praying to the carb gods for alittle advice!

[freemoRR]

Hello all! Long time listener, first time caller haha
I'll start by giving a big thank you to all that have posted helpful hints and info on here. I've learned alot just by reading thread after thread after thread while doing my first xs build this winter. Saved a 71 xs1b from the scrap yard and turned her into quite a nice little hardtail bobber. I am, however, having an issue and I'm hoping that you esteemed elders may be able to offer some guidance.

Before I list the specs on what I've done, I'll preface with the issue. hard to start hot or cold (its kick only). if I give it the ole 2-stroke throttle roll on startup she'll get going and run ok. mid and upper ranges feels alittle sluggish but no popping, accel or decel. ride for about 15-20 minutes and the bike no longer wants to idle. will die at lights if I dont keep alittle throttle into it. engine is hot and plugs indicate a lean condition. so here goes, if I miss anything please feel free to point it out to me.

-new rings, cam chain and guides (adjusted warm, flush and 1mm movement, no noise)
-new boyer ign (red box micro) timed with dial indicator and degree wheel, no kickback on startup. no detonation or pre ign. light timed. its on.
-plugs B7ES, 5k suppression caps, wires, 4.5 ohm coil, all new.
-valve adjusted. .003 intake .006 exh cold as per manual
-compression 135 both sides
-tested charging system warm and cold, all working ok.
-not losing spark hot (coil ok)
-no smoke or soot (also leading me to lean)
-new VM34 carbs, 180 mains, PF9 needles clip #3 pos., 25 pilots, air jets removed, k and n pods (no rubber boot restriction) air screws 1.5 turns out,2.5 slides, synced. no idle hang, no air leaks, great throttle response in neutral. feels maybe alittle sluggish on accel.
-new battery
-new PM charging system
-rewired the bike from scratch. all new.
-idle set 1300 warm
-clutch adjusted to spec at case and handle (ie not a warm clutch drag, no bike lurching)
-new oil, 20-50
-stock front pipes with shorty megaphone mufflers (from lowbrow)-no leaks, baffled but still flowing alot more than stock I'm quite sure.
_float height adjusted to 23mm as per tuning manual (yes I've read it)

Bear with me gentlemen. mikuni carbs are new to me.
I'm thinking I need to up pilots and possible move needle clip? Am I on the right track? or out to lunch? If so, what would you elders recommend? 30s? 32.5? 35? needle up? needle down? I'm in Edmonton, Alberta. approx 670 metres above sea level, with an average temp of 25 degrees C (approx 80 F? for you yanks) in riding season.

I rode it today to get it to act up. came down the street strong and rolled it into my driveway. stalled within 5 seconds off the throttle. engine was pretty hot. pulled plugs immediately, bone dry and alittle too light for my liking. i should probably mention I am a licensed and certified master automotive and heavy equipment tech, so no need to dumb anything down for me! bikes and classics are just a hobby.

If I missed anything, please feel free to inform me. Again, thanks for all of your help over the last few months. You school alot of people without even knowing it. Just because we don't post doesnt mean we arent learning. thanks from a fellow XS guy in Canada.
-FR

 

[retiredgentleman]

Here' a link from out Tech section:
http://www.amckayltd.com/VM34-36.pdf

That's a fine looking bike you have. Not my style but it sure looks to be well put together.

 

[TwoManyXS1Bs]

Now THAT's an excellent resurrection of an XS1B!

Your thinking on the carb jetting sounds good to me, there's baselines, followed by fine-tune for your configuration.

Just for fun, see what happens if you re-install the air jets...

 

[TwoManyXS1Bs]

Here's some fun reads:

http://www.xs650.com/forum/showthread.php?t=6570
http://www.xs650.com/forum/showthread.php?t=28289

 

[gggGary]

Your very thorough bike set up and description is most appreciated!

Very sharp bike! Is the tank logo a reprise of the brass knuckle kicker theme?

