Far as I know, Greg, you can't install those adjuster with the engine in situ. You have to pull the rocker box to get 'em out.
-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Yam_Tech314's official build thread
- Thread starter G_YamTech_314
- Start date
I appreciate the reassurance. It leads me perfectly into the next small bug I can't crack on my own. You're mentioning the advance bringing on higher idle... I can notice a slow but steady rise in RPM when the bike is just idling... If I start the bike and set my idle to 1100 then in about 5 minutes or so I'm right up to around 1500rpms. Turning down my idle screw will temporarily solve the problem, but it doesn't fix it permanently because then on a cold start my idle is so low that the bike wants to shut off.
Welcome to the world of carburetors
If you do a search here in the forum, there was a thread from quiet a while ago on making your own knurled knob for the idle screw on the BS38's. Easier to adjust on the fly...
That's pretty much just the nature of this beast, lol. Set the idle when cold and it will be too high once warm. It will need to be kept running with throttle blips when cold. Once it starts warming up a bit, it should idle on it's own. It will take some tinkering and fine tuning to make that happen. I routinely have to "tweak" my idle speed a couple times a season, turning it down a little as we get into the warmer Summer months, than back up a hair once the weather starts cooling off in the Fall. To make that easier, I've started installing knurled caps on my idle speed screws .....
It just seems to be a fact that an XS650 will idle at higher revs once the engine is good and hot. I always set idle low - when I kick the bike into life, I have to hold a smidgeon of throttle until we set off, and maybe at the first one or two junctions. But then it's fine and settles down to a reliable idle at 1100 or so.
Set the idle to 1100 when you get back from a run. On cold starts, you will need to hold that smidgeon . . .
You ain't making us listen, we mostly like bikes and helping folk get them sorted. But I'd suggest you are over thinking this and worrying more than you need to - sure doesn't sound like that engine is about to destroy itself!
Just congratulate yourself for bring the bike back to life and giving that engine the opportunity to tick and tock happily away to itself for years to come..
Set the idle to 1100 when you get back from a run. On cold starts, you will need to hold that smidgeon . . .
You ain't making us listen, we mostly like bikes and helping folk get them sorted. But I'd suggest you are over thinking this and worrying more than you need to - sure doesn't sound like that engine is about to destroy itself!
Just congratulate yourself for bring the bike back to life and giving that engine the opportunity to tick and tock happily away to itself for years to come..
As far as tuning goes I'd say I'm right there at the finish line. There are only two possible little hiccups I can think MIGHT be an issue still.
Number one: when the bike is cold and I try to give it gas at idle it wants to sputter at 2-3k rpm's still and MAYBE lightly backfire once or twice when trying to keep it in the 2-3k rev range (runs completely smooth at idle, no choke.) Once it's warmed up it all goes away completely and rides like a dream. My spark plugs are a really nice dull white/gray with toasted brown tips so my fuel mixture is damn close to perfect.
Finally, there is the issue that it will fire off with the choke but will not run on choke AT ALL. Is this due to the warmer weather? Or is there sumthin' not working with my choke circuit..? Other than the small hiccup when cold, and the non running with choke, it's a dream of a runner. Especially now that it's quieted down.
Thanks for always bein' such a positive, uplifting guy, Raymond. I appreciate it.
Number one: when the bike is cold and I try to give it gas at idle it wants to sputter at 2-3k rpm's still and MAYBE lightly backfire once or twice when trying to keep it in the 2-3k rev range (runs completely smooth at idle, no choke.) Once it's warmed up it all goes away completely and rides like a dream. My spark plugs are a really nice dull white/gray with toasted brown tips so my fuel mixture is damn close to perfect.
Finally, there is the issue that it will fire off with the choke but will not run on choke AT ALL. Is this due to the warmer weather? Or is there sumthin' not working with my choke circuit..? Other than the small hiccup when cold, and the non running with choke, it's a dream of a runner. Especially now that it's quieted down.
Thanks for always bein' such a positive, uplifting guy, Raymond. I appreciate it.
I'll once again suggest dropping the pilot jets one size, readjusting the mix screws and see if that helps.
As long as the dealer has them in stock I'll be picking them up today right after work!
Gonna roll the dice on the #22.5 pilots instead of the #25 as suggested. Will be running the bike shortly to see what me thinks.
EDIT: What do we think about jets with side holes vs without? Make a huge difference? Negligible?
EDIT: What do we think about jets with side holes vs without? Make a huge difference? Negligible?
The air bleed holes down the sides of the VM22/210 pilot jets make no difference in the BS38 carbs because of how the jets mount down into the bowls and because of what they flow. They flow straight fuel and the air is added afterwards, on top of the jet. Now if you had older BS38s that used the BS30/96 pilots, you would need the air bleed holes because air is fed down an angled passageway to the side of the jet and it flows a fuel/air mix. This explains why the BS30/96 pilots are sized so much larger (sized in the low to mid 40s) than the VM22/210s (sized in the mid to upper 20s) ......
Now, that all being said, I'm thinking those 22.5 pilots may be too lean. Break-up and stumbling can be caused by either being too lean or too rich, and it's often difficult to tell which it is, but poppimg and backfiring usually indicates a lean condition, as does the fact that the problem goes away once the bike is warmed up. A motor needs a richer mix when cold. So, you may need 27.5s, one size larger than stock. What mods do you have, if any? Freer flowing exhaust and pod filters maybe? If so then I think the 27.5 size may be called for, along with larger mains (132.5 max) and leaning the needles a step (to compensate for the larger mains).
