1987 RM125....I”m a sucker for old Suzuki”s..

MXVet261
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5/8/2019 7:33am
You are motivating me to finally restore my 1988 RM125. Had this buried in the shed for a while.


sandman768
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5/8/2019 7:40am
This is my favorite build to watch
Thanks man! Here is another minor setback for your enjoyment.....had crank rebuilt by Ken O’Conner racing in CT. Did a great job, buy when I checked the wrist pin & bearing fit....the fit is loose, too loose. Suzuki must have had several top end/ or bearing failures in 86-87? For 88 they increased the size of the wrist pin, bearing and rod likely to increase durability. This also means the 87 piston does not work as the wrist pin hole is too small. Pro X states on their web site that they only sell the 1 rod and the 87 model requires a special bearing, I”m hoping I just need the bearing to accommodate the 87 piston kit, if not then I need the 88 piston kit....what do you know, sometimes they actually make all those little changes they claim.... you can see the difference in the size of the bearing in photo


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sandman768
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5/8/2019 7:41am
MXVet261 wrote:
You are motivating me to finally restore my 1988 RM125. Had this buried in the shed for a while. [img]https://p.vitalmx.com/photos/forums/2019/05/08/345339/s1200_88RM125.jpg[/img]
You are motivating me to finally restore my 1988 RM125. Had this buried in the shed for a while.


That looks a lot better than what I started with!
sandman768
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5/8/2019 7:46am
Suzuki made a ton of changes from the 87 to 88 with not much of a change in performance......drum to disc in rear, additional clutch plates, updated water pump setup, beefed up top end bearings, gearing different, that’s just what I have found since working on this 87. Most eBay sellers state the parts fit 86-88, they are wrong most of the time...
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The Shop

sandman768
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5/10/2019 1:07pm
Functional test of transmission assembly before crank installation, everything works good!

1
sandman768
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5/10/2019 1:09pm
Picked up some Renthal Jimmy Button bend bars off eBay, I used to run these back in the 7/8”s days
lcgordon711
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5/10/2019 1:11pm
Are those things super high? They almost look like atv bars.
sandman768
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5/10/2019 5:22pm
Are those things super high? They almost look like atv bars.
They are a higher bend but not atv high....I like higher bars...
lcgordon711
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5/10/2019 5:53pm
Yeah button was like 6’2 or somethin
nippers51
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Waterford, MI US
5/13/2019 10:20pm
This is my favorite build to watch
sandman768 wrote:
Thanks man! Here is another minor setback for your enjoyment.....had crank rebuilt by Ken O’Conner racing in CT. Did a great job, buy when I checked...
Thanks man! Here is another minor setback for your enjoyment.....had crank rebuilt by Ken O’Conner racing in CT. Did a great job, buy when I checked the wrist pin & bearing fit....the fit is loose, too loose. Suzuki must have had several top end/ or bearing failures in 86-87? For 88 they increased the size of the wrist pin, bearing and rod likely to increase durability. This also means the 87 piston does not work as the wrist pin hole is too small. Pro X states on their web site that they only sell the 1 rod and the 87 model requires a special bearing, I”m hoping I just need the bearing to accommodate the 87 piston kit, if not then I need the 88 piston kit....what do you know, sometimes they actually make all those little changes they claim.... you can see the difference in the size of the bearing in photo


Having same problem I have an 87 piston and an 88 rod I need the bearing. 14x19x20 haven't been able to find one. Let me know if you do thanks

Don't want to buy a new piston
sandman768
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5/14/2019 4:53am
nippers51 wrote:
Having same problem I have an 87 piston and an 88 rod I need the bearing. 14x19x20 haven't been able to find one. Let me know...
Having same problem I have an 87 piston and an 88 rod I need the bearing. 14x19x20 haven't been able to find one. Let me know if you do thanks

Don't want to buy a new piston
I”m currently waiting on mine to arrive, so not sure if they are back ordered, but I found them on eBay or you can go directly to Wiesel/pro x and get the bearing. The Pro X rod kit states you will need this bearing to work for the 87. The wiseco/pro X part # is 21.3205, when/ if I receive it I will update if it allow the use of the 87 piston kit. Always fun working on old bikes....
sandman768
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5/14/2019 12:04pm
nippers51 wrote:
Having same problem I have an 87 piston and an 88 rod I need the bearing. 14x19x20 haven't been able to find one. Let me know...
Having same problem I have an 87 piston and an 88 rod I need the bearing. 14x19x20 haven't been able to find one. Let me know if you do thanks

