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Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 3:01 pm
by Phatsalmon
Ok this project went completely south yesterday evening. The good thing is when it hard fails it has the tendency to point you in the right direction. Yesterday when Idling the bike began to smoke terribly. Oil started dripping from the tail pipe. This is the same problem that later model Enduros have with failed crank seals. I have replaced the left seal twice now and done leak down tests both times. All seems to be well. I will do the leak down test again today and will let all of you know what the results are currently. I took this project thinking it would be simple but it has been a big kick to an already inflated ego. It is indeed humbling. Time for expert help I believe. Probably something I am doing wrong.

Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 3:36 pm
by 250_Sprint
How did the two seals fail?
Did they fail the same way?
Did you get the seals from the same place?
Where are you getting your seals?

It can be a frustrating way to learn.
Good luck.

Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 3:44 pm
by Backyard Bob
Sorry to hear about this. My ego's been taken down a few pegs in the past also so I had to laugh a bit about your remark. I do wish you the best with this though and hope you don't give up trying to find the solution.

Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 4:11 pm
by Phatsalmon
Seal number SKF 6816. Not sure if this is the problem till leak down test is done.

My previous post was indeed a typo. 50 thousandths is correct.

Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 4:35 pm
by Mutt
NOS #5 jet is .030" #7 is .034" im not so sure those leak down tests are even worth messing with. I made up a special gauge setup. I changed the seals, shafts were good. Did the pressure test and the seals bubbled, not bad, but enough for bubbles. It sorta irritated me, after taking the motor apart a few times and retesting, that the motor started and still runs fine. If you are using the modern 6816 seal, it is designed for an 11/16" shaft. The sprocket shaft in your motor is smaller, at only 17mm. I am the only person I know that sells the correct seal.
Amsoil dominator 2 stroke oil is designed at run at 50:1. Even that will weep out the exhaust pipe. Your rings have to be sealing, or all that oil would stay down in your crank case.

Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 4:51 pm
by Phatsalmon
Mutt, thank you so much. I left a message with my phone number. Would you please call me.

Thanks so much

Re: 1948 125 Hummer will not rev up

PostPosted: Mon Jan 23, 2023 4:53 pm
by Mutt
Give me a call (903)880-3933

Re: 1948 125 Hummer will not rev up

PostPosted: Tue Mar 07, 2023 6:13 pm
by MrMarty51
I have never tried to drill a carb jet. I have read much advice against doing to, so, I buy the bigger size jets and if a jet has been drilled, toss it.
I built a tank tumbler from a BBQ rotisserie motor and gear box. Put sheetrock, decking screws, washers and any other kind of pointy devices I could find intto the fuel tank and tumbled it. Turning the tank to clatter a different area within every day, I made the tumbler so the tank could be pivoted to different positions. Kept that up for about two weeks until that rotisserie unit failed. By then the tank was quite shiny within.
I then rinsed the tank with detergent and hot water. Many rinse outs and detergent and hot water treatments, drying it out with compressed air after each wash/rinse cycle.
Got the bike all together. Running great, for a while, then it started getting sluggish and dying. Checked the spark, timing, all is good.
Off with the carb, dismantled and cleaned it out real good. Back together, not much improved. Back off with the carb, cleaned it out again. About this time I notice a very small bore from the float bowl tank going across, right at the very bottom of the float bowl housing. It was plugged. Cleaned it out thoroughly, along with the jets.
Bike run great, for a short while. That rifling was once again plugged. Cleared it out. Carb back together. Removed the fuel tank. Filled it with apple cider vinegar, shook it up real good every day for about two weeks.
Rinsed the tank out thoroughly and dried it out real well.
There was still a small amount of some kind of particels within. Back in with the vinegar, shook it real well, emptied the vinegar, more detergent and hot water, rinse with more hot water, bloweder dry. Looked mighty clean.
Installed the tank, fired up the motorcicle, little bird runs great now, no more plugging carb and no fuel filter between the tank and the carb.
Oh yeah, save that vinegar. It is mighty handy stuff for cleaning parts and dissolving rust. Pour it back into the jugs and save it.
I have one of those yellow squarish kitty litter buckets in the garage that is filled with apple cider vinegar. When I have parts to clean I hang them in there for several days. Works mighty fine. Even dissolves some of the old paints they used to use back in the day.

Re: 1948 125 Hummer will not rev up

PostPosted: Tue Mar 07, 2023 6:40 pm
by Brent
Glad to hear you got it running right!

Re: 1948 125 Hummer will not rev up

PostPosted: Wed Mar 08, 2023 4:58 pm
by MrMarty51
Brent wrote:Glad to hear you got it running right!

Dont know how I missed that post where Mutt had responded and the bike is now running.
My apologies.