phbh rich slide vs rich mid range

[olliewtf]

Saw an interesting topic from way back when, essentially an argument between two forum users that raised an interesting point; one argued that a super 'rich' atomiser needle combo in conjunction with a leaner slide would ride well and be far safer than a rich slide and therefore compensated leaner mid range. As an example, one was arguing the benefits, say on a reed valve + advanced lower rpm ignition, av268+x2 and therefore also a leaner main jet, whereas the other, something leaner like av266 x13 with a far bigger main. slide on the first option was then also leaned out to help progression. (ive paraphrased and may have got some of the detail / representation inaccurate).

This got me thinking about my set up; I never have managed to run a 40 slide without a big lean spot in the mid, even with av268 x13 on piston port 190. Ive now fitted a reedvalve, and still have the issue with the 40 slide, and in both scenarios have opted for a 30 slide, currently with av266 and x13 top clip; this runs well, but is generally very rich when not in the power. It has always plagued me that I cant get the 40 slide to run without thinning out when de -throttling, so Im planning on playing with some jetting on friday.

Ill stick the 40 slide back in, lowering the pilot to 53 (55 is a tad too rich), and try the av268 again (I remember adam winstone saying that av268 was necessary (in some applications) if running advanced ignition lower down) and start with x2 top clip. I imagine thatll be way too rich; I can work down to x13, and x7. I may leave the main jet out for these tests.

Interested to hear if anyone else has messed with slides? And am I right to be sensitive over the fact that I cant get the 40 to work?

(tuned 195 (186exh with 30 BD) reed, open 28phbh, reedspeed cdi from 15/16 up to 23 back to 15/16 at 4.5k +jl3 - no egt or cht so blind as a bat!)

[warts]

On my guzzi, 36 PHF's
I had problems with the mid range being rich, having done a lot of faffing with the jets I had accumulated, in desparation I started messing with the slides. At that time new slides were ££'s, so I started with some old ones to see if it would at least get it to go in the right direction. I think I started with a 5. I turned a millimeter off the lower edge, to make them 4's and it improved the pick up greatly for a year or so, I used the old ones before I got it together to get new ones. I think I could have shaved another .5mm off if necessary.
Climbing Alps became much better.

[drunkmunkey6969]

Every engine is different, and each setup should be treated treated individually....however there are some patterns which do emerge.

For example, I would try to run an AV268 (richer) with a 50 (leaner) slide to help with the 'pre-pipe dip' or an AV266 (leaner) with a 40 (richer) slide. But I would try not to run an AV266 (leaner) with a 50 (leaner) slide where possible.

Same for needle/atomisers: I would run an X13 (leaner) needle with an AV (richer) atomiser, or an X2 (richer) needle with an AS (leaner) atomiser....but I wouldn't run an X13 (leaner) with an AS (leaner) atomiser.

Of course you have atomiser diameter, needle clip settings, mixture screws, pilot jets and main jets to work into the equation......(not withstanding air filters, ign timing, comp ratios, squish etc) but I'm just trying to illustrate basic jetting patterns which can crop up.


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[olliewtf]

Cheers guys.

I think what im trying to explore is the following: ' I would try to run an AV268 (richer) with a 50 (leaner) slide to help with the 'pre-pipe dip' or an AV266 (leaner) with a 40 (richer) slide.'

The argument I read suggested that these two differing set ups actually are not the same; running a richer slide and therefore leaner atomiser needle combo has the potential to create a lean spot which is hard to trace, and its better to have a leaner slide and richer atomiser needle combo.

I have noticed that my 40 slide created a lean spot no matter how rich I tried to go with the jets available; I would richen the needle and it wouldnt run (4 stroking) so on the next leanest setting it would run but lean out. I didn't have an x2 slide at this time however. So Im going to see if I can get the 40 slide (which for me is lean) to run, to test if i do indeed need a rich mid range, not clouded by the richer slide (30) that I eventually used to get rid of this lean spot.

I hope that's easy to follow! Anyway, gonna play with it today and see what happens!

I will also be leaving out the main jet to check that the mid range hasnt been restricting flow to it.

also in the interest of collating solid jetting advice, here's a test i will do for pilot jet, which invariably will also affect what imm doing with slide and midrange: 'easy way to check idle jet , ride up to full revs in first pull clutch in close throttle coast to stand still ,if it stalls or revs drop below tick over then pick up its rich(smaller pilot jet req) if revs hang high then drop its weak(bigger pilot jet req) had the same prob on my dtc easy fix'

best

[drunkmunkey6969]

Just to reemphasise one thing: Every engine is different, and each setup should be treated treated individually.

And just to add one thing: I never found a suitable application for a 30 slide, ever (except filing them to 40's).

[olliewtf]

^^^^^ thats very interesting. I figured it was worth exploring! I hear what you're saying re; each engine is unique, but I knew something must be amiss to need such a rich slide, when I dont think Ive ever seen anyone else use one. Just about to strip carb and have a play.

[olliewtf]

So I cleaned the carb out and fitted the av268. I fitted an x13 needle on second clip. I left the 132 main in. I fitted the 40 slide, and dropped the pilot to 53.

Mid range was way too rich. Interestingly, the main was now also way too rich, so its apparent that the av266 x13 combo was potentially leaning out the main.

I swapped for an x7 needle 2nd clip and a 125 main. This was still too rich. I dropped the clip to top, and this is better. The main still needs work.

It is still a bit spluttery and hesitant in the mid, but the engine wasnt fully warm yet; I will try a leaner main and go for a proper run.

I am thinking though that I may fall into that category of needing an av267; which as far as im aware, no-one has made yet.

this is all hypothetical atm, so will go for a proper run when the weather clears. What is interesting is that the 40 slide doesnt create the same lean spot that it used to, so I think im making progress!

[mawso]

I've had a few iron piston port 190's in the past and run one again now, they've all run PHBH 30's and always a 40 slide, X7 needle (1st or 2nd clip) and an AV266 combo. Managed to get down to a 118 jet on one with a clubman, but now run 122 main, 70 choke, 53 pilot with an expansion. Every engine's different as been said, but I've never needed to deviate away from 40 slide, AV266 and X7.

[drunkmunkey6969]

Good advice from Stu (Mawso).

Also worth noting X7 needles work quite well on Clubman exhausts and, as Stu's example outlines, are good with AV266 atomisers. But once you go to an expansion pipe, X7 needles are lean at 1/4 throttle on 90% of applications.


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[olliewtf]

Right. That's interesting.

I agree, av266 x7 is a good combo. As im running a jl3, how would/have you cured the lean spot? x13?

I tried av266 and x13 on 2nd clip and that's still too rich. I seem to be working my way back to where I started, but with the leaner slide. One thing that is bugging me though is that now, with the 40 slide and av266, Im getting a lean spot again; It manifests itself when shutting the throttle, the revs hang slightly above tickover before dropping. I'll try upping the pilot but I think it has more to do with the slide. (Due to the fact that fitting the 30 slide gets rid of this problem.)

Today Im going to see if I can get the av266 x13 combo to work; I imagine top clip will do it.

I did read though that the clip settings affect the mixture more in the mid range; whereas the taper length difference is noticed more on progression, and then through the mid. Either way Im starting to get a bit confused, but I've nearly tried all available combinations so will just have to tease it out!