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Carb swap

  • Thread starter Thread starter Guest
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Guest

Guest
Hey Guys,

I bought a 1982 GS850 for $300. It's got a couple carbs that are leaking. The seller said: "The bike will turn over but it then leaks gas because the left and center carbs leak. " when I asked if the bike ran.

Question is, if I need a full carb replacement, can I swap in carbs from a 1981 GS750E?? They are both the BS32ss carb models but some of the specs are a bit different.. (mainjet, needle jet, bypass, etc)

Thanks!
Rich


(I am referencing this page for specs: http://gsarchive.bwringer.com/bikecliff/images/carbspec_float_height.html )
 
Wether they swap right over I dunno, but what about just fixing the carbs...? Gaskets, O-Rings, Jets etc. are all still available, if I'm not mistaken.
 
roeme said:
Wether they swap right over I dunno, but what about just fixing the carbs...? Gaskets, O-Rings, Jets etc. are all still available, if I'm not mistaken.
Click to expand...

That's definitely plan number one - but my friend is parting out an 81 GS750E and it seems to be the same carb so I didn't know if it would be worth asking him to hold on to if the fix doesn't work out.
 
They will work, but you will need to move all the jets over, and the diaphragms (or at least the needles, but the whole diaphragm is easier).

If you want to tackle the process of doing a FULL "strip and dip" carb cleaning, there are instructions here how to do it.
If you don't want to try it yourself, there are some of us that will do it for you for a modest fee.
Click HERE to see what I can offer you.

By the way, you will also want to check valve adjustment, so look into that procedure, too. Click HERE for the keys to the library where you can learn all about your 'new' bike.

.
 
As stated above, the bodies and main air jets are the same size but all the other jets will have to be moved over from the 850 carbs. You'll need to at least clean those parts. By the time you've done that you might as well do a complete strip and dip of your carbs. Something I'd do no mater which set you install.
 
JTGS850GL said:
As stated above, the bodies and main air jets are the same size but all the other jets will have to be moved over from the 850 carbs. You'll need to at least clean those parts. By the time you've done that you might as well do a complete strip and dip of your carbs. Something I'd do no mater which set you install.
Click to expand...

Thanks, the plan is to rebuild the 850 stock carbs. I'm not sure what's causing the gas to spill out of the carbs though. I can replace an O ring or gasket but if it's rusted through it might be worth it to make a swap.
 
The carb rebuild tutorial linked in my signature may help you.

Short cuts are long cuts so consider this your warning.

The 1981 750 uses a significantly different engine than the 850. You should compare the spacing between the two sets of carbs before committing to the swap if it comes to that. Even if you decide to use the 750 carbs you would be wise indeed to go through them and clean/swap all the O-rings.

Good luck
 
Ok, looking for a little assistance. The carbs are clean and seem to be working, here's where I'm at:

-complete carb disassembly/cleaning
-new K&N air filter installed
-new spark plugs installed
-new battery charged/installed
-all new fuses
-confirmed carbs are getting gas (opened petcock to PRI and gas flowed to all 4 carb chambers; checked while installing new air filter)
-fuel lines checked


...she still won't fire. :'( Any ideas on what I could be missing? She'll crank all day long now but just won't get roaring.
 
I had the same problem with my 850. Carbs all cleaned and it would just not fire. I went to my neighbors place and got an insulin syringe, filled it with gas, removed the first and fourth plug and shot a bit of gas down the plug holes. Not much as I did not want to flood the engine. It fired right away. I think there was an air lock that was preventing gas from flowing through the venturi. Once it fired the first time I had no problems after that. It seemed that all it took was a bit of internal engine pressure to clear the air lock. To this day I don't know how I figured out how to do that. But it worked.
 
OK, I have made a little progress. Today I got her to roar up a little. Died out after about 5 seconds and haven't been able to get it going again. I did begin to see exhaust coming out of the pipes. I have pulled the battery for a re-charge. SOOO CLOSE!!! haha
 
After it sits for a while it will start up, then die down. After the first or second time of getting a little roar up, it won't start again until I let it sit. Might be flooding the engine with some over-aggressive choke use?? lol. Thoughts for any fixes?
 
I pulled all the plugs to look for spark and found oil on the tip of 1 plug. Thinking this means I'm going into the engine??
 
Did you go though the carbs properly, following the tutorial? Is the airbox installed and sealed properly?
 
Nessism said:
Did you go though the carbs properly, following the tutorial? Is the airbox installed and sealed properly?
Click to expand...

Definitely went very thoroughly through the tutorial and actually found a few errors from a PO in the carbs. Cleaned everything up and also replaced the air filter. I have taken everything off and pulled the intake boots. The O-Rings are looking extremely flat, and one looked to be leaking. I am going to replace all the O-Rings, although the boots themselves are in pretty good shape. I am also going to try and improve the weather stripping on the airbox panel but I'm not thinking a small air leak there would be the cause of a no-start & oil-on-plugs situation.
 
Be sure to do a bench sync with the carbs, and a lot of the time hard starting like that can be caused by the idle screw not being screwed in far enough and as stated before in the thread, check the valves..

V
 
gustovh said:
Be sure to do a bench sync with the carbs, and a lot of the time hard starting like that can be caused by the idle screw not being screwed in far enough and as stated before in the thread, check the valves..

V
Click to expand...
Actually it's usually they're screwed in too far. Start with the screws set at 3 turns from lightly seated. Adjust as needed. They usually end up around 2.5 turns +-.

Bad valve adjustment is more common of a problem with hard starting.
 
OK, more progress made, still won't stay running....

-intake boot o-rings replaced
-oil change
-oil filter changed
-confirmed all plugs are sparking
-adjusted the idle screw to 2.5 turns


...after replacing the intake o-rings, it sounds much stronger as it's trying to start. I know we're not huge Quick Start fans around here but I grabbed a bottle and the engine ROARS for like, 2 seconds after a squirt but then dies right back down. I have checked the bowls of the carbs to confirm the gas lines are working. I'm thinking this is most likely a fuel issue? The bike fires right up with the ether quick start but I'm not getting anything with the tank. Time for a petcock change? (I thought it was working fine...)
 
I think Gustov was referring to the single Idle Adjustment Screw and not to the 4 mixture screws. I think maybe he was suggesting the idle is set so low it dies.
 
1948man said:
I think Gustov was referring to the single Idle Adjustment Screw and not to the 4 mixture screws. I think maybe he was suggesting the idle is set so low it dies.
Click to expand...

I have re-set the single idle screw in the center of the carbs to 2.5 turns. I also went through and re-checked all the seals on the airbox, as far as I can tell there are no major air leaks.
 
RJordan09 said:
I have re-set the single idle screw in the center of the carbs to 2.5 turns.
Click to expand...

There is no pre-set adjustment for this screw - it simply gets adjusted in or out until the bike is idling at the correct RPM.

However, the individual idle mixture screws (one on each carb) are adjusted to pre-set turns.
 
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