makes sense.

I will follow your advice as kindly posted before.

Regards,

Chris

Urbancamo wrote:Only reasonable way is to beef up the idle jets. If you have possibility to have them within 0.01 increments, just increase one step at the time and find a compromise you are happy with.

Hi!


Good posting Tommi!!

Just a quick input:

I think You have a second option as well - if the air bleed on the idle circuit can be reduced, the transition phase will become richer. Never worked on the DRLA carb, but in principle it should be the same thing as on other types of Dell`s. I have experienced lean conditions during transition on DHLA`s twice, and the problem was solved both times by fitting richer idle emuslion tubes (or maybe its called idle jet holders??).

Best regards

Remi

I have experienced lean conditions during transition on DHLA`s twice, and the problem was solved both times by fitting richer idle emuslion tubes (or maybe its called idle jet holders??).

The idle jet holders are fixed and only come in one fitting I'm afraid for the DRLA. They all have 4 holes.

DRLA's have air bleed screws(air bypass screws) but these are to allow balancing at idle. They just allow air to pass from above the butterfly to below to balance front and back barrels.

Brit01 wrote:

I have experienced lean conditions during transition on DHLA`s twice, and the problem was solved both times by fitting richer idle emuslion tubes (or maybe its called idle jet holders??).

The idle jet holders are fixed and only come in one fitting I'm afraid for the DRLA. They all have 4 holes.

DRLA's have air bleed screws(air bypass screws) but these are to allow balancing at idle. They just allow air to pass from above the butterfly to below to balance front and back barrels.

Hi!

As I said - no experience on DRLA`s.....
Well that complicate things..... Your only option is - as Tommi said - a bigger idle jet, unless You want to modify the idle curcuit air supply hole.

Best regards

Remi Lovhoiden

Ok let's try to recap the missing posts.

We discussed that the stutter/lack of power issue could be an ignition coil failing.
The tachometer also flickers at around the time it begins to hesitate.

I have sourced a new Bosch coil today and will pick it up next week.

Part number is 0 221 122 317

Fingers crossed that this brings the engine back to life and smoothes out the flat spots.

If not well then back to the drawing board. Possibly looking at the float height.

The current old coil has been doing it's job for 24 years I suspect.

Just FYI. Couple of months I picked up a set of fairly cheap trumpets.

Would like to try them out once I've got the other issue sorted.

What are your opinions on the design?

Those are exactly the same trumpets that I have in my engine. Best quality for reasonable price, I'm not personally really eager to spend 80 bucks or more for trumpets.

I'm not an expert but profile is much better than ordinary trumpets have. Benefits? Should be tested in dyno. If you notice something different after installation, please report.

-T

Great good to hear.

Yes the wide lip/edge appealed to me (and the bargain price). Most are way too expensive.

If you still use the "spider" inlet manifold going to trumpets will cost you low rev torque. They seem a bit short to me. For road use I'd use longer, because these will not really work until well into the rev range.

hi guys,

I don't know how tall the original stacks are, but those trumpets look fine by themselves. Profile elliptic (optimal) or circular (quite good), inlet opening about twice the diameter at the carb and total height of the radiused section about the same as that carb diameter. All as described in the paper that Whizz mentioned a while back (interesting stuff, thanx. based my drawings for several stacks on it.)
Any chance of a comparison pic 'original <-> new ones' Chris?

regards
Tom

best way to test 'em Chris is bolt 'em on and press the loud pedal very hard.

GC

best way to test 'em Chris is bolt 'em on and press the loud pedal very hard.

yep that's what I intend to do :)

Chris

p.s endoscopy went fine. But got to wait 1 month for the biopsy results so 1 month suffering with gastritis until they can prescribe the right medication!!!! Wonderful! How long does it take to grow H.Pylori on a dish?

Brit01 wrote: But got to wait 1 month for the biopsy results so 1 month suffering with gastritis until they can prescribe the right medication!!!! Wonderful! How long does it take to grow H.Pylori on a dish?

It takes a while to do test runs with your strain of H. pylori and several antibiotics to see which ones work and which ones don't. You don't want to go for meds that wipe out 99% and then you have a new resistant strain in your stomach. They are going for 100% and it takes a while to make certain.

Pressing the loud pedal will work for full throttle and if you do some timings and/or have a G-meter, you can even tell where in the rev range it helps or costs you. Doing the same for light loads will be harder. The butt dyno is inherently unreliable, but then again, if it feels good and sounds good, you're probably not going to complain.

It takes a while to do test runs with your strain of H. pylori and several antibiotics to see which ones work and which ones don't. You don't want to go for meds that wipe out 99% and then you have a new resistant strain in your stomach. They are going for 100% and it takes a while to make certain.

yep whizzman agree 100%. My parents worked as microbiologists up until their retirement and said a month to cultivate the stomach biopsy (H.Pylori in this case) is excessive.
2 weeks paperwork and admin most likely. Hospital - lab - report - hospital - local clinic - appointment! :(
Maybe the 3 hit antibiotic course is required. But for the next month just lots of anti-acid drinks and pills!

if it feels good and sounds good, you're probably not going to complain.

Indeed sir. I bet these trumpets are going to bark!

Bosch ignition coil found and purchased. Last one in stock (been out of production since 2011).

Primary measures 1.5 ohms. I will measure the old one at the weekend.

No Iridium plugs I'm afraid. These will need to come from an internet auction site as the companies here will take 5 months to order them!!

Also ready for an oil change. Picked up 5 litres of Castrol TWS 10W/60.