REPETE'S XS650B Preservation Carburetor

[REPETE]

Good Morning -
I reached a stumbling block that has me perplexed .
I’m really hoping I’m simply missing something basic - I’ll take the embarrassment to get over the hump.
I really want to get this started today and timed with the timing light.
The breaker points have been installed as shown and with the point gap in an open position I’m still getting continuity across the two sides of the breaker....
no change whether open or closed.
I keep reviewing the installation and for the life of me cannot see anything wrong with it.
But yet, there must be!
As a check I opened and closed a set of the old points while checking continuity and as I expected the continuity is broken when the points are opened. But not with my installed points.
At this point I’m just wasting my time and not getting anywhere.
This is occurring in both sets, so it wouldn’t be defective breakers.
What could be causing this?
What am I not seeing?
I sure could use some help on this one so to get back on track with original issue.
And if I missed something really obvious, my feelings won’t be hurt if I become today’s entertainment!
Thanks all

Pete

 

[gggGary]

I'd start by taking the wires apart at the condenser junction and see if it still is grounded, then remove the wire off one set repeat, If so start taking points apart looking for the ground path. If not then the issue is in the wires from there to the coil and or condenser. Ignition off you will get some continuity through the coils and other components. While doing this recently on WJL the "tail light" test bulb glowed dimly with ignition off and points open, the other lead was on battery +12.

 

[REPETE]

Thank you gggGary -
I had to step away away from it.
I’ll get back on it after lunch and go through these steps with fresh eyes.
I’ll report back on the status.

Pete

 

[REPETE]

I went back and removed and reinstalled the points.
Still don’t know what the issue was but all is good.
Moving forward, I set the gaps and static timing.
Upon initial startup with left carb still choked right carb appeared to be functioning.
I didn’t spend any time studying it cause I wanted to get her warmed up and use the timing light.
Right side timing was dead on. Left side was a bit advance so I adjusted while running with the timing light.
Timing is now set.
IMHO I’m now back at where my journey began - right carburetor.
If I’m wrong, tell me.
I can’t post a video for you all to see first hand, but in a nutshell, the right carb is not functioning at idle.
A slow increase of throttle will result in sputtering and a backfire and when approx. 2K rpm is reached it’ll kick in and run great.
I’ve had it apart and believed it was cleaned (couple of times now) to near perfection.
I’ve gotta believe its coming off and apart again.
If I’m right, where do I need to focus my attention?
Thank you all for sticking with me through this,

Pete

Addl. info: if I cover the left carb throat with three fingers, it functions & responds - and I’ll get gas wet fingers for whatever that’s worth - but it’ll function

 

[5twins]

Are you sure the idle adjustment is turned up enough on that right carb? Set too low and the carb will be effectively shut off at idle, it's butterfly plate closed completely. If you do pull that carb again, with the idle speed still set where you now have it, look through the carb from the engine side with it held up to a good light. Look around the edges of the butterfly plate and see if it is cracked open a sliver. It has to be or the carb isn't going to idle. I seem to recall some talk recently about the idle speed screws needing to be turned in different amounts side to side on some early carbs to achieve the same butterfly plate opening on each carb.

So, that would be the simple problem and solution. If that's not it then my next guess would be plugged passageways in the idle circuit, somewhere between the pilot jet and the exit holes in the main bore for it's mix .....

 

[REPETE]

Good Morning and hope everyone had a good weekend.
Thank for sticking with me on this.
5T, I'll give a synopsis of where I'm at and address your points in the process.
Recap:
Ignition is functioning as it should.... timing is correct
Right cyl. spark plug "sparks" when idling.
While right carb was still mounted on bike I advanced the idle screw as far as it would go but it doesn't open the butterfly to the point that the carb "wakes up".
I returned it to it's original position and removed carb.
Butterfly position verified as being "cracked open" - daylight showing around edge and visibly not in a perfect vertical position.
Carburetor reviewed & cleaned for 4th time. All passageways appear to be clear. I can spray carb cleaner through them and blow air through them. Specifically, those Pilot Fuel Outlets shown in 5T's picture are clear... . they spray beautifully.
Reinstalled carb and no change!

