Pulling the head on a 1969 TC120

[gr120]

I recently pulled my 1969 TC 120 out of the back of the barn. I Purchased this puppy new right after I got out of the military and had some great times on it. Decided to get it out when my grand children discovered it and thought it was "really cool". With that said I had to clean the tank out and gave the carb a good going over. I now have spark and fuel but no luck in getting it to start. I checked and the compression seems really really low. So I am thinking I need to pull the head to take a look. I really would like to find some instructions procedures to follow rather than just getting in there and "winging it". If anyone can provide any info to the process I would really appreciate it. As near as I can recall it has been at least 6 years since the last time I cranked it over and took it for a little spin.

Thanking you in advance,

GR

[Craig380]

hi and welcome!

There's the Suzi shop manual for the B100 here, which is pretty much the same engine, to help with any jobs you take on.

http://www.oldjapanesebikes.com/mraxl_G ... /index.php

I would lift the head and see if there is anything strange going on - it's only 4 nuts. You can re-use the cylinder head gasket for the purposes of trying to get it running; you can always fit a new gasket once it is running.

Have you tried using easy-start spray or similar, just to see if you can get it to run for a few seconds? If that works, it's probably the enrichening circuit in the carb is gummed up. Worth a try before breaking out the spanners.

Good luck and keep us posted.

[gr120]

Hey Craig,

I really appreciate the manual, after viewing the B100 does look a lot like the TC120. Sure wish I could have printed some of the pages.
With that said, I did spray "a smidge" of starting fluid into the cylinder on day one in a attempt to get it to go. It made no attempt to "fire up". I am going to pull the exhaust down and take a look to make sure it is not plugged off. I think the problem is (big on the think) that the problem the lack of compression perhaps a ring may be stuck or broke. I will let you know hopefully this weekend.

Again I really appreciate the feed back,

All the best

[gr120]

Well good news bad news! Removed head and piston and found the piston and ring groves are both damaged. The cyl will need to be re-bored. I have been looking for what is available in the way of parts (over sized pistons etc) and so far I have been unable to find a listing for my 1969. I did find a listing for 1971 TC 120, but by then they were "ramping up" the power starting in 1970. Moral of story while it appears that there are parts available for the 1971 I really need to verify if the parts listed for the 71 will fit my 69.

If anyone can help to ID the proper parts I would be sooooo appreciative. I would hate to retire this puppy its been a great friend for 46 years!

Gus

[jabcb]

A printed parts manual that covers the 1969 TC120 is a good start.

eBay doesn't list much:
http://www.ebay.com/sch/Suzuki-/38663/i ... zuki+tc120

I have a few manuals from this New Zealand seller. Takes a little longer for the manual to show up but its worth the wait.
http://www.ebay.com/itm/SUZUKI-Parts-Ma ... 1016718061

[Craig380]

It's really hard to know if Suzi did significantly change the piston type on the 120 motor: infuriatingly, sometimes they'd use the same part for years and across several models; other times, they'd fit unique pistons to one model year only.

My 10 cents is that the 120 motor was so long lasting, they probably did NOT change the piston part #, but that's only a guess.

The B100P parts manual is here, for what it's worth: http://www.oldjapanesebikes.com/mraxl_G ... /index.php" onclick="window.open(this.href);return false;

[gr120]

Hey Craig thanks again for access to the parts manual. I have found several pistons and attaching parts but it appears the real problem is going to be the ring set. I contacted several dealers in the area and they are trying to locate them for me. It was so cool that some of these parts guys were really "pumped" up in trying to help me get this one back on the road. In looking at the parts off this manual it really looks like the same but we all know how that goes........

I am going to send the numbers first thing on Monday and cross my fingers! Really appreciate all the input!

All the best,

GR

[gr120]

Well its been awhile and a lot has happened since I posted last. I dismantled the top end and started the process of finding parts. Finding a parts manual was a bonus, it is listed for the 1970 but the engine parts are the same for the 1969 and 99 percent of the body and frame parts. I took the "Cyl Barrel" to a machine shop and they recommended that I go with the 2nd over sized piston and rings. I found both the piston 12110-20730 (2nd over sized as well as the ring set 120140-20731. I listed the part numbers just in case someone else out there is in the need to ID the parts as I was. I also picked up the piston pin and cir clips, needle bearing,gaskets and carb seals and of course the parts manual. I managed to get that done for UNDER $100.00. All parts were NOS and in original boxes. A LOT of patience to keep my cost down, but worth it.

