Fresh bobber build, need carb help

[Capslocker]

Hi all, my build is finally coming together. I just fired her up and rode some 10 miles or so. It pops a little from RH side when iddling and at deceleration. Reving goes ok without popping. I must say I never rode an XS before so no clue what to expect. I have read the carb manual but I must say this is first time carb adjusting for me.
Engine has a fresh rebuild top end with Heiden tuning 750, new valve seals and a new (never used) pamco iginition with mechanical advancer. compression is +- 165psi each side. Open exhaust and velocity stacks. BS34 with still stock jetting, 3 full turns open. (Heiden tuning recommends 145 main, 45 pilot and 3 turns open) The floats are new plastic ones and are set to 22mm. This is what the spark plugs look like after 10 miles.

 

[Jan_P]

Nice Bike
I am No carb expert
Plugs a bit black but I would keep it for a while
The popping is often a leak on exhaust or intake ..spraying fex starter fluid around the intake re tightening after that first
Heatcycle ..nothing strange
I guess exhaust leak but was recently wrong it was an intake leak on another bike

 

[Capslocker]

Thanks! I must say I haven't changed the throtle shaft valves yet. It might be a good idea to do that as the carbs where not used for at least 8 years.

 

[Jan_P]

Those are difficult to get out ( throttle shaft seals )
Because of the locking compound on the angle bar screws holding the carbs together .
I would avoid that as long as possible
Sometimes things gets a little better after getting heat and oil on them if sitting --in a box for eight years.
Depending on how much it is I would wait probably all this season.
And perhaps all together .. But I am used to " C*ap " bikes
If no compromise on those one would not ride anything at all .Only be on the knees working.
But since it is only ten miles yet
I would at least wait 100 miles or 200 There can be things needing to settle like
Float valves and . So.
Do a recheck of ignition timing and re tightening intake bolts . and hose clamps

 

[hovel]

If those plugs were fresh when you started out, they now indicate you're running too rich. With open pipes and velocity stacks, just the opposite should be true. Aside, I'm a big fan of good (real) air cleaners and equal length pipes, open or not.

 

[WideAWAKE]

If it were me, I’d double check all my areas of air leaking (carbs, exhausts...)

as for those plugs - I wouldn’t read too much into them unless you did a plug chop.

if you drove around and then putted down the street to get home and pulled em and that’s what they look like ehh maybe rich down low or at idle, maybe it’s lean up top. Who knows?? Been my experience that a plug chop will give you useable info at a specific rpm range to dial in carbs.

 

[Capslocker]

So, Running those exhaust pipes and Velocity Stacks, instead of going higher in jets it's best to go down?
I'll go over the carbs en exhaust again to check for leaks

 

[Capslocker]

Okay. I just opened the carbs again. Turns out In the carb bowls I have a 132.5 main jet and 42.5 pilot jet. At the back of the carb where the airfilter goes I have a 130 jet. Also I noticed I have a adjustable needle with what looks like EJ51x11 but I can be 5Ix11 too. It was set in the 3rd notch and I leaned it to the 2nd notch (counting from top, like the carb manual says).
I also rechecked the float level and set it to 22mm. Please check pics, is this the correct way to measure and adjust floatlevel? For the popping, I believe I will need new boots if you see the pictures? Cracks and damage everywhere.

 

[Jan_P]

Yes to that
They are perhaps not leaking but ..it is best to replace once they are out

For the popping, I believe I will need new boots if you see the pictures? Cracks and damage everywhere.

I Also can see on the picture that there appears to be Hex head Screws holding the Angle bar between the Carburetors .
Not stock --- So they have been apart .and that makes the separating an altogether different story it can now be possible to do.
Should one go for replacing the throttle axle seals.

 

[5twins]

Yes, you need new carb boots. When I set these floats, I measure to the rounded part of the float like so .....

Measured and set at that higher flat area will make the setting richer. It also appears that you are missing the rubber plugs that go over the pilot jets. This will also make the bike run rich .....

These BS34 carbs are set up rather lean from the factory to meet emission standards. Usually any little change you make to the exhaust or intake requires re-jetting (larger jets). With your mods and stock jetting, your plugs shouldn't be black (rich) like that. If anything, they should be lean. I think the missing plugs over the pilot jets and having the float levels set too high (rich) are what's making the plugs black.

Correct all the above stuff and then I think you will need larger jets. I would go one up on the pilots (42.5 stock to 45) and at least 2 on the mains (to a 137.5) to start. Then you could keep experimenting with the mains, increasing them one size at a time, until you find what works best. You may not need to go as large as 145's, but only testing will tell.

 

[5twins]

I'll also mention that once you install larger pilots, you probably won't need 3 full turns open on your mix screws anymore. You will probably find 2¼ to 2½ works better.

 

[Capslocker]

Thanks for all the advice! I will change out the boots and re-adjust the float level. As for the rubber plug, there was a new one installed. It was just taken off for taking the photo.

What about the jetsize for the jet here? It says 130 and it goes in the hole where my thumb sits.

 

[5twins]

That is the air jet for your idle circuit and can be used to fine tune it. It has less of an effect than changing the pilot jet. You can probably leave it be for now. On mine, a 130 air jet and 45 pilot combination proved to be a little too rich so I installed a 132.5 air jet.

Your needle is a 5IX11 and set in the leaner 2nd slot from the top will probably be good once you install larger mains. Larger mains will bleed over into the upper midrange, making it richer, so leaning the needle setting is often needed when you install them.

You made no mention of removing and cleaning your needle jet, the jet the needle sticks down into and operates through. It has rows of tiny air holes down the sides and if they're plugged, the bike will run rich .....

My buddy's bike exhibited similar symptoms to yours. It was modded but still had stock jetting and was running rich. Even though he swore to me he had completely cleaned the carbs and replaced most of the parts, it turns out he didn't touch the needle jets. When I pulled them, I found them all gummed up and the air holes plugged.

 

[Capslocker]

Thanks for the help. I ordered everything I need new. When removing the RH exhaust it was obvious there was a leak at the exhaust seal. Probably the reason why it popped on that side. Got new seals inbound!

 

[Capslocker]

Right. Changed the boots and changed pilot to 45 and main to 140. Running 2.5 out. Still testing but biig improvement already. Popping is completely gone.

Next issue: glutch slips when driving slow in let's say 4th and 5th. When I floor it revs goes up but speed doesn't. I have:
- new 20w50 oil
- new long pushrod from heidentuning.
- excellent shape worm wheel
- 3mm Thick plates + steel plates are not bend.
- new clutch cable.
- hole aligned with Boss.

Went to YouTube and adjusted cable accordingly.

Setup is 1 ball in wormwheel + long rod + ball.
When engine is hot switching gears at low speed becomes harder. Funding neutral when hot is impossible. Am I missing a plate/disk? See pics.

 

[5twins]

The usual "fix" for a slipping clutch is new heavy duty clutch springs. It's pretty common for the original springs to get weak, probably because of their age.

 

[Capslocker]

Forgot to mension: new reinforced clutchsprings from heidentuning as Well.

 

[Jan_P]

What oil ?
- new 20w50 oil

 

[WideAWAKE]

How far do you need to pull in the clutch lever before the clutch engages??

 

[Capslocker]

The one sold at heiden tuning