72/125 restoration

[fishshaman]

I have just completed my 72 125 Penton "restoration to ride".  I swapped out the bing for a mik. carb because it ran mucho better.  The bike runs strong at upper revs, but can I expect it to stay together for a 75 mile trail ride? I have never been a huge fan of 125's but to keep this thing moving at a reasonable clip the engine is squeeling.  Also, what can be done about all the missed shifts, is it me or do we need to be very carefull when shifting this bike?

 

[john durrill]

Fish,
 is the mikuni jetted right in the middle from 1/4 to 3/4 throttle? ( good plug reading). If its a B engine it will rev up quick but should pull well as long as you are in the pipe. Did you burn out the pipe when you did the restoration?
 sounds like you need to adjust the shift mech. you need a special too that Al carries and  wrench thinned down on a grinder to do the adjustment.
 You do have to be deliberate when you shift a sachs 5 or 6 speed. Just hold the lever up a bit linger while you release the clutch. if its adjusted right it will work fine shifting like that.
 if you don't have a shop manual for your bike you need to get one. it covers shifter adjustment.
John & Peter

 

[fishshaman]

Thanks for your reply John.  I think I have it jetted correct, and it runs much better than with the Bing, pulling stronger-cleaner down low and midrange.  I don't quite understand all this hoopla I have been hearing about the shifter adjustment, but I did have the whole bottom end rebuild by a good KTM shop guy. I'll take your advice and get the shop manual. How does one burn out a pipe? Sounds like trouble, can it be worth the effort?

 

[john durrill]

you will need to adjust the shifter on the little Sachs. not many people understand them that work in Bike shops today. not a fault on their part is just something that takes some pratice like learning to weld. its  a skill job. most folks can do it. Doug is an expert on the 100/125. we have some info posted in the library that will help also.
 the shop manual will save you lots of grief later when you working on the engine.
 The pipe cleaning can be a big improvement.
 we have had in as little as 600 miles  Hodakas that were running 20 to 1 oil mix plug up the pipe. all 2 strokes will do it some just sooner than others. carbon and unburned oil builds up in the walls of the pipe and plugs the air flow out of the engine.
 Basicly chokes it down. if you didnt burn it out and you dont know how many tanks of gas have gone through it, its a must.
 we had a guy with a husky ,at last years reunion ride , that was complaining about how the bike just didnt have the power it use to. we were kicking around ideas as to why and the subject on cleaning the pipe came up. when he got back home he got to thinking about it and decided to burn it out.
 he sent us an e-mail and thanked us. said it was like a different bike. had much more power and ran a bunch cleaner than it had in years.
 we use a 55 gallon drum and some scrap wood.
 hang the pipe inside , suspended buy a bar and some wire. build a small fire in the bottom and keep it fed till the pipe quits belching smoke. then turn it over and do the other end. it takes an hour or so to do the whole pipe. use a wire brush on the pipe in a drill and wipe it down with some acceton or lacqure thinner and then heat it up with a tourch to drive out and moisture or solvent , use a good brand of hi temp hedder paint and your good to go for a while.
 make sure and double check your timeing and the air cleaner, you know all the stuff we can over look some times or miss.
 retorque the head . if you put in new rings or have a new bore give it 3 or 4 tanks of gas to let everything seat befor you run it hard.
 that little 125 will go ( with clean air and the right jetting ) 6000 or better miles on a bore unless your MX ing. its a tough reasonable powerfull motor.i dont know how many medals were won buy bikes powered buy that engine in the 6 Days but it was a lot over many years.
Hope this was some help.
 John & Peter