Author Topic: PHM40 mysteries and magic  (Read 2947 times)

Offline rusty rotor

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PHM40 mysteries and magic
« on: September 13, 2021, 12:50:10 PM »
Mysterious to me anyway.

Context: '78 LMI, big bore, big valves, ported, polished, Dyna, dual plugs, etc. A Hecht beast.

Everything fresh by a Gooz resto pro. New Dyna, coils, cables, wires, plugs, hoses, petcocks, you name it. Full carb rebuild, or so I'm told, this guy has some very weird ideas about how to refresh a bike.

Had issues with carburetion when the bike was first delivered. Oh and it was dumping fuel out of the carbs. Back it goes, the old-style floats got filed or dremeled or something, as they were 'swollen' and sticking.
Then another round of carb tuning.

Get the bike back and everything is 'pretty good', until I finally get it on the freeway and discover rough running on steady throttle at 70mph-ish, also and especially when you whack the throttle.

Now the bike seems to fairly quickly detuning itself. Starting to run rougher, and bogging pretty strongly when you smack open the slides. Smooth and gentle inputs all the time result in 99.9% smooth running. What fun is that!
Right pipe a little smoky, right tip a little sooty, left side clean.

Weirdly, this bogging on acceleration seems to be intermittent. I can't reproduce it every time.

And just to add a pinch of fun, as I do this I hear some knock from the left cylinder only. But this bike has always done this. Huh?

Start with the low end needle? Are these screws inclined to move by themselves? I twiddled em, carefully putting them back where they were, and I notice one moves very freely and the other has some resistance.

Offline guzzisteve

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Re: PHM40 mysteries and magic
« Reply #1 on: September 13, 2021, 01:09:09 PM »
Have you re-torqued the heads & reset valves since getting it back? Might be time. If you have the chromemoly pushrods it is .002" in & ex. Screws don't move on their own. There is an accelerator pump jet, make sure it's a #38 and squirts across the room.
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Offline rusty rotor

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Re: PHM40 mysteries and magic
« Reply #2 on: September 13, 2021, 01:16:14 PM »
Have not, it's been under 500mi. I (ahem) expect that was all done, but am finding my mileage to vary if you know what I mean.

Sorry to bother, anyone have the sheet with the torques?

Online Antietam Classic Cycle

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Re: PHM40 mysteries and magic
« Reply #3 on: September 13, 2021, 01:33:10 PM »
Mysterious to me anyway.

Context: '78 LMI, big bore, big valves, ported, polished, Dyna, dual plugs, etc. A Hecht beast.

Everything fresh by a Gooz resto pro. New Dyna, coils, cables, wires, plugs, hoses, petcocks, you name it. Full carb rebuild, or so I'm told, this guy has some very weird ideas about how to refresh a bike.

Had issues with carburetion when the bike was first delivered. Oh and it was dumping fuel out of the carbs. Back it goes, the old-style floats got filed or dremeled or something, as they were 'swollen' and sticking.
Then another round of carb tuning.

Get the bike back and everything is 'pretty good', until I finally get it on the freeway and discover rough running on steady throttle at 70mph-ish, also and especially when you whack the throttle.

Now the bike seems to fairly quickly detuning itself. Starting to run rougher, and bogging pretty strongly when you smack open the slides. Smooth and gentle inputs all the time result in 99.9% smooth running. What fun is that!
Right pipe a little smoky, right tip a little sooty, left side clean.

Weirdly, this bogging on acceleration seems to be intermittent. I can't reproduce it every time.

And just to add a pinch of fun, as I do this I hear some knock from the left cylinder only. But this bike has always done this. Huh?

Start with the low end needle? Are these screws inclined to move by themselves? I twiddled em, carefully putting them back where they were, and I notice one moves very freely and the other has some resistance.

Why don't you just come right out and say who worked on it Jose/Jerry?

