I really didn't want to have to resort to doing this...

[WOLFHAWK]

I have an '81 XS 650S

No idea what previous owner did but it would't run at all

Tore it apart

Fingers crossed...

Installed:

Pamco Ignition
Hugh's PMA swap
Mikes XS Pod filters #15-0035
http://www.mikesxs.net/product/15-0035.html

Exhaust is 2-1 no muffler

I've read the carb bible at least 4 times
www.amckayltd.com/carbguide.pdf



ANYWAY


I can get the bike to start (kick only-by choice)

And it will idle fine, not perfect, but I will fine tune it via the "dead cylinder" method

Bike had no/poor throttle response, carbs leaked gas back out through the filters

Disassembled the carbs (for what seemed like the 7th time)

I have replaced:

floats
http://www.mikesxs.net/product/20-6502.html
float needles
http://www.mikesxs.net/product/48-5014.html
and the seals as well

new rubber passage plugs
http://www.mikesxs.net/product/48-5002.html

took everythinig apart and cleaned multiple times

I had put in a #140 main jet
http://www.mikesxs.net/product/48-0121.html
Mikes XS 5IX11 needle
http://www.mikesxs.net/product/48-0663.html
did not see the note about the matching needle jets nor read about them until after the fact, so those are on the way

also installed #47.5 Pilot Jet
http://www.mikesxs.net/product/48-0608.html


still very poor throttle response

I know these carbs supposedly ran lean as it was stock, so by opening up the exhaust and switching to pod filters, the stock lean jetting isn't going to cut it. that's why I upped the jetting.

I've gone through and read other members testomonials/ threads/ trial and errors/ headaches and burdens

I put the bike back to a stock main jet #132.5 stock pilot jet, stock needle, hoping I would at least have a solid throttle response at least to start with

wrong.


It seems to be ok from idle -> 1/4 throttle
anything above that it seems like it gets bogged down (so I believed it was running too rich and the gas was drowning it)

however I pulled the plugs and the weren't soaked with gas, nor was the exhaust giving out black smoke

so then I figure maybe it is running too lean?

with the filters off, it seems that gas is kind of spitting about like when little kids perform a "raspberry"

I assume this could be due to an influx of air:fuel and the air overpowering it sending the gas all over?

the mixture screws are set at 3 turns out

floats are at about 22mm


still has the same throttle issue, poor response above 1/4 turn -> WOT whether easy or hard on it

the fuel also seems to come back out of the carbs via possibly the Main Air Jet from time to time
Any clue why that is? All passages were cleaned with solvent and blown clear with compressed air...


Thanks, there's warm weather here in upstate NY and this is preventing me from enjoying it.



If it matters.......... stock tank, single vacuum petcock, choke works as well as it should


I'm hoping that when I get the matching needle jet for the 5IX11 needle, it will richen the mixture and solve my throttle problem.

 

[Phail]

Mine was doing something similar to yours. Gas coming out the pipe. Wouldn't run without choke on. I finally put new spark plugs in and now it runs great with stock jets.

 

[mouser]

my '80 was doing just that! It turned out to be the TCI module. It started and ran perfectly but puked gas out the intakes above 1/4 throttle and bogged...

 

[xjwmx]

If gas is leaking out an air jet, either the float level is too high (mm numbers too low) or the needle/seat is leaking, or the o-ring is leaking.

Having said that, 5twins says the floats you bought are the pits. I say the needle and seat you bought are the pits, although it lasted me about a year before the rubber tip decided to balloon up; maybe I was lucky. If you have original floats put them back in. If you have original Mikuni needle and seat consider putting them back in. First thing is get the floats and etc right.

 

[grizld1]

BS34's vent the float chambers through the two holes in the intake bell (at 3:00 and 9:00, above the air jets), as do 78-79 BS38's. Right--use OEM Mikuni floats and float valves (they're still available) or suffer the consequences.

Fuel spitting back out of the venturi when running can also be caused by insufficient compression, sometimes due to misadjusted valves. Do the needful.

 

[pamcopete]

Wolfhawk,

Well, you could have multiple problems. Sounds like mostly a carb problem, but the fact that you installed a PAMCO in an '81 means that you had to install the three brass bushings and the advancer. Pressing the bushings in my hand can sometimes result in the bushings being canted and binding the advance rod, which screws up the advance, which would explain your poor throttle response, so check for free movement of the advance mechanism per this video:

If the advancer returns with a snap like in the video, then next check you advance with a timing light.

If the springs are too tight, full advance will occur later than it should. If the springs are too loose, full advance will never occur because some of the available advance is used up at idle.

Also, the air vent on the carbs may be blocked by the rubber on the filters. I think that grizld1 was alluding to that in his post but just didn't follow through.

 

[WOLFHAWK]

Wolfhawk,

Well, you could have multiple problems. Sounds like mostly a carb problem, but the fact that you installed a PAMCO in an '81 means that you had to install the three brass bushings and the advancer. Pressing the bushings in my hand can sometimes result in the bushings being canted and binding the advance rod, which screws up the advance, which would explain your poor throttle response, so check for free movement of the advance mechanism per this video:

If the advancer returns with a snap like in the video, then next check you advance with a timing light.

If the springs are too tight, full advance will occur later than it should. If the springs are too loose, full advance will never occur because some of the available advance is used up at idle.

Also, the air vent on the carbs may be blocked by the rubber on the filters. I think that grizld1 was alluding to that in his post but just didn't follow through.

Pete I made sure to lube up the advance rod when installing so it wouldnt bind.

The advance unit returns with a snap like in the video, I checked that already.

So I'll check timing tonight.



As for the filters, I do not believe that they block the vents on the back of the carbs, as all of the symptoms persist with the filters on or off.

