No choke/Kicks back - Sanity Check request

[Hyde]

Gents, need some help on "tuning" / "post-assembly". Homework submitted for grading below lol. Before we go there, forgive me XS gurus for I have committed the cardinal PMA/CDI/Engine rebuild/Carb Rebuild all at once sin.

82 XS with BS34 Carbs

Symptoms:
-Kickback like a mule
-Left Carb occasional pops back through when kicking
-Choke is non-existent in functionality (rpm increase not present on cold start)
-Throttle cracks required to start
-Choke on after start, bogs and dies

Parts:
Hugh's PMA/CDI/mosfet regulator/new BP7ES plugs (gapped)
2nd oversize rings (end gaps to spec) spaced per Tech section during install
New Valves / Seals / Collets / Tappets / Ground properly to seats
New cam chain / front rail guide
New JBM Intakes - thick new gaskets torqued to 80 in/lbs - sat overnight and re-torqued in morning post compression to be sure of seal
Pandemonium Open pipes - new exhaust gaskets
New Yuasa Battery
New Ramair Foam pods

Carbs Rebuilt by Rick (Oldskool)
Jets - 137.5 & 45
New diaphragms
New brass T linking carbs

Troubleshooting / Reviewed:
Cam Chain adjusted to 1mm push out during rotation
Valves set to 0.003 & 0.006 both sides - 650Twins video viewed 47251338585926 times now lol
Floats 22mm from the body surface (not from gasket) - plastic floats
Rick put in a new float needles - visually inspected each - pristine. Did not check for screens in behind, will do tonight
New gaskets in carbs - hole present and unobstructed for choke. No fuel leaks occurring.
Choke pipe and ports in bowls shows light/spotless
Carb cleaner with choke open passes air and carb cleaner no problem
Carbs Bench Synched - right was closed, left showing light (corrected)
Air/fuel mix - left 2.5 turns, right 2.75, corrected to 3 - understood this will need to be adjusted further up to 3.5
Pilots / main pass air/carb cleaner without a problem
Stock clamps screwed down as far as I can go on Intakes to carbs. I've had the old
Metal intake covers chromed and am unable to get the clamp ends to completly touch, close though.
Static timing - Reinstalled stator, TDC, validated hole in cam right side aligns with plug top and screw hole for plate (straight line).
PMA Marked using prior stator's position for TDC - Timing light shows almost spot on for Fire Mark
Retard a bit - Not as mule'ish as before but bogs out with throttle. Prior setting had crisp throttle response/rev
No issues with hanging throttle, quick returns on throttle release
Pressure from both pipes - both warming/heating up

So there we have it.....I'm "almost" at wits end here and looking to see if there anything I've missed and should dig into while she's still apart. There's 3 things I have not performed yet them I'm aware of:

-air leaks around intake boots to carb body
-the "dark side" - throttle shaft seals
-dreaded compression test to check for a bent valve....the mule disagrees with this conclusion.

I'll review during re-assembly this coming weekend (final harness wiring now). The kickback has the arch of my foot a tad scared and lack of choke perplexed. Throw in a dash of paranoia I'm off a tooth but TDC/Cam disagree. Any input you guys can provide would be gold & insanely appreciated.

 

[5twins]

It really sounds like the timing isn't right. Having the timing off is one of the major causes for kick back.

 

[Hyde]

Thx for the reply 5twins. What does a 1 off in a tooth look like for the right cam hole withTDC Just how discernible is it?

 

[5twins]

It would be quite noticeable. The hole would point to something like 11, 11:30, 12:30, or 1 o'clock. You'd easily see it. Yours looks good.

 

[Hyde]

Anyone else know of a potential kickback cause or reason for the lack of choke? Other than my last 3 outstanding check points I'm fairly confident I've hit all the marks. Really perplexed.

 

[TwoManyXS1Bs]

I don't know anything about BS34s, but the BS38 enrichners and plungers I think are similar. On those, there's 3 passages:

Air into enrichner body from vent under the diaphragm.
Fuel/mix into enrichner body from carb/bowl.
Air/fuel mix out of enrichner body to large port in throttle bore.

