So I watched this TC120 in the flea market for a bit but travel wasn't convenient at the time. The seller offered to deliver it within a few states away though so I had to bite. Delivered by stand-up inmate @concours on Christmas eve. His pictures from the ad: Something about this little bike spoke to me, and I was largely done with my first Covid project, a 1981 CB750 cafe. I've never dealt with a seized engine before, so this should be educational. I still can't understand how the fuel tank is so pristine inside. Anyway, the bike is 100% complete with the owners manual and tool kit.
I dragged it into the basement, nearly losing control down the hatchway stairs. I should have waited for help but all's well. Started by cleaning things up a bit and researching availability of parts. Most of the chrome cleaned up with a lot of work to a presentable level. With the exception of the rear rack which all these bikes seem to have but must have been an aftermarket item since the finish was not up to Suzuki quality chrome. I ended up painting it black but unsure if I'll ever reinstall it. The seat was ripped and pretty crusty I managed to find an aftermarket cover in Thailand. I was reluctant to purchase something on unknown quality but figured, who knows, these might not be available much longer and I couldn't find one anywhere else. Hardest part was the 10 tiny nuts and bolts holding on the chrome trim piece. 8 of the 10 stripped so I cut them off with a dremel and found replacements at Lowes. Obviously repainted the pan while it was off. Photos taken before I polished up and reattached the trim.
With the head off and cylinder soaking in Liquid Wrench, I moved onto the oil tank. In good shape but filthy and the decals are shot. Might as well get new ones while they're available too. Cleaned up the tank and thought about repainting it but went with a good polish. I don't plan on painting the fuel tank so figured I'd leave some wear on the oil tank as well. Repainted the sump guard and bolt-on drop tube of frame. They were beyond being presentable.
The front brake lever was broken and the kickstarter rubber piece was brittle and broken. Managed to find both NOS. Onto what scares me, the engine. The exhaust nut would not move. Not with heat, force, or swearing. Looking at it, the pipe was already split and twisted slightly at the nut. That made my decision to just cut the pipe off, to minimize damage and time, hoping it can be welded back later since it's already perforated. Hacksaw. The piston was seized at nearly BDC so I made some wood spacers to fit under the cylinder before attempting to move the piston down. It took over 2 months of penetrant and beating to make it move. Knowing the piston would be ruined, and the cylinder scarred, I ordered some NOS piston and rings (0.5mm over) and a used cylinder with stock bore. Might not need the cylinder but they seem to be a little rare so bought it while I could. Finally. Rings were rusted pretty good to the cylinder wall.
Any experts here on old 2-strokes I have a couple questions. -Does that piston look like it seized from running or just from sitting 35 years? -The original exhaust cleaned up nicely but as I said, I had to cut it. Any advice on where to go from here on the exhaust when the time comes? Thanks for the interest, so far this has been fun.
I'm far from an expert and only tinkered with Bultacos, but do you see (feel) any vertical scratching, notching or groves on the piston? How does the cylinder look? Perhaps a light hone and a new set of rings.
I already bought a NOS Suzuki piston, 0.5mm over, as well as rings to match. So I do plan to hone, or bore, it out. Or, hire someone. I do have one of these at home purchased from an estate sale years ago: As far as putting the exhaust back on when the time comes. Weld it? Braze it? Try to find a new one (not likely)? And, I'm curious what caused the engine to seize. Just sitting or oil starvation or?
I'm not sure it sized, unless you're certain it did. Fine business on new 0.5mm piston and rings. Depending on where you cut the pipe, perhaps a larger sleeve over the two pieces and Tig weld would work. Or, you could replicate the entire bend to the exhaust guard and use new material. Some vendors sell pre-bent mandrel radius curved pipe, but that's more welding and fit-up. Curious if the entire pipe is available on ebay as an OEM, new-old-stock unit? If so, that may be a time saver and the way to go. Good luck.
Suzuki TC120 CAT 1969 GENERAL EXPORT (E01) MPH SKID PLATE- MUFFLER - buy original SKID PLATE- MUFFLER spares online
Nice little project you have there. Enjoy getting it running again, should be fun, and some good learning.
Thank you for that link. Unless I'm reading it wrong, they only have the baffle and guard, not the actual pipe/muffler. I haven't seen one available but I'd prefer to use the original one over if I can repair it without it looking too offensive.
You're welcome. Unfortunately, that pipe is not available from CMS. Understand your desire to use what you already have. I'm sure that exhaust (part 1430120200) is elusive to locate and expensive when found. You may be able to piece the two cut exhaust pieces together, tack weld (check fitment) and weld together. Then, sand down the weld (best by hand, not grinder) and the repair will not be visible. I've done that with expansion chamber exhaust headers and they come out looking very nice. Not sure if the TC120 header was originally a chrome finish, but you can always paint (header black paint) up to the exhaust guard on your pipe.
And, the oil tank back on the bike with new line. Changed the transmission oil. Manual calls for 20w-40 motor oil. I used 15w-40. Flushed out the engine with some thin oil. While putting in the new oil line, I retapped the mounting threads for the side cover screws as they were all a little funky. Painted the "Suzuki" embossing black, just because I thought it would look good: Cleaned up the original cylinder and spare on the exterior, as well as the head: In the background you can see the painted cargo rack and heat resistant painted skid-plate and frame drop. Removed the mag rotor in prep for replacing the crank seal. One thing that surprised me is how frozen the carburetor is. Soaked in penetrating oil and cannot get the slide to budge. Of course, without moving the slide one cannot remove the cable. The mechanism for the "Dirt/Touring" gear selector was interesting and had to be removed to get the side cover off to access the mag. Hopefully I remember how it goes back together. And, a box of parts that have been cleaned, polished, etc.
Enjoying the rebuild Do you have access to an ultrasonic parts cleaner? Drop the carb and cable and all in and it should free up. It worked for a set of 36mm Dellorto’s which were on a shelf for 10 years with fuel in them. If you know a good welder then replace to first few inches of the header pipe. Also know the the old steel gets brittle with age. My PE175 powered RV125 blew a small hole in its chamber
I would say the piston looks cold seized to me. How does the bottom end look? I was wondering how long it's been sat for, crank seals tend to harden up in a relatively short time. If you're not going to split the engine I would keep a really good eye out for leaks when you fire it up, be a shame to seize a brand new piston.
The bottom end looks...okay I think. I flushed it with thin oil. The bike sat for at least 35 years and I will change the mag side crank seal at the least.
That would be good, the later Yamahas I've worked on are captive so you have to split the cases. I seem to remember you can clearly smell the gearbox oil in the smoke when the other side goes, it was a very long time ago I had one go though so might be wrong.