I'm thinkin' you're onto something. I threw in the 22.5's and the carbs blew out of the boots on the second kick with choke on. I'm so tired of that happening lol. I found that the bike runs better with the 22.5's when warmed up. Otherwise there's a dead spot and the 1/4 throttle response when cold SUCKS. Tries to shut off, and then catches up to itself.
I'm running (I THINK) stock exhaust and mufflers, and UNI pod foam air filters. I've got stock main jet sizes (I'm pretty sure) and I just lowered the needle one setting. Lowering the needle one setting and running #25's seemed to have the plugs looking REALLY good. Especially compared to the constantly fouling plugs I was experiencing before starting any of my ridability tuning. I wanna say you're probably right about enriching the pilot circuit. If it's backfiring NOW but wasn't with just one size bigger, then I probably wanna move in the other direction. Oh well. $5.43 worth of jets to learn that I was headed in the wrong direction is a pretty cheap lesson. Though, if the carbs keep leaving the chat via backfiring out of the intake boots... Eventually I might be seeing a more expensive lesson.
Here's a picture of the spark plugs for reference. This was after 37 miles of riding, idling, cruising, FLYING, and all around just having fun on it.
I'm running (I THINK) stock exhaust and mufflers, and UNI pod foam air filters. I've got stock main jet sizes (I'm pretty sure) and I just lowered the needle one setting. Lowering the needle one setting and running #25's seemed to have the plugs looking REALLY good. Especially compared to the constantly fouling plugs I was experiencing before starting any of my ridability tuning. I wanna say you're probably right about enriching the pilot circuit. If it's backfiring NOW but wasn't with just one size bigger, then I probably wanna move in the other direction. Oh well. $5.43 worth of jets to learn that I was headed in the wrong direction is a pretty cheap lesson. Though, if the carbs keep leaving the chat via backfiring out of the intake boots... Eventually I might be seeing a more expensive lesson.
Here's a picture of the spark plugs for reference. This was after 37 miles of riding, idling, cruising, FLYING, and all around just having fun on it.
Well, they are burning very clean, maybe too clean. lol. What you want to look at is the "smoke" or "mixture" ring. This is a dark ring of color and should be at the bottom of the porcelain, coming up no more than about 1/4 of the way .....
If this ring extends half way or more up the porcelain, you're too rich, no ring means you're too lean.
If this ring extends half way or more up the porcelain, you're too rich, no ring means you're too lean.
I'll have to cut these up and take a look.
You guys weren't kidding. This really is a long and painful process. If I'm too lean after putting a #27.5 in for a pilot jet, and I know that raising my needle back up one notch would make me too rich, then I guess what I'd need to do is lower the size of my main jet and keep the needle in the middle until I see improvement with lesser jet sizing.
You guys weren't kidding. This really is a long and painful process. If I'm too lean after putting a #27.5 in for a pilot jet, and I know that raising my needle back up one notch would make me too rich, then I guess what I'd need to do is lower the size of my main jet and keep the needle in the middle until I see improvement with lesser jet sizing.
No need to cut the plug, just look down into it with a good light. You'll be able to see the ring if it's there.
Something you need to keep in mind while jetting carbs is that the 3 circuits overlap the one next to them and changing one affects that overlapped portion of the other. In the case of the midrange (needle setting), it affects both the idle to midrange transition area and the midrange to main transition area ......
Many times the pilot jet size will be fine - until you lean the needle a step. Then that leans the idle to midrange transition area, often creating a flat spot there, and requires a larger pilot jet to "fix" it.
Something you need to keep in mind while jetting carbs is that the 3 circuits overlap the one next to them and changing one affects that overlapped portion of the other. In the case of the midrange (needle setting), it affects both the idle to midrange transition area and the midrange to main transition area ......
Many times the pilot jet size will be fine - until you lean the needle a step. Then that leans the idle to midrange transition area, often creating a flat spot there, and requires a larger pilot jet to "fix" it.
You're referencing three circuits... I know there's a pilot jet and a main jet. Is the needle jet the slide needle??? I'm a lil fuzzy on that detail. I've known about three circuits in a carb for a while because I knew there was three main sections of change in air velocity and volume (and which circuit was affected.) 0% to 1/4 throttle is usually one, 1/4-1/2 is usually the second circuit, and 1/2 to 100% is the final one... Or something similar to that science... I'm gonna jump down the rabbit hole tonight to try and better understand the overlapping. What you're saying makes sense so far so I'm diggin' the lesson!
5twins has more experience than me with the BS38's, so I'll bow out on jetting.
I will say this though... any engine I've dealt with that will fire on choke, but won't run on it, is because it's too rich to begin with and adding the choke pushes it past the point of running. Simple logic tells me that if you're too lean, adding choke richens it so it should run.
So here's my question... If If it's lean enough to pop and sputter, why does adding choke make it die? When the choke richens the mix, it should run without all the fuss. And if you richen the pilots, what's the choke gonna do to it now? if it wouldn't run on choke when it was too lean, how's the choke react when it's richer to start with?
