83 GS850G boging issue

[Guest]

I bought an ’83 GS850 without and carbs. I bought a set (Mikuni BS32SS) off eBay that came off a ’80 GS850. I cleaned them according to the carb tutorial on BikeCliff website. I sprayed carb cleaner in all the orifices and jets and everything is open. I replaced al the o-rings (cycle-orings) and the rubber plugs. I checked and set the floats levels. In addition I:
- replaced 2 intake pipes and replaced all the intake o rings
- sealed the airbox and cleaned the filter
- adjusted the valves
- synched the carbs
- replace spark plugs
- replaced petcock
- checked engine compression (#1 & #2 – 162 psi, #3 - 142 psi, #4 - 152psi)

The bike starts right up with the choke on. The choke is a bit fiddly as the engine revs up high so I quickly start closing down the choke. The revs will drop and then go back up. I close the choke some more and this repeats for several cycles till the choke is almost closed. This all happens in about 30-45 seconds (temps in mid 40s). Once warm, it idles OK.

However it bogs badly beyond idle. I can’t make it up a hill in first. I’ve tried adjusting the pilot screw from 2 to 3.5 turns out and doesn't seem to make any difference.

The carbs had never been open before, so the jets have not been changed. I checked the diaphragms for holes and they seem find.

So my question: Is there and issue using carbs from an ’80 GS850 on an ’83? What am I missing? Any suggestions? It seems to be an issue with the carbs so I am planning to take them off again and check them. But if there is something else I should check before I do that, let me know. Thanks!

[Burque73]

Hmmm, well if it makes you feel any better I'm running carbs from an 81 on my 83. I think the only difference from 80 on up is the choke linkage. I had mine rebuilt by the way so more technical info I'll defer to someone else.

[mmattockx]

The bike starts right up with the choke on. The choke is a bit fiddly as the engine revs up high so I quickly start closing down the choke.

<snip>

However it bogs badly beyond idle. I can’t make it up a hill in first. I’ve tried adjusting the pilot screw from 2 to 3.5 turns out and doesn't seem to make any difference

Sounds to me like you may have an air leak. Try spraying some starter fluid around the carbs and intake boots once it is warmed up and idling smoothly. If the revs go up you have a leak. As for climbing a hill, the pilot circuit only affects from idle to ~1/8 throttle so if you have it opened up more than that you are getting onto the needle. Your 1980 carbs should have adjustable needles, where are they set? Adjusting the mixture screws from 2 to 3.5 turns out is a big change, did it affect your idle problems with the choke at all? Did you write down what jets were in the carbs or just assume they were correct?


Mark

[Steve]

As Burque says, the main difference is the "choke" linkage. How did you connect your bike to the "choke"?

Mmattox suggests you might have adjustable needles. The Canadian carbs might have, but the US-spec carbs did not.

Set the pilot screws to three turns out. That is three FULL 360-degree turns, not three "flips" of the screwdriver.

Did you DIP the carbs or just spritz some carb cleaner around for a bit? You mentioned that you sprayed in all the orifices and they all appeared to be open, but if you don't know these carbs intimately, you might not know where all you should be seeing spray come out. Some of the smallest passages are the ones that are clogged the easiest, and you may not know it by spraying cleaner, the carbs need to be dipped to soften all the gunk in the passages so it can be sprayed out.

.

[hillsy]

If there is no difference when you adjust the idles mixture screws from 2 turns to 3.5 turns then you either still have some sort of blockage in those circuits or air leaks.

When you sprayed the carbs did you blow out the circuits with compressed air?

[mnferwerda]

I completely disassembled the carbs and cleaned them in an ultrasonic cleaner. After spraying carb cleaner through all the orifices, I also blew compressed air through them. I'm pretty confident the carbs are cleaned as I've done this before.

I did have to change the way the choke cable attaches to the choke rail. I bought the later style hw for the rail off eBay to make it work, and it works fine.

I'll spray some starter fluid to see if there is any difference.

Thanks for the replies. I'll report back later ...

[Nessism]

Did you hold the pilot jets up to the light and verify the orifice was open before reinstalling them into the carb body? Did you run a wire or spray carb cleaner through the choke tube to assure it's open all the way to the plunger?

Realize too that GS bikes require a warm up period before they will accept heavy throttle.

[850 Combat]

GS 850s are the worst about being cold blooded. People dispute that, but you will not find a contemporary road test that doesn't mention it. The 1000Gs is far less cold blooded. Still, this sounds far worse than it should be. I wonder about the pilot emulsion tubes or something. Are the rubber plugs installed in the bottom of the pilot jets? I don't know what that would do, I've never done it. Certainly it would do something. I have had the tiny air passage from the bell mouth to the pilot circuit get clogged. It took me a few carb R&Rs before I figured it out. Did you verify the two air jets in the bell mouth?

[bobgroger]

The choke behavior you mention is normal. Full choke to start, then fiddly little adjustments until it will idle on its own. I can usually jump on and ride with the choke slightly open in ~30 seconds, close it after 2-3 blocks. Ride it for a while, see if it improves. If not verify the pilot jets, idle air jets, and main jets are correctly sized for your application. Start with as many known quantities as you can.....

[mmattockx]

Mmattox suggests you might have adjustable needles. The Canadian carbs might have, but the US-spec carbs did not.

Really, even back in 1980 (since OP says the carbs are off an '80)? My '82 1100E still has adjustable needles from the factory up here. The EPA sure shafted you guys early on the emissions stuff.

GS 850s are the worst about being cold blooded. People dispute that, but you will not find a contemporary road test that doesn't mention it.

A 1/4 turn on the mixture screws should help quite a bit with that without causing any other issues.


Mark

[mnferwerda]

I started it up and sprayed starter fluid on all the intakes. No change. I didn't have much gas (actually very little) in the tank so I added some gas and it seems to act better but still some bogging. I may give it another go when there is time, otherwise it carbs off and re-inspect/clean.

New rubber plugs are installed.

I appreciate all the replies!

[mnferwerda]

I took of the carbs to re-inspect it. One of the floats was sticking (overflowing). I fixed that and re-checked the other floats - 2 needed a small amount of adjusting. I also installed a jet kit from 6sigma (replaced mains, pilot jets, shimmed slides, and a couple of other small mods). Re-installed the carbs and voila, she runs! No more bogging. Took her out for her 1st ride in 15 years. Seems to run well but may need some more tuning. Tach is a bit flaky. Shifting on a drive shaft bike is quite a bit different. It is more lick a "click" rather than a "clunk". Once it gets warmer, I'll have to take it for a longer run.