Carb diagnosis question on my 96

[Dr. Mordo]

So I got my carbs back from the mechanic who has had them for a few months and did very little to them.  I had new floats, so I put them in and tested it to see if it was leaking, them put them back in.  

I looked at the float height and they were just a smidge over 14mm, not quite 14.5mm like the service manual recommends.  I figured my measuring stick might not be accurate down to 0.5mm so I just installed them.  

The bike fired right up but is running very rich and fouling the plugs.  Could 0.5mm of float height inaccuracy foul the plugs in 15-20 mins (maybe 30-40 mins including time at idle)?

[Mustang]

I will pm you the page from the factory service manual and it shows how triumph sets the floats on a mikuni . and to answer your question YES float hieght will drown the plugs especially at idle where it is not burning off the excess gas fast enuff (too much incoming) also will run very rich !

[DesertDog]

So I have not broke down and bought the Triumph parts to check float height yet.  They wanted $22 for the adapter and $22 for the marked sight cylinder.  Figured there had to be a way to check them with the bowls off.

Do I have to adjust as the service manual states (measure height against float bowl sealing surface) or is there a way to measure with the carb bowl off?  
thanks

[Mustang]

While this is not the correct way to check them .......you can compare the hieght of all three and see if they are the same . the odds of all three being out the same amount from the factory are slim to none , if you know what I mean .

[Dr. Mordo]

I have been working on mine, and as far as I can tell, my center carb is pissing gas (or perhaps not passing enough air?) from some place other than the needle/seat.  I've played with the float height a ton and it always does the same thing, which is foul out the center plug after about 15-20 mins of idling.

Any ideas about what could be happening?  I was thinking it might be the choke, so I pulled it and moved it to another carb, which had no effect.

BTW, thanks again Mustang for helping all us dudes who don't know much.

[Mustang]

I have been working on mine, and as far as I can tell, my center carb is pissing gas (or perhaps not passing enough air?) from some place other than the needle/seat.  I've played with the float height a ton and it always does the same thing, which is foul out the center plug after about 15-20 mins of idling.

with the carb bank off the bike hook up a fuel source to them and see if gas is pissing out the overflows , if it is you have a bad seat on the fuel needle .They should shut off all flow of gas once the floats come up .

Now if the carbs are working properly and you are still fouling plugs , are they totally gas soaked . cuz thats what a bad fuel needle will do , on the other hand when were the intake valve clearances checked last ?

Are you sure the center plug even sparks , check it with a new plug .
The triple will idle pretty damn good on two cyl. and you won't even realize one aint working !

[JetdocX]

It even runs on one.  DAMHIK!

[Dr. Mordo]

Man, I sure appreciate all the help, but this bike is beating me.  

I swapped the float assemblies between 2 and 3.
I checked for spark on 2.
I turned the pilot screw out a full turn.  
I pushed on the choke with a screwdriver to make sure it was seating.

Nothing.  It still fouls the plug very quickly.  I noticed tonight that if I open it up from idle it bogs down really bad, but I'm not sure what that means.

I'm almost ready to truck it 40 miles to the dealer.

[Mustang]

so let me get this right no more pissing gas just fouled plugs ? This is almost starting to sound like a coil nightmare .  I have used an old style chevy coil to troubleshoot coils b4 on a steamer . just hook it up to # 1 cyl . then try it on #2 and so on .
Your problem seems to be #2 fouling plugs so start with the chevy coil hooked up to #2 and see if it fouls the plug or not .

You need an old style chevy coil you know the ones that have a + and - post on them for power and the center plug wire socket , something that would be on a 57 chevy LOL

[JetdocX]

Or swap the coil to another cylinder and see if your problem moves with the coil.  May as well swap the sparkplug with it as well.

[aeronca]

brother dr.mordo - i feel you'r pain :shock:   it does sound like a coil thang. listen to mustang, he's like a yogi or a swami with this stuff. i was going through the same crap as you, but so far(knock on wood), it seem's ok.

[Dr. Mordo]

I swapped the coils a couple of days ago after reading about Aeronca's problems awhile back.  It didn't help.  I tested them with a multi meter, and they look to be in specs.  That is a great idea to use an old Chevy coil to test; I would never have though of that one.

I've also tried a brand new spark plug, and I've pulled the plug to be sure it was sparking.

I am freaking stumped.  I do think that it is still pissing gas - when you crank the throttle from idle the bike bogs really bad and starts spitting black smoke.  Also, of course, it's still fouling plugs.

Argghh!

[Mustang]

If it is pissing gas that bad you will probably find that the float and or needle valve is screwed up or not seating right .
I like the Keihins carbs they are simple compared to the Mikunis and they get better gas mileage too .

If you are fouling the center plug that quick , I would check for gas contamination in the engine oil and would not run the bike too much more if there is . it will wash the oil off the cyl. walls and then you will be up shit creek so to speak ! :shock:

I had an old bonneville once that was pissing gas and it filled the engine oil with gas and would foul th eplugs when you tried to run it  LOL
If you have spark and compression , you have to have a buggered carb

[JetdocX]

Are you sure you are making compression?  I don't think that has been established yet.

[Dr. Mordo]

I have not tested it for compression yet.  I don't think that's the issue because it purrs like a kitten until the cylinder drops out.  I don't have a compression tester, so maybe it's time to buy one.

I dropped the needle  1 notch today and it was the first thing I have done that made any difference; now the bike seems starved for fuel.  It's late here, so I only played with it for a few minutes.  Tomorrow I'll figure out if the needle jet is the culprit.  My fingers are crossed; at this point I'm thrilled to get any reaction to my adjustments.

Thanks again for all the help, and I'll let you know tomorrow what I learn.