Well that was the good news! Finally got some free time to get the "show on the road" and dropped off the "barrel" and new piston at the machine shop. Got a call from them 3 days later telling me that there was a problem and I would need a bigger piston. I told them them I purchased the 2nd over piston as recommended and there is nothing bigger. The story is that the wear in the "middle" of the barrel is worn past the dimensions of the new piston, so everything has come to a halt. I did ask them to mic the piston to make sure it is 1.0 over (2nd OS as advertised by the seller. He also said they would try to find a after market piston bigger than what I have. Sure as heck wished they did a better job of measuring the ID in more than one place.......

Any suggestions out there are more than welcome, I really hate to shut this down. I did find a new Cyl but the price is WAY out of my budget.

GR

[Craig380]

Sorry to hear that. However, it could be well worth cross-checking the part number of the cylinder against other models, like the ordinary roadgoing B100P / B120P. It could well be the cylinder is common to all of them. Even if it's a different part number, I bet a cylinder from the road / commuter version will fit the cases and work fine.

In which case, you've got a wider range of new or used parts to go for.

The other possibility is look for an aftermarket manufacturer's piston kit, which may be available in a larger oversize than 1mm. Mitaka pistons are well-known and widely used in the UK in classic Suzis, Yamahas and others (they are the OEM in Japan for 'Genuine Yamaha' pistons and others) and typically make pistons up to 2mm oversize (i.e. 4th oversize!)

Try calling or emailing the UK stockists, Grampian Motors in Liverpool: sales@grampianmotors.co.uk / +44 151 931 5009.

PJ Engineering also carries Mitaka pistons: https://www.pjme.co.uk/acatalog/Contact_Us.html" onclick="window.open(this.href);return false;

Knowing both of them, you're best served making a quick call, I think - neither is particularly fast at replying to emails!

[oldmanhonda]

I recently pulled my 1969 TC 120 out of the back of the barn. I Purchased this puppy new right after I got out of the military and had some great times on it. Decided to get it out when my grand children discovered it and thought it was "really cool". With that said I had to clean the tank out and gave the carb a good going over. I now have spark and fuel but no luck in getting it to start. I checked and the compression seems really really low. So I am thinking I need to pull the head to take a look. I really would like to find some instructions procedures to follow rather than just getting in there and "winging it". If anyone can provide any info to the process I would really appreciate it. As near as I can recall it has been at least 6 years since the last time I cranked it over and took it for a little spin.

Thanking you in advance,

GR

I too have a 69 TC120 (yellow) only I bought mine a year after I entered the military. I bought it in Alameda CA, and
like you I held onto it all these years.
..........................Perry................

[Coyote]

I'd be suspicious. It sounds to me like the bore man scrapped your cylinder. 1mm oversize amounts to 20 thousands per side. That's a LOT -- unless the piston in the bike was already first OS. I'd go get it and have a look and /or have someone else mic it. I think the shop made an oops and are trying to cover their a**. Get it take it somewhere else and have the bore miced. If they are telling you the truth, the center should not be cleaned up. If you can't visualize 20 thou in you mind, get out your feeler gauges and have a look at the .020 blade. And remember, that's per side !!

I have my reasons to be suspicious. Take a look at this horribly scored cylinder that was on my 550. It cleaned up with room to spare on first OS (.5mm). That's 10 thou per side.

[gr120]

WOW!

From the bottom ring up, that sure looks like my piston.

Where it stands right now I am waiting for the machine shop to return my cyl and piston. My barrel looks NO WHERE as damaged as your 550. We had a slight exchange of words and I told him not to touch anything just return it to me as is. I agree that .020 is a lot! That is why I was kept telling him that it something is just NOT on the up and up. I've had this bike since day one, so I figured something happened in the boring process. The dealer that shipped the cyl recommended the 1.0 piston so that's what I got. I was shocked that he was asking for the 2nd OS because the barrel just did NOT look that bad (damage) to me.

I should have it back by the end of the week. Still hoping that I can resurrect the bike, but budget restrictions are in place.

Really appreciate the follow up,

Hoping to put a 100 miles on the "Spirit" tomorrow, good weather coming!

[Coyote]

The PO said he rode it home but it didn't run very well. I thought it was going to be quick fix and go riding. Got it home and did a compression check first thing. 120, 115, 18. Eighteen That's what prompted me to tear into it. Those photo's are when I first opened it up. After seeing it I was surprised it showed any compression at all. What really blew my mind is the spark plug looked normal - just like the other 2. Medium tan. Never did figure out what caused it to self destruct. The other 2 pistons and cylinders were fine.