1992 GSF400 Carb Conundrum

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SevenThreeSeven
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Re: 1992 GSF400 Carb Conundrum

Post by SevenThreeSeven » Tue Jan 12, 2016 4:24 pm

Watched the video, your B4 sounds great. The engine sounds very healthy, seems like your carb work was spot on (including the bench tune effort to sync them up).

You're absolutely right about the riding experience with this bike. I'm 50 years old now and I've found that I have to be in the right mood for the B4, it's definitely not for when you're in a "mellow mood" and just want to cruise across town. When I feel that way I ride my Kawasaki EX250 instead.

You'll have to let me know about your other B4, the "parts bike", because if it's going to be a true parts bike (never to operate as a motorcycle again) I might be interested in the frame if the price is right. My B4 was a "salvage" titled bike when I got it. It had been "lightly wrecked" at some point in it's past. As a result it has a slight misalignment in the rear sub-frame portion (the seat and tail light area). It's a small thing but it bothers me so I'm always on the lookout for a substitute frame.

lknbandit400
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Re: 1992 GSF400 Carb Conundrum

Post by lknbandit400 » Tue Jan 12, 2016 4:35 pm

Greg,

I may have misspoke. The bike in that video was the "parts bike". I bought the bike with the guy mildly confident that with new spark plugs the thing with fire up. Hence my question last night about gapping multielectrode spark plugs. Turns out I threw $30 worth of new spark plugs in that "parts bike" and the bike fired right up without having to touch the carbs at the first touch of a button.

Unfortunately, my "pretty" bandit 400 is still sitting with the tank off and carbs dismantled. Those two stock jet needles are on national backorder and so until those come in I won't be able to put the carbs back together with the new O-rings.

Until that time, I'm going to ride this "parts bike" around and get used to it. It doesn't have a title but it did come with a Vermont transferable registration that will allow me to get a Vermont tag and put the bike on the road.

I wish all state DMV's operated like that.

Hang in there, I'm still going to need your help when I go to put these carbs from my pretty bandit 400 back together :). If the parts don't come off of the national backorder soon, I may just order a couple off of eBay.

lknbandit400
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Re: 1992 GSF400 Carb Conundrum

Post by lknbandit400 » Tue Jan 12, 2016 5:21 pm

SevenThreeSeven wrote:You're absolutely right about the riding experience with this bike.
"Giddy" is unfortunately the only proper word to describe me when I got to ride it up the block last night. Ha.

SevenThreeSeven
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Re: 1992 GSF400 Carb Conundrum

Post by SevenThreeSeven » Tue Jan 12, 2016 8:09 pm

Your concept of "parts bike" vs. my concept of "parts bike" = separated by a common language.

lknbandit400
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Re: 1992 GSF400 Carb Conundrum

Post by lknbandit400 » Tue Jan 12, 2016 8:34 pm

SevenThreeSeven wrote:Your concept of "parts bike" vs. my concept of "parts bike" = separated by a common language.
Ha, no I get it. Honestly any bike that enters the garage looking rough is subject to being a parts bike. Just so happens that upon closer inspection this one was closer to road worthy than my garage queen is. Go figure. Diamond in the rough.

lknbandit400
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1992 GSF400 Carb Conundrum

Post by lknbandit400 » Wed Jan 13, 2016 1:05 am

This is the last thing I anticipated, but I ended up taking "parts bike (haha)" for a 1 hour ride tonight. What. A. Blast.

Just when you think it's gonna explode, it goes 5 thousand more RPMs. It's a riot! It took me a while to get my confidence with the steering and suspension (it has a GSXR 750 rear shock and the PO dropped the forks in the triples about 3/8"), but once I did you can really flick the bike around.

The one problem it has, besides looking like a turd, is a high idle. I'm actually thinking it's as simple as the idle adjustment knob. In first gear, you *almost* don't even have the give it throttle when you let out the clutch and it pulls away. Clutch engagement is fine. It's not pulling while the clutch is engaged.

I didn't have time to adjust the knob and take it back out for a spin, but I'll do that before pulling the carbs to see where the idle air screw is set, and see if the idle adjustment solves it. This problem makes for a very jumpy first and second gear because the revs are so high that it wants to just grab and go. You have to feather it quite a bit to keep acceleration from first smooth. Also it's like the idle hangs when switching gears or quickly jabbing the throttle. I'm out of town for work till Friday, but I'll report back some experimentation then.

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Re: 1992 GSF400 Carb Conundrum

Post by lknbandit400 » Sun Jan 17, 2016 1:17 am

Made some huge progress with the carbs today. I will document the process below for learning of anyone reading this, and also so you guys can catch any mistakes :)

First things, first. I used a lift coating of silicone grease for my brand new o-rings from Litetec. I have to say, these are super high quality. Fit is just like OEM. Superb work!

I started with the slide holder o-rings. Initial installation of the slide holder will show that it is above flush with the bore because of the o-ring thickness.

After installing the emulsifier tube and the new 102.5 main jets on the other side, the slide holder is pulled flush while the main jet is tightened.

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lknbandit400
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1992 GSF400 Carb Conundrum

Post by lknbandit400 » Sun Jan 17, 2016 2:07 am

Next up was the idle air screw. I'm at 2.5 turns right now...I hear the bike idles better there - hopefully you guys can chime in?

New washers (with sharp side facing the screw) and o-ring.

[img]http://i904.photobucket.com/albums/ac25 ... 2ujllb.jpg[/img]

lknbandit400
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Re: 1992 GSF400 Carb Conundrum

Post by lknbandit400 » Sun Jan 17, 2016 2:12 am

Next up was the slow jet. After a soak in the ultrasonic cleaner and a TAD of WD-40 for thread lube to prevent galling, I installed the jet and the runner plug. The plug fit is still pretty snug so I chose not to replace them.

I also installed the air jet at the intake side of the carb. Unfortunately I could only source a 1.5 jet and not a 1.45 jet.

[img]http://i904.photobucket.com/albums/ac25 ... hrlij2.jpg[/img]

[img]http://i904.photobucket.com/albums/ac25 ... rpqyyz.jpg[/img]

lknbandit400
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Re: 1992 GSF400 Carb Conundrum

Post by lknbandit400 » Sun Jan 17, 2016 2:16 am

Next up was the float o-rings and level. Once again, I will emphasize that a tiny amount of silicone grease makes installation a breeze. With new o-rings, the flit had a nice "pop" when snapped into place. I set to float height to the spec of 14.6 mm and got probably within +\- 0.2mm which is well within spec.

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And last up was the new float bowl gasket. And the bottom is done...

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