Help - Won't Run/Miss on 3 and 4

[Laptop_geek]

I've been chasing a gremlin with my bike for a really long time now and have finally decided to take it to you guys. I've had my bike for about 14 months now and haven't been able to ride it very much at all do to one problem or another (some problems related to the bike, some not). This latest problem seems to be with the fuel system, here are the symptoms. My bike is very difficult to start, I have to choke it and give it a couple squirts of starting fluid in each carb for it to even think about it. When I finally get it started the #4 cylinder wont hit at all and #3 will only hit about 25-33% of the time. I am afraid to try and get it really warmed up to see if that changes anything because it runs so bad, but I have got it warm enough that when I spray water on the 3 & 4 exhaust headers, #4 wont do anything, #3, will sizzle a little but, and #2 & 1 evaporate immediately (or at least very quickly).

Here is what I've tried so far:

Bought a new tank - has very little rust inside (just a little from sitting)
Checked for spark several times on all cylinders (using different methods) - all have good spark at the plug
Shimed the valves - only one was in spec at the time, all are good now
Replaced the battery and replaced some burnt wiring (that's the reason the PO was giving for selling it)
Replaced the fuel lines - I had to use auto lines as I am having great difficulty finding motorcycle specific fuel lines
Checked the wires under the left cover (I'm forgetting what these are called, pick-up wires?)
Checked that the cams were in sync
Taken apart and cleaned the carbs countless times - I've cleaned them, set the floats, cleaned the choke circuit, etc.
Checked the compression - I didn't get solid numbers for all four, but they were all above/around 140 or 150
And I know I'm missing some stuff that I can't think of at the moment.

I can't think of anything more to do, every test I do says that its fine, but it still wont run. Any thoughts would be greatly appreciated. If nothing else it will get me or someone else headed in the right direction.

[bikerphil]

Do all the bowls have fuel in them? You can open the drain(s) to confirm this. If no fuel, might be a problem with a plugged/inoperative petcock or kinked fuel line. How long ago did you clean the carbs? Did you clean them properly by removing every jet, most importantly the pilot jets?

[Laptop_geek]

Do all the bowls have fuel in them? You can open the drain(s) to confirm this. If no fuel, might be a problem with a plugged/inoperative petcock or kinked fuel line. How long ago did you clean the carbs? Did you clean them properly by removing every jet, most importantly the pilot jets?

Yes, every time I've drained them they all have about the same amount of fuel in them. I have converted it from a special tank (PO put it on there) back to a standard tank (using different petcocks of course) and the issue still persists. When I cleaned them I took out every jet, checking the jet, cleaning it if need be, then replacing them. I've done this everytime I've cleaned the carbs.

When I first got the bike I took off the carbs to clean them as it had been sitting for about a year with gas in it. When I did that I took off everything but the butterfly valves and soaked them in pine-sol, then cleaned them and put them back together. Could this have something to do with it?

[Petersg_99]

I know 3 & 4 don't share coils (I think the coil packs are split with one coil for 1 & 4 and the other for 2 & 3), so it's a safe bet it's not the coil.

The one thing that cylinders 3 & 4 do share is the fuel supply, but you said that you've got fuel in the bowls of all 4 carbs.

You know, I was just thinking, you know you've got spark, but what if you got the plugs wires for 3 & 4 swapped? You'd still have spark, but you'd be getting the spark at the wrong time.

Just thinking out loud...

[mack]

Fuel supply

It sounds like a fuel supply issue. Check the screens on the right side petcock first. Easy way is to just pull the line off the petcock and check the flow rates from side to side.
I see you have a 79, so i assume you have the older carbs. These carbs have both fuel and vent t's, when you cleaned the carbs i gather you didn't split them apart. The vent t between 3&4 may be plugged. You should also look closely for a kink in that line. When the tank is sitting up a bit they look ok, but when you drop the tank down into position they can kink right at the petcocks.

[Shamus]

Xs1100g1980

Hi all

Just signed up, looking forward to all interaction in this club have watched a over number of years and enjoyed some of the issues brought up and can say assisted me no end. I have neglected my poor XS but time to get things going again, but just paging through posts and need to add to this!
Have had my XS since 1984 and have not ridden it much but over the past 5 years noticed small flooding problem when off and returned to garage intermittent though then started firing intermittent on 3 & 4 Cyls on startup and seemed to come good after few minutes - felt possible due to fuel problems old fuel as sometimes not ride for 6 months, until cylinders 3 20% & 4 not at all!
Due to illness in family gave bike to mechanic and that was waste of time and $1500.00 as after 300klms cylinders 3 & 4 started to fail again and refer photo. (hope works) lol, have now given up with mechanic start working on it myself bring bike back to spec.
Have purchased to new pet cocks - Grrr only one side obtainable but will refurb old ones!

[bikerphil]

Matt, you said you switched to a Standard tank which has vacuum operated petcocks. Have you checked to make sure they operate properly when vacuum is applied? Try running them in the prime position to bypass the vacuum function. As Mack suggested, check with your own eyes that fuel is flowing sufficiently from each one. If you have inline filters, make sure they are pointing in the proper direction and not plugged. All I can think of now, GL

[TopCatGr58]

Oh boy...where to begin!

Okay, You said you cleaned with Pine Sol....was this WITH an ultrasound unit, or just soaking? If just soaking, then it probably wasn't enough to really get to the small pilot jet passages of the carbs. And the fuel is flowing adequately thru the petcocks because the float bowls are full when removed, and they aren't flooding/leaking, so the upper Vent T's are probably not clogged.

