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Running rich, I need some advice, please

  • Thread starter Thread starter gs450sjip
  • Start date Start date
Steve said:
You can't go by what was on his bike, you have to go by what is on yours.

He has a bike that was sold in a different world market, the jetting might have been a bit different over there ("Down Under").

If YOUR pilot jets had holes, you need to replace them with pilot jets with holes, but why are you replacing them in the first place? Stock ones work quite well, until you install a big-bore kit and extra-lumpy cams, along with a race header and pods.

.
Click to expand...
Steve,

I was trying to determine what made his bike rich or lean as far as the pilots go. We sell these here at my employer so I though I'd just replace all the jets with new ones, just so I had a starting point. I actually talked to a tech rep at Mikuni, he claims they are interchangeable. Right now, I can't tell any difference between them. If I get the richness out of it, it may make a difference then. I hope I get that far. GS450SJIP
 
koolaid_kid said:
I cannot disagree. gs450sjip has done everything by the book as far as I can tell. Something very fundamental is going on here, it will be discovered. Most likely followed by a slap to the head and a "Doh!". ;)
Click to expand...

Gents,

I ran a test today and it could be revealing. I removed the foam filter and the lid on the airbox. The idle cleaned up considerably, almost no burbling.
It idled much smoother. However, when I tried to rev it into the mid range, it hesitated as expected. It was lean. At idle, it is still rich, but not as much as before. I actually turned the mixture screws in until seated, and it kept on running. I opened them to 1 1/2 turns out and there was no discernable difference. That suggests to me that the problem is in the idle circuit, or lack of one.

Any thoughts? Thanks, gs450sjip
 
That is why I was questioning the statement that you could not remove the mixture screws. Who cleaned your carbs?
 
koolaid_kid said:
That is why I was questioning the statement that you could not remove the mixture screws. Who cleaned your carbs?
Click to expand...

I dipped them, but the mix screws were not removed because I could not get them out, as I explained. I tried tweezers but they would not get a good grip. Suggestions? Thanks for all the help. gs450sjip
 
Excuse me just a minute..
BANGS HEAD!
BANGS HEAD!
BANGS HEAD!
BANGS HEAD!

O.K. I'm back. Do you have a dremel or something similar? What you will want to do is to turn the mixture screws all the way in. Then using a dremel or something similar, cut a slot across the cylinder that the screw fits down into. Then turn the screws back out and see if you can get to them. I'll try to find a description of the procedure. Back in a moment.
 
Tweezers will not work until the screws are completely unscrewed and sticking up over the tops of their towers.

If you are adjusting the screws and finding no difference, it appears that the tips of the screws might be broken off and stuck in place.

Once you (finally) get the screws out, you will need to check for broken tips before installing new screws.

There was some earlier discussion about re-setting the float height. You said you were going to check into that, but I don't recall seeing that you did. If you float height is still at the wrong figure, that will explain the richness.

.
 
koolaid_kid said:
Excuse me just a minute..
BANGS HEAD!
BANGS HEAD!
BANGS HEAD!
BANGS HEAD!

O.K. I'm back. Do you have a dremel or something similar? What you will want to do is to turn the mixture screws all the way in. Then using a dremel or something similar, cut a slot across the cylinder that the screw fits down into. Then turn the screws back out and see if you can get to them. I'll try to find a description of the procedure. Back in a moment.
Click to expand...

KOOLAID KID, AND OTHERS,
I do have a dremel and was considering a relieving procedure to get some room for tweezers or needle nose. I'll try that next week. I did reset the floats to the middle of the correct spec from the Suzuki manual. It did help. As I explained, running without a filter and lid from the airbox did lean the bike, except for the idle . That is still rich, will not restart when hot, it does restart when cold. It does idle better without burbling. So I'll concentrate on removing the mix screws, redipping the carbs and seeing what happens. I still am baffled as to where all the fuel is coming from when in the idle circuit to allow it to be rich even with the airbox components removed. Thanks to all, gs450sjip
 
There will likely be some crud preventing your mixture screws from seating correctly or something along those lines. You will also have gummed up O rings on the mixture screws from the carb dip as it destroys them.

When I took my mixture screws out, I had to use two flat head jewelers screw drivers and lever them out as the head will not come above the surface when it is completely unthreaded. Make sure each screw has its spring too.
 
gs450sjip said:
Pete,

Please clarify the pilot jets on your bike. Were they originally with or without the side holes? I think some call them air bleeds. When you say too rich until you put the stock back in. I need cleared up on that, please. gs450sjip
Click to expand...

The stock ones don't have the holes down the sides. The genuine Mikuni's I bought in the larger sizes have the holes.

Steve said:
You can't go by what was on his bike, you have to go by what is on yours.

He has a bike that was sold in a different world market, the jetting might have been a bit different over there ("Down Under").