Speaking of tank
I will guess you have checked this, but is the sporty tank vented? through the cap or internally? Might try a loose cap see if anything changes. If you are running fuel filters you might also try running without them for a bit?

 

[freemoRR]

It is! the knucks and pin striping are done in Gold leaf to give it that almost tie-dye effect. with small lettering in them. "xs" on one side, "650" on the other, and my initials on the tip of the rear fender!. I bought that knuckle from fabkevin and fabricated my stock kicker to work.

Anyways thanks for the reading guys, I did go through it, but I'm still kind of running in circles. Apologies, I forgot to mention that yes, one of the first things I tried was a capless run with no filters. no change. fuel lines, filters and petcocks are all new. I guess it's pretty safe to say I've tried everything that's been written in any thread I could find that was even remotely in the ballpark of this issue haha! BESIDES re-jetting...which has led me here to pick some brains before I go hunting for brass. This bike is 12 years older than I am, and I'm sure some of you may have been doing warranty work on them I'm just strapping on the water wings and wading into the deep end of the experience pool, hoping for a lesson.

I guess what I'm asking is, if this was your bike, running VM34s, pods and practically open pipes (slight baffling) What would you use as your jetting???. Pretty much everything I've read (including panics tell-all if I remember correctly) states that the air jets should hit the trash...so they did haha! I thought I could just tune around that. And would it be a good idea to maybe drop the float arm height to 22 mm? I'm alittle wary of that, seeing as how I dont want to swamp the motor with fuel. All I know about bike carbs is self-taught. so I consider this a day at school.

 

[5twins]

Your jetting looks correct but you didn't mention which needle jet you're running. I think a P-4, P-5 , or P-6 is the norm on a 650. Other than that, it's time to start experimenting. I would get the size above and below what you have in pilots and mains. Make one change at a time. I would start with the mains.

 

[gggGary]

Just will weigh in with how a set of Michael Morse VM34's came set up for a 650

Pretty much what you have
2.5 slide
180 mains
25 pj
6F9 needle. didn't check the needle jet.
These are "new type bodies" with deep floats and Z bend float arms.
I have not run these on a 650.

 

[ANLAF]

FreemoRR, welcome, my friend - you have done some good work there, and I like to see someone doing the reading, too.

One thing I noticed in your set-up was you renewed the piston rings but not new pistons and no re-bore. I say that because hard to start etc are familiar symptoms. If you eliminate everything else (and there is some great advice as you know) you might want to think of getting back in there. Bear in mind, you have given new life to an old bike - it might have been stood for a long while, and rust can have a poor affect on unused cylinders.

That is an impressive build.

Anlaf

 

[5twins]

The needle jet is very important on these. The generic VM34s come with a richer one, a Q-2 or something, and it really needs to be changed to a P-something to tune them on a 650.

 

[TwoManyXS1Bs]

The cams on these engines are somewhat aggressive, and with their long durations the engines are sensitive to exhaust configurations. The customizers like to go to short/open exhausts that compromise mid range, and reversion effects make jetting difficult and unique for a specific combo. Try searching 'reversion'. You can eventually get a running combo, but if performance minded, may want to reconsider the exhaust layout...

 

[5twins]

Yes, those darn straight pipes. I say, if you want a bike the runs like and has the power of a Honda 350, buy a Honda 350, lol.

 

[grizld1]

If anything your jetting is a little on the fat side, and that's consistent with the bike running better cold than hot. But don't assume that your problem is in the carbies yet; remember, 95% of carburetor problems originate in the ignition. Check the voltage that's actually being delivered to the coils, and if it's less than 1/2 V lower than what you find at the battery, start tracking the trouble spot. If you have high resistance in a switch or connector it's going to heat up, when it heats resistance will rise, and the vicious circle will start to spin.

 

[freemoRR]

thanks for the responses guys. It is a battle, that's for sure.

5twins, I realize now that while making my list I forgot to write down the needle jet. I will pull em and check, thats no biggy.

