evans_search
XS650 Enthusiast
I didn't think you were serious at first but then I read some other posts and now I think you actually are serious. No mice by the way.
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Bike starts up idles on choke, dies with choke off our when warm
- Thread starter evans_search
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- carburetors electrical
I didn't think you were serious at first but then I read some other posts and now I think you actually are serious. No mice by the way.
littlebill31
Smells of Raw Fuel
Do you remember what size pilot jet is in there? main jet size?
Stock exhaust?
Stock exhaust?
have you bench synched the carbs?
jd750ace
Front Toward Enemy
You didn't say as much, but how is the float height? Is the air bleed and the atmospheric vent to the float bowl open? It's still not fueling correctly by the sound of it, but you have eliminated the air leaks at this point, which is good.
evans_search
XS650 Enthusiast
Everything is bone stock. Although I'm thinking maybe I should get some new pilot jets that are a bit larger and a new jet needle that is adjustable. On the 1980 bikes they are not adjustable. According to the Chart that 5twins put together here are the stock specs for the BS34mm Carbs and components.
Main Jet:132.5
Needle/Clip Slot: 5HX12 Fixed Clip
Needle Jet: Y-0
Pilot Jet: 42.5
Mix Screw setting: Factory Preset but runs best at 3 to 3.5 turns out
Float Level: 27.3 +/- 0.5mm for brass floats
MISC: BS30-96 Style Pilot, All Pilots in 40s are this type, 80-Brass Floats 81-on plastic floats
***All BS34's have a removable air jet (#135). A small round type main is used for this.
evans_search
XS650 Enthusiast
Not sure what you mean by bench sync but I did adjust the sync screws between the carbs and eye balled how the butterfly's in the throttle body open and close. They open and close equally as best as I can tell. other than getting a sync kit I don't know how else to get this any better. Is that what you meant by bench sync?
evans_search
XS650 Enthusiast
I reset the float height on the brass floats to 27.3mm +/- 0.5mm. I'm not sure what you mean by air bleed and atmospheric vent on the float bowl being open. I will read up on this today so I can get educated on those parts of the carb and double check. Thanks again for all your support everyone!
Synch is critical, a very acurate bench synch can be done by looking through the bores at a light source. Adjust idle speed screw till left side is just barely open, tiniest sliver of light you can see, adjust RH to match. Fiddle till you are sure they are the same. then add a turn or two of idle speed, install. search home made manometer on here for a cheap on the bike synch tool.
Did you know that BS34's have a tiny filter screen located above the float needle seat? The o-ring that seals the float seat to the body is often (always) bad, hard, brittle, cracked.
Another way to check what you see is to place a narrow(1/2-3/4") strip of paper under the butterfly. Check for the same or close amount of drag when you pull it out.
You may need to back off the idle screw for this.
evans_search
XS650 Enthusiast
That's a really good point. When reading the Carb manual by 5twins it mentioned the O-rings being worn and the tiny screen. One of the first things I did on these carbs was a carb rebuild kit. I replaced the o-ring seals you are talking about but I didn't see a screen. Is the Screen inside the hole of the brass piece the O-Ring goes around or is it inside the chamber where the Float needle seat goes into? Either way I didn't see a screen anywhere. Should I be putting one in there? I gather that a lot of problems happen with this screen because the holes are so small and it gets clogged often.
Scrambled
Motorcycle Man
I got fed up and sent my old BS 38s down to Oldskoolcarbs today. Can't wait to get them back , should be about 2 weeks .
jd750ace
Front Toward Enemy
I use #40 drill bits to bench sync the butterflies, essentially in the same manner as the paper, except I pin one at BDC on the master carb barrel, then adjust the other one for medium drag at the same position in the other. All good stuff. I used to eyeball them, but for some reason felt I needed some form of feeler gauge to get closer, even though they always get the sticks.
littlebill31
Smells of Raw Fuel
I would still check them. If the blind plugs were not covering the mix screw (even if they were), after 30+years, there is a really good possibility that they have been messed with.
I've found some really messed up stuff in "bone stock original" bikes.
Well if the screens aren't there it means a PO has been in these carbs and all bets are off as far as adjustments correct parts etc. No big deal one way or the other. I like 'em and keep them as a last defense against junk on the float seat.
Did you check the vacuum diaphragm on the petcock?
littlebill31
Smells of Raw Fuel
As a note, I don't think I have ever seen the little filters for sale as an aftermarket part. I've collected tons of them and tried, sometimes failing, to remove them without snapping the plastic.
evans_search
XS650 Enthusiast
gggGary, thanks for the reference and I will totally put together one of these homemade manometer tools. However, I have a larger problem to deal with first. Those screens covering the float needle seat have been removed and that means a couple of things. I'm not sure i understand that you mean by a "PO" being in these things but it means they have been tampered with. I have not checked the vacuum diaphragm on the petcock yet. It's on my to do list.
evans_search
XS650 Enthusiast
So those screens were NOT on the seats. What do I do from here? Do I get a jet kit with all new jet pilot and main jet components and just rebuild the entire thing? Here is a pic on what it looks like.
I apologize for the dog hair on the towel. We have two back labs and they are shedding this time of year!
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jd750ace
Front Toward Enemy
I check the vacuum with a syringe and a piece of tubing. Also how I operate my fuel valve while synching carbs, for those without a test tank.
