79 RM125 build - FINISHED!

Hammer 663s
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Hammer 663s
Edited Date/Time 7/5/2021 12:48pm
Picked this up a couple weeks ago. This weekend was the start of the full tear down. I plan to restore it and let my boy ride it in vintage class stuff. Here's where it started - in remarkable shape for 42 years old.





Here's where I got to. I believe 90% of the parts are original. Plastics were rattle canned but appear original. I think the headset grease was original and bearings were actually ok, as are the races. I don't think the cases have ever been split. It looks like it's on the original swingarm bearings. The original hubs, spokes, and rims are on it. Pipe is original and almost perfect.









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Hammer 663s
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Hammer 663s 2/15/2021 4:19pm
2/15/2021 4:19pm
Round 2 of photos.

The big question is powder coat the frame black or Suzuki blue to match the stock graphics I will put on?






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Mr. Robinson 2/15/2021 4:24pm
2/15/2021 4:24pm
I hope you bought a lottery ticket at the same time, because it was your lucky day. That is one nice find right there.
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sandman768
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sandman768 2/15/2021 4:30pm
2/15/2021 4:30pm
Nice bike! Low hr for sure... the rear fender & chain guide were the first to go back then. I would keep the frame black, I just don’t think these bikes look good with too much blue. These were good bikes back in their day....
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Hammer 663s
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Hammer 663s 2/15/2021 5:22pm
2/15/2021 5:22pm
sandman768 wrote:
Nice bike! Low hr for sure... the rear fender & chain guide were the first to go back then. I would keep the frame black, I...
Nice bike! Low hr for sure... the rear fender & chain guide were the first to go back then. I would keep the frame black, I just don’t think these bikes look good with too much blue. These were good bikes back in their day....
I had one in 1980, which is why I bought this one. Relive the glory days. This will have number 40 on it, since that's how many years since I last rode one. I am leaning towards black since I want to stay close to stock.

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pvangel
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pvangel 2/17/2021 6:10pm
2/17/2021 6:10pm
Check the left case where the crank bearing sits, they tend to be bad and the bearing will not sit in firmly causing the seal to fail. Very common problem now on the 79/80 bikes as the Magnesium has weakened with age.
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Hammer 663s
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Hammer 663s 2/17/2021 6:34pm
2/17/2021 6:34pm
pvangel wrote:
Check the left case where the crank bearing sits, they tend to be bad and the bearing will not sit in firmly causing the seal to...
Check the left case where the crank bearing sits, they tend to be bad and the bearing will not sit in firmly causing the seal to fail. Very common problem now on the 79/80 bikes as the Magnesium has weakened with age.
Thanks. Motor will come apart this weekend so I will see what it looks like then. So far I am finding a lot of original parts with little wear so it seems to be a super-low hour bike. Any options if it's loose? Assume very hard to shim that type of bearing.

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pvangel
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pvangel 2/17/2021 8:00pm
2/17/2021 8:00pm
You can try setting bearing with one of the bearing retaining liquid products which might work? See what it looks like when it comes apart. I raced one for years in a vintage class but the cases kept failing and I would by everyone I could find on Ebay and 1/2 of those were no good. You might get lucky with that one!
Hammer 663s
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Hammer 663s 2/17/2021 8:29pm
2/17/2021 8:29pm
pvangel wrote:
You can try setting bearing with one of the bearing retaining liquid products which might work? See what it looks like when it comes apart. I...
You can try setting bearing with one of the bearing retaining liquid products which might work? See what it looks like when it comes apart. I raced one for years in a vintage class but the cases kept failing and I would by everyone I could find on Ebay and 1/2 of those were no good. You might get lucky with that one!
Is the mag soft so it wallows out? I’ll set the bearing that way unless it’s a tight fit right off. I plan to take it pretty easy on this. It’s more a toy to pass down than a race bike. I have a 350 for racing.
1
miketherider 2/18/2021 8:11am
2/18/2021 8:11am
The metal gets soft or can corrode due to moisture to the point it will start to break. A lot of late 70s Huskys that end up "down by the river? suffer similar fates, especially on the stator side. The bearings can then "waller" around and cause wicked vibration. Some of those too were taken apart and cooked one too many times to replace main bearings that the metal fatigues and becomes out of round due to so much heat expansion and cooling. From the sound of it you may have lucked out with a low hour example, hopefully that was not sitting in the elements too badly.
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Hammer 663s
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Hammer 663s 2/18/2021 8:36am
2/18/2021 8:36am
I read a post somewhere in which it was suggested that perhaps a set screw (or 2) could be placed to hold the bearing in place. I'll check and see if there's room for that. Even with a good case, this might prevent the bearing from moving and reduce the "waller" potential.

