400 Bing carb info needed

[400gs6]

 I've got an old '76 Penton 400 GS, it's all stock (480 orig miles) I've had it for years. With the help of my buddy Raymond, we got it running again last weekend.  The problem is is runs very rich and blubbery.  The only way it will idle is with the slide idle screw bottomed out and the cable  slack adjuster turned out a bit.

 I pulled the carb to find a 50 pilot and 180 main. the needle was in the second position from top. My old manual calls for a 35 pilot..

It also pings very badly on 91 octane.  Could this be a carburetion issue or should I run race gas? (timing is spot on)

Thanks in advance, this site is terrific.  I rarely post but do visit here every day!

Kurt

[400gs6]

...Another thought.  Should I even try to get the Bing sorted out or would it be in my best interest to just spring for a brand new Lectron if I'm going to try to use this bike again?  I've had Lectrons in the past and was very impressed with how well they work.  But they are pricey.  $299.99 for the complete bolt on carb assy.

Thanks again,

Kurt

[firstturn]

Kurt,
  A new 27mm Bing cost more than that if you can find one.....

Ron Carbaugh

[Gordon Brennan]

I know I can't compare my Bing 24mm Trials Carburetor to yours Kurt. But I will tell you I had trouble with it for a while and even put a Mikuni on the bike. That didn't solve all the issues, so I went back to the Bing and put a lot of R&D & $$ in to it. When I finally got it right, I'm very pleased with the Bing now, and glad I spent the time trying different jets and needles; pilots, needle jets, jet needles, float needles and seats.
If your carburetor has a choke, the plunger would be where I would start. If the bottom of the plunger (inside) is soft and gooy, that might be your problem. It doesn't seal off the orfice at the bottom of the hole properly.

[400gs6]

Thanks guys, my carb has the cable operated "blade" style choke that is located within the slide.  I'm suspect of the 50 pilot.  Should it require that big of a pilot?

Also, would a 180 main be considered too lean for a 400 and contribute to the pinging on hard acceleration?

Kurt

[Doug Bridges]

Search the forum for a post entitled "Mikuni Questions Again". There is a reply to that post from John Durrill that includes Bing carb jetting info for all sizes of engines. I used these specs for my Jackpiner and they were spot on. Good Luck!

Doug Bridges
73 Jackpiner
74 Jackpiner/FrankenPenton
project
82 XR200R

[Big Mac]

Kurt - I have two 400s and have used 40-45 pilots and 185-190 main jets, but both have had GEM reeds so jetting can be a bit different than stock. No problems with either on blubber or ping.

Problem with older Bings is that slides wear. The ones with relatively tight and non-worn slides will idle and start well, plus are easier on jetting adjustments. Well-worn slides with a "smile" on the filter side pass air at idle and minimum throttle, so get richened with jetting to compensate, then are tougher to jet for 3/4+ throttle.

Manual says 50 pilot is standard, may be a bit large but not too big to cause an issue with a smallish 180 main. A 40-45 pilot and 190 main with a decent slide and needle clip in 2nd groove oughtta be pretty close to good for most conditions.

With timing spot on, your ping could also be from compression being a bit high due to thinner base gasket than stock after the last rebuild. If you're using premium pump gas, try 50/50 with race gas or AV100 and ping will probably disappear.

New Bing slides are awfully expensive. Lots of old Bings on shelves though and if you dig through many slides with calipers to find the least worn, you can get by. Few that I've had idled well, but for most riding and racing, idling's not a necessity and Bings run like a spotted ape at speed.

I have extra old slides that I've picked over, might be one better than yours, can check if you can take an accurate measurement. Should be a #2 slide(?), there are #1s and #3s with differing cutaways. Hope this helps.

Jon McLean
Lake Grove, OR

[tomale]

I have had alot of experience with Bings and the best thing I ever did was to call Bing International... they not only had the stock spec's but all the parts to make it run well again, Replacing the slide is important but I also found the air can leak from other places too... So I replace all of the gaskets and all of the rubber parts, after that, the bike ran alot better..The problem with stock jetting is the fact that it will change depend Altitude mostly  but also Humidity and temperture. I find that I have to change my jetting from summer to winter....

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[garrettccovington]

Bing internation sells a manual and I think its around $11.00. As I recall the shipping was more than the manual.  The good thing about it is it covers all bing carbs, so I can use it for my BMW's, KTM and Penton.  It also means, that I don't have my bikes running correctly.  But then again, I'm not the sharpest tool in the shed.

G

72 six-day
79 KTM MC80 250

[brian kirby]

My MC5 400 has a 50 pilot and a 180 main, but I went down a LOT on the needle jet to get it to run clean in the middle, stock is a 3.22, it had a 3.20 in it and I have a 3.18 in there now. With a new 3.18 needle jet, and a new needle it runs clean and crisp and with 50/50 race fuel and pump gas, zero ping. The air cooled KTM engines, especially the 250 and 400, are very high compression engines and in my opinion it is mechanical suicide to run straight 93 pump fuel in them. When those engines were originally built pump hi-test was 99 octane leaded and you didnt need race fuel, plus with the ethanol in pump fuel I would just go strictly AV100 or 100% race fuel.

Brian

[Kip Kern]

Kurt

I ride the same bike (76 GS 400) and this is my 38mm Bing setting at 800' above sea level.  #1 slide, #1 needle, 170 Main Jet, 2.82 Needle Jet, 45 Pilot, 40-404 Atomizer, Air Screw 1/2 turn out and needle clip 2nd from top.  Runs perfect, a little fat but I like it that way!

[400gs6]

Thanks guys!

Kurt

[Steve Minor]

For what it's worth, these are the settings and prices that Bing International sent me some time ago.

1977 Penton 400cc GS6
Stock Jetting Specs @ sea level are:
44-051-185 Main Jet @ $4.38
45-120-3,22 Needle Jet @ $8.15
46-360-401 Jet Needle in position 2 from top @ $7.07
44-353-50 Idle Jet @ $11.72
54 Soft OHGK ( contains gaskets, o-rings, float needle, pivot pin and cable
grommet) @ $30.17
We accept Visa or MasterCard. You may order by email or call 800-309-2464.
Respectfully,
Fay

Steve Minor
Wilmington, NC

[brian kirby]

I was wrong, my main is 185 like Steve's info from Bing, but I went down to a 3.18 needle jet.

Brian