shift/cold pipes

[usmc_scott]

My bike is coming along sloooowly but surely. Now iv ran into a few problems. The worst bein that when running for a minute exact. Then shut off the number 2 and 4 pipes are cold and 1 and 3 are hot like they should be. Also when I was testing I shifted from nutral to first just fine scooted up the ally and back then went from nutral to second then back to nutral. Then when I shifted to first it made this god awful grinding as if I wasn't holding the clutch or something. Then I went up to 2nd gear. Same thing. Then back to first and it clunked hard into gear. But after that it was normal again. It is normal for these bikes to "slam" into gear right? Like a tractor or whatever? And as for the ehaust what should I check if I'm getting spark?? Important- I noticed the number 2 carb coughing/back sputtering a mist of fuel. When I put my hand infront of it I feel the fuel being spat on my hand.....HELP!!!

[DGXSER]

The most likely issue with your exhaust is the carbs. Fuel is paired 1-2 and 3-4. Spark is paired 1-4 and 2-3.

Yes, it is normal for these things to shift clunky and loud. And shifting while riding takes a firm effort and not just a tip of the toes like some bikes.

[usmc_scott]

well what do i have to do to fix the carb problem? but i dot think its that because like i said the cold pipe number 2 carb coughs a mist of gas you can barely see but can feel when it backfires

could i swap the boots? put the left side plug bootson the right and right on the left? or would that mess with the timing?? that would eliminate bad coil possibility if i can do that

[DGXSER]

If your wiring is correct, and it should be or it would run like total crap if at all, one coil fires cylinders 2 and 3, the other coil fires 1 and 4. Since your having issues with 2 and 4 it would be very unusual for it to be electrical. I am not sure how it could be, but TC has explained a theory before of how it could happen with week spark.

Carbs, well, they can be a real PITA at times. Just when youthink all is right, something isn't, but then once you get them sorted, they should work fine for years and years.

[petejw]

not sure on your model,
but if you have the early model carbs
they are prone to have the mixture screw
tips break off.

[usmc_scott]

damn a broken screw would really pizz me off! they dont seem cheap or easy to fix

[petejw]

what model have you got?

[usmc_scott]

79xs11 special

[petejw]

k,
id start with looking at the mixture screws and
going from there, there not that hard to snap off
unfortunately.

[MindWebs]

sparky...

HMM.. ??? he said pipes 2 and 4 are cold.

that is coil or pick-ups for those cylinders.

find out if you have good spark on those cylinders.

then you will want to check the carb sync.

carbs that are not fully sync'ed can and will pop and burp and backfire.

sf's are ficle creatures... but hopefully you can work though it. (79 xs11 special are SF)

they ride nice. and got the power.

[Crazcnuk]

Also, make sure you start with new spark plugs. I found this out the hard way.

I had 1-2 not firing at all, went through the fuel system, checked the p/u wires etc.

All was good. Put new plugs in and voila all 4 running!

[ninjajim]

To me, it sounds like the carbs if you are getting spark in the cold cylinders. I'm not going to try and play the expert here, most of these guys have been working their bikes longer than I have, But I'm 30 years with these things and 20 with my current MNS.
What I have found, is that the channels in the bowls need to be completely clean. The one in particular is the one that seems to channel through the bottom of the bowl and to one of the sides. That channel being the slightest plugged will cause the cylinder to starve from fuel and not run. I had my carbs off several times before I realized where the problem lied.
Yamaha made (not sure if they still do) some really good carb cleaner. It came in a white quart bottle and they suggested to mix it with gas 50/50. An old Yamaha mechanic friend suggested I buy it, but don't mix the way it says, rather 50/50 with the cleaner and boiling water. That solved my problem. You need to let it soak, possibly overnight and you may need to do it a few times depending how bad the gum is in the bowls.
I have a friend with and XJ750MK MNS that is suffering the same problem. That's my Saturday project this weekend.
It's easy to see if you have all the jets cleared in the carb body, just make sure those in the bowl are clean.
Don't forget to add Sta-Bil when you store it and allow it to flow in to the carbs. I put it in my bike before storage 2 years ago and no issues when I fired it up this year to my surprise. Bone-headed move not running it last year, but that's a separate issue.

[ebock112]

if fuel is spitting back out the carbs it sounds more to me like you got bent intake valves in 2 and 4 also because cylinder 2 and 4 both come up at the same time on the compression stroke

[Crazcnuk]

The 78E I am working on right now, would fire up fine when the weather was cold. The other day it was 30C out and it would not fire at all.

I pulled the plugs and I was getting spark, but it still wouldn't fire. I cranked it for about 1/2 hr and got maybe 6 sputters.

I put 2 plugs in from one of my other XS's and it fired, up on those two cylinders. Once I got it running smooth, I put the two plugs back in, and took it for a ride.

It was sputtering, and hesitating, like it was running short of fuel. However, I had already cleaned these carbs very thoroughly, so I was pretty sure it wasn't the carbs.

A couple days later, after doing other things, I took it out on the highway and it was still not running on cyl 1-2.

The next day, I tested the petcocks, had good flow. Took off the fuel hose to that side and blew through it. I actually dislodged on of the floats, which I noticed in a few moments.

In the meantime, I pulled the plug from #2 (easiest with the fairing on, tank off.

Cranked it and was getting spark, not strongvbut steady. I also noticed fuel spitting out through the spark plug hole, and then out the exhaust pipes, and the air cleaner box.

I tapped the float bowls until the overflow stopped. Went and bought 4 new plugs, and it fired up instantly and has been running on all 4 since.

Unless there was a blockage, right at the T, and I managed to blow it right through the seats, It had to be the spark plugs.

[usmc_scott]

Well I have spark! So...next step will be new plugs all around because I know its getting fuel. It mist out thru the plug hole into my face :-(