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PJRAUS
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PJRAUS 2/20/2021 3:35pm
2/20/2021 3:35pm
That's a fantastic find and should restore fantastic...please don't paint the frame blue!
They were a great looking bike in their day, in my opinion it would look best with stock colours and graphics
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Hammer 663s
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Hammer 663s 2/20/2021 5:34pm
2/20/2021 5:34pm
PJRAUS wrote:
That's a fantastic find and should restore fantastic...please don't paint the frame blue! They were a great looking bike in their day, in my opinion it...
That's a fantastic find and should restore fantastic...please don't paint the frame blue!
They were a great looking bike in their day, in my opinion it would look best with stock colours and graphics
It will stay black. I'm going to try to keep it close to original. I started on the motor today. It's still at a 54mm bore, so stock. Most of the parts I've touched inside are in great shape. No slop or play in anything. So far I feel very lucky to get one in such good shape.






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tahoeacr
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tahoeacr 2/20/2021 7:29pm
2/20/2021 7:29pm
If you get serious about the racing, I have an R&D built engine for the '79's. Those bikes were pretty slow in the day. I kept it because I thought I would put it in my Redline XR-75 someday. That project will never happen. Might as well sale it. It's been sitting in my garage since the 81 Suzukis came out. Nice find. Should turn out great. Would love to ride one.
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Hammer 663s
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Hammer 663s 2/20/2021 9:18pm
2/20/2021 9:18pm
tahoeacr wrote:
If you get serious about the racing, I have an R&D built engine for the '79's. Those bikes were pretty slow in the day. I kept...
If you get serious about the racing, I have an R&D built engine for the '79's. Those bikes were pretty slow in the day. I kept it because I thought I would put it in my Redline XR-75 someday. That project will never happen. Might as well sale it. It's been sitting in my garage since the 81 Suzukis came out. Nice find. Should turn out great. Would love to ride one.
Send me a few photos to mike@hamershock.net I'd def be interested. I'm not gonna get serious about racing it. I plan to build it to be as reliable. functional, and beautiful as I can. One day I will give it to my boy to enjoy it. I hope when he is 60 he can still ride what will by then be a 90 year old motocross bike. Assuming you can get 92 octane and 2t oil in 2079!

Seriously, some parts are getting hard to find. A spare motor would be great. The frame on this is very solid, as is the swingarm. With an extra motor that I can refresh to like new it will last a long time. I plan to replace (but keep) the original electric system with a new one. It runs fine on the original magneto, CDI, and coil, but those are almost irreplaceable now.

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Hammer 663s
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Hammer 663s 3/8/2021 10:02am
3/8/2021 10:02am
Quick update - bike is totally stripped down (except for pulling magneto off crank - puller should be here today) and ready for vapor blast. I've got a crapload of new parts now and some on order. Next up will be powder coat, paint, ship cylinder/head for bore/port, and crank for rebuild/true. Then it will start going back together. Hope to ride it in June.

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tahoeacr
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tahoeacr 3/8/2021 1:13pm
3/8/2021 1:13pm
Got the motor out. It's missing the piston. Could you post a picture of the intake side of your piston? I think the one you posted is of the exhaust side. As I remember, R&D opened up some ports on the intake skirt. I'm going to get a hold of Rudy's son to see if they still have the specs on the piston for this motor. Right now I can't find the ignition cover and the clutch plates are in a zip lock bag. I'm getting ready for a trip to Colorado so I don't have any extra time right now. When I get back I'll pull the side case off and see what's up with the clutch. Can't wait to see your build finished.
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Hammer 663s
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Hammer 663s 3/8/2021 2:14pm
3/8/2021 2:14pm
tahoeacr wrote:
Got the motor out. It's missing the piston. Could you post a picture of the intake side of your piston? I think the one you posted...
Got the motor out. It's missing the piston. Could you post a picture of the intake side of your piston? I think the one you posted is of the exhaust side. As I remember, R&D opened up some ports on the intake skirt. I'm going to get a hold of Rudy's son to see if they still have the specs on the piston for this motor. Right now I can't find the ignition cover and the clutch plates are in a zip lock bag. I'm getting ready for a trip to Colorado so I don't have any extra time right now. When I get back I'll pull the side case off and see what's up with the clutch. Can't wait to see your build finished.
Here's several shots for you.

Exh side


Intake side


Cyl Exh


Mike
Hammer 663s
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Hammer 663s 3/8/2021 2:19pm
3/8/2021 2:19pm
Dropped some stuff for powder coating today. Decided to go that route instead of anodizing. This pile will get a 60-70% gloss silver. Not super shiny but not dull either. At least parts will be consistent color and look. Frame will be gloss black as will lots of the small parts.