ANLAF, when I pulled the jugs during the overhaul process, I checked for cross-hatch, scoring, taper, OOR, all the normal stuff you would check for...to see if I would need to sleeve it and change pistons. everything checked out. so I ringed it and checked/staggered the gaps. (before and after pics below) unless I'm getting hot oblonging on the piston, but I would think that would leave scoring on the thrust side and a wet/oily plug, which I'm not getting. What makes me think carbs is that it started much easier with the stock BS carbs that were originally on the bike when I got it. I guess my mistake was not actually driving it more than a block before teardown (the thing was a god damn death trap).

Grizld1: I chased the electrical system first, hoping that would be my issue...mostly because I'm much better with electrical than I am with carbs haha! anyways the bike is rewired front to back by yours truly. whatever was left of the haggard stock harness hit the trash. through my ignition circuit when warm, I have just under 13 at the battery at idle, a voltage drop of .1v on the positive circuit and .07v on the ground side. a total voltage drop of .17 across the ignition circuit, which I would think is acceptable, considering every connection is in itself a minuscule load. Also, in theory I would think a weak spark would produce wet plugs? These are dryer than a monte python skit. I also ran it around to get it malfunctioning and then held up the rpm while I popped on the timing light. let it down to idle it begins to sputter, the timing light doesn't skip a beat. My heart sinks alittle more with each failed attempt, but persistence pays off. I'll keep at it and post any progress. Any other ideas you want to bounce off me are more than welcome.

 

[freemoRR]

Also, lets say hypothetically that I have the wrong needle jet installed (I wont know until I get the time to yank them, currently on call for Finning so I wont for a couple days)...would this have its greatest effect at idle? or off idle? I keep coming back to a pilot circuit issue in my head because of the fact that It seems to perform decently off idle, but wants to die at idle when warm...and a rich condition would make sense seeing as theres no popping/backfiring, no decel noise etc...and it does get worse when warm....it sure gets your head in a spin discerning between lean and rich problem when the symptoms are a bit cloudy! makes me miss the fuel trim and sensor readings of an automotive system! hah

 

[5twins]

The needle jet is mostly midrange but you have to realize that the three circuits in your carb overlap a bit and have an effect on the ones next to them. For the midrange that means it will influence the upper part of the idle circuit and the lower part of the main.

Where did you get the VMs? Were they a 650 specific kit supposedly pre-jetted or did you just buy generic VMs and jet them yourself?

 

[xjwmx]

I would have the brass knuckle held on by a pin that you could just quickly pull and have the nuck come off A wired pin like a miniature of those that hold dragster hoods down.

 

[freemoRR]

5twins: I have read the panic tutorial, and do grasp the concept that there are no hard boundaries....a change in one system affects the others, and that gaining in one spot may mean losing in another.....that being said, what do you think about playing with needle position to see if it affects performance without re-jetting for the moment? I haven't yet, but seeing as how it takes only a minute to change that...it might not hurt to try and see if I gain or lose?? might help educate my guess alittle better...

I got them from ebay...*prepares for a scolding* I didn't know of the generic ones being sold...and from what I've read in previous threads, I guess I got lucky and got xs650 jetting (they were listed as pre-jetted)...they did, however, come with the sh*tty cone pods that block the passages in the intake bell....they're in the trash, not to worry...they have independant floats...which werent adjusted (carbs started pouring out the overflow the first time they took fuel). That has since been corrected.

xjwmx: my mid pegs are also brass knuckles (chromed though), they flip down, and do disconnect I hail from the murder capital of Canada, no shortage of bad neighbourhoods to park/break down in here

 

[TwoManyXS1Bs]

A quick/cheap/easy way to tell if idle mixture is off is to cup your hand over the intake a little bit, like a choke, while it's idling. If it speeds up, you're lean.

 

[5twins]

Yes, you could play with the needle setting. That would tell you if richer or leaner ran better. Then you could work the jetting from there. But really, you may just be chasing your tail until you find out what needle jets are in there. Many times on those "pre-jetted" eBay carbs, they won't change the needle jet because it costs too much. Best you check it.