I'll "out myself": I worked on this Le Mans for him, the first time was in January and I had a one-day, 50 degree, window where I could test ride it, put 40 trouble-free miles on it. Delivered it to him, he rode it around his neigborhood, all seemed well. But as warmer weather arrived, he was complaining about the bogging issue, so he bought it back here. Floats (replacement white ones) had expanded and were dragging on the carb body. I trimmed them slightly so that they moved freely (since no better replacements are available), went down one size on the idle jets, test rode it 150 miles over the next several days, in every type of environment (backroads, town, interstate, etc.) and all was well. No "bogging".

Whenever a bike I've never worked on before comes into the shop, I do "everything": head retorque, valve adjustment (to Manfred's specs. in this case), check tightness of every fastener on the bike - all in addition to the repairs or modifications asked for by the customer. I corrected a lot of issues on this Le Mans.

There was no "knock" at any time when the bike was here, and it not being present, I could have never said it had always done it.

« Last Edit: September 13, 2021, 01:35:21 PM by Antietam Classic Cycle »
Charlie

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Re: PHM40 mysteries and magic
« Reply #3 on: September 13, 2021, 01:33:10 PM »

Offline rusty rotor

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Re: PHM40 mysteries and magic
« Reply #4 on: September 13, 2021, 01:53:57 PM »
Well, it's very simple. The forum rules are clear, and my exactingly factual observations about the results of your work could be construed to be in violation of those rules.

Plus this is your livelihood. To me this all seems to be an awfully small thing to mess with a guy's, an individual uniquely skilled craftsman's, livelihood. What you do, is you don't do business with that person again.
You, or at least I, don't flame that craftsman or as you say "out" him.

I will say this:

The electrics that you redid from stem to stern seem impeccable and they are in fact awesome. All the hoses cables controls etc, ditto.

After that, things become less rosy, (cough, braking, cough) and in point of fact, the bike is quickly losing tune, and was never tip top.

And yeah, this bike has always, as in before, long before Antietam, demonstrated some knock on the left side.

As I say, mysterious to me. Maybe Manfred had a twitch in his wrist.
« Last Edit: September 13, 2021, 01:55:05 PM by rusty rotor »

Offline guzzisteve

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Re: PHM40 mysteries and magic
« Reply #5 on: September 13, 2021, 02:19:59 PM »
I usually go 3-5 heat cycles, so quickest is around 50mi. 32ft lbs is torque. Check pushrods w/magnet to see if steel.
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Online Antietam Classic Cycle

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Re: PHM40 mysteries and magic
« Reply #6 on: September 13, 2021, 02:27:05 PM »
I usually go 3-5 heat cycles, so quickest is around 50mi. 32ft lbs is torque. Check pushrods w/magnet to see if steel.

Steve,

This bike has already been well beyond "3-5 heat cycles" - as I wrote above, I retorqued the heads and adjusted the valves the first thing when I began working on it. I did it again when it was here the second time, to rule it out as a factor in the "bogging". The first time the head nuts were found to be tightened to spec., but the valves out a bit (right intake was at .004" and the left exhaust was the same). Pushrods are steel, so all adjusted to .002". Second time nothing had moved - not surprising given that it hadn't done many miles.   
Charlie

Online Antietam Classic Cycle

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Re: PHM40 mysteries and magic
« Reply #7 on: September 13, 2021, 02:44:58 PM »

I will say this:

The electrics that you redid from stem to stern seem impeccable and they are in fact awesome. All the hoses cables controls etc, ditto.

After that, things become less rosy, (cough, braking, cough) and in point of fact, the bike is quickly losing tune, and was never tip top.

And yeah, this bike has always, as in before, long before Antietam, demonstrated some knock on the left side.

As I say, mysterious to me. Maybe Manfred had a twitch in his wrist.

The mystery to me is how a bike that runs perfectly well over the course of 150 miles of different conditions, can be "never tip top". Maybe I'm supposed to ride it 500 miles (all non-billed hours BTW). I am very exacting about how a bike runs and can feel when something isn't right, even when a customer may not be able to.

