carbies ignition?

[yamtom]

Hi Guys,

I cleaned the carbs on the sf last week, put them back on, put the plugs in, and after a bit of coughing it started. It seems to run ok on the stand, that is it sounds fairly good with just a bench synch. All plugs fire when out of the cylinders. Number four is not running right, I switched the number four plug with number one, still doesnt run on number four as per my laser thermometer. The right side backfires thru the pipe now and then, and the exhaust smells gassier on that side. I did check with propane by running it into number four carb and it made absolutely no difference. I did clip the plug wire back a quarter inch at the connector , exposed fresh metal, gave the connector, wire and plug a bit of elec cleaning spray, makes no difference. I did set the floats a little higher this time, only twenty thousanths though, since the plugs were carboned looking. The bike is sitting on the sidestand, that puts number four up higher than the rest of them, obviously I will put it on the centerstand first off to see if that makes any difference, and put a new plug in number four for good measure. I think Ive got to clean the carbs out again, what think yee? Any body have any better ideas?

[DGXSER]

So only #4 is giving you problems. Does it clear up and run better at higher RPMS? I would adjust mixture screws in 1/4 turn before moving the float heights. How many turns out are you on the mixture screws now?

When I did my first set of carbs for an XS11, I had a similar issue. #1 would foul out a plug at idle, clean up and run ok above 3K RPM. What I eventually figured out was that when I pulled the needle out of the carb slide on my newer style carbs, I put it back together in the wrong order. I had the spring UNDER the needle keeping it elevated instead of on TOP of the needle holding it down. This caused the carb to be VERY rich at idle.

Otherwise, check your pilot air jet is clean and clear. Also, are the PODs new? Do you have velocity stacks on them?

[yamtom]

hi Don

Hi Don,

I have the original carbs , the old style with the screws covering the pilot jets. I did clean out the air jets real good but will check them again, who knows maybe there is something blocking that one. I did not pull the needles, and the last time I ran the bike, it ran just fine. The fuel screws are two and a half turns out, and I will adjust them this am to see if it makes a difference. It does SEEM to run ok at higher rpm on the stand, but I havnt tried to run it under load, and I know, if its on three cyls, thats where the proof will be. It does SOUND OK even at an idle, but the thermometer says the pipe is staying stone cold, even though the pipe feels warmer than that, so maybe I better take the bike off the stand and see if there is power there even though the thermo says that cyl is dead cold. Re the pods, I dont have them on the bike, the last time, they worked fine with or without the pods. Actually those pods were stolen last year so I have to buy some new ones. I did not have the pods on the oem velocity stacks at all, just attached to the carbs, when I did have them on. So my plan of action, is to, check the air pilots to make sure its still clear. Adjust the fuel screw in to see if that improves it, just check the pipes with my hand to see if my thermo is lying to me, and try a new battery in the thermometer just in case. Put the bike on level to see if that cures it, tap the carb bowl with a screw driver in case the float is sticking, and lastly, take the bike off the workstand and ride it in the parking lot to see if it has normal power instead of just three cylinder power and to open the throttle while riding to see if its just the pilot circuit. If anyone has anything other than that, send it on in.

[yamtom]

I should add,,,,,,,,,,,,,,,,,,,,,,,,,,,,

I should add, that I did add some rubber to the diaphragms for all the carbs, there is one, that I had to put a little more on than the others, perhaps I put too much rubber on that diaphragm, will have to check it, and I think I have an extra diaphragm here if I need it. Would a too stiff diaphragm hold the needle up at idle? I put a max of three very light coats on the one diaphragm, the others a little less.

[DGXSER]

One other thought Tom, did you bench synch the carbs? Make sure all the butterflies are equally open? I just finished the work on the carbs for my GSX600. When I first fired it up, no 1 was stone cold, no vacuum on the Carbtune, nothing. Checked for spark, had good spark. Took the carbs back off, realized I forgot to bench synch. Performed the bench synch, and wahlah!! Vacuum and power on no 1.

[yamtom]

yes I did bench synch, the Todd method

Hi Don,

I did bench synch using the Todd method, it seemed so easy, but Ive never used that before, and if I do end up taking them back off, I will go back to the other method. Thanks

[DGXSER]

I believe the Todd method is using the carb holes to make sure they all cover the first hole evenly. That method is fine, that is how I did it on my GSX600.

[yamtom]

the method

Yes, it specifies that the tiny hole in the roof, should be covered exactly half way, and thats what was done, I only needed to make one very small adjustment to get it there in that spec. The carbs were previously vacuum synched and I will be doing that again when I get this problem solved.

Its great to have you on the other end Don, thanks. Now I better git down there and git this stuff done. Its sposed to be ninety degrees again today, but we have clouds now, so its only seventy five here, youre three hundred miles south, so you prolly have something similar.

[DGXSER]

It has been scorching hot lately. Was on a roof of a building most of yesterday, no fun at all. Good luck with it Tom!

[MPittma100]

Had the Same Issue

Once upon a time I had number one cylinder "cold" with the heat gun at idle. Took too long to warm up enough to be ready to ride also.

Turned out to be a hanging/sticking float. Wasn't sure what it was hanging on - maybe the bowl gasket. I took it back off and trimmed the gasket. Went ahead and replaced the float. Been over a year now and still running like Yamaha said it would.

MP

[yamtom]

so far, whats done and results, 3 tiny holes in throttle bore

Hi,

I know the air pilot jet is clear, it returned cleaner out the back end of the carb. I adjusted the fuel screw, and four runs best at two and a half turns out. I sat the bike totally upright on the stand, that didnt help. I tapped the carb bowl, no improvement. Number four is running some, but by water spray on the pipes, it is still a little cool. The other three steamed off instantly, number four, not so much. I changed the battery in the temp gage, and now number one and number four are showing about fifty degrees cooler than two and three after three minutes of running, so I will check coil connections next as well as the specs for the primary and secondary on the coils. Number one still steams off the water instantly, so I have to assume that its just the end cylinders not heating up as much as the middles.

I took the bike off the workstand, and rode it in the parking lot, at wide throttle openings it jerks forward like it should, just doesnt seem to want to idle, in fact the idle is worse now, in fact, the throttle has to be winged to keep it running at low speeds. This morning it was idling fairly decently before I started this. I pulled the carbs, hey this is getting a lot easier, haha. Also I found the pods that I thought were stolen last year in another part of the shed, right where I left em.

I will do the triple clean again with the carbs, do the bench synch the old fashioned way with bread wire ties and try it all again. QUESTION, just where do the three tiny holes communicate , I know that one at least is the fuel screw and that is the one right forward of the throttle plate, another one is the ,,, enrichener if I am thinking correctly, just what part of the carb does the third tiny hole communicate with.????
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[DiverRay]

Try running at about 3,500RPM for a minute, then check all 4. (don't forget a fan!) If they are close to the same, the pickup coil wires need to be fixed. BTDT

[yamtom]

pickup coil eh,,,well yes,,,

Hi Ray,

Well thanks for the reminder, both my elevens need the pickup coil wires done, I had forgotten that since I have been sick for a year and a half or so and basically did nothing with anything. Since Ive got the carbs off already, I am going to take number four carb apart and see if Ive done something wrong, then I will do what you said, but I know the pickup wires in both those bikes are bad. I already have bought the materials for fixing them. I had never had trouble, except once in a great while,, maybe once every fifth time I would ride it, it would do the hiccup, then catch again. They would have the symptoms, but it was so rare that it didnt really bother me.