B Sachs powered penton 125

[pklinck]

As anyone who rides a penton with the Sachs motors knows it has a specific and high rpm power band.  Having said that, typically when the rpm drops way down and just before you have down shifted, the engine sound gives the typical bogged down performance and sound as with any bike.  On my penton 125, not only does it show the bogged down feel, it gives the appearance as if the spark also begins to cut out and so longer time to clear it out before getting going again.  The ignition with the old motoplat performed this way as well as with the new MZB ignition system.  Keep in mind, that when the rpm is up, both systems are per formant. This situation is a problem when you get in a mud hole....?


 I have not yet installed special spark plugs with the fine tip used with the MZB system yet.  I had to order them special for the new MZB ignition system.  
I have the 2.73 jet needle and the needle is new along with the float and float adjustment. Ignition timing problem is ruled out since it
was checked and cross check by using 2 different ignition systems.  

Any adjustment comments would be grateful.

peter klinck

[pklinck]

Another thing to clarify,  when it is "loaded up" as I mentioned above, that could mean a momentarily wet plug for as giving too much throttle when it is bogged down in attempts to get the rpm back up. Is there are carb. or plug adjustment recommendation?

peter klinck

[t20sl]

You might check the choke plunger and see it it still has the wax / rubber bottom on it.  Another idea is the slow jet size.  Might also check the needle jet for wear.  Drop your new needle into the carb from thew top and hold up to bright light.  Try and see around the needle from the bottom.  If this is worn it usually wears oblong.  Ted

[pklinck]

Ted,

Thanks for the comments.  Yes, I bought an NOS choke plunger (for 2 125s)and noticed today that in one bike that wax seal was and is not there anymore.  I'll check the race bike plunger and maybe order more new  plungers from Bing Int'l because both my 1973 pentons 125s have the same problem.

Secondly, could you give me an example of a "slower jet size"?  My pilot jet is a 45, the needle jet is a 2.73 purchased with a relatively new needle in 2011.

peter klinck

[Paul Danik]

Peter,

   Those little Sachs engines have a lot of usable power below the "hit", and in my opinion finding and using that power is one of the joys, and challenges, of riding a small bore machine.  That is also why I chose a 125cc KTM EXC over the 200cc version as my "modern ride".

   That being said, if I were in your shoes and were able to lower the needle, I would drop it a notch, or even two, and see if you notice a difference. If you notice a difference and the engine is running cleaner, you know you are looking in the right area and can start to fine tune the carb.

    I also want to mention that when looking for that low end power, I have always felt that it is important to coordinate the slide opening with the engine RPM with the use of the throttle. If you are pulling up a grade and the engine is pulling hard, and you know you can't pick up much speed or RPM, try to have the slide positioned just a little more open than needed, not wide open, and work the throttle just a tad. To often a lower gear is engaged to soon and while engine RPM is gained, often all you get is wheel spin.

Hope this helps.
Paul

[slvrbrdfxr]

Peter,
I agree it's best to buy the new choke plungers directly from Bing Intl. as I recently did. I learned a hard lesson by buying a NOS plunger from a seller on eBay thinking it would save me a few $$. As it turned out, the eBay plunger was no good and fell apart as soon as the fuel got to it. I notified the eBay seller and they sent me a couple more at no cost but they were badly degraded due to age and were unuseable. In the end, the cost of buying a new plunger from Bing was $14.83 shipped which was approx the same as what I paid the eBay seller for one that turned out to be no good. From now on I'll only get them from Bing. The Bing part number is 22-935-05 and they describe it as a "start piston". Good luck !!
Dave McCullough

[pklinck]

Paul,  Greetings.

Yeh, a same bore motor like the sachs engine is what I have also like about them is that specific power band, how to stay in in and work around it.  It takes more skill and this challenge is always what drives me.

POINT: So you suggest to "lower the mail needle one notch" to be leaner to confirm.  Secondly, because of so many adjustments in rebuilding a bike, I have not fine tuned the carb., etc.  I arrive in Mass. on the 21st. via 51 tk and two 125s. I hope to see you there.

