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Gs425 choke issue

  • Thread starter Thread starter wfoerk
  • Start date Start date
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wfoerk

Guest
Hi,
I have a '79 GS425 that is a bugger to get warmed up. The bike starts right up, but it will not go into high idle. As such, it takes forever to warm up. Does this carb not have a high idle circuit? Or do the carbs need a really good cleaning? I've had them off quite a few times; the bike was a mess when I got it. It runs great once it's warm, but waiting literally 10-15 minutes for it to run without the choke is trying my patience.
Thanks
 
Several years ago, one of the popular motorcycle magazines (Cylce, Motorcyclist, etc.) did a write-up and proclaimed the 425 to be one of the worst-carbureted bikes ever. They said it was a shame, because it was otherwise a nice bike. They then went on to show how to rectify the situation, virtually for free. Of course they were doing this with a new bike, so the carbs could be assumed to be clean. You may have to clean yours to get to the same starting point. They pulled the diaphragms out of the carbs, then pulled the needles and swapped the metal and plastic washer/spacer. This has the same effect as raising the (non-adjustable) needles about 2 notches. They also turned the idle mixture adjustment screws out another turn, to about 2.5 turns.

We now have better tuning options available and have found that going two full notches richer on the needles might be too much. What works better is to find small washers (get the assortment pack at Radio Shack, then use just the smallest ones), build a stack equivalent to the height of the nylon spacer, then cut it in half. Usually, that's two washers. By doing this, you can tune the needle height by half-notches, if you need to. I still recommend turning the mixture screws out. Start by bottoming them lightly, then backing out 2 to 3 full turns. When the bike is warmed up, turn each one slowly, listening for highest engine speed (won't be a whole lot of difference). If you don't notice any increase, turn them in slowly until you notice a decrease, then turn them back out 1/4 turn.

.
 
Thanks for the info, but I am pretty satisfied with how the bike runs once it's off choke. It's getting it off the choke that's the problem. Do you have any advice as to what's going on with this?
thanks again
 
Read Steve's post again.

Do what he advises. Clean the carbs, do these easy adjustments. If you don't like how it runs, you can put the needles back where they were, turn the screws back in, and put a bunch of crap back into the carburetors.
 
Last edited:
wfoerk said:
Do you have any advice as to what's going on with this?
thanks again
Click to expand...

Yes.

It's running too lean, requiring it to stay on "choke" for quite a while. Raising the needle and turning the mixture screws out will richen the mixture at the lower throttle openings and will get you off the "choke" setting quicker.

The factory settings were not set that way because the bike ran best. They were set that way to satisfy the EPA, which was starting to throw around a bit more weight at the time.

Side benefit: since the bike will actually run better, it will even get better gas mileage, even though you are richening the mixture, seemingly giving it more gas to burn.
 
Sounds like Steve is right.
In '82, I had a brand new 3/4 ton Chevy pickup, 305 Quadra jet carb, and mild RV cam that I bought in IL. Transferred to San Diego, CA, (home of record at the time), had to get it smogged to register it, of course. It cost me $120 for the $45 smog check. They had to de-tune my truck, retarded the timing, way leaned out the carb and then it passed CA smog. It ran so crappy when I left the station I had to re-tune it before I got home. It was missing and spitting, backfiring under load and everything imaginable. It only had 3500 miles on it at the time. I went through that every time I had it smogged except when one lobe of the cam went flat and it was running bad on its own.
Stupid EPA regs, and CA bought every one of them lock, stock and barrel and then added to them.
 
tkent02 said:
Read Steve's post again.

Do what he advises. Clean the carbs, do these easy adjustments. If you don't like how it runs, you can put the needles back where they were, turn the screws back in, and put a bunch of crap back into the carburetors.
Click to expand...

Dude, the carbs are clean. This isn't my first day working on a motorcycle. Save the sarcasm for your buddies.

Thanks, Steve, for the further explanation.
 
wfoerk said:
Dude, the carbs are clean. This isn't my first day working on a motorcycle. Save the sarcasm for your buddies.

Thanks, Steve, for the further explanation.
Click to expand...

So why did you ask if they need cleaning?
Your first question after the one about the high idle circuit, which you would also know if it wasn't your first day working on a motorcycle.
You haven't seen sarcasm.
 
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