If YOUR pilot jets had holes, you need to replace them with pilot jets with holes, but why are you replacing them in the first place? Stock ones work quite well, until you install a big-bore kit and extra-lumpy cams, along with a race header and pods.

.
Click to expand...

All good Steve, there're only two differences between the US and Aus models on these carbs... mains in Aus are 117.5 but US are 115 and we got adjustable needles whereas the US ones are non-adjustable.

All other spec's are the same :)
 
koolaid_kid said:
Look at post #5 about the slot: Cutting the slot
Click to expand...
Pete, Steve, Koolaidkid, and all,

I am armed with good info here. I will tear into them next week.First will be to see if the mix screw tips are damaged, both screws do turn freely. I'll take it from there, thanks for the advice..gs450sjip
 
Once you cut the slots you should be able to grab the screws and pull them out.
Good luck, keep us posted.
 
koolaid_kid said:
Once you cut the slots you should be able to grab the screws and pull them out.
Good luck, keep us posted.
Click to expand...

Gents,

Does anyone have part numbers for the mixture screw, o-ring, etc.? My on-line Suzuki source/diagram does not show these parts.
Thanks, gs450sjip
 
I have looked a lot of places and not found a rebuild kit that has those, you may have better luck picking up a second set of carbs on ebay and scavenging a set of mixture screws. If you are going to get a new set of screws one thing I have seen work was gently tapping an oversize bit into the head of the screw when it was bottomed in the bore so it had a bit of extra purchase once you have it screwed out of the threads, that or possibly a strong magnet to coax them out? You could also try a small bit of epoxy putty(not liquid epoxy) like JB Weld on the end of your screw driver, let it set up a bit to give you some extra purchase. Last resorts as although you will get the screws out, they may not be usable again. Let us know what a mess the o-rings are in there : ) after the dip.
 
gs450sjip said:
Gents,

Does anyone have part numbers for the mixture screw, o-ring, etc.? My on-line Suzuki source/diagram does not show these parts.
Thanks, gs450sjip
Click to expand...
A Canadian parts fiche might show them. U.S. parts fiche do not show them because they were not supposed to be user accessible.
You might call Z1Enterprises; they carry a lot of parts that do not show up on their web site, and they can also order stuff for you.
 
Cdnpt1 said:
I have looked a lot of places and not found a rebuild kit that has those, you may have better luck picking up a second set of carbs on ebay and scavenging a set of mixture screws. If you are going to get a new set of screws one thing I have seen work was gently tapping an oversize bit into the head of the screw when it was bottomed in the bore so it had a bit of extra purchase once you have it screwed out of the threads, that or possibly a strong magnet to coax them out? You could also try a small bit of epoxy putty(not liquid epoxy) like JB Weld on the end of your screw driver, let it set up a bit to give you some extra purchase. Last resorts as although you will get the screws out, they may not be usable again. Let us know what a mess the o-rings are in there : ) after the dip.
Click to expand...
cdnpt1 and Koolaid Kid,

I did remove the screws with tweezers, it was quick after cutting the slots. The screws appear undamaged, but oddly there were no springs present. I was the owner that drilled the plugs out, so it seems the factory did not install them. The screws and orifice look OK. I will re-dip them in Berryman's carb cleaner and start the process over. I did learn from Basscliff's site the operation of the Mikuni. There is another source of air/fuel mix to the engine that is not controlled by the mix screws. That would explain why it runs when those screws were turned in until seated.
Hopefully this will be the last time the carbs are off! I emailed the O-Ring guy about the o-ring on the mix screws, asking if they are the same as the needle tube o-rings, he says no, but they sure look the same according to the dimensions he gave. 3.1mm x 1.1mm. No matter, the originals look fine yet, they still fit snug. Thanks, GS450SJIP
 
Last edited:
Sorry, haven't been on for a few days...

Missing those springs is very odd... and yeah I've never found the part numbers either! I almost lost one of the springs when re-assembling the carbs and I had to order one from an earlier model 400 that shows the springs, but unfortunately it didn't fit. Luckily my house mate found the spring and all was returned to order...

One thing someone suggested when I was struggling was trying a spring from a biro pen...

As for O rings, I'd just buy another kit from cycleorings.com given how cheap they are...
 
There should be 2 small washers as well that are going to be important, I believe the proper order for those on the mixture screw, from top to bottom is: spring, washer, o-ring. without the washer to give the spring a solid base you may have the same situation all over again. I am pretty sure that is the order of things, it's been a while, I think there may be a pick in the carb rebuild tutorails on BikeCliff's website.
 
Yeah, those springs are in there. They may be difficult to extract, but those springs and the washers are critical to re-assembly. I use a very small 90 degree pick to get them out.
 
I agree with koolaid_kid,

the springs can stick in there. Doesn't take much to get a little corrosion. I'm surprised all 4 would be stuck, but they are probably there (or maybe you have one of those GSes with carburetors assembled at 3:53 pm on a Friday). Have a really good look under bright lights
 
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