When the plunger is down, it simultaneously plugs the bottom fuel/mix port, and its cylindrical body blocks the connection between the air-in and air/fuel mix out.

When the plunger is up, all 3 passages are connected.

There's also a preliminary intermix zone, where bowl fuel is mixed with a separate air source. Similar to the jets, air bleeds, and emusion holes, in the other jetting systems.

The enrichner system is like its own little separate mini carburetor.

A bad plunger body, bottom rubber seal, and enrichner body, can all conspire to ruin your day. Something to check...

 

[Hyde]

Thanks TwoMany, definetly will dig into that. Carbs are still on the bench, hesitant to throw them back in before feeling positive I've gone over as much as possible in advance.

 

[Hyde]

For clarity of my own understanding - BS34's on the later models, where does the vacuum originate to draw in from the ports in the carbs? Is this a post-combustion condition and when the intake opens creating a suction effect forward creating the next draw in? Just curious, wanted to clear it in my head.

 

[5twins]

When I said timing, I meant ignition timing, not cam timing. I think I'd be experimenting with that setting a little more. The idle timing spec for your later model is 15° BTDC. On the points models, this was given as a range, 13° to 17° BTDC, probably so you could deal with wear in the advance unit. If you're using the timing marks sticker from Hugh, the "Fire" mark is rather thick. I'll bet it easily covers 2°. I'd be shooting for idle timing just to the right of that "Fire" mark, right next to it. That would put you in the retarded end of the acceptable range.

 

[xjwmx]

The "Throttle cracks required to start" could be flooding. "Choke on after start, bogs and dies" says it isn't clogged and also kinda points to flooding.

 

[Hyde]

5twins, with a timing light I'm having a hard time holding a 1200 RPM idle smoothly which may be contributed to by XJW's flooding possibility. Between timing being off a couple of degrees and an excess of fuel from flooding, it would explain the kickback symptom (at least in my mind). Didn't reallly correlate a 2 degree difference in just the thickness of the fire mark, great point!

Going take the carbs apart again and inspect/clean/blow out then shoot for a re-assembly-timing light. Appreciate the input gents!

 

[xjwmx]

To get it to where I could check the timing I'd temporarily put the idle adjustment screw where ever it took. Unless it's so erratic you have to keep twisting on the gas to keep it running... You and Rick have been all over the carbs already, so I don't know what to make of that except having to crack the throttle is good evidence... I had a non-genuine float needle swell up and get stuck cause a flooding problem. That came from my beginner mistake of wholesale replacement of everything. Fortunately had the good intuition to keep all the old parts...

 

[timbeck]

Subscribed

 

[Hyde]

Hey TwoMany so I took a break from the carbs a bit to work electrical (for my own sanity). Took apart the choke assembly this past week:

A bad plunger body, bottom rubber seal, and enrichner body, can all conspire to ruin your day. Something to check...

Plunger body had a lot of play in the port. Rubber gaskets on retaining nuts were rock hard and I could see a microscopic loss of seal arround the middle section of the plunger body. Bottom rubber seals looked good, they were not hard and had well worked in ridges for seats. Picked up new plunger bodies and seals as replacement....wow...big difference in how body sit in the carbs. Also pulled throttle shaft seals, those were hard, not a lot but they not soft and pliable.

Thrown all these in new and watching Gggary's thread on float heights for outcome before putting these back in for another fire.

5twins - pulled PMA, put in the stator, reset to TDC, used Hugh's brass gage to reset CDI fire plate. Definetly off roughly 5-7 degrees. Something must have shifted during my original install just ever so much.

Now the kicker...the real kicker here for anyone who comes accoss this thread looking for Hugh's CDI and issues post install.... I hope you kept ALL your documentation together ... or end up with my fate....



FIX those wires during install. Itll throw you out a good chunk of degrees in timing otherwise. Talking to Hugh, the pickup is for an opposite rotation, hence the need to reverse the wiring. Pickup ends up reading the timing as advanced. I'm playing the blame the wife card here - I found the sheet one afternoon in the trunk of the front living room...you know...the one no one ever steps inside... ha!

