White plugs, New guy

[Salboy]

Hey everyone,I'm new to the site and enjoy it very much.I bought a 1979 xs 1100sf in great shape and low miles.Did'nt run right.Bad idle,hesitation,popping you know.That's why he sold it.I removed and cleaned carbs,set floats(two where way off).It ran much better,but still a bad hesitation from idle to 3000rpm.Took the carbs off again and found the pin hole in the tip of the pilot jets was pluged in at least two carbs.It ran great,it has a 4-1 exhaust and stock air box for now.The point is I installed 145 main jets up from stock 137.5 and the plugs are WHITE.Checked for vac leaks and found none ,timming ok ,it runs great just a little lazy at low rpm.The only modification I did so far is dyna coils.Why so white plugs? I just don't want to cause any damage.From what I read 145 should be more than enough.

[Ivan]

I had a terrible hesitation like you said on my 4-1 exhaust with a straight through cherry bomb muffler. Top end was incredible but the hesitation was terrible.

I had some success changing the pilot fuel jets, but never cured it entirely.

The fix came in a set of jardine spaghetti pipes, which were much quieter and increased the drivability ten fold. Once I got the jetting set right, they nearly performed as well as the cherry bomb and are much more quiet.

I think the backpressure has a bit to do with that, even though it confuses me, since it is a 4 stroke. You might check your exhaust for a complete baffle. Every exhaust I have bought, save the Jardines, has had the baffles torched out.

As far as your plugs being white, you may check your needle clip position, as most all driving is done in the mid range, and not at the top end. If your needles are set low, it could cause it to be a touch lean. In the real world, plug color depends on several other things than mixture. Additives in the fuel, heat range, and such cause different readings. If your scoot sounds happy and isnt getting hot or detonating, it probably is happy. Also, if you are getting a grey/white build up, that is usually an indication of leaky valve stem seals, which are more of a nuisance than a problem.

[TADracer]

Are your plugs in the stock heat range? If you are running a plug with a higher heat range they could be burning white while everything else is dead on.

Your machine should be running NGK BP6ES (or equal) plugs. BP5's are a higher heat range.

[dbeardslee]

Salboy - Main jet size of 145 sounds about right for your setup. Where are your floats set? They affect lean/rich conditions through the entire rpm range. On a 79, assuming you have the original carbs, they should be set between 24.5 and 26.5mm measured from the gasket seating surface, with 26.5 being leaner, and 24.5 being richer. When you set them you need to use a gauge that hangs over the floats (I personally like a carpenters square for the operation, but there's a bunch of ways to make a gauge) and they need to be set on both sides of the floats. When I do mine I set the carpenters square to the measurement I want plus one mm. I then adjust the floats so I just see about 1mm of light between my gauge and the top of the floats. You don't want the gauge actually touching the floats as they are very easy to push down with the gauge yielding a bad reading.

Also, when you cleaned your carbs did you remove the emulsion tubes and clean them? Kind of goes to what Ivan was saying about the emulsion needles. The tubes and the needles work together, so both the height of the needles and the condition of the tubes need to be correct. You also want to make sure the small jets in the bottom of the bowls are clear - a problem below 3k can often be due to a plugged enricher circuit.

[Salboy]

Thanks for the help!I'm using stock plugs.Floats are set at 25.5.I'll try 24.5.I was wondering how the emulsion tubes are removed?Should I also try going up 1 size on the pilot jet.

[dbeardslee]

Salboy - To remove the emulsion tubes you have to remove the main jets as well as the slide diaphram assembly. The end of the emulsion tube is what you screw the main jet into. Using a wooden dowel of the appropriate size tap the emulsion tube from the main jet end. It will emerge in the center of the carb and can be removed through the carb bell. When reinserting there is a pin inside the tunnel that matches up with a notch in the emulsion tube. While you've got the slides out it might not be a bad idea to check the diaphrams for pinholes too. To check, take them to a relatively dark place and hold a flashlight up to the diaphrams and see if you see any light on the other side.

Before you change the float setting, in addition to the above, I would make sure the bowl jets are clean. 25.5mm with 145 mains should be about right. A bread tie with the paper stripped off works well for this operation. When you put the straw from a can of carb cleaner in the hole at the bottom of the bowl and pull the trigger on the can you should get a nice, consistent, well-atomized stream from the hole on the bowl flange. Make sure it's pointing away from you when you push the button - carb cleaner in the eyes really hurts. DAMHIK

[dbeardslee]

On the pilot jets, I'm assuming you have the stock 42.5 pilot jets - 45's may be a better choice. The pilot jets work in conjunction with the mixture screws. How many turns out are you on your mixtures? Also, make sure you don't have any broken tips on your mixture screws. A tip broken off and lodged in the orifice could cause lean running (on the affected cylinder or cylinders) at low rpms, as well as making it impossible to accurately adjust your idle mixture.

[Salboy]

Diaphrams are ok.I'll ckeck the holes in the bowls and mixture screws are at 1 1/2 out.The have all been out and look ok.It's raining out here so it's a good time to go to work!

[dbeardslee]

Salboy - How did you arrive at 1.5 turns out for your mixtures? That's the recommended setting to start with, but with the 4/1 and stock pilots I would be surprised if it's correct for your setup. I would think somewhere between 2 and 3 turns out is probably closer to where they should be.

Personally I find two tools indispensable for working on carbs - a carbtune and a colortune. The colortune will allow you to accurately set the mixtures, and will also tell you if your jetting is correct. The carbtune (or a decent set of synch gauges) will allow you to synch your carbs - something that should be done anytime you open or adjust them.

Some folks like to use an auxiliary tach to adjust their carbs (the stock tach isn't accurate enough), but I've never been able to get that method to work for me. You might be able to get along without the colortune, but a good synch is critical.

[Salboy]

Thanks again!I'll turn the mixture screws out and see what happens.I have a synch tool but its a cheap one and I don't know how accuate it is.I'm going to look into a carbtoon and colortune.

[dbeardslee]

Salboy - What kind of synch tool do you have - mercury sticks or gauges? With mercury sticks (assuming they haven't ingested any fuel which creates 'bubbles' in the mercury) they're as accurate as anything. If you have gauges, you need to calibrate them. Pull the cap off one of the carb boots and attach each gauge, one-at-a-time, and check the readings at the same rpm for each gauge. Make a note of any discrepancies in the readings, and use 'kentucky windage' when doing the synch. When properly calibrated even cheap gauges can do a good job.

When I adjust my carbs I first connect the synch guage to all four taps and adjust the synch. Then I adjust the mixture on a carb, and check the synch - adjusting if necessary. Then I repeat the process until I run out of carbs. When you synch your carbs you're adjusting the volume of the fuel/air mixture. I do the synch first to insure that all four carbs are drawing the same volume before I adjust the mixtures. It might be slightly anal to do it that way, but it sure works good. You will need something to tell you what's going on in each individual carb - either an accurate tach or a colortune. Some people can do it by ear, but I'm pretty sure those people can hear dog whistles too .

[Salboy]

I have gauges and I calibrated them, they were off a little.I turned out the mixture screws 2 1/2 turns from 1 1/2 and synched them again.Nice smooth idle,easy start and much better at low rpm.Still waiting for the pilot jets.The local yamaha dealer only had 1 in stock(That figures )When I change those I'll check the other items everyone has mentioned.No use in taking them off twice if I don't have to.It runs much better with the mixture screws at 2 1/2 and a good synch.Thanks again!I'll try to get a picture soon.Very clean bike.