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81 Gs750l

  • Thread starter Thread starter tlachance
  • Start date Start date
T

tlachance

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From reading a few posts, It seems that the main jets come in two different sizes. I assume the larger ones go inside. I believe mine are 97s and 105s. Do the numbers correspond to the area, low number small size, large number bigger jet? I also pulled the plugs from the pilot air screws and cleaned the needles. Started them off at 1 turn, but now they are at about 1/2 turn. Runs well for a while but fouls #1 and 2 plugs.
 
This doesn't make any sense; how many carburetors does your engine have? You're describing "siamesed carburetors", which weren't used on the '81 GS750 engine... Unless some PO swapped the carbs, you SHOULD have FOUR carbs, not the odd-ball siamesed carbs used on some of the GS550 engines of the mid-1980s...
 
I think he's confusing the difference between main jets, pilot jets, etc...? Is that what you mean by big and small?
 
t3rmin said:
I think he's confusing the difference between main jets, pilot jets, etc...? Is that what you mean by big and small?
Click to expand...
Well, he mentioned the two main jet SIZES used on the bizarro GS550 engine of the mid-'80s, which is why I think he's confused...

See this thread for more info:

http://www.thegsresources.com/_forum/showthread.php?t=110845

In fact, I'm pretty sure he got those numbers from that same thread... which has NOTHING to do with the GS750 engine... Just for the record, the stock main jets in '81 GS750L carbs are 112.5s, while the pilot jets are 42.5s...
 
I was looking for info on why #2 cyl was fouling. I thought I had it fixed when I pulled the pilot screw plugs, removed the pilot jets, and put it all back together.
I read in a post here that someone had a 550 that had two richer mains for the two inner cylinders and two normal ones for the two outer. I was looking for possible reasons for the fouling.

I took my 81 750L down to the frame this winter and cleaned it all up, painted
what needed painting. The bike had sat outside for a couple of years up here in the Northeast. Had the carbs apart a couple of times to clean crap from the bowls and fuel passages. Flushed out the tank, cleaned the petcock, and added an external filter to try and trap any more crap. I've removed the carbs so many times that I can remove them, tear them down, put them back together and reinstall them in what seems like no time at all.
 
tlachance said:
I was looking for info on why #2 cyl was fouling. I thought I had it fixed when I pulled the pilot screw plugs, removed the pilot jets, and put it all back together.
I read in a post here that someone had a 550 that had two richer mains for the two inner cylinders and two normal ones for the two outer. I was looking for possible reasons for the fouling.

I took my 81 750L down to the frame this winter and cleaned it all up, painted
what needed painting. The bike had sat outside for a couple of years up here in the Northeast. Had the carbs apart a couple of times to clean crap from the bowls and fuel passages. Flushed out the tank, cleaned the petcock, and added an external filter to try and trap any more crap. I've removed the carbs so many times that I can remove them, tear them down, put them back together and reinstall them in what seems like no time at all.
Click to expand...
I'd like to add some more background info. I hit the post button before I was done. Stock 81 GS750L, stock air cleaner, stock exhaust. Had a few issues last year with dirt in the carbs, sticky floats, residual crap in the tank, etc..
I thought I had it licked when I was road testing it while tweaking the pilots and had good throttle response off idle. Went to go for a ride the next day and again, the plug fouled (not wet but carboned up). Right now I'm hoping that it's just the plug(s) as they were pulled, cleaned and swapped.
Any info will be appreciated, thanks
 
Once again, I would like to add to my previous posts concerning my 81 750L carbs.
While scanning various posts, I came across a reference to a problem with #2 cylinder fouling the plug. a poster replied to check the petcock diaphram as #2 carb was the source of the vacuum signal for the petcock. I went and pulled the petcock, took it apart and lo and behold, not only was there a pinhole leak in the diaphram ( a situation that can cause many different problems! :wink:), but the spring washer was in pieces.
If the original poster is reading this, I want to give you specificaly, and all the members in general a great thanks for making the vast knowledge out there available in this site. If the poster is known, please relay this info to him.
THANK YOU!
 
It is common, on any old bike that has sat for years THE first thing that should be done is to flush the fuel tank & make sure the petcock is working properly
 
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