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Hammer 663s
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Hammer 663s 3/10/2021 12:39pm
3/10/2021 12:39pm Edited Date/Time 3/10/2021 12:43pm
pvangel wrote:
Check the left case where the crank bearing sits, they tend to be bad and the bearing will not sit in firmly causing the seal to...
Check the left case where the crank bearing sits, they tend to be bad and the bearing will not sit in firmly causing the seal to fail. Very common problem now on the 79/80 bikes as the Magnesium has weakened with age.
Pressed the crank out today. Had to get the correct puller for the magneto first - that bad boy was ON there and I fought it for a while. Crank pressed out easy, and the left bearing came out with some effort. It was not loose for sure - felt perfect coming out. I might put a dab of Loctite 638 in there when I press them back in but I think both sides are fine.

I am more and more confident that this was a very low hour bike. I am finding untouched OEM parts under every bolt I pull out - when I took the chain tensioner apart the tiny @ss o-rings for the bushing were still there, and still fine!

For now the crank heads to Crank Works for a rebuild, true, and balance. The rest of the motor is going to the dip tank then vapor hone before I start putting it back together. Max RPM will do the jug and head for me - going to the first over at 54.5mm so lots of life left in the cylinder. PVL ignition on the way as well. I will set the original CDI, coil, and stator aside in a box. They all work but are essentially irreplaceable now. I see no point in running them till they fail.

Getting excited - won't be long before I can share some shots of the rebuild. It is gonna look, run, and ride awesome.

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mpeters
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mpeters 3/10/2021 7:03pm
3/10/2021 7:03pm
Nice that your restoring it. These barn finds are all over. My friend just picked up a 1980yz125 and 77-78ish yz 100 for $1500.00. Been sitting in barn for 30some years. Tested compression on both. 125 was good 100 was not. Checked the 125 for spark, good. Gas tank was dry with oil residue in bottom. We dumped some premix in. Bitch started on second kick. Smoked like hell
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Hammer 663s
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Hammer 663s 3/22/2021 8:16pm
3/22/2021 8:16pm
Making progress. Forks done (new tubes and all Race Tech internals) and a number of parts powder coated in super silver. Other items off for 90% gloss black, and a few for cerakote. Crank being rebuilt and trued. Most everything is cleaned and ready to start rebuild in another 6 weeks or so.




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Hammer 663s
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Hammer 663s 4/2/2021 10:16am
4/2/2021 10:16am
Vapor blasting done on some stuff. All the black powder coating will be completed today, and the crank is almost done. Next up will be ship the jug off for rebore and port. Then I can start reassembly. LOL - the other day my wife asked where the bike I just bought was. I told her it's all over town, and then some. Not a lie for sure.

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SmokinJoe439 4/2/2021 10:43am
4/2/2021 10:43am
You do know that places like power seal usa. Offer hard plating services for the old steel lined bores. Yeah sure a boring to the next size is less expensive. But having it plated will make it last longer like a modern cylinder.
2
Hammer 663s
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Hammer 663s 4/2/2021 1:12pm
4/2/2021 1:12pm Edited Date/Time 4/2/2021 1:23pm
SmokinJoe439 wrote:
You do know that places like power seal usa. Offer hard plating services for the old steel lined bores. Yeah sure a boring to the next...
You do know that places like power seal usa. Offer hard plating services for the old steel lined bores. Yeah sure a boring to the next size is less expensive. But having it plated will make it last longer like a modern cylinder.
I didn't so read up on it. Makes perfect sense, and that's likely the route I will take. Thanks for helping me spend even more $$$ on this build. Wink

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PS - Mountainview Saturday!
Hammer 663s
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Hammer 663s 4/2/2021 6:14pm
4/2/2021 6:14pm
Got the cerakote back today. Came out nice. Will look good on semi-gloss black cases.

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SmokinJoe439 4/5/2021 4:32pm
4/5/2021 4:32pm
SmokinJoe439 wrote:
You do know that places like power seal usa. Offer hard plating services for the old steel lined bores. Yeah sure a boring to the next...
You do know that places like power seal usa. Offer hard plating services for the old steel lined bores. Yeah sure a boring to the next size is less expensive. But having it plated will make it last longer like a modern cylinder.
Hammer 663s wrote:
I didn't so read up on it. Makes perfect sense, and that's likely the route I will take. Thanks for helping me spend even more $$$...
I didn't so read up on it. Makes perfect sense, and that's likely the route I will take. Thanks for helping me spend even more $$$ on this build. Wink

Hammer 663s

PS - Mountainview Saturday!
I'm good at those suggestions. I had a 1980 RM125 with fox air shocks and a 1979 RM400 once. I mostly collect two stroke sport bikes from Japan.
I've been wanting to bring one for display at the 125 dream race.

Pps - washougal was primo Saturday.
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Hammer 663s
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Hammer 663s 4/12/2021 6:36pm
4/12/2021 6:36pm
A little more progress. Painted crank cases today too. Hope to get the crank back soon and get bottom end together and into frame.

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Hammer 663s
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Hammer 663s 4/14/2021 1:11pm
4/14/2021 1:11pm
Cases painted and bearings in. Crank will be here Saturday so I can build the bottom end.




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