new build, no idle.

[wolfy77]

Let me start out by giving many thanks to all that take the time and energy to contribute and help out all in need.
Here's what I have:
78 SE- bought as a non-runner.
Like many of us posting I've popped in HHB PMA, PAMCO ignition (temporarily set at the mid point as per Pete's instructions) with the ultimate coil. Running with a single cap (gets 12+volts while kicking). The ignition and charging systems are all that's wired in presently.
I bought a set of barely used and very clean VM34's from someone on here, which originated from 650central along with aluminum carb holders and fresh boots.
I'm trying to baseline them with the following:
pilot - 22.5
needle clip - 3rd (mid)
main - 190
float height - 24mm.
I begin each attempt with the idle screws 1 turn out and the slides set 1/16" to start (might be too much but only cause I can't get it to idle).
cam chain tension is good and the valves are in spec.
BPR7ES plugs gapped to 35
Rotella 15W40
compression reads 135 Left & only 120 on the right. (too low?) Seems to hold.
The bike fires up immediately but will only continue to run if i hold the throttle open approx. 1/4. No amount of adjusting the mixture screws or the throttle screws seemed to help achieve idle.
I have swapped the pilots both up (25) and down (20). The 25 only increased the already gassy smell in the exhaust and the 20 caused the RPM to run away a few times (indicating lean). I'm back to 22.5 for now. I've also adjusted the float height to 23mm, then 22 and now I'm back to 24mm.
After spending a few days swapping jets, resetting screws etc I noticed that at some point I lost the left cylinder. I swapped the plug wires to see if the problem followed but it kept to the left. I pulled the plugs and the left was clean and wet (gas) and the right was black and sooty. Once a fresh plug is put back the cylinder comes back to life.
I have been thinking that up to now that it's soley been a carb tuning and timing problem , so I've read and re-read all the mikuni tuning info on this site and others and even picked up a Sudco manual. I understand the theory and procedures well enough (or so I think) and am starting to think that if it where only a carb issue i would have at least achieved a rough idle by now.
I'm hoping some one may provide some new train of thought on this or tell me to keep at 'er.
Apologies for being long winded here but I didn't want to leave anything out.

 

[grizld1]

If your bike sat for a long while before you fired it up, the rings may need some use to seat properly. It's always a good idea to have a couple of spare sets of clean plugs on hand for any tuning job.

Check everything in those carburetors--slide numbers, needles, and needle jets. Seller may have said they're from MMM, but we had a guy on here awhile ago making some questionable claims about a pair of VM34's he was selling; maybe you bought from a good guy, maybe not. Why are those fat mains in there?

Try setting your ignition just a very little bit more retarded and see if that helps, then check with a strobe as soon as you get the motor to behave long enough to inspect. You might try installing a battery, at least temporarily during tuning. Before you put your bike on the road, read a few of the posts from guys who've fried their Pamco ignitions by running them with PM charging systems.

 

[gggGary]

Yeah disconnect the charging and runthe pamco off any 12 volt battery. (one less variable)
I spent a few quality weeks messing with several VM sets. For me new float valves and very carefully checking float action finally got it running well. There are a couple styles of VM floats. and they can be fussy about everything being just right. Did you check slide cutaway?

 

[wolfy77]

slide cutaway is 2.5.

Gary, you're suggesting to just swap out the cap for a battery or disconnect the PMA also?
I think I will order some new float valves just to make sure. I noticed during one of my jet swaps that one of them was stuck closed as there wasn't any fuel in the bowl. I have blown some compressed air through all the ports. It's working now but it does make me suspect. Just to make sure i have the float properly adjusted... I'm measuring from the raised ridge that would seat against the bowl gasket to the part of the arm that crosses over to connect the two sides. The floats are independent plastic type.

The bike has been sitting for several years Grizld. Is there a way I could help the rings along with the sealing if that is a problem? Or is running it the only way?
Also, I was going to swap the main to 180 but haven't been that concerned with that guy just yet.

 

[gggGary]

Well Pete likes to have his PAMCO run by a battery not tied to the charging system until you are sure the PMA, voltage regulator,capacitor, are behaving, ie wire in a volt meter, showing it isn't going much over 14 volts.
Hint; A PMA run without some decent load, IE a lit incandescent headlight, a few other lit bulbs, is a meltdown waiting to happen. Especially one without a battery in the circuit.

 

[grizld1]

You're not measuring float level correctly; did you read the VM Carb Guide and the Sudco Tuning Manual, or did you just give them a fast skim?. Measure from the gasket seat to the point on the float arm that contacts the horizontal pin on the float. Re. ring seating, give the motor a hundred miles or so to seat the rings and check compression again.

One more time: strip the carbs, check slide, needle, and needle jet numbers and compare to baseline, and get 180 and 185 mains on hand.