Braking? You mean that the bouncy ride home in a U-Haul trailer dislodged an air bubble somewhere in the brake system and you had to bleed it? Despite me bleeding the brakes extensively, pushing the caliper pistons in to remove any air there and tying the lever back overnight to allow any bubbles to escape, it still happened. Not sure what more I could have done. 
Charlie

Offline guzzisteve

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Re: PHM40 mysteries and magic
« Reply #8 on: September 13, 2021, 03:37:40 PM »
My LM3 would be changing sync on carbs every time I rode it, the quick change levers on the tops. In a few days it would run the same, nature of the beast. Using the normal carb top is a better set-up. I lived w/it and new cables made it worse.
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Offline rusty rotor

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Re: PHM40 mysteries and magic
« Reply #9 on: September 13, 2021, 03:42:51 PM »
Mr. Mullendore:

What you’re perpetrating here is a completely unsolicited and unhelpful hijacking of a request for assistance with carburetion.

If you really want to argue with me, you have my number.

Otherwise…

Online Antietam Classic Cycle

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Re: PHM40 mysteries and magic
« Reply #10 on: September 13, 2021, 04:09:21 PM »
Mr. Mullendore:

What you’re perpetrating here is a completely unsolicited and unhelpful hijacking of a request for assistance with carburetion.

If you really want to argue with me, you have my number.

Otherwise…

Not arguing. Putting the facts out there that others might need to help diagnose your issue. And to defend myself when you make comments like this: "this guy has some very weird ideas about how to refresh a bike".
Charlie

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Re: PHM40 mysteries and magic
« Reply #11 on: September 13, 2021, 04:19:52 PM »
Mr rotor:
Did you disassemble the carburetors or any other part of this bike after you got it back from Charlie the last time?

Online Tony F

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Re: PHM40 mysteries and magic
« Reply #12 on: September 13, 2021, 05:14:04 PM »
Is the right hand coil the issue? Try another coil or swap the coils side to side and see if the pipe and plug symptoms follow. This does remind me of an issue (a long story but..) I had many years ago, a coil was breaking down when it got hot. Very difficult to track down what was going on and only proved when after two hours on a coil tester the coil stopped sparking.
« Last Edit: September 13, 2021, 05:14:53 PM by Tony F »

Offline rusty rotor

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Re: PHM40 mysteries and magic
« Reply #13 on: September 13, 2021, 07:10:05 PM »
I have studiously avoided futzing with the carbs. They constitute a known unknown to me.

And I really thought it was ok. Only after I got it up to highway speeds did I see the symptoms I’m describing.

Since then there’s been a noticeable slide in performance around town, similar to what I saw on the freeway.  Can’t think of a reason to expect it to be any better on the highway now.

I AM interested in jetting. But am working under the assumption that jetting is very much in the ballpark, or it would never have run well in the first instance.

My shocking observation is that something’s changed and may be continuing to change.

My ask is for help through that process.

Offline guzzisteve

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Re: PHM40 mysteries and magic
« Reply #14 on: September 13, 2021, 08:00:03 PM »
I'd check the valves, .002" isn't much to tighten up when hot, round town driving.
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Online rschrum

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Re: PHM40 mysteries and magic
« Reply #15 on: September 13, 2021, 08:22:06 PM »
Brake problem is obviously rusted rotors.
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Offline Motorad64

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Re: PHM40 mysteries and magic
« Reply #16 on: September 14, 2021, 01:37:43 PM »
Rusty-

Intermittent, under-load carb problems in my past have frequently been traced to ignition system issues: coil, wires/caps, condensers.  I sourced a NOS coil for one of mine that was swollen/rattly on my LM1 and am careful not to leave the ignition 'on' when not running to avoid overheating.  Have heard the Dyna's can be sensitive to that, too. 

