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gs won't run/running poorly. help.

  • Thread starter Thread starter tipwise
  • Start date Start date
T

tipwise

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So I got this gs 850 not running and went through and fully disassembled the carbs and cleaned and replaced everything. New intake boots and o- rings. New air box to carb boots. Bike didnt have stock air filter so I got a stock air box but doesn't have the filter installed at the moment as I don't have one yet. The bike fires up after several tries with the choke on but only runs with choke on. Occasional backfire occurs as well. Struggles to start back up again and only with choke on. The backfiring thing tells me timing may be off? Also, I have not done a valve adjustment yet and probably should be doing that asap. Any help or advice that you can lend me is very much appreciated as I have an idea why the bike isn't running great just need some advice and direction as to where to go with it. This is my first gs. Also, compression reading is 120 across the board which is on the low side. Thanks
 
Problem may well be the missing air filter. Running on choke indicates lean, which indicates too much air to fuel, explained by missing air filter. Get the filter in then see how it runs. May still have problems, but that's step 1 IMO.

You could adjust valves while you wait for the air filter.
 
Also, I have not done a valve adjustment yet and probably should be doing that asap.
Click to expand...

+ 1 on the filter being part of your problem but you should do the valves first IMHO and also put in the filter to see what you have.

Since your bike was a non runner most likely the PO did not ever do the valves and that is why it was not a runner. Did you bench sync the carbs after you cleaned them and are your mixture screws even?
 
There's no point in doing anything else to the operating conditions of the bike till you get an air filter.
 
Actually got it fired up and running great with no choke but only on 2 cylinders. Only running on 3 and 4 right now which is weird because when I first started it it was only 1 and 2 that were firing. It revs great and decelerates great and idles great as is but only 3 and 4 firing. weird.
 
Do a compression check.
Adjust valves
Split and dip each carb body and only use Mikuni jets.
 
Did a compression check. 120 on all four which is on the low side. What you think?
 
Octain said:
There's no point in doing anything else to the operating conditions of the bike till you get an air filter.
Click to expand...
+1 get everything back to normal, then work from there, esp. with a missing air filter. Doing the valves while you wait for the filter is a great idea. Also, a bench sync will get you going, but is in no way a substitute for a true carb sync.
 
thanks. i'll get the filter and valve cover gasket ordered and start tackling the valve adjustment.
 
C.V. said:
+1 get everything back to normal, then work from there, esp. with a missing air filter. Doing the valves while you wait for the filter is a great idea. Also, a bench sync will get you going, but is in no way a substitute for a true carb sync.
Click to expand...


And how do I do a true carb sync. Is there a website out there that explains it? thanks.
 
tipwise said:
And how do I do a true carb sync. Is there a website out there that explains it? thanks.
Click to expand...

A Bench sync it taking a pin or wire, and making sure each butterfly is set pretty close to all the others. It will get them close enough so that one cylinder isn't pulling a ton more than the others. It's the "close enough for government work" that you do after tearing carbs apart before you even mount them to the bike. If you're good this will be very close, but it might not be.

A "real" carb sync requires a special tool, a manometer that measures vacuum. There is a small screw on each intake on the head you may have noticed. You screw an adapter onto it, hook it to the gauge, and it tells you exactly how much vacuum is sucking at that intake, which is a measure of how much fuel and air is getting sucked into the engine. the gauge has 4 towers/columns in it. You adjust the carbs until they are all the same (or #2 carb slightly higher than the rest, have to look at the manual). It can be the difference between a bike running "ok", and running "great".

You can make a manometer for $20 that works ok (or so I have heard), or a nice one called a Carbtune is about $120.
 
carb question.

carb question.

I also forgot to mention that on the two cylinders that are not firing there was something weird with the carbs. There is a clip thing that mounts near the needle seat that I assume is for float height and on 1 and 2 that is deteriorated and almost gone. I just left if for the time being but I may need to source some parts carbs to replace those. Anyone know what I'm talking about or know where to just get that piece?
 
tipwise said:
I also forgot to mention that on the two cylinders that are not firing there was something weird with the carbs. There is a clip thing that mounts near the needle seat that I assume is for float height and on 1 and 2 that is deteriorated and almost gone. I just left if for the time being but I may need to source some parts carbs to replace those. Anyone know what I'm talking about or know where to just get that piece?
Click to expand...


Post pics if you can.
 
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