Dave,  Yes, you are correct, Tom G. sells the NOS choke kits and I just blew one out this week. It is age (wax) and the ethanol issue.  However, I am using non-ethanol 91 octane gas now. I ordered this morning 2 plungers and they arrive this Friday.  Thanks.

peter klinck

[pklinck]

Paul,  yes a small bore not a "same bore"

and lower the main needle not the "mail needle"..sorry for the errors.  I should be in bed it's 11pm.  cheers.

peter klinck

[Paul Danik]

Peter,

Yes, if you find that the choke is working properly, I would suggest that you lower the needle one notch, that would be leaner.

Paul

[pklinck]

Paul,

Thanks for the advise.

peter klinck

[gooddirt]

There is something called silicone that I think can replace that old wax from the sixty 's and seventy's , someone told me the stuff is cheap too [:0]

[Dale Fisher]

I have been working on transforming the Berkshire MX for use at the Dalton RR.  First to come off was the Circle F pipe to be replaced by the OEM quieter exhaust.  Once only that change was made the performance changed considerably to the worse.  What was once a very quick bike had no top end.  Mine has a Mikuni and and the symptoms sound similar to what you are describing with your bike and the Bing.  I tried everything possible to get the Mikuni dialed in with no luck.  Having one advantage over yours with the easily adjustable PVL I made a slight change to the timing and the bike came back to life. Now it's zippy and quiet  Photos for the what did you do to your bike coming soon.  

Working lights with a PVL? (Mini 12V battery)

Dale Fisher
Penton Owners Group - Memberships
Facebook - Cheney Twinshock Racing Group - Administrator

'70 Six-Day 125 - V2017
'71 Six-Day 125 (Dave Fisher's) - V5553
'72 Mudlark - W257
'73 Jackpiner - 175 21159727
'74 Berkshire 100 - 40171056
And some silly other bikes...

[Daniel P. McEntee]

One thing to check that gets overlooked on these old bikes, even when rebuilding them sometimes,(I've forgotten it myself sometimes) is a clogged exhaust system. Pull it apart as much as you can and burn out all the carbon and spooge, and get it as free flowing as you can.
 Another trick I learened from the great Speedy Clasen is to file a notch at the bottom of the slide, 1mm deep and 2mm wide. This lets in a bit more air as the slide starts to come up and helps low end and mid range. I think Speedy said they did it to the 27mm Bings they used on Zundapps, but I tried it on the 36mm Bing on my '77 250 Hercules GS/7 and it helped out a lot on that bike. Someone else mentioned timing and after checking all the before mentioned areas, maybe just a careful tuning session with the air mixture screw to finish it all off. I'll bet you are closer to what you want than you think. My third bike back in the day, was a '72 125 SixDays, and I liked to ride it in the enduro bike class at observed trials meets. I replaced the Bing with a Mikuni, changed the ignition it to a point system with a heavier flywheel from a sand cast 100 Berkshire that I had at the time also (mainly because I burned up the motoplat and couldn't afford a new motoplat yet) and it performed quite well in trials, and would still hold it's own against most 175s on the top end. Wish I were the same size and weight I was back then!
   Type at you later,
   Dan McEntee

[pklinck]

Dale, Daniel,

Interesting info about how to modify or adjust something so the bike performs better, especially at the low rpm end (the slide, etc.).  I will also check more carefully how dirty the pipe is too.  And yes, the bike is getting closer to what it should be, especially with the MZB and the uridium spark plug.  I will also test the low end rpm on my land tomorrow with the new choke plunger.

Gooddirt,

Yes, the Bing Int'l Co. choke plunger cost me 19.76 dollars, arrived today.  The idea of trying a silicone can work too if it firms up similar to the original choke plunger gasket.

Another point,   according to technician Jerry at Penton Racing Products, the modern MZB and the older motoplat ignitions operate better with a platinum, uridium or similar spark plug with the fine tips.  That should also contribute at the low rpm when being bogged down too as a plug could begin to get wet.

Thanks,

peter klinck

[gooddirt]

Blue or black RTV type (using it from 1996 on 10 bing cups ); one is 33% softer than the Wax the other is 5% harder than the Wax, but then it all depends on the base line of the OEM factory hardness and if it was stored at sea level; was the storage baggie air tight? and for how many years.... [^]