Don't want to buy a new piston
Just received the bearing from Wiseco/ Pro X, it’s the correct part, your 87 piston will work when this bearing is used in the 88 rod.
sandman768
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5/14/2019 1:39pm
Clutch cover/water pump rebuilt with all new seals.
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PRM31
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5/14/2019 1:55pm
Great job! I bought an ‘06 RM125 and thought I’d do a few things. It turned into a complete rebuild. I can appreciate what you’re doing! Looking forward to seeing it progress.
sandman768
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5/14/2019 6:50pm
PRM31 wrote:
Great job! I bought an ‘06 RM125 and thought I’d do a few things. It turned into a complete rebuild. I can appreciate what you’re doing...
Great job! I bought an ‘06 RM125 and thought I’d do a few things. It turned into a complete rebuild. I can appreciate what you’re doing! Looking forward to seeing it progress.
Thanks ...PRM31. I knew going into this one it would need a good amount of work. I”m more patient with my builds now, I enjoy the whole process, I learn something new every build I do.
5/15/2019 2:47am
Thumbs up for the good work! Read through your topic and love the result so far. Keep it up bro.
sandman768
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5/15/2019 3:30am
Thumbs up for the good work! Read through your topic and love the result so far. Keep it up bro.
Thanks...
sandman768
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5/15/2019 2:46pm
We”ll thought I was going to have the bottom end together rather quickly today....no such luck... crank dropped in nicely with the freeze/heat method, then rt case slipped on pretty easy, soon as a I tighten case bolts, crank won’t spin, spins good before bolts tight. Tried, pulling crank to the side that appears to have a slight gap, nothing....tried some light taps with dead blow plastic hammer, nothing....so...split cases ..... heated cases around crank bearings, crank bearings appear seated, but gave them a few more pretty hard hits with a hammer & socket on the outer races. Manual gives an outer crank web measurement of 53.0mm +- .01 mm. Mine measures 54.0mm....not sure if that 1mm is the issue but I have to discuss with shop that did the crank rebuild....Not sure what else to do?
The photo shows how I use a socket set on the inner bearing race, then heat with torch,then drop in frozen crank, works good but....I received a major beat down in the garage today! Either my crank bearings are not seated correctly or the crank webs are 1mm too wide....
sandman768
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5/15/2019 3:51pm
I think I found my problem..left side crank bearing not seated 100%, took a level to it, slightly high on 1 side...
40
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5/15/2019 6:45pm Edited Date/Time 5/15/2019 6:46pm
sandman768 wrote:
I think I found my problem..left side crank bearing not seated 100%, took a level to it, slightly high on 1 side...
Have been there before too......
If you've done anything to the transmission, it's probably a good idea to first assemble the cases with transmission only installed, without the crank. You'll only need to install a few case bolts to tighten the cases with center case gasket installed. Run the transmission thru the gears, make sure all shifts are correct. Might have to spin the mainshaft by hand and sometimes add some drag to the countershaft while operating the shift lever. Simulates a running engine. After you're satisfied with the gearbox shifting performance, split the cases again and then put the crank in. The cases will split with only finger pressure without the crank installed.. Takes a little extra time, but saves putting the assembled engine into the frame only to later find out there's a problem. Have previously learned this lesson the hard way.
Nice work, and you're light years ahead of where you were just a few years ago with your builds.
sandman768
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5/15/2019 7:27pm
40 wrote:
Have been there before too...... If you've done anything to the transmission, it's probably a good idea to first assemble the cases with transmission only installed...
Have been there before too......
If you've done anything to the transmission, it's probably a good idea to first assemble the cases with transmission only installed, without the crank. You'll only need to install a few case bolts to tighten the cases with center case gasket installed. Run the transmission thru the gears, make sure all shifts are correct. Might have to spin the mainshaft by hand and sometimes add some drag to the countershaft while operating the shift lever. Simulates a running engine. After you're satisfied with the gearbox shifting performance, split the cases again and then put the crank in. The cases will split with only finger pressure without the crank installed.. Takes a little extra time, but saves putting the assembled engine into the frame only to later find out there's a problem. Have previously learned this lesson the hard way.
Nice work, and you're light years ahead of where you were just a few years ago with your builds.