New update will come shortly on this large assortment of corrections and outcome.

 

[Hyde]

So..no dice on any of the above, she runs like a poopsicle. Totally perplexed as to what in the hell is going on. What I do know is the following:

-pull breather after a run arround the block
-push up on the slides
-can see gas bubbling popping around top of the slide
-area arround slides is soaked
-clear tube tests show zero issues with floats
-fuel droplets forming to drops at filter bells
-temp gas tank hole to breath large enough to prevent vapor lock
-propane test for leaks, none, no rise in idle at all arround the Intake boots and carbs (i.e. Throttle shaft seals/enricher seals)
-pull carbs, Intakes inside are soaked with fuel
-idle, pull throttle & the slides are bouncing like a basketball on the initial lift
-gas it in gear and she takes off
-throttle off and she stalls out
-new set of plugs, same issue
-put on my "show" wires/caps, same issue

Vacuum/Air missing for fuel atomization is the path in my head right now but beats the hell out of me where it's lacking and/or why. One of the local guys lent me a working/trusted set of BS38's and intakes to test with tomorrow. If these run then it's something internal to the carbs I can't get my head arround...if she remains the U.S.S Poopsicle...we're at ignition issues.

 

[TwoManyXS1Bs]

-idle, pull throttle & the slides are bouncing like a basketball on the initial lift...

This is a BIG clue.
Should be very little slide flutter when coming off idle.

Compare to your next set of carbs.

 

[Hyde]

Alright so.....BS38's in, 1 fuel inlet for each carb, rig a T up to supply fuel. Intakes in rough shape but whatever...throw'em in, gas'em, enrichner on .... IT FIRES RIGHT UP .... idles smooth with a few pops from the exhaust. Grab timing light, a bit advanced, retard and the pops on idle disappear. Rev's give pops on throttle crack closing. Potentially the old boots and the owner did warn me they were not synched....what in the bloody blue gives. These half charred carbs have a few tricks left in the bag but my fresh and rebuilt 34's make me want to scream.

-Prior to new enrichner plungers/seals, if you plug the diaphragm Intake really firmly with ur thumb on the back of the bell, lift slide, release & count - 17 secs on drop.
-bike ran the same after enrichner/seal replacement and throttle shaft seal replacement, however, the drop counted 24 sec
-port in the slide up to diaphragm area is pristine and clean. There is only 1 port open
-diaphragms match the circular pattern in the carb top, no additional nub present and they also read BS34 in the rubber (these are new JBM's)

I don't get it, the flooding symtoms you guys posted did pan out as root cause but I'm at a loss as to the lack of atomization/air mix going on unless there's some sort of crack in the body I can't see but that would imply both bodies have a crack as they are behaving the same with the symptoms I listed above.

 

[Hyde]

Update....After writing the above I must have run flooding through my mind 1000 times....so open the nightmares yet again.

Theory as follows:
-hardcore vacuum, these are sealed tight
-Main jet needle, if that sits too high in the jet, hard vacuum could theoretically pull fuel from the bowl and wash everything out
-pulled the diaphragms/slides/needles out
-5IX11, scraped forums cause every other post about needles on BS34's states 1 setting
-but...no no....not if you're a Canadian....you have 5....

But...Rick would slide that back to the original slot wouldn't he? Not according to the rub marks center of the needle showing original clip install and semi-fresh shavings on the very bottom slot where it was positioned which moved my theory forward on wash out.

Restored clip position with doughnut... didn't have the patience to touch the choke, cracked throttle and she's rev's up. Smooth, steady and alive. Rip arround the block, sounds beautiful and smooth on acceleration and gear decel but once warmed up I'm getting a small skip every once in awhile are low RPM. No backfires or pops though. Tomorrow I'll Sync with meters and try to dial in the mix screws (currently at 2.5 turns) and untouched.

What a Canadian problem to have lol. More to follow for those still paying attention to my self-ramblings.