 

[wolfy77]

ok, I'm going to admit to this for other peoples benefit... the slides were reversed , resulting in the cutaway being on the wrong side. I realized this after re-reading the sudco manual and studying the diagrams. To my defense though, that is how they were shipped to me, which is probably why the carb po decided to give up on them and sell them to me.
Anyhow, it's a good day for me. I disconnected the charging system and hooked up a spare battery. The cap measured approx 14.5 volts, no spikes. sounded good to me so I hooked up the system again and started it up. Measured again and it's reading 15V. there is no other load in there yet. I'll wire in the headlight next and re-check.
Needle jet: 159 series, P6
Needle: 6F9, mid clip
Pilot: VM22/210 series, 22.5
Main: 4/042 series, 180
Float hight: 24mm
Mixture screws: 1.25 turns out
Idle screws: 5/32" to start
Was able to set timing. Looking good.
Results:
-steady idle.
-smooth acceleration of rpm
-a little white-ish/ grey smoke from left cylinder, right was clean
-plugs, black and sooty.
I'll play with the mixture screws some more turning to 1.5 and 2 to see if that will lean out the plug symptoms.

So thanks for the help thus far.

 

[grizld1]

Wolfy, for future reference: no matter what carburetor you're looking at, the cutaway always faces the intake side, never the outlet side. A few tips: Don't take short cuts with the mix screw settings. Run the motor on one cylinder at a time and ground the plug on the cylinder that's not running to the head. Work in 1/8 turn increments, seeking highest idle, and back off the throttle stop as idle speed increases; you'll get best response to adjustment changes at the lowest rpm the motor will hold. Setting mix screws for highest steady idle will result in a mixture that's a little bit too lean; when you've found the high idle point, richen 1/8 turn. If you get more than around 300 rpm difference between first steady idle at start up and idle at full warm up or exhaust popping under engine braking, go in another 1/8 turn.

 

[gggGary]

Great update post wolfy77! Yeah we all get spanked now and then. Good reinforcement of the never trust ANYTHING the PO said or did rule.
Will splain a bit about PMAs, They produce power all the time and the amount of power increases with RPM, the voltage regulator must dump off any power not consumed by other loads ie a headlight ,not enough load to use up the power produced will overheat the regulator causing it to fail.

 

[wolfy77]

So the more load ie. taillight, headlight, = less heat to the reg/rec. Is taillight and headlight enough load to keep the heat to the reg/reg at a manageable level?? Can't count signals obviously.

 

[wolfy77]

Hey Griz, is there a trick keeping one plug grounded while attempting to kick the bike and playing with screws? Clearly there is a danger to frying the Pamco if it becomes ungrounded accidentally.

 

[angus67]

I use alligator clip to hold the plug to the fins.

 

[grizld1]

Just clamp the plug to the head or any other part of the motor. The metal body of the plug, including the flats, is continuous with the ground clip, so it's pretty hard to mess the job up.

Edit: +1, Angus (you hit that "Post" button faster than I did!) Anything that holds the plug in place will get 'er done.

 

[grizld1]

Wolfy, re. load, that all depends on how much current your head and tail light draw, how much juice your PMA kicks out, and how hard you're running. Even OE PMA systems are vulnerable. GS series Suzukis, for example, tend to cook diodes in the rectifier element of the reg/rec. Then AC starts getting fed to the battery. Batteries don't like to eat AC; the wet ones will show their displeasure by boiling over and puking acid, sealed ones get hot and sometimes crack the case. Your best bet is to install a good onboard volt meter and keep an eye on the thing. If voltage starts to spike you can get off the hammer and on the horn. Install the highest wattage halogen headlight you can buy, and if you're running at highway speed, use the high beam.

 

[gggGary]

PMA's are rated in watts. so are bulbs.
From hugh's site
"**** If you are planning to use far less wattage (LED Lights, Low Draw Accessories, etc..) then check out our MOSFET Regulator Upgrade! Much Needed if you aren’t using stock style lights, ignition, guages, etc… "
His PMA is sold as having 200 watts but the site didn't state at what RPM so it's a bit meaningless. So lets guess full watts doesn't happen till 4000 RPM.
so a typical halogen headlight 55 watts but check yours, an H4 bulb can be anywhere from 35 to 80 watt draw.
An ignition coil is about 48 watts but its only on about 1/2 the time so say 25 watts.
Tail light about 8 watts instrument bulbs another 8 or 10
I think if your load is about 1/2 the rated PMA output you will be OK. Which should serve notice that regulators need to bee out where they get some cooling airflow not buried in an electrical box.

 

[angus67]

Byw, our spokes have the same threads. Jamb one end into the boot, thread tother half into the thing that threads on top of a plug, if you have one around, and wrap any wire around the spoke, and clip tother and to a fin. Its a bit more solid than a plug layer ng on a fin