The hard starts are probably also due to the Start/enrichener/choke jet in the float bowl that is clogged....or the enrichener circuit in the carb is clogged. Have you seen the carbs 101 tech tip/thread??

You've got good compression values, but that doesn't rule out a vacuum leak! Did you take the intake boots off? They can harden on the engine side, crack/flake, etc., and develop a leak there. Either using a gasket, or variations of the Yamabond/grey stuff can help make a good seal when you put them back on. Also, the synch port rubber caps also harden and can leak, so even though they are in position, they can still leak!

Hate to say it, but you probably need to pull the carbs, disassemble removing all of the jets, and get the carb cleaner spray, goggles, and ensure that the cleaner will pass thru the pilot jet tower....to the pilot jet screw port, and the little orifices in the upper front engine side of the carb throat.

Soak the metal bits in real carb cleaner, then use tooth brush on jets, main jet EMULSION tube....it comes out up thru the carb body once you remove both the main jet, and the vac. slide...you did remove that in your previous cleanings didn't you?? Spray cleaner into the hole in the float bowl and you should see it spray out thru the pressed in jet in the bowl...if not, use a fine wire to poke thru the jet, and down in the bowl lip hole, SOAK in cleaner, REPEAT until you can get it to spray thru....until then, your choke/enrichener will NOT WORK!

MC fuel line can be lawnmower fuel line...most auto parts stores sell small engine supplies...1/4' ID. Also, volkswagon line is supposed to be single walled vs. the fat/thick double walled auto line!!! OR..visit your local MC shop and buy a few feet from them.

T.C.

[Laptop_geek]

I've had the coils off when I was doing the valve shims, made doubly sure that they were in the correct way.

Sorry for not mentioning it earlier, I have the later carbs on it right now. I do have a set of early carbs that I'm working on though.

Everytime I've taken apart the carbs I've made sure and cleaned every passage with carb cleaner and compressed air. When I soaked them in Pine-Sol I took all of the jets/small parts out of the bodies (except for the butterfly valves) and cleaned each and every small port, if I couldn't get it cleaned out I took out a small wire and was able to get it unclogged. I just recently cleaned the choke circuits, they all were a little clogged and that did seem to help a little, but still no start.

The intake boots (from the carbs to the head) have been replaced by the PO. They don't show any cracking inside or out. I have also replaced the vacuum caps on the sync ports with new ones with the exception of number 3, that one looked fine.

I checked the petcocks for flow. I hooked up a vacuum pump to the vacuum port them gave it a little vacuum and they both flowed very well. I have inline filters, but haven't put them on yet as I didn't want to add extra variables until I got it running.

As far as the fuel line goes. One of the many times I've checked my carbs, there was some small pieces of rubber in there, but nothing in the valve seat screens, and none in the jets. In fact, the jets have been clear everytime I've checked them since I cleaned them the first time in the beginning of the summer (with the exception of the choke pickup in the bowl).

I actually just had the carbs of yesterday and swapped the CV slides from 1 to 3 and 2 to 4 to see if that changed anything, but wasn't able to get it going to see if that made a difference, then I got cold and made a post here.

I have been starting to think it is a vacuum leak also, as I've checked everything else I can think of, but I'm still not quite sure what else I have to check for the leak. I guess the next step is to take off the 3 and 4 intake boots and reseal them to see if that makes a difference. Hopefully I'll be able to do that soon. Any other thoughts?

[Laptop_geek]

Oh boy...where to begin!


Hate to say it, but you probably need to pull the carbs, disassemble removing all of the jets, and get the carb cleaner spray, goggles, and ensure that the cleaner will pass thru the pilot jet tower....to the pilot jet screw port, and the little orifices in the upper front engine side of the carb throat.

Soak the metal bits in real carb cleaner, then use tooth brush on jets, main jet EMULSION tube....it comes out up thru the carb body once you remove both the main jet, and the vac. slide...you did remove that in your previous cleanings didn't you?? Spray cleaner into the hole in the float bowl and you should see it spray out thru the pressed in jet in the bowl...if not, use a fine wire to poke thru the jet, and down in the bowl lip hole, SOAK in cleaner, REPEAT until you can get it to spray thru....until then, your choke/enrichener will NOT WORK!

T.C.

BTW: This is how I've cleaned/checked to make sure they were clean every time I take them off.

[skids]

OK, you hooked a vacuum pump to the petcock to see if it flows. Did you open the float bowls when you did this to ensure that the flow goes all the way to the carbs? (use a tray to catch gas).

[Schming]

[QUOTE] Replaced the battery and replaced some burnt wiring (that's the reason the PO was giving for selling it) [QUOTE]

What, exactly, burnt and why ?

[yamtom]

three tiny holes near the butterfly

You may have mentioned this, maybe not, but there are three very tiny holes near each carbs butterfly that must be open. I also had a float bowl passage that was clogged, I assume that you ve got that though since its visible. Hope this helps.

[oldyam80sg]

I get my fuel line (yellow Tygon) off of E-Bay as my local Home Depot doesn't have it.3/16" ID X 5/16" OD is the size.I get it from all season parts plus.I think it took a week to get it during the holidays.

[Laptop_geek]

I have been checking those little holes, but I don't remember where they come from. Anyone know?

Thanks for the eBay reference. I'll order some line tonight.