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Old bike, new project. The little bike that could

thrill-billy85

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When I was 10 I was issued a dirtbike. Or, well... Dual sport.

It was a 1983 Suzuki SP100. Street legal cousin of the DR100. Produced for one year when Suzuki only sold like 13 of them in the US.

I rode this bike every day almost, until I was about 16, and my interests changed. Then it was my pickup, and what girl ws in the passenger seat.

I beat the piss out of this bike. Id ridden it as fast as it would go, most of the time (55mph). This was a time when people didn't loose their minds when a kid rode in the neighborhood, as long as they stayed out of their yard, and weren't passing their house 50 times in an hour.

Not to say me and my best friend didn't find trouble to get into, me on my sp100, and him on his ct70.

We got permission to ride on this guys land that was situated behind my neighborhood. It was 70 acres of terraced hills, cedar trees and oaks, and tons of fun trails by the time we were done with it. We called it 'The Mountain' and also camped out there every weekend.

Some of my fondest childhood/teenage memories were out there, and on that bike.

It also spawned what would be a life long lust of riding dirt bikes (legally) on the roads to trails.

So this dual sport thing, I came by in the truest sense of it.

I finally burned up the clutch in the sp100, but with a newer yz125, and a pickup truck, and a girlfriend, I wasn't too concerned. Bike got put in the shed.

After highschool I joined the navy, did six years of that, and the Suzuki still sat, patiently in the shed. Waiting its time, for me to repay it.

A few years out of the navy, I was at home visiting and decided to dust the old bike off.

I cleaned the carb, put some fresh gas in it some fresh oil, and I'll be slammed if it didn't start the first time I kicked it.... Like it ALWAYS had, without fail.

I couldn't NOT go on a little ride.

Long story short, the cam chain broke. (At the time I didn't know what had happened, just that it lost compression, and wouldn't run)

I figured the resulting damage would be huge. I kept an eye out on eBay for a new motor, though I'd not yet even taken this motor apart.

It's like this bike and I were meant for one another.

I found a good bottom end, and "won" it for $35 shipped. Guy probably lost money on this thing.

Anyways, I recently got the bike to my house, along with all the other carp I've bought for it over the last few years. Clutch pack. Chain guide. Some other miscellaneous doo-dads

I got the motor apart, and this is when I learned the cam chain had broken.

I feared the head, and cylinder were trashed. Not the case. The piston did not contact a valve. The chances of that are almost nil when a cam chain breaks. But like I said, we were meant to be together.

On top of all that, this engine, cylinder and piston included show almost ZERO WEAR. I've measured the bore several times, the correct way, and there is zero taper, zero out-of-round, and not even a slight wear line in the bore, or on the piston.

What's so weird about this is that I never took very good care of this bike. I can remember changing the Oil a handful of times. I always checked the oil, and did add some from time to time. I never cleaned or replaced the air filter but only a couple times.

Basically this bike took care of me.

Now it's time for me to repay the favor.



IMG_20151106_232106325_zpsspopwrlk.jpg


Bottom end I bought----
IMG_20151106_232117921_zpsxkfc9uri.jpg


Bottom end that came out of the bike---- (zero play in the rod, will reuse)

IMG_20151106_232126118_zpsxnv81lwm.jpg



Comb chamber-----
IMG_20151106_232749291_zps5tvdcrih.jpg


Valves still seal----(fluid test with solvent)
IMG_20151106_232918179_zpsnbx4bhsy.jpg



Piston-----
IMG_20151106_232630317_zps7qmiz3sg.jpg


IMG_20151106_232619982_zpspl1ishfo.jpg



The bore. I actually laughed when I saw this----
IMG_20151106_232444613_zpsjrpjatpz.jpg



Anyways, that's it for now. I've got parts on order, and stuff arriving daily.

Here's the bike in stock form---
P1000266_zpsseecws4i.jpg
 
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I'll try to find the thread I did on my dad's 76 yz125. It took like 6 months of me working on it every day after/before work. I was single at the time, so I put alot into it. Lol
 
Yeah, it just kinda collects dust now days. Kinda pisses me off, but whatever. It's in a climate controlled garage, under a bike cover. It's just a bike, and my parents are SUPER busy.

Actually, I've been wanting to get it back, and un-mothball it. Maybe ride it some.
 
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I think I still have the gold caps lying around somewhere that are on the top of the forks. Have not looked at them in forever. Might have been air assisted?
 
I got some stuff done on the sp100 today.

It's been weeks since I've put a wrench on a bike so I tried to be productive. I also did a fork seal job in a kx250f. I feel like I'm getting slower at these. Lol.

Anyways, I disassembled the cylinder head, soda blasted it, the cylinder, and rocker box, then it all got a coat of paint. The head got the valves checked, cleaned, and lapped, along with new valve seals. The valves and seats looked great. It's so weird because I remember abusing the crap out of this bike.
IMG_20151124_114210768_HDR_zpsxjtkgc5i.jpg


IMG_20151124_160553947_zpssbze3iao.jpg


Also got a little seat time on the orange bike yesterday. I had to help my mother in law unload, and hook up their new washer, so I rode over, and went sightseeing on the way home. This was at Jennings mountain. Tallest hill in the county.

IMG_20151123_150225134_zpsx10oim1b.jpg


I was gonna take the road up it, but instead blazed my own trail right up the side. This 525 is exciting. Ha-ha

There's a graveyard and a cell phone tower at the top.

