Dellorto PHM40 - mixture and idle

i would get a 33PJ. ask loonyberg what it did to his bike!

i would say that your pilot air circuit is still blocked. ok you blew it out but did you feel the air in each orifice coming out? always blow backwards up the carb. the sh.... has to go out the opposite way to which it came in!!!!

i would also buy a 40-42 choke jet.

regards

Taffy

i have them in stock if they struggle fella.

Taff
What should the PHM jets typically cost? My bike is still standard but I want to try some of your suggestions to try & fix a dead spot just as it comes off the idle stop. With the big donk it is hard to get good control at low speed.

I bin lookin' on ebay here but all there seems to be is downdraught ones. Do you know if any of the automotive Dell jets are the the same as the PHM?

the atomiser and needle are £11.75 each. the choke jet is a #40 that i have here and thats £5.95 with 'O' ring, pilot is £3.60. i suppose australia would be a coupla quid.

regards

Taffy

Coastie said:

I've got a couple of problems with mine.

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What exhaust system have you got on there?

Everything else remaining stock in the engine?

Simon

Thanks Taff. I think when converted to Australian dollars that equates to your first born plus the equipment required to make more. :shock:

Really though, thanks. Will keep it in mind if the usual loving care and attention of the standard jets doesn't help. All the best, BW

Hi, Brad.......

This is my source for Dellorto parts, jets, needles, gasket kits.
They are on east coast USA. Jets are USD $3.95, mains a bit more - $9.95, needles around $11, gasket kits are about 13, with all o-rings. They can suppy all the other parts, too, including slides.
http://www.herdan.com/dellorto/

no problem, i get them for just under that.... the usa wins on most prices hands-down.!

regards

Taffy

Coastie said:

Simon
Stock exhaust and everything else pretty much.

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OK. I don't know what the conditions are normally like where you live but on the basis you're running stock, I would say that you can happily keep your 38 pilot. You could go to a 35 or a even 33 but for a minute I'll assume it starts fine hot & cold (which at the end of the day is a good indicator) and your experience with the mixture screw tells us you don't want to go leaner on that jet just right now. I've happily run both my 650s with 38 pilots even at 30 degrees C plus.

I reckon you should first try raising the needle a clip position or two. Then, and I know this will surprise everyone, go down to a 185 on the main but no further. The slightly black plug is coming from this, not your pilot circuit.

Hope this helps,
Simon

moving the circlip down raises the needle

Coastie said:

Hi Simon

Live on the coast around the Sydney area - 0 to 35°C and up to a few hundred meters.
At the cooler part of the scale this time of year.
Doesn't raising the needle make it come onto the MJ earlier?
You do mean moving the circlip down don't you? - Always confuses the hell out of me.

Coastie

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Hey Coastie,

You're absolutely correct in that raising the needle will make it come onto the main earlier and it also effects the pilot and transition circuits. If the needle sits too low then at partial throttle openings, i.e. just off idle for example, the needle may not have reached the conical part of its shape which can cause a lean condition such as the one, by the signs of things, you seem to be experiencing. It will even effect the throttle response.

As you probably already know, the needle is simply there to balance the vacuum at throttle positions where the main jet would either provide too much fuelling, or too little and if the conical part of the needle isn't in the right place for the throttle opening the system gets out of balance.

In real terms though, all jet and circuits effect each other. When the 01s came out they came from the factory with massive 200 main jet in them and we resolved most of the initial starting difficulties simply by putting in a smaller main which also leaned out the idle circuit to get them starting easily.

I do mean moving the clip down - it confuses me too sometimes, this raising the needle, lowering the clip nonsense. It's such a simple issue to test out it's worth doing before spending any wedge on anything else. To begin with, try the clip in third position from top and see how it changes things.

The other thing that might be useful to check is that the 01-03 engines had the screw-on intake boot and it's not uncommon for it to work its way loose letting it air between the carb and the engine intake. As your problem has only happened recently it could be as simple as that and a tighten up might sort it out for you.

Good luck.

All the best,
Simon

Coastie said:

Hi Simon

I checked the intake boot and raised the needle a clip.
Still the same.
I only rode up and down the street a few times though.
I'll have to take it out for a full session to see for sure.

Coastie

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Do you know how many turns your idle speed screw is turned out?

Here's something else worth testing:

Write down the current idle mixture and speed settings.

Get your engine nicely warmed up, set your idle mixture screw to 1.5 turns out and then turn your idle speed adjuster outwards (anti-clockwise) as far as you can while keeping the engine running and counting the number of turns. Then test with a few blips of the throttle.

I know we're just going step by step but we know that you're in the right ballpark so it's got to be something pretty simple going on. Once this is resolved, then you can spend money on refining it further if you want to.

Simon

Coastie said:

Yeah it's 1.5 turns.
I can turn it all the way in with SFA difference.
It starts to change note at about 4 turns out.

Coops

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That's fine, that's your idle mixture screw - keep it at 1.5 turns for now.

What we need to find out is where your idle speed screw is positioned and go through the above mentioned procedure on that.

Cheers,
Simon

OK Coops.

This may be where your problem is coming from.

The idle speed screw lifts or lowers the throttle slide and what can happen is that if it is turned in too far the pressure drop across the idle circuit reduces and it doesn't work correctly. The transition circuit of the emulsion tube/needle may also become partly engaged. Then you get a situation whereby the idle mixture adjustment doesn't work properly either - something that you're getting in there being no response to your adjustments other than really rich at 4 turns out.

On my Dellorto, and of course this will vary from carb to carb, with the 38 pilot I have the idle speed screw at approx 4.5 turns out.

Now, once your engine is warm if you screw out the idle speed screw a good couple of turns and you then blip the throttle, does the idle speed now return straight back to normal?

Cheers,
Simon