Not Running Right...

[qwqb]

Hey Guys,

Looking for some of your expert opinions on this.

The background story is I picked up this non-runnin 81 GS850 over the winter. The PO had isntalled pods and a 4-to-1 exhaust, but had never got the bike to start.

I cleaned the carbs, installed #130 main jets, and shimmed the needles using 2 of the radio shack washers. I also replaced all the carb o-rings and the intake boot o-rings.

I also checked the valve clearances and they seemed to be alright.

Anyways, she fires up and runs now, however it backfires while idling and riding at low speeds, and when riding, it has a pretty severe power loss from about 1/4 throttle to 3/4 throttle. When I open it up all the way, it seems to run nicely. This would indicate that the needle circuit is running either rich or lean, right? Also, what does the spitting and backfiring mean?

I plan on doing some plug chops tomorrow. Should I buy new plugs before I do that?

If all else goes wrong, the PO gave me the stock airbox with the bike, and I may just end up installing that and putting the jetting and needles back to stock. That should be safe bet, shouldn't it?

 

[almarconi]

If it were my bike, I'd put the stock airbox back on, return the jets to stock (possible rejet for the pipe) and get the bike running reliably. If you must have the pods, get a dynojet stage 3 kit.

 

[qwqb]

I'm starting to not like the pods haha. How much of a rejet would be required for the pipes?

 

[TheCafeKid]

I'm starting to not like the pods haha. How much of a rejet would be required for the pipes?

The problem your having isnt really in the jet sizes (if it runs good at wide open throttle, which is only the last 1/4 turn of the throttle, then the main jet is probably pretty close) Your problem is that the STOCK GS needle doesnt have a 'fast' enough tapper to let fuel thru at the volume required by the bike to run properly. No amount of shimming will fix it. The stock needles just do not work with pods and a pipe. Too much air, not enough fuel, no matter how you slice it. Ive seen, and read, guys saying they get the bike to run using HUUUUUGE main jets, which will make up some for the lack of tapper, but then your going to foul plugs at WOT. Even my 1100ES when it came to me had a relatively huge main, seemed to run ok, but once I installed the PROPPER Dynojet kit, with propperly designed needles for this set up, it was a COMPLETELY new bike.

I am with Almarconi, either switch back to the airbox, or buy a Dynojet kit. If you get the kit, you install the stage three kit as per the instructions and you'll find that the bike runs better than youve ever known.

As far as jetting for just the pipe, using the stock airbox, REALISTICLY, to get the most out of it, you still want a Stage One DJ kit. BUT, a bump of two or three sizes on the mains, with your current shimmed needles will probably get it running pretty good. Thats just a guess, baseline, on the sizes. If you go that rout, find out what your stock main jet size is SUPPOSED to be, (we will say, for example, 112.5) and get the jets both two sizes up and three sizes up,(117.5 and 120) and find out which works best (they're only a few bucks each at Z1,)

 

[bwringer]

You'll also likely need bigger pilot jets as well. Plus, yours might be plugged up if it won't idle.

Personally, I'd seal up the airbox and put that back on. A bit of rejetting will still be needed for the pipe, but everything will be easier and the results better.

I'm no expert on rejetting, but 130 sounds awfully rich for the main -- stock is 115.

 

[qwqb]

Thanks Guys!

Am I able to piece together a Dynojet kit by just buying the size jets and type of needle that come with it? Or is there more to it? Because I notice they are pretty expensive...

Also, any idea of what might be causing the backfiring?

 

[Rick65Cat]

Thanks Guys!

Am I able to piece together a Dynojet kit by just buying the size jets and type of needle that come with it? Or is there more to it? Because I notice they are pretty expensive...

Also, any idea of what might be causing the backfiring?

I personaly don't have the DJ kit myself. But what you would be buying wouldn't just be the jets..you're buying the knowledge on what setup works best with the equipment you have, (pods and pipe, no pods but a pipe, etc etc) I'd go the DJ route myself. Maybe you'll pay a little more, but for what you gain in speed of installation with very little guesswork..if you're like me with little carb knowledge it seems a no-brainer.

Backfiring could be ignition timing, valves, or a lean condition.

 

[qwqb]

It just seems to me that there's really only 3 options which are: pods, exhaust, or both. It seems like the appropriate jetting for the 3 different setups would be public knowledge, and that I could just just buy the necessary jets for a couple bucks each, isntead of shelling out 100 bucks for the DJ kit. Just my thoughts, am I wrong?

 

[almarconi]

It's not just the jets, its the NEEDLES that make the difference.

 

[qwqb]

Right, so I can't get the needles that are in the DJ kit anywhere else but from the kit itself?

 

[almarconi]

Right, so I can't get the needles that are in the DJ kit anywhere else but from the kit itself?

I don't know of any other place except the kit.

 

[qwqb]

I /think/ I may have found my problem, tell me if you guys think this is right.

I checked my plugs today and they were pretty black. I went out and bought new plugs to do some plug chops with, however right after I got the new plugs installed, the bike ran like new. It pulled nice and strong through every gear, no hesitation or popping or anything. After about a half hour or so of riding though it went back to its old ways. I pulled the plugs and they were black and fouled again. I'm thinking that I went too big on the main jets (130 vs 115 stock) and that is what is causing them to foul, so maybe I'll try something closer to 120 and see how that turns out.

What do you think? Could the large mains have caused the plugs to foul like that?

*Edit* My petcock was left on "prime" could this have caused my fouling issues?

 

[qwqb]

Update, today the bike would not start at all. I feel like I'm chasing my tail on this one.

 

[almarconi]

I feel like I'm chasing my tail on this one.

Not trying to sound sarcastic, but what did you expect? You've got a 29 yr old, non running bike that was more than likely mistreated by the PO.

Do you have a service manual? If not, you can get one off of Basscliffs site.

Go through each system on the bike and repair/replace as needed. It's going to take you some time but when you are done you will know for sure that everything is working properly. There is no easy solution you've got to put in the time to repair the bike.