I also went to double fuel-banjos from single after some starvation issues on an experts suggestion that really helped a mid range stumble.  Just had an intermittent running issue on my BMW R69s turnout to be a failing condensor.  Might be worth checking. 

My setup has stock 850 cyls, stock PHF36s with some mild port work, a V7 Sport cam, Lafranconis with stock headpipe diam and lightened flywheel.  It's jetted richer than stock care of the prev owner w/ 152 mains, 62 idle 70 starter and K5 needles.   Stock ignition.  Carburetes great across the rev band.  Just pulls smoothly from idle to redline.   Whacks of throttle at midrange give a nice, solid surge.  Zero pinging and good looking spark plugs. 

Good luck getting to the bottom of it.


Offline Motorad64

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Re: PHM40 mysteries and magic
« Reply #17 on: September 14, 2021, 01:43:48 PM »
Meant to add...have recently had a partial-plugged main jet from random gas/tank schmutz throw my old BMW off it's game.  Made it feel like I was running on 1 1/2 cylinders.  And I guess it was. 

I usually drain/clean my carb bowls at the end and beginning of riding season, but can happen anytime.  So another +1 to dropping and cleaning carb bowls/jets and making sure some detritus didnt find it's way to one of your jets.  Luckily that's super easy on these bikes. 

Offline Stevex

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Re: PHM40 mysteries and magic
« Reply #18 on: September 14, 2021, 03:04:56 PM »
I've never heard a good thing said about those white replacement carb floats.
Luckily my LM2 is still using the originals.

Online lazlokovacs

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Re: PHM40 mysteries and magic
« Reply #19 on: September 14, 2021, 06:44:07 PM »
just a thought, cable adjuster backing backing itself off?

Those widdly 8mm nuts can wander....


Offline Scout63

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Re: PHM40 mysteries and magic
« Reply #20 on: September 14, 2021, 07:03:51 PM »
I'd start with plugs and wires and work back to the coils.  Then check valves and timing.  Then carbs.  I don't know PHM's, but most carbs stay in pretty good tune if set up right and used regularly (Norton Concentrics excepted of course).  Good luck with the diagnosis.  If all else fails, ship the bike to 12 Shore View Drive in Orleans MA with the title signed in blank and I'll get it running right eventually.
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Online Antietam Classic Cycle

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Re: PHM40 mysteries and magic
« Reply #21 on: September 14, 2021, 09:58:05 PM »
I'd start with plugs and wires and work back to the coils.  Then check valves and timing.  Then carbs.  I don't know PHM's, but most carbs stay in pretty good tune if set up right and used regularly (Norton Concentrics excepted of course).  Good luck with the diagnosis.  If all else fails, ship the bike to 12 Shore View Drive in Orleans MA with the title signed in blank and I'll get it running right eventually.

I replaced the plug wires (solid core Belden), caps (NGK) and outer plugs (NGK also) but not the inners (dual plugged). I don't know how many miles Jerry has put on it since it was here, but I set the valves and timing (new Dyna III ignition) then. 
Charlie

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Re: PHM40 mysteries and magic
« Reply #22 on: September 14, 2021, 10:19:57 PM »
On a modified 43 year old bike it can take some chasing.  So many variables to check. I’ve had float needles that were perfect but would intermittently stick closed. I found that by putting on clear float bowels and watching them as I was blasting down the hiway. Stuff like that makes you want to wander in the wilderness.
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Offline Scout63

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Re: PHM40 mysteries and magic
« Reply #23 on: September 14, 2021, 10:21:49 PM »
How did the tank look?  Maybe something clogging a float needle?
Ben Zehnder - Orleans, MA USA

Online Antietam Classic Cycle

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Re: PHM40 mysteries and magic
« Reply #24 on: September 14, 2021, 10:25:38 PM »
just a thought, cable adjuster backing backing itself off?

Those widdly 8mm nuts can wander....

