Help BS38 needle jet leak

[zoomoto]

hey guys! Long time no see.

Wrapping up my winter build on my 1977 XS650 and have come across an issue i can’t correct for the life of me.

I’m running 78-79 bs38s btw (yes, correct internals have all been identified and replaced upon purchase of bike)

Started lean on my jetting after installing open side pipes and uni pods and couldn’t dial in anything. Contacted local gurus who have experience in similar setups who helped with recommended jetting but still couldn’t get her running right. Still too rich. The right cylinder (longest exhaust pipe) is dead and won’t even fire but still maintains strong exhaust pressure.

Compression test yielded 143 and 140 btw

I pulled off the pods to look inside to see why I was still running rich after setting my floats to 25 and was surprised to find this.

I had replaced the o rings on the nozzle and greased them as directed.

After discovery I tried the recommended yellow Teflon trick which helped seat properly. Took my time to get proper thickness around the o ring and removed excess to further ensure tight fit. I thought problem was gonna be solved.

Any other thoughts before I order a new set of nozzles?

Thanks guys

 

[zoomoto]

Anyone have any input?

What is the likelihood of the needle jet holes being bent by removal?

 

[Mailman]

I was going to suggest checking to see if the o-ring was good, but you said you’ve already installed new ones.
I dismantled a carb that had had the needle jet stuck in the body, and when I got it out, there was no o-ring on there at all. Is there any wiggle in that jet?
That’s all I got.

 

[zoomoto]

I was going to suggest checking to see if the o-ring was good, but you said you’ve already installed new ones.
I dismantled a carb that had had the needle jet stuck in the body, and when I got it out, there was no o-ring on there at all. Is there any wiggle in that jet?
That’s all I got.

Thanks for the response. Yeah, there is wiggle in the emulsion tube. I bought a harbor freight kit cause the local hardware store didn’t have that size o ring. The 4x1 o rings were a little loose on the groove in the needle Resulting in damage upon insertion no matter what I did. Tried 3x1 and that was a good fit on the tube but clearly more loose.

 

[zoomoto]

The 4x1 made for tight fit though with no wiggle. Video is of 4x1 o ring

 

[zoomoto]

I wonder what the likely hood of a stretched hole is.

There’s a set of the correct carb bodies on eBay right now that sounds enticing

 

[Mailman]

Yeah, I couldn’t tell you what the likelihood of that is. Maybe some of the more experienced carb guys might have seen that. I did have to swap out a carb body once that had wear inside from the butterfly , that caused an air leak.
So I can see how you might think that. But there might be an easier less expensive fix, I’m just not aware of.

 

[zoomoto]

That’s what I’m hoping for! Hahah

Thanks a ton, Mailman

 

[Mailman]

You bet. Good luck, I hope it’s something simple.

 

[zoomoto]

Here’s an update. I turned petcocks off after allowing them to fill.

There’s maybe a third of the gas that there was before in the throat.

Also lapped the old float needle and seat with toothpaste and installed that.

 

[zoomoto]

The replacements that were in there seemed to be knock off replacements. Originals I had sitting around we’re Mikuni.

Also. Dead right cylinder came back at 2500rpm. Issue in pilot circuit??

 

[TwoManyXS1Bs]

Hey, Mack.
Found a couple of threads with similar issues.

http://www.xs650.com/threads/emulsion-tube.41756/

http://www.xs650.com/threads/bs38-needle-jet-leaking-w-new-o-rings.50143/

This is one of those situations where I'd really rather have the carbs in-hand, or be on-site. Maybe some close-up pics of the hole in the carb body, where the needle jet (emulsion tube) fits. I'd be wanting to use pin gauges to measure the holes' diameters, and the emulsion tube diameters, compare to known good parts.

Aside from that, grasping at straws, all I can think of is fuel level. Setting float heights is a documented procedure, but to confirm the setting sometimes requires doing the "clear tube method". A good indicator of incorrect fuel level is if things get better when the petcock(s) are turned off while the engine is running.

There *are* aftermarket floats that'll make the fuel level too high, because they're thinner than the OEM floats. Been watching for signs of these showing up.

http://www.xs650.com/threads/cruzinimage-bs38-carburetor-floats-review.51657/

 

[peanut]

Interesting video ...... needle jets should be pressed out ideally.... not yanked with pliers or wiggled out etc.
Surely a new set of needle jets would be a cheaper and better alternative to try than an unknown used pair of carb bodies ?

You're going to find it a lot easier if you split the problem up into throttle positions rather than trying to tackle all of it simultaneously.
Convention is to split the throttle up into 4x roughly equal quadrants .
I always start with the idle mixture as this influences the mixture right through the range from idle to 3/4 throttle and also deceleration and throttle response too. The idle mixture is a crucial factor in protecting against burnt pistons during decel as well

Get the idle right on both carbs first would be my advice but others will probably disagree .

 

[zoomoto]

Thanks for the input guys! Going through the list and marking off stuff as I check it.

Did the clear tube test and have pics of 10 minutes in shown below.

 

[zoomoto]

When I put this pair of floats in they had come from a set of carbs I picked up from a swap meet. They looked untouched. Carb bodies were gross though, hahah. Managed to get a few parts off of them though!

I set them in vinegar to clean them. Dunked several times. Checked seams. No bubbles no fluid inside. Set to 25

 

[zoomoto]

What I might do after this is pull the needle jets and test them in my older style carb bodies I had cleaned. If the needle jets fit right, carb body is to blame. If they are loose in the other bodies they may be the Issue.