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carb trouble can anyone help

  • Thread starter Thread starter buff
  • Start date Start date
B

buff

Guest
i have just replaced my valve stem seals on my gs 1000 hc (1979)as it was smoking for a couple of minutes on startup, also did compresion test first and was ok, also my plugs have been getting fouled up for a few months now, gradually getting worse 1 and 4 are sooty 2 is slightly lean and 3 gets wet with petrol, checked floats they seem ok, i also adjusted pilot air screws to one ane half turns, the carbs have not been balanced since i have put them back on bike, but i had trouble before taking them off,also i am now getting smoke from exhuast, could this be down to the carbs ,if anyone could help please let me know
 
Is the bike stock (exhaust, air box and filter or pods), have you checked the entire air intake side of the engine for leaks? What were your compression numbers? How many miles on the bike? What color is the smoke from the pipes? Are the fouled plugs from oil or fuel? So many questions! :-D
 
carbs

carbs

motad 4into1 exhuast original box and filter,did wet and dry compression test,cant remember exactly i think compression was 130or 140 ish whitish smoke, 1 and 4plug are sooty carbon 2 is slightly lean 3 is petroley,have not yet checked air intake for leaks yet,
 
buff said:
motad 4into1 exhuast original box and filter,did wet and dry compression test,cant remember exactly i think compression was 130or 140 ish whitish smoke, 1 and 4plug are sooty carbon 2 is slightly lean 3 is petroley,have not yet checked air intake for leaks yet,
Click to expand...

Compression numbers look good enough, the white smoke (as long as there is no tint of blue to it) is moisture in the pipes on a cold enging, burning off...normal. Have you or a PO jetted the bike? Have you set everything to spec, as far as the book calls for? We can work with sooty plugs, lean plugs, and air leaks...the oily plug, draws some concern.

First things first. Check the all the fuel/air screw settings on the carbs and set to spec. Next, did you check the float height settings? When you say that 2 is lean, is it showing light gray or light tan? Is it running on all four at this point?
 
have checked float heights ok do u know the best setting for the fuel air screws because in the manual it says they are factory set , also i have my negative pressure pipe coming from number 3 cylinder which goes to the fuel tank, could this be anything to do with the fouled plug
 
The air screws should be set to 1 1/2 turns out from lightly seated. If the factory caps/pluge are still there, they will have to be removed. A 1/8" drill bit and some caution will do the trick...don't drill too deep or you are going to hit the heads of the screws. Also, that "air pipe" is the vaccume port for your petcock. It is actually on the #2 carb...numbered from left to right as seated on the bike. If this is the spark plug that is getting wet, it means that your petcock is leaking through the diaphragm and running fuel down the vacuume line and into the #2 carb / cylinder. BUY A NEW PETCOCK...don't waste your time on the rebuild kits....in a word, JUNK! We'll get this figured out. :-D
 
carb

carb

my vacum is on number 3 cylinder, i will switch it to number 2 and see what happens, i cant get the carbs balanced properly at the moment, i havent got the equipment, but will be borrowing some after the easter holiday,from the local college,do you think the plug could be getting wet because of a weak spark from that coil
 
Dave,
This is on a '79 bike with the BS carbs. I think the vacuum port might be on #3, but can't say for sure.

Buff,
Let's say that your vacuum line is on #3. You can't just move it to #2 because the #2 carb will not have the nipple for it.

Just so everybody is on the same page...

#1 is on the CLUTCH side, #4 is on the THROTTLE side. 8-[


.
 
Since you have the BS carbs, your vacuum (negative pressure) hose is on #3. You said that is the one that is wet with fuel (I assume that is what petroley means :-D ). This would indicate a leaking diaphragm inside the petcock. The rebuild kits are junk (I tried one). Replace it and be done with it for the next 25 years.
 
Carbs

Carbs

Each Carb Has A Nipple Roughly Half Way Up The Carb 3 Of Them Have Pipes Just Running No Where But One Goes To The Fuel Tap
 
Carbs

Carbs

By The Way I Appreciate You Lot Taking The Time Out To Answer My Queries, I Think You Lot Know More Than Me About Bikes, So Thanks For The Patience:-d
 
buff said:
Each Carb Has A Nipple Roughly Half Way Up The Carb 3 Of Them Have Pipes Just Running No Where But One Goes To The Fuel Tap
Click to expand...


Wow, I have never seen that before. Are the others (the ones with out the vacuum line) plugged?


buff said:
By The Way I Appreciate You Lot Taking The Time Out To Answer My Queries, I Think You Lot Know More Than Me About Bikes, So Thanks For The Patience:-d
Click to expand...

This site is the stuff for getting help with these old beasts. I would probably still be futzing with a rich problem on my #2 carb if not for this site.
 
buff said:
my vacum is on number 3 cylinder, i will switch it to number 2 and see what happens, i cant get the carbs balanced properly at the moment, i havent got the equipment, but will be borrowing some after the easter holiday,from the local college,do you think the plug could be getting wet because of a weak spark from that coil
Click to expand...

The original carbs for your 79 GS1000 should be VM 26's. They are the same as the 850's of that year. The vacuum line comes off the #3 carb.
 
Correct, and the nipples/lines coming off of 1,2 and 4 are for vent hoses that are left open to atomsphere.

E.


49er said:
The original carbs for your 79 GS1000 should be VM 26's. They are the same as the 850's of that year. The vacuum line comes off the #3 carb.
Click to expand...
 
Just to back up the last posts, your VM carbs have the vacuum at #3 and the two vent lines you see at 1 and 4 are to vent the float bowls. 1 vents both 1 and 2, and 4 vents both 3 and 4.
Your plug colors could be many things. You really do need to bench synch closely and then vacuum synch with a gauge to get true performance/plug reads.
One possibility for 1 and 4 being sooty is a weak coil. Test resistance on both primary and secondary sides. Keep in mind all the connections should be clean/tight before any testing. Check timing and if points, inspect for clean/no pitting and correct dwell. Check advance action. If it passes these tests, which are basics anyway, focus on the carbs.
Clean carbs are a must. If clean, turning the pilot fuel screws underneath 1 turn out from lightly seated is suggested for your bike as a starting point. Initially set the side air screws to 1 3/4 turns. Fine tune when ready by using the highest rpm method.
Your lean #2 could be a vacuum leak. The vacuum synch attempt would verify this. It could of course be a dirty carb or poor valve clearance. I'm assuming no one has made jetting changes/adjustments and the carbs may all be mis-matched? Check that the pilot fuel screw is in good condition and there's no broken tip stuck in the secondary pilot circuit passage to the throat.
A wet plug at #3 could be a leaking petcock diaphragm allowing fuel to drain straight into the carb/cylinder. Capping #3 and running/testing the bike with the petcock on prime position would verify this because, if so, you would see the plug dry out quickly.
 
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