IMG_20151123_145948369_HDR_zpsketheaxg.jpg



IMG_20151123_150039587_zpskdu4pvxi.jpg
IMG_20151123_150039587_zpskdu4pvxi.jpg
 
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It is looking good so far. These small bikes are so much fun. Going to try to get a KE back up to snuff early next year.
 
Ohh man. So I've been in the shop alot letely. I bounce between like 4 different projects to keep myself entertained.

I have a good used bottom end I bought for this bike a long time ago. It was $30 shipped, so why not.

Anyways, I've been debating which one I should use. I've also been wondering WHY the cam chain broke in the first place.

I decided to clean up the original bottom end. Upon doing so, I removed the cover for the oil screen..... What did I find???? Well friends, I found what was once an alignment dowel.

IMG_20151125_110940203_zpsfbjkbdhr.jpg


IMG_20151125_110948088_zpshmuzrewp.jpg


Okay.... I NEVER took this motor apart. Like.... Never. I've not found any evidence that would suggest it ever being apart either. That said..... WHEN the cam chain broke, I could not move the kickstarter. I put the bike in gear and rolled it backwards. (Give me a break, I was like 19 at the time). After that, I could turn the motor over with the kicker.

How did this dowel get in there??? I never replaced the clutch pack. I'd had a new one sitting there the day I got it started and subsequently broke the cam chain. Did I take the cover off, and maybe not notice I lost this dowel, decide I didn't feel like messing with the clutch that day, put it back together, and start it? I really can't recall.

Maybe.
I'm at a loss here.

Anyways, I will now be using the other bottom end, and just swapping the starter, oil pump, and clutch stuff over. The stator and flywheel are already off.

There is no play in the rod on the original bottom end, but I know it was run low on old crappy oil, most of the time. It's really BAFFLING how nice it all looks, considering.

The new (used) bottom end looks better on the outside, and I'm sure it's no different inside.
 
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Good stuff. I had a Honda XL80 that I tried to kill with lack of maintenance, but I just couldn't. I sold it to a coworker when I was about 24. He was looking for a cheap bike for his kid to learn on. I wish I had kept it.
 
Good stuff. I had a Honda XL80 that I tried to kill with lack of maintenance, but I just couldn't. I sold it to a coworker when I was about 24. He was looking for a cheap bike for his kid to learn on. I wish I had kept it.


I'm really glad I kept mine. I rode this bike almost every day of my life from the age of 11-(about)16, when I got a yz125. I can remember finding a muddy spring fed spot in my buddies pasture and riding through it over and over and over. The cooling fins were packed with mud, and it was so hot it like baked that crud in there.

Imagine now as an adult, someone hands you a bike and says, "kill it". What'd you'd do, now, knowing what will kill an engine, is EXACTLY what I ignorantly did as a 13 year old. Lol.
 
Thanks Philip. That means alot, coming from a gent like you.

So I was rolling the original motor by turning the countershaft with it in first. I noticed the clutch basketat the top was moving in and out. Like the mainshaft had run out, and was bent.

Turns out the mainshaft somehow IS bent. Go figure.

No problem, I've got a good bottom end.

Got everything swapped over tonight. Clutch basket is nice and true when I spin the countershaft with the motor in gear. Good deal. Onwards.
IMG_20151126_244748411_zpsnwbo6rvn.jpg
 
Coming along. I got antsy and wanted to see the cylinder and head on it....

The only stuff left to buy before this thing is going is a new carb, and a set of rings.
IMG_20151215_125628102_HDR_zps4nqkgtet.jpg
 
Oooh oooh good news!!!

Here's the deal- the choke plunger in the old carb was seized into its bore. I litterally snapped the dang thing trying to get it out. Even IF it'd come out, I'd have to replace it, as I bemt the poo out of it. It cannot be had as a seperate item from the carb body... Of which is no longer available.

So I needed to find a carb. This was a specially made mikuni vm20 carb. It is spigot mount, like most carbs. It had a 20mm throttle valve cutaway, but it was long oval shaped.

The current offering from mikuni is a vm20, but its flange mount. The flange is also the wrong size. The next size smaller is a clamp on. No go.

There is an offering from Keihin, but its spigot OD is 5mm too big.

Not to mention, NONE of these have that weird long oval tvc.

The sp100 was sd for 1983 ONLY. the dr100 was sold from 83-94, but used a flange mount carb. Aside from that, the powerplant is almost identical.

The only option is to wait for a decent used sp100 carb to pop up on eBay, which I have been.....

That is...


Until this evening


I saw a picture of a drz125 carb. Can't remember what I was actually looking at, but the choke lever, and bore caught my eye. A Couple of Google's later, I learn that it's a mikuni VM20SS carb. Spigot mount. Same choke lever. Same carb bore shape and size. Same exact carb, only they added a coast enricher!

So I am ordering one, and the sp100 gets some love tomorrow!!!
 
Heck yeah!!!

On the other hand, I've been testingvarious cleaning products in the ultra sonic cleaner to see what works best on aluminum pot metal using the old carb body.

Needlessto say, the old carb looks brand new, aside from the broken choke plunger, which is "part" of the carb body in terms of how its ordered. Had it been ANY other part of the carb that was bad, I could order it, but not the carb body, and choke plunger.
 
Nah, not really man. I've been so busy buying a house, fixing and selling a rent house me and dad have, building a shop, doing the Round Mountain Roundup. Hopefully things will settle down soon.
 
Shoot, I also had my neighbors Arctic cat ATV, and a coworkers power washer.
 
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