Carb Adjustment

[ccmnova]

Having trouble wit my 1974 Penton 6-days trying to get the bike to idle and just cant seem to get the air mixture screw adjusted  - maybe doing something wrong.

I gently seat the screw and then back it out half a turn and go from there. when using the throttle the keep the bike running, it seems to be bogging and then dies. any thoughts to this condition - ?  any suggestions as to how many turns out from seated the mixture screw should be at least initially ??

[Daniel P. McEntee]

If you have a factory manual, consult that, but I think it says to be out at least 1 1/2 turns. all the way in, and then out 1/3 turn will make for a rich setting. The engine needs to be warm and at operating temperature. Make a small adjustment and then ride it around a bit and then see how it idles. Where your idle is set at will make a difference. Make sure your pilot jet is clean and open, and that float level is correct. All of these adjustments work together.
  Type at you later,
  Dan McEntee

[ccmnova]

Is it 1-1/2 turns or 1/3 turn ?  My book says lightly seat the mixture screw and then back it out half a turn. But i'm not sure if that means a half turn at a time or ??  My newer bikes for example say lightly seat the mixture screw and then back it out 2-1/2 turns.

[Rick Bennett]

There a lot of factors that change the way an engine runs. What ignition and timing do you have? What oil and ratio? What fuel? My Six Days has a 45 pilot jet, PVL at 2.6 btdc., Spector oil at 50 to 1, and 93 octane auto gas. The mixture screw is out 5/8 turn. It runs very well. Last week I needed fuel and dumped in some race fuel with 32 to 1 Yamalube. The engine bogged off of idle badly. I dumped this fuel out and went back to 50 to 1 and it runs great. I would have to reject to run 32 to 1.

Rick

[Carl Hill]

Many things can influence mixture requirements, including all those mentioned above. If you are running the mixture screw in and out and nothing changes you may need to look deeper. Pilot jet may be wrong size for your set up or elevation. Double check float level. Also look at your "choke" plunger, I have seen several that were deteriorated and let excess fuel in.

[ccmnova]

the specs on the Bing type 84-2 28mm carb are as follows: they are also listed on the bag the carb came in from Germany (will post a pic)

135 main jet
2.76 needle jet
6G1 jet needle in position 2 from top
35 idle jet
air screw setting 1 turn out

ignition is a new HPI with timing at 2 to 3 mm BTDC. Fuel mixture is 33:1

any comments to these specs for a 1974 6-days 125 ?

[ccmnova]

heres a pic of the carb specs

https://photos.google.com/photo/AF1QipPcmueDbey090rCzc9lXxjSyAAeAC6czTAYIZu6

[Larry Perkins]

Is your carb for sure the Type 84 Bing?  I think it came with the Type 53 but the 84 was the go fast hop up.  I have better luck with a 273 needle jet and always use a NEW needle jet as they wear.  I also use a #2 needle.  I am not at all familiar with the needle you refer to.  It almost sounds Mikuni.  Also be sure slide is not worn a happy face in it.

Larry P

[Steve Minor]

The spec you posted calls for 33:1 fuel mixture. That's probably the 1974 ratio. Modern oils allow you to use 40:1 and 50:1 ratios.

Steve Minor

[ccmnova]

quote:Originally posted by Larry Perkins

Is your carb for sure the Type 84 Bing?  I think it came with the Type 53 but the 84 was the go fast hop up.  I have better luck with a 273 needle jet and always use a NEW needle jet as they wear.  I also use a #2 needle.  I am not at all familiar with the needle you refer to.  It almost sounds Mikuni.  Also be sure slide is not worn a happy face in it.

Larry P

Yes its a new carb I bought from Bing 4 years ago and its "type 84-2". the needle that Bing said is in the carb is the 6G1 - that's the term they used

[ccmnova]

quote:Originally posted by Steve Minor

The spec you posted calls for 33:1 fuel mixture. That's probably the 1974 ratio. Modern oils allow you to use 40:1 and 50:1 ratios.

Steve Minor

Should I switch to the 40 or 50 :1 ratio ??  its not excessively smoking - is there a benefit to the higher ratio of fuel to oil ?

[Steve Minor]

The fuel/oil ratio is an on going topic...many theories and preferences. Some people say oil burns slower, therefore creating more heat with a higher oil ratio. Other people say more oil means more lubrication. All I know is my Stihl chainsaw uses 50:1 at about 12k rpms...never had a failure. You might want to use the search option on this message board and read what other riders do.

Steve Minor

[firstturn]

Thanks Steve Minor.  I have used Stihl for over 20 years.  No failures.

Ron Carbaugh

[ccmnova]

'74 6-days carb specs again. Can't get the bike started now and wore out my leg and wits.  Can anyone please comment on the jet needle number from Bing ?  Could this be right ?  should I switch to a 140 main, 2.73 needle and 40 idle jet ? What are others running ?

135 main jet
2.76 needle jet
6G1 jet needle in position 2 from top
35 idle jet
air screw setting 1 turn out

[Steve Minor]

That carb has a white plastic spring retainer...right? Make sure it's above the needle clip and not under the needle clip. I made that mistake once...drove me crazy until I disassembled the carb and figured it out.

Steve Minor