Additional info to consider:
When idling, operating right carb throttle only results in right cyl/carb sputtering, popping & occasional backfiring and then a near instantaneous activation at about
2k rpm +/-
If I block off the air supply at the carb inlet by covering approx. 1/2 to 2/3 of the opening it will begin operating beautifully. It idles and it'll function if I accelerate the throttle.

Thoughts I'm pondering... and perhaps going down the wrong path:

• Am I somehow getting too much air? Thinking maybe I had an air leak/suck somewhere I sprayed the entire carb a bit at a time with starter fluid while motor was idling to see if I got any sudden reaction. And I got nothing.

• Can an issue with the intake valve have an effect on the ability to draw in the fuel mixture? i.e. needs the higher rpm's to "vacuum" it in? I did set all the valves to spec as a part of my going through the bike from nose to tail. I believe it called for .002" on the intake. And, I had to make little to no adjustments.

Lastly, the mixture screw is totally ineffective regardless of position. The passage is clear as I indicated earlier.
I think I covered everything for consideration.
I'm hoping there's something really basic that I keep missing but I don't think so.
Thoughts???
And as always, everyone's ideas & guidance is appreciated

Pete

 

[grizld1]

When the engine doesn't respond to moving the mix screw, the first thing I look at is fuel level (I know you've already checked float height, but that's an indirect measurement of fuel level and can be deceptive). Ggggary came up with a fast sight tube inspection plug. Get a 6x1.0 mm. grease zerk from Big Box Auto Parts, drill it to remove the ball and spring, and install it in place of the float bowl plug. Carefully level the carbs on the bench, connect them to a fuel source, attach a snug fitting plastic line to the inspection plug, hold the line up beside the carburetor, and turn on the fuel. Fuel in the line should rise to the line of the carb body where it overlaps the float bowl and not more than 1 mm. below that line.

 

[5twins]

You'll need a bigger grease fitting than an M6. I'm pretty sure the drain bolt is an M8. Instead of trying to make something, I just went ahead and bought this "tool" off eBay. It works great .....

https://www.ebay.com/itm/Carb-Float...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Yes, there is an air jet in the bell mouth that feeds the idle circuit. It is the small opening on the right side .....

However, the jet is pressed in place. But maybe yours has been messed with (drilled out) or come loose and fallen out? To confirm it is this air jet giving you problems, instead of covering 1/2 to 2/3 of the bell mouth, just put a finger over the jet hole. But if it is the issue, I don't know how you'd go about fixing it. The jet was never available and I've never seen it's size listed.

 

[5twins]

A couple more things you could check would be to confirm you have the correct BS30/96 type pilot .....

..... and the correct matching float bowl for it .....

The VM22/210 type bowls deliver the air supply from that air jet across the top, to the top of the pilot jet. The VM22/210 pilot jet flows straight fuel. The BS30/96 type bowls deliver the air down an angled passageway to the bottom of the BS30/96 pilot jet. The jet flows an air/fuel mix.

 

[grizld1]

Yep, if the PAJ is missing or mangled you'd have two alternatives. The easiest one would be a new carb body. Since I'm suffering from acute TMS (Too Much Shit) I'll send you one free if you need it, but it would need some TLC: new throttle shaft seals and a thorough cleaning . The other alternative would be to measure the PAJ orifice in your good carb with a pin gauge or similar, try to match it to the threaded air jets used in Mikuni VM, RS, and other carbs, then drill and tap. Sudco or Carb Parts Warehouse might be able to tell you what size orifice the Mikuni numbers correspond to, or you could get a range of jets and tune.

 

[REPETE]

You'll need a bigger grease fitting than an M6. I'm pretty sure the drain bolt is an M8. Instead of trying to make something, I just went ahead and bought this "tool" off eBay. It works great .....

https://www.ebay.com/itm/Carb-Float-Level-Tool-Yamaha-XS400-XS500-XS650-XS750-XS1100-XZ550-77-83/273099883552?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

Yes, there is an air jet in the bell mouth that feeds the idle circuit. It is the small opening on the right side .....

