running after 25 years

[G8GT]

Just got my old 1977 RM 125 running after about 25 years. Thought it was ignition component(s) malfunction originally, as I couldn't get a spark for anything. Didn't have money then, so I put it away until a few weeks ago. Still don't have any extra money but only one kid still in college. I was going to clean out the old garage and decided to fool around with the old bike a little. Pulled off the magneto cover and sprayed everything with Blaster and cranked it over and had spark, but a weak one. Pulled the tank and carb and cleaned them, mixed some new gas at 20:1 and after a few cranks had some backfire and sputtering. Messed with the timing a bit and finally got it to run with the choke on. Spark still seemed weak. I couldn't find the owners manual so I bought Clymers shop manual for $32 so I could get timing and carb settings right.
With everything set to stock specs it ran fairly well up and down the driveway, but not well at an idle then started missing at higher rpm. Pulled plug and went from intermitent spark to no spark. Plugged in a good lawnmower plug and got good spark so went to parts store and got 2 new NGKs.(2 because they only stocked 2 of that number and I was optimistic).The new plugs sparked consistantly but still seemed weak. Figured I still was going to have to get coil or other parts from what I was reading in this forum.
You guys know the difficulty in finding key parts for these old bikes and things were looking bleak. I noticed that the old fella who had the old Hodaka motorcycle shop when I was in high school (1980), was still there and stopped one saturday evening when the sign said open. He was mostly collecting old antique outboard motors mostly but I wanted to pick his brain . I told him what the motor was doing.
He said with the new high energy plugs get it totally dark around the plug with it grounded good and then see. "You'll be amazed" were his words. I told him I had adjusted the plug gap through the entire range the manual called for and was out to.030. He said with the high energy plugs to go the other way and to try .010. He though my problem was my gas/oil mix. He said to get Stihl chainsaw mix and mix it at 32:1. and clean the carb out again blowing it out with air. I had already gotten the offroad gas and mixed 2 gallons at 20:1, and had 3 gallons of straight left. I was alittle skeptical of the ratio, and questioned him. He said the Stihl mix had additives in it to help it last and the lubrication quality was so improved over what I used to run it wouldn't hurt the motor and it would still smoke like it was meant too. I decided to try his advice.
I mixed the new ratio, cleaned the carb again.(manual is very good). Pulled it all apart. Blew out jets, and replaced needle valve with one out of my brothers old RM(which is so far gone I might never get it to run), which seemed to have a better spring action. Put it back together and it ran on the 3rd crank. I rode it for an hour all over, adjusting idle after it warmed up. Never died at all, and started every time I shut it off. Ran like it did years ago.
I know I got lucky probably, but wish I,d tried harder years ago. My son who just graduated with a civil engineering degree, figured out how many ounces of gas I needed to added to the 20:1 mix minus what I'd "thrown out" from the tank, to get it to 32:1 for complete recovery of the gas investment.
Now since I weigh 50+ more than the 160 when I was "Racing" in '81 and had geared the bike up to where 1st was about 1/2 way to the stock 2nd mph (great for holeshots back then), I need to get the gearing back towards stock or maybe even alittle lower to haul my weight around the trails with less clutch slipping. Currently 12 teeth on the counter shaft and 48 on the rear sprocket( #151X from sprocket specialists, 520 chain). Anyone have any suggestions for what I want to do? Remember money is still tight and my hours for work get cut back in winter so buying a 250 which is what I really need/want isn't a feasible option.

[AJ_YFZ]

Welcome to ... Great introduction.....

[Spikester]

It's hard to clean carbs, sometimes it takes 2 or 3 times to find all the crud. I would set the plug gap to standard,.010" is not enough. Congrats!

[G8GT]

Thanks. Still have improvements to go like shocks as the old seals are leaking. Can't remember what teeth changes I made with the sprockets as I changed both and went to the 520 chain back in '80. I didn't keep the originals because they were worn out. I think adding teeth to the rear would drop the gearing but how much? Stock top speed was about 69mph with stock sprockets. Current gearing I estimate allows about 75mph with 12 tooth counter and 48 tooth rear.

[dogger315]

Add two teeth to the driven sprocket if you want to return to stock
gearing. If you need more, try a 52T sprocket. Any bigger and you
may run into problems clearing the chain guide. I don't recommend
dropping any lower than 12T on the countershaft sprocket.

dogger

[G8GT]

Thank you very much. Just the info I was hoping for.