The PHMs have bellcrank tops, no adjuster except the one in the cable, at the throttle (2C).

How did the tank look?  Maybe something clogging a float needle?

No rust inside when it was here. Has inline "Visu-filters". 
Charlie

Offline huub

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Re: PHM40 mysteries and magic
« Reply #25 on: September 14, 2021, 11:54:48 PM »
personally i would change coils plugs etc, and bring it to a carb specialist with a dyno.
a few runs on a dyno can pinpoint any issues with the carbs, to get the same info you will spend days swapping jets and needles and checking plugs.
it is just not worth the efford if you cant do it yourself and enjoy tinkering wit carbs.

Offline lucian

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Re: PHM40 mysteries and magic
« Reply #26 on: September 15, 2021, 06:46:28 AM »
It sounds to me like your carbs are out of sync. You mentioned one pipe is sooty . Have you tried pulling off one plug cap while idling and and seeing if ,or how long it will run on the opposite side? Do the same on the other side, if one side is continuing to run longer/stronger than the other ,they are out of balance and need to be re synced.

Offline Scout63

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Re: PHM40 mysteries and magic
« Reply #27 on: September 15, 2021, 10:16:53 AM »
Maybe switch plug leads from one side to the other and see if the problem shifts?

I know that I am a boy among men in this discussion.
Ben Zehnder - Orleans, MA USA

Offline moto

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Re: PHM40 mysteries and magic
« Reply #28 on: September 15, 2021, 11:45:28 AM »
Has the owner tried operating the choke and/or the fuel petcock at 70 mph to determine if he is lean or rich there? From the Dellorto Guide:

Quote
3.6.5 Selection of the correct size of main jet
The correct main jet size should be selected by running on the road, preferably by first starting with an over-large size jet and gradually reducing it.
At full throttle, turn the starting device (choke) on, thus further enriching the mixture and, if this produces a worsening in engine running ie. it reduces engine rpm, it is advisable to reduce the main jet size until you finally get satisfactory operation.
Other signs revealing the main jet is too big are a very dark exhaust pipe, dark exhaust gases and damp spark plugs and an improvement in engine running when the fuel supply is temporarily shut off.
In a case where too small a main jet has been fitted at first, and the running with the choke on makes a noticeable improvement, you should increase the main jet size until the conditions mentioned above occur.

Contrary to implication of the section title and the recommendations for changing main jet sizes, the method really applies at any steady throttle opening. The Guide asserts earlier that the atomizer/needle combination determines the mixture from 1/4 to 3/4 throttle, which is where this bike would be operating at a steady 70 mph. So the results of the method applied at a steady 70 mph would implicate the atomizer/needle combo rather than the main jet.  (From the Guide, section 2.2: "In the "D" period of full throttle and, with all the circuits of the earlier periods operating correctly, the size of the main jet is now finally selected.") If the method shows a lean mixture, the correct response would be to raise the needles in the slides by one notch and try again. If rich, drop them one notch and try again. If moving the needle in the required direction is not possible, either a different needle or a different atomizer jet would be the next step.

The combination of rough running at a steady 70 mph and bogging when the throttle is whacked open at the same speed suggests leanness there to me. It is really important that the bike should not be running lean at 70 mph. The owner should take the responsibility of completing this very simple diagnostic procedure requiring no tools.

Since the owner said new "Dyna, coils, cables, wires, plugs" were included in Charlie's refresh, I wouldn't expect an electrical problem. Except maybe a loose connector or spark plug wire. Has the owner fiddled with any of those?

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Offline rusty rotor

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Re: PHM40 mysteries and magic
« Reply #29 on: September 15, 2021, 07:57:55 PM »
Thanks for that.

I have checked every spark plug cable, coil wire, fuel line.

Chokes not present on these carbs. Tickle 10x, crank the fast handle 10x, fires right up.

Oh and another symptom: sputtering and a little backfire from the right side which is the slightly smoky sooty side.

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