However, the jet is pressed in place. But maybe yours has been messed with (drilled out) or come loose and fallen out? To confirm it is this air jet giving you problems, instead of covering 1/2 to 2/3 of the bell mouth, just put a finger over the jet hole. But if it is the issue, I don't know how you'd go about fixing it. The jet was never available and I've never seen it's size listed.

In my poking around I did do that. I failed to mention it though.
I did all of the orifices one at a time and it had no effect.


EDIT: I JUST PURCHASED THE FLOAT BOWL ADAPTER/FUEL LEVEL CHECKING DEVICE.
Thank you for sharing that!


P

 

[REPETE]

Yep, if the PAJ is missing or mangled you'd have two alternatives. The easiest one would be a new carb body. Since I'm suffering from acute TMS (Too Much Shit) I'll send you one free if you need it, but it would need some TLC: new throttle shaft seals and a thorough cleaning . The other alternative would be to measure the PAJ orifice in your good carb with a pin gauge or similar, try to match it to the threaded air jets used in Mikuni VM, RS, and other carbs, then drill and tap. Sudco or Carb Parts Warehouse might be able to tell you what size orifice the Mikuni numbers correspond to, or you could get a range of jets and tune.

This is outstandingly kind of you, but I don't think it'll be necessary. I will look in them later today to see if the brass jet is intact.

P

 

[REPETE]

A couple more things you could check would be to confirm you have the correct BS30/96 type pilot .....

..... and the correct matching float bowl for it .....

The VM22/210 type bowls deliver the air supply from that air jet across the top, to the top of the pilot jet. The VM22/210 pilot jet flows straight fuel. The BS30/96 type bowls deliver the air down an angled passageway to the bottom of the BS30/96 pilot jet. The jet flows an air/fuel mix.

I've been looking at this stuff so often I know it in my sleep.
That said, I know that both the bowl & pilot jet are correct. There's no doubt.
And, i have clear passage down that kind of a sloped tunnel that connects into the vertical shaft where the pilot jet is screwed in. I can spray carb cleaner through or blow air through it without issue.

P

 

[grizld1]

Oops! Thanks for the correction, 5twins--right, the float bowl plug is 8x1.25 mm. Pete, if it turns out that you need a right side 74-75 carb body, send me a PM with your postal address and I'll send you one, just pass the favor on to someone if the opportunity arises. Have you compared your mixture screws and seats to see if there's damage on the right side?

 

[gggGary]

I forget; was a compression test done?

 

[REPETE]

Oops! Thanks for the correction, 5twins--right, the float bowl plug is 8x1.25 mm. Pete, if it turns out that you need a right side 74-75 carb body, send me a PM with your postal address and I'll send you one, just pass the favor on to someone if the opportunity arises. Have you compared your mixture screws and seats to see if there's damage on the right side?

VERY KIND OFFER!!
Thank you. I’m hoping that won’t be the case. I am absolutely the kind of gut that goes pay it forward. I offered my later model air box for free earlier in this thread - but nobody needed it.

to answer your question - I haven’t done a side by side comparison of the mixture screws. I did have both carbs fully apart early on when I was cleaning them up and ordering parts to rebuild, but I don’t think I ever matched them up.
I’ll do that tonight.... as well as look into the pilot holes for the grass inserts. It’ll only take a few minutes.
Ongoing story here!

Pete

 

[REPETE]

I forget; was a compression test done?

 

[REPETE]

No. I haven’t done a compression test. I can do that tonight also and report back.

P

 

[grizld1]

Oh yeah, gotta have vacuum to pull in fuel--good catch, Gary, I assumed, and we know what that does! One more time, guys: the first rule of carb work is everything else first!

 

[TwoManyXS1Bs]

Please describe for us your bowl venting...