I”m learning...nothing is easy...I had an issue with the trans after the first attempt, I figured out I had the shift detent on the end of the shift drum on backwards...I had pulled it out after my functional test to polish the shift drum, then I ran into the crank not spinning...with the case bolts tight, nothing binding on the trans, so I put a level on the left side crank bearing & it’s not sitting level, I have heated up the case & attempted to drive it in deeper but no movement. I will try again tomorrow with a flat punch on the outside of the bearing cage, if no movement I will knock the bearing out, get a new one...the education continues...
40
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5/15/2019 7:49pm
sandman768 wrote:
I”m learning...nothing is easy...I had an issue with the trans after the first attempt, I figured out I had the shift detent on the end of...
I”m learning...nothing is easy...I had an issue with the trans after the first attempt, I figured out I had the shift detent on the end of the shift drum on backwards...I had pulled it out after my functional test to polish the shift drum, then I ran into the crank not spinning...with the case bolts tight, nothing binding on the trans, so I put a level on the left side crank bearing & it’s not sitting level, I have heated up the case & attempted to drive it in deeper but no movement. I will try again tomorrow with a flat punch on the outside of the bearing cage, if no movement I will knock the bearing out, get a new one...the education continues...
Be careful when hitting the bearing outer race with the flat punch trying to fully seat the bearing. That puts stress on the case which can crack resulting in a new headache.
The more time consuming way would be to remove the crank bearing. Measure the bearing width to make sure its the same as stock if you put new ones in.
There might have also possibly been some debris under the crank bearing when it was installed.
Also, if the bearing was not perfectly perpendicular to the case's bearing pocket when it was installed, a sliver can shave off the case pocket race and wedge underneath the bearing as its driven in. Results in the bearing sticking up too high..
40
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5/15/2019 7:52pm
Also, almost always need to center the crank in the cases with the plastic hammer at the end of assembly.
sandman768
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5/16/2019 4:13am
40 wrote:
Be careful when hitting the bearing outer race with the flat punch trying to fully seat the bearing. That puts stress on the case which can...
Be careful when hitting the bearing outer race with the flat punch trying to fully seat the bearing. That puts stress on the case which can crack resulting in a new headache.
The more time consuming way would be to remove the crank bearing. Measure the bearing width to make sure its the same as stock if you put new ones in.
There might have also possibly been some debris under the crank bearing when it was installed.
Also, if the bearing was not perfectly perpendicular to the case's bearing pocket when it was installed, a sliver can shave off the case pocket race and wedge underneath the bearing as its driven in. Results in the bearing sticking up too high..
Point taken, I will just remove the bearing and start over..
sandman768
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5/16/2019 1:56pm
Removed crank bearing today, had a sliver of aluminum on backside, likely from going in crooked. I had also lightly raised the surface of the case with a punch to attempt to tighten up the bearing interface fit, as The bearing pocket is slightly worn, this may have contributed to the sliver of aluminum behind the bearing. Going to try a new bearing after cleaning up the pocket tomorrow.....I got the wheels sorted today. New Bridgstones, tubes, Tusk rim lock nuts & Honda style valve stem rubbers, JT aluminum sprocket. Wheel bearings were good ,I just repacked them, spokes are a little dull but still adjust well & have good tension, rims are actually pretty clean for originals...
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sandman768
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5/20/2019 2:09pm Edited Date/Time 5/20/2019 2:13pm
Will a Yamaha YZ Ti spring fit? Fits on shock good, slightly larger O.D. ....pretty tight clearance with the swingarm, I will have to wait until engine is installed before I can check final clearance...at least I have it rolling now, this project may have to take a siesta for the summer....while I get back to doing some actual riding...



1
sandman768
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5/21/2019 1:13pm
Evo-MX graphics & seat cover came in the mail today....test fit, still have some sanding to do on the original plastics but these graphics make life a lot easier.... had enough of the sanding plastic routine....




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5/21/2019 2:28pm
So you went with the '88 year graphics on the rad shrouds?
sandman768
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5/21/2019 4:05pm
So you went with the '88 year graphics on the rad shrouds?
Yes, 88 graphics & seat cover... I like the 88 graphics better
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sandman768
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5/25/2019 5:28am
Sent crank back to machine shop that rebuilt it, turns out the thrust washers in the Pro X kit are too wide! Thus the 1mm too wide crank....shop owned it & will redo with Suzuki thrust washers to get proper web width.....always something with these builds......
1

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