I've also visually checked and there is no inner lip on the filter boots to cover the vents.



I've adjusted the cam chain as per specs in the service manual, will pull the tappet covers and check valve clearance as well.





SIDENOTE: only the left carb leaks gas back out. I'm leaning towards the float being the issue there.

I have all of the stock jets, floats, etc that I pulled out of the carbs, so I will try the OG floats and valves and see if that changes anything.



thanks for all the feedback

hopefully I can get her purring for a ride sunday, it's supposed to be 70 here...

 

[adk_rider]

WOLFHAWK

Good luck with the bike...I see you are a fellow NY stater....where about are you located? I'm just north of Albany in the Lake George region.

 

[WOLFHAWK]

WOLFHAWK

Good luck with the bike...I see you are a fellow NY stater....where about are you located? I'm just north of Albany in the Lake George region.

I'm in the Hudson Valley, about 45 mins south of Albany.

Lots of cool places to ride around here, as I'm sure there are up your way.










UPDATE:

Put in old floats and valves, no more gas leak.

Re-adjusted Timing and Mixture screws

She runs smoother off of idle up until about 1/2 throttle, black smoke, too rich, and stumbling and back firing from midrange on up to WOT

Still waiting for my friend to come over withat timing light so I can square that away and move on to the needle and main jet settings


Thanks again all for the help.

 

[WOLFHAWK]

Haven't touched the bike in a while, had to put a motor in my Volkswagen and make it daily drivable...



Well, I took out the Pamco setup and reinstalled it just to be sure it was in properly.

(seems to be the same as it was but now I have peace of mind there)

Adjusted the valve clearance to spec. Right side had a little more gap than it should've.




It seems to me that the slides aren't lifting all the way when i give it gas, they stutter or hesitate. (with no filters on the bike, so no vents are blocked)

but if i take the carbs off and cover the long vacuum port for the diaphragm/slide at the top of the intlet side, and blow into the air jets, the slides rise smoothly just fine and fall slow and steady as they should.

also when out of the carbs and held to light, there are no holes or tears in the diaphragms, so that rules them out.

any ideas?

It is no longer running rich, I'm thinking maybe the carbs need to be synched.

Or it may now be running too lean. (raise the needle)

The right side seems to run a bit hotter than the left.

During my lunch break I will go home and pull it apart and get specifics on what size jetting is currently in it.

Thanks everyone.

 

[pamcopete]

WolfHawk,

Without being specific, and after you started this thread, there have been a couple of posts here about strange engine problems that would go away if the PMA was disconnected for test purpose and the ignition just ran on the battery. So, try disconnecting the PMA. If you have a capacitor PMA, then substitute a known good battery for the test.

 

[WOLFHAWK]

Pete, I must've overlooked them with my mind being set on the issue being carb related.

I'll try that before I disassemble the carbs again.

Thanks.

 

[WOLFHAWK]

Well Pete, it seems to run fine with the PMA and capacitor disconnected, with a battery hooked up in place.

Why would this be though? Faulty regulator on the PMA?
The grounds are all good, I made sure of that when I first wired it all up.
Maybe I had the capacitor wired up wrong? (didn't really think that was possible)
It seems to run no different sans battery with or without cap.

I didn't have time to check with a voltmeter to see how much power the alternator or regulator was putting out
(mostly because my roommates don't put my tools back after borrowing them)


I'm assuming this is a somewhat common or even just reoccuring issue for people trying to run no battery-kick only, setups?

I was/am using the Sparx capacitor sold by LowbrowCustoms if it matters.

I hate to ask for advice and help, but I'm at my wits end and nobody in town wjo has or had an XS has done their own work to ask.

But thanks again.

Nice weather is around the corner and I really look forward to the riding season.

 

[WOLFHAWK]

Well, thanks to it being dead at work, I was able to do a little reading.

I'll check my voltage at the capacitor at idle and under throttle.

I'll doublecheck yellow wires going into regulator and rewire everything just to be sure (I wanted to clean it up anyway)

Will keep all posted on progress.

May need to consider running with a small battery due to my headlight demanding more power. (all my testing was done with the headlight disconnected)


I wanna figure out why it will only run on standalone battery power though. Otherwise I forsee myself being stuck down the road with a dead battery.

 

[pamcopete]

WolfHawk,

Well, do some searching for the problem because it has occurred before with a variety of causes.

1. Battery had a bad cell, therefore battery could not do it's job of filtering the output from the reg / rect causing the ignition to trigger sporadically.
2. Too small a capacitor and /or too big a load so voltage was noisy and low causing the ignition to be erratic. Similar to #1 above.
3. Voltage mysteriously would actually drop instead of increase with higher revs to the point where there was insufficient voltage / current to run the coil.
4. Voltage regulator not wired up correctly.
5. Regulator not grounded properly.
6. Defective capacitor or capacitor not wired properly. This matches your comment that the capacitor does not seem to make any difference.

If you bought the PMA from Hugh, he wil be here soon with some addiitonal help.

 

[WOLFHAWK]

I have a few hunches on what the issue may be. Once I dig into the wiring I'll probably slap myself a few times and then chew up the old worn rear tire in celebration tonight before putting the new one on tomorrow.

 

[WOLFHAWK]

I had the capacitor wired up wrong.

So after slapping myself in the face for 20 minutes, I took her for her first ride and she runs great.


Thanks again Pete and everyone else for the tips.

 

[Punkskalar]

I had the capacitor wired up wrong.

So after slapping myself in the face for 20 minutes, I took her for her first ride and she runs great.


Thanks again Pete and everyone else for the tips.

Thanks for the update! I just saw this thread this morning, and was going to chime in. Lots of folks wouldn't admit they did it wrong, making Pete and I's job pretty hard sometimes Glad it's running proper my man!

Hugh