1 is the loneliest number?

[davem222]

Hey all,
I hope you're all still healthy and happy. I have gotten my xs up and running. I am about to go through my carbs and re-clean them and re-set them because I THINK I am running only on 1 cylinder. Here are the reasons I think this:

1) feels like I don't have tons of power on accel from rest
2) feels like I need to stay in first even up through 20mph and down at 10mph it starts to sound like it's lugging.
3) when I turn the engine off, a gorgeous but disturbing puff of blue flame ignites from my 2-1 exhaust
4) I've looked at the plugs and one (the right one) looks kinda dark/covered in blackness.

Reasons I doubt the diagnosis of running on 1 cyl:

1) both sides feel hot after a 10 min ride.
2) tested spark plugs and they both fire (hence why I think it's maybe a fuel/carb issue if it is firing on 1 cyl)

What do you guys think?

Dave

 

[Bushyeyed1]

Need to rejet your carbs for the 2-1. I bet your rich on your pilot jet or needle. What kind of carbs do you have? And yes if your running on one cylinder you don’t get much power. If both sides of the header is hot then it should be running on both. You can bench sync the carbs and get close but need a vacuum tester to dial them in.

 

[davem222]

Heya Bushy. Thanks for the advice. I’ve never rejetted. I’m running the stock carbs on my 79 and I’ve got the mikes 2-1.

 

[Bushyeyed1]

Don’t ignore the ignition make sure it is adjusted before you go rejetting your carbs. If you had the bs34 carbs I would be able to get you pretty close, but I’m not familiar with the bs38 with a 2 into 1.

 

[davem222]

Gotcha. Good point. So do you think this is a good plan of attack: 1) check ignition timing 2) check which carb exactly I have 3) try to tune the carbs with ignition dialed in 4) if step 3 doesn’t work, then consider rejetting.

btw everyone: I am currently reading through the carb guides. It’s a LOT to get through but is amazing. Thank you to those who wrote it (who I think is 5twins and inxs? Am I missing anyone?). Either way: amazing. Thank you!

 

[davem222]

Plot thickens: looked at my spark plugs, which I guess I should have done first. Both are covered in dry black sooty deposits. My manual says that means the mix is overly rich. This squares with the beautiful blue plums of flame igniting from my tailpipe upon turning the engine off (unused fuel in the exhaust being lit by the heat of the tailpipe, I suspect). Here’s the rub: when running POF filters (which I am) and mikes 2-1, isn’t there more air flow? So wouldn’t rejetting generally be to allow MORE gas in to mix properly with the higher air flow? That’s odd, no? I suppose I’ll Check the timing and seek to lean the mixture out a bit first without rejetting first.

 

[Bushyeyed1]

I think if I’m not mistaken you have just got this bike running for the first time, but either way if not still do the following before you mess with jets. The very first thing I would do while the engine is cold is check and adjust your valves if necessary. Then I would adjust my cam chain while cold, but keep in mind you need to check it later after it is warmed up. Next check and set your points statically if you don’t have digital ignition. If you installed your own digital non-stock ignition check it with a timing light or if stock points check it as well with the timing light making sure they fire on the F and advance no further than the full advance mark. I would probably run the engine during these checks with the pod filters off. By the way what pod filters do you have? Some cheap ones block the air passages. I think you have bs38s if they are stock. I am glad you are reading the carb guide it will help with the knowledge you will need to adjust and tune them. Also go buy some new plugs and have a few extra. They are like $2 a piece for the NGK BP7ES and check the gap is between .028- .032 inches. You will need to jet for more fuel with the pods and 2-1 because they are flowing more air basically. The 2-1 has a weird spot around 4500 rpm where it is most efficient. I could only get my bs34s to work with the Heiden needle. IMHO it needs the longer needle for the cv diaphragm slide location at 4500 rpm. If you have VM slide carbs you may not need the Heiden needle. So make sure everything ignition wise is good before you fault and tune the carbs.

 

[5twins]

These bikes are so old and gone through so many owners, it's possible your carbs have been messed with and have larger than stock jets in them already. I would verify the sizes in there to make sure they haven't been changed. Here's a chart I made up showing the stock sizes .....

I would also check the needle and it's setting. It has 5 clip slots and can be set richer or leaner than stock (middle #3 slot). Also make sure the spacer and washers are in the right spots. The thick plastic spacer goes above the e-clip, plain washer under it. If they have been reversed, the needle will sit too high and run rich .....

 

[davem222]

You both are so kind to comment given that theres so much in those carb guides. Bushy, I am running aftermarket electronic ignition, and I will hi through your checklist. Merci! 5twins, thank you! I feel bad as I feel like you’ve repeated stuff from those carb guides. Seriously though, thank you. I’m going to check all of the timing and plugs (got new ones today Bushy! You were right. Total came to $4.37. My kinda price!) and then head into the carbs should I still have the problem. Based on what I’ve read from the carb guide already, I’m going to FIRST just try to lean out the pilot mix screw (they are definitely B38s) and see if that helps as I think the problem area is 0-1/4 throttle