a matter of ping

[TGTech]

Tom,

   In cross country racing, you're on the throttle for longer periods of time, so that heat build thing can definitely come into play. By dropping the deck height, you lower the compression and reduce the chance for heat build.

Dane

[Big Mac]

Man Dane, you're a moto-genius. Wish I had you down the street from me when I had parts strewn across the bench, I'd buy the beer for the occasional advice.

Any houses on your street for sale, about 800 sq ft would do it, but with a 3-car garage and minimum 1/2 acre lot for test runs out back?
[)] My two boys need a godfather too...

Mac

[tomale]

Dane, that is what I thought, no wonder my Maico does not like Cross country. It has a 12:1 compression ratio... Last year I rode a CC event and the longer I rode that maico of mine the worse it ran... I found myself really backing off the throttle and riding as easy as I could with out loosing too much time. It was shortly after that race that I found out how badly worn were a bunch of the parts in the Bing carb. I rebuilt it replacing almost everything inside and wham! it ran a bunch better...
Funny thing was... it had the wrong slide and the wrong jet needle and needle jet...It does not start quite as easy anymore but it sure runs nice.
sorry about riding something other than a Penton but I just love that thing.... But as I have discovered it has its limits too.. No I am not getting rid of my Pentons...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (project bike)
72'sixday (project bike)

[Rain Man]

Great, Great Information,  wow   [8D] This thread is waht makes us unique!!


Raymond
 Down East Pentons

[Merlin]

.............when using a Bing carb on any brand be sure to use the later type vaporizor with one small air correction hole,the one with 4 big holes will in most applications cause pinging if you are jetted clean and run too rich when jetted to stop the ping............

[tomale]

Bings are good carbs but you need to understand that they do wear out. The Bing on the maico started having problems and I could not figure out why, I was begining to think that I was having a leaking problem so I started running test to see if that was it. Nope, What I soon discovered is that the Bing was wearing out. A call to the Bing agency brought even more infomation. The Bing had the wrong slide, needle jet and jet needle. As a result the pilot jet needed to be changed too. I was told that the needle jet and jet needle need to be changed from time to time because they wear out. The slide looked ok but I figured I might as well change it out too, and the other thing was that the little rubber boot on top of the carb needed to be changed because it became loose and did not seal. With a bing it is really important to seal up all air leaks,,, another potenial for air leaking is around the air mixture screw.... These are going are all small things  but can add up to be a big thing.
My question about Pinging is related specifically to fuel and tuning specs and how they related to one another. This tread has been really informitive and yes we are unique.... What amazes me is why other sites are not more like this site... the bar is set high and I for one like...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (project bike)
72'sixday (project bike)

[Mike Lenz]

I set the timing and deck hieght at stock and then play with the needle and main until I get rid of the ping (and get a good clean running bike). Always works well, espically with the newer needles (4k2 or 8L2 and corresponding n jets). Using 93 oct pump gas. I could get you pretty close on a 400. I have the different combos I have come up with written down somewhere. Let me know if you want them.

[tomale]

Mike, yes I would. my concern is as we move into the hotter months I may run into heat build up on longer events....My 250 always seem to be really loud... alot of noise coming from the fins... not sure that it is pinging and I know it is not piston slap. While I was in Oklahoma I did run some race fuel in with premium... and that seemed to help but not too sure about that....
All of this is fun to me... cuss I love to learn. I figure the more I know about the bikes I ride the faster I can ride them...besides that a well prepared bike is always faster....
Thanks for the help.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (project bike)
72'sixday (project bike)

[Mike Lenz]

OK here is what I have. All work but the 4k2 and 8L2 combos work better but may be only be able to run in the newer style carb. Im not sure you can get the needle jet sizes in the old carb?? 4 ring needle/324 nj - 4k2n/282nj - 8L2n/286nj. I run at least a 190 main with the airbox plug out (frame breather).  I have never been able to get the 400's to run good with that plug in?? A 185 may work for the main if you havent cleaned up the ports any but Id start with a 190. Also start with the needle all the way up to be safe and work from there. I run a 50 pilot in all but again I run all newer style carbs so Im not sure about all this in an old style. I live in the midwest, so if you are on the coast or mountians???. Pinging is usually LOUD under full throttle and a frightning sound so Im not sure thats what you are hearing. Hope this helps.  Email me if you need further help.

[Merlin]

.........spark plug heat range is only governed by combustion chamber temp ie spark timing,jetting,fuel quality,compression,use the hottest plug without over heating the insulator of the plug,my Pentons large and small run fine on NGK B8HS or Bosch W280,if one were riding to an extreme of extended low
speed or high speed a plug change may be in order mainly to keep the plug clean or prevent boiling the insulator..............

[tomale]

Merlin,
The NGK B8HS  is what I am what I am using. I never did know just how that all works... as far as sparkplugs go.... I have never had a problem..... what can I say...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (project bike)
72'sixday (project bike)

[dkwkid]

Just a word to the wise:
 you should always jet your midrange a little rich. You almost never seize on the main jet- it will stick when you roll off the throttle back on the needle. This applies mostly to desert and cross country racing- if you are poking around the woods at 15 MPH you most likely will not have a problem. Remember, the Sachs factory GS heads were higher compression and they seemed to hold up O.K.

[Mike Lenz]

Thom,
FYI with those jetting specs I use the orig recommended NGk equivalent "9" range of plug.

[tomale]

Thanks Mike, Dane and to all that have added to this thread... it was fun....I learned a bunch...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)
75' GS400 (project bike)
72'sixday (project bike)