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77 gs550 fuel problems PLEASE HELP!

  • Thread starter Thread starter Hell or high water
  • Start date Start date
H

Hell or high water

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Ok guys so this is my first bike, i got it with stuck carbs and fried wiring so I reworded it with new dyna 3 ohm coils and replaced the points with a dyna 3s ignition. I verified I have spark at the plugs by pulling each one and grounding to bike then rolled it over to see spark. So I know that's not it. I also disassembled the carbs and cleaned them to make sure everything's open. The problem I'm having is that it will start for just a few seconds and die. The bike was missing the petcock so I ordered a universal one that I realize now was a non vacuum type, so my question is this. Will using a differant petcock than the original not supply enough fuel to the carbs because it doesent have the vacuum assist? Also I adapted a 4-1 header from a later gs750 to this bike which stops after the collector and added pods, so will these changes be enough that the bike is simply just to lean to stay running? Sorry again if these are stupid questions but I'm at a loss here. Thanks!
 

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A vacuum petcock is not mandatory. Be sure to plug the vacuum line on the carbs that normally feeds the petcock though.

Any time pods are installed you have to rejet the carbs as well, and this is not as simple as just bumping the mains a couple of sizes. Hopefully you got some decent pods instead of the junky generic Emgo type.
 
It does not take much fuel to get the bike to run at idle, and I can't imagine a petcock small enough to restrict fuel flow to the point that your 550 will not run. And, it's not a "vacuum assist", it is a "vacuum turn-on". When the engine starts and there is vacuum in the intake port, the petcock opens to allow fuel flow. Since you don't have a vacuum line running to your petcock, make sure that the port on #3 carb is plugged, or you will have a MAJOR air leak.

When you "disassembled the carbs and cleaned them", how far apart did you take them? If you just dropped the bowls and spritzed around some carb cleaner, you still need to clean the carbs. Unless you KNOW that the bike was in regular use within the last month or so, assume that you need to go through the entire list of maintenance items to get it running properly. That would include (but not be limited to): carb clean, valve adjustment, electrical checks, brakes, tires, suspension.

The header will not affect your bike's ability to idle, but it will change the jetting requirements while going down the road. Your choice of pods on the intakes will also affect your jetting requirements.

For the longevity of your bike and the preservation of the little bit of good will that still exists in the general population, please consider adding to your exhaust system. An open exhaust does nothing to promote our reputation among the general population and can actually go the other way, in the way of road closures and lack of access to public areas that are open to non-motorcyclists.

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I did cap off all the ports on carbs two three and four. As far as cleaning the carbs I left the body's in the rack so I dident mess up the sync but I pulled all the jets and cleaned them out, sprayed carb clean through all the passages until they were open and cleaned out the choke tube wells in the bowls. I dident remove the jet needle or slide but sprayed cleaner down through to clean it best I could. I have been kicking around the idea of sending them to chief here on gsr any suggestions? Unfortunately I bought the pods before I knew about this site so yeah eBay specials lol. Do they provide more restriction than the better (insane priced) pods? I did not adjust valves so that's on the to do list however I did the electrical checks and was good. I had to rewire the whole bike. I thought about building a short muffler or baffle, I like the short exhaust look, any suggestions as far as short exhaust alternatives?
 
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First of all, remove the caps on carbs 2 and 4. Those are vents, and need to be open. With them capped off, your float bowls might not be filling correctly.

Unless you ungang the carbs from the rack, you can not properly clean all the passages that need to be cleaned.

Chef (not 'chief") and I both rebuild carbs, but he has more experince with the VM carbs and has a better idea for jetting in situations like yours. I am also a bit behind in carb work right now, so will definitely suggest sending them to Chef.

Valve adjustment is not just 'important', it is CRITICAL. Especially if you don't know the history of the bike. The clearance is VERY small on these bikes. As the valves wear, that little bit of clearance gets even smaller, leading to burnt valves. Tight valves are also one of the primary causes of not starting easily, especially with a cold engine. The other primary cause of hard starting is dirty carbs.

No suggestions here for a short exhaust, but anything has got to be better than an open collector. There are sites dedicated to bobbers and cafes that might have something, but the overwhelming majority here opt for something much quieter. Not always as quiet as stock, but definitely not open, either. Thanks for at least considering the idea. :encouragement:

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I will send them to chef then people on here really seem to like his work and I just don't know enough about these carbs to effectively fix them. They are totally differant than an old holly double pumper lol. I ordered an original petcock today for the vacuum on feature since I found the other one to leak. I dident know about the vents I thought they were vacuum ports, that might explain why pipe 1 was hot and 2,3 essential. I'm sure that's not helping things. That does raise another question though, how come carb 1 doesent have one? 2,3,4 all have a tap somewhere on the carb but 1 doesent...was far as the valve adjustment I seen in your signature you have a spread sheet could you send me that please? I'm always open to suggestion, the people on here are to knowledgeable to not listen to. Thanks for all the help so far! It's getting warmer here in Iowa and I'd really like to ride soon.
 
I'm not gonna lie it's slightly intimidating. I think I could figure it out from the instructions provided but I can have them built by someone extremely competent and will replace any broken or damaged parts for 225 bucks, and 80 for a jet kit from 6 sigma. So 305 for a compleate carb work up and peace of mind they have been done right doesn't seem to crazy. I've spent twice that on a decent bbc carb lol. To me it seems like the best place to not cut corners. I did drop the points and original coils for a set of 3 ohm dyna coils and a dyna s ignition. So hopefully that with the carbs lined out by chef and jet kit will be a reliable system. Any thoughts suggestions out there?
 
Hell or high water said:
I dident know about the vents I thought they were vacuum ports, that might explain why pipe 1 was hot and 2,3 essential. I'm sure that's not helping things. That does raise another question though, how come carb 1 doesent have one? 2,3,4 all have a tap somewhere on the carb but 1 doesent.
Click to expand...
You will have to look closely to see them, but there are small hoses between carbs 1&2 and 3&4. The nipple on #2 (which originally had a hose on it that draped back, over the airbox) connects through that small hose to also vent #1. The nipple/hose on #4 similarly vents #3, also. The nipple/hose on #3 is the vacuum port that connects to the petcock. Even though it is in the same location outside the carb, it connects differently inside, to provide the vacuum.


Hell or high water said:
...was far as the valve adjustment I seen in your signature you have a spread sheet could you send me that please?
Click to expand...
Thanks for noticing that, but please also read the next line. Send the e-mail request. You are fortunate that I followed up in this thread, I might never have seen this. :-\\\

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Sorry my brain shorted out, I'll send an email. So today while messing with the carbs I broke the #2 intake boot... they are so hard to get on and off properly! :mad: now to find one of those. This things gonna be the death of me lol
 
I found a new set from some place in Japan for 50 bucks...any experience out there with what works and what doesn't?
 
So I decided to break the carbs down today and found two of the fuel pilot screws had the tips missing...obviously they need replaced but I was curious if there is better replacements for these from some where or if someone has a few on here they could let go of? I heard the aftermarket brass replacements aren't as good as originals. Thoughts suggestions?
 
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Check the two carbs that had the missing screw tips. If the broken pieces are still stuck in the carbs, you will damage the new ones when you put them in.

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The bore is so small any experience getting those out of there without damaging anything? Also still having a hard time finding a set of just the fuel screws, anyone have any or know where to get them?
 
Thanks for all the help so far guys! Waiting on parts and hopefully can report back with some good news soon.
 
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