Any 79 RM250 threads?

notme
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7/10/2014 8:15pm
I have spark now. Wink
notme
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7/10/2014 9:40pm
I went through some old mags and found this in the MXA sept 79 issue.







edgo897
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7/11/2014 3:42am
Does the article say drop the intake port 4mm? It's hard to read. I'm looking at the last page.
notme
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7/11/2014 7:15am
edgo897 wrote:
Does the article say drop the intake port 4mm? It's hard to read. I'm looking at the last page.
Yes 4mm

The Shop

DoctorJD
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7/11/2014 7:30am
Wow, those articles are a trip down memory lane. The crap we had to do to keep a bike running back in those days. I remember those intake boots being like silly putty. Over-tighten the clamp the slightest bit and they'd rip. I think I ended up using a Fernco coupling as a replacement...after a couple of DNFs, that is. Also remember changing out those motor mount bolts. I put a DG silencer on my bike and it canted the pipe in just a little bit, enough to melt a hole in the airbox. That's when I got my first taste of fiberglass work.That bike was the best of class (125), but damn it has some issues.
notme
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7/11/2014 9:01am
Doc did you have to drill the cases out or just the mounting plate?
DoctorJD
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7/11/2014 10:17am
notme wrote:
Doc did you have to drill the cases out or just the mounting plate?
If I remember correctly (and this was 35 years ago), I don't think I had to drill through the cases. That would have required me pulling the engine, and I don't recall doing that. I do remember running a drill bit through the mounts, however.

Sadly, this is one of the only pictures I have left of my old moto days. Here's my 79' 125 with a 80' rear fender and a PP front fender. I'd work all Summer to raise enough money to buy a new bike in the fall, and I'd race it for two seasons. Yes, it was a chore keeping a late-70's 125 running for two years.


edgo897
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7/11/2014 12:26pm



My on my 79 250 at Gatorback.
captmoto
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7/12/2014 9:02am
I remember drilling the cases out for the bigger bolts. I used a SAE thread bolt but would just use 10mm now. I have a 79 project but will look to see if it was modded.
245
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7/13/2014 1:57am
edgo897 wrote:
The rear hub will fatigue on the 79 and the result will be that the wheel bearings won't fit tight. Also check the threads on the...
The rear hub will fatigue on the 79 and the result will be that the wheel bearings won't fit tight. Also check the threads on the drive shaft as they can wear out and make it impossible to tighten the drive shaft nut. The frames also can crack on the bottom area where the chain guide it welded on, below the swingarm.
Edgo897 told you right. The left side of the hub in 79 had only one bearing From 1980 up they use two bearings in the left side. Between my 1979 250 & 400 I blew up 5 hub's in that area. Suzuki gave me one. Same for the frame it starts to spider web crack around the chain guide. I didn't catch the first one till it got bad. All three of mine crack and Big hearted Suzuki gave me one. Whatch for cracks and get them welded early. Try to find a 80 model up hub. Good motors, on the 250 I was able to run stock shocks with Luft reservoirs. 250 & 400 hubs are the same for 79 & 80. Good luck!
notme
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7/13/2014 11:22am Edited Date/Time 7/13/2014 5:58pm
Thanks 245, I might look into having my hub machined to accept a second bearing.
Once I tear it down I will be looking for frame cracks throughout. I suspect that a lot of the frame cracks were caused by excessive engine vibes/too small mounting bolts.
Going to try and fire it up today. Holy shit is it a bitch to get the airbox + carb boots mounted, not much wiggle room.

Edit: It runs!
245
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7/14/2014 4:44pm
The oringal boot between the carb and cylinder would tear. I found some Triumph ones that worked good. I think Suzuki updated them after awhile.
CamP
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7/15/2014 5:17am
DoctorJD wrote:
If I remember correctly (and this was 35 years ago), I don't think I had to drill through the cases. That would have required me pulling...
If I remember correctly (and this was 35 years ago), I don't think I had to drill through the cases. That would have required me pulling the engine, and I don't recall doing that. I do remember running a drill bit through the mounts, however.

Sadly, this is one of the only pictures I have left of my old moto days. Here's my 79' 125 with a 80' rear fender and a PP front fender. I'd work all Summer to raise enough money to buy a new bike in the fall, and I'd race it for two seasons. Yes, it was a chore keeping a late-70's 125 running for two years.


Man, you must have really had your work cut out for you racing those bikes for two years. My 125's were totally clapped out in 6 months.
DoctorJD
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7/15/2014 5:34am
CamP wrote:
Man, you must have really had your work cut out for you racing those bikes for two years. My 125's were totally clapped out in 6...
Man, you must have really had your work cut out for you racing those bikes for two years. My 125's were totally clapped out in 6 months.
You think thats bad? You should have tried to make a 77' YZ100 last for two seasons. Lets just say that I became really handy with a wrench. In retrospect, it probably would have been cheaper to buy a new bike every year.

notme
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7/15/2014 10:27am
Anyone know where I can find an aluminum silencer for this rm? Excluding DG.
BigAl
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7/16/2014 9:25am
notme wrote:
Anyone know where I can find an aluminum silencer for this rm? Excluding DG.
I'm in the same boat. I was going to run the stock pipe, maybe do the mod mentioned above.

I wonder if you can purchase just a Pro Form silencer?
tb901
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Fantasy
7/16/2014 12:31pm
notme wrote:
Anyone know where I can find an aluminum silencer for this rm? Excluding DG.
BigAl wrote:
I'm in the same boat. I was going to run the stock pipe, maybe do the mod mentioned above. I wonder if you can purchase just...
I'm in the same boat. I was going to run the stock pipe, maybe do the mod mentioned above.

I wonder if you can purchase just a Pro Form silencer?
I'm pretty sure that picture on page one is a stock pipe with a Pro Form silencer. I must've sold the bike with that silencer because I found the stocker in the garage. I wouldn't stop with a silencer. The pro form pipe made a huge difference in power. It was like a different bike. If you're going to ride it, buy both the pipe and silencer.
BigAl
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7/17/2014 10:24am
anybody see anything wrong with running a 1984 RM125 rear wheel assembly and a 125 size tire?
edgo897
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7/17/2014 12:37pm
I have a spare 250 cylinder so we'll do the intake like the article says to and see how it runs. I have an after market pipe and Answer silencer too.
sandman768
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7/18/2014 5:31am
BigAl..... I have an 82 or 83 rm 465 rear wheel on my 79 250. my origial hub was worn as stated above. fit right on! slightly wider but no issues. 125 wheel will not be as wide, but you still run same width tire, if ithe 125 rim assy fits, I would run it, these bike dont make 50 hp, slightly smaller width wont make huge difference. is the 125 wheel a 3 bearing hub?
edgo897
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7/19/2014 6:55am
Can anyone ID this pipe?

edgo897
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7/19/2014 6:57am


BigAl
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7/19/2014 9:12am
sandman768 wrote:
BigAl..... I have an 82 or 83 rm 465 rear wheel on my 79 250. my origial hub was worn as stated above. fit right on...
BigAl..... I have an 82 or 83 rm 465 rear wheel on my 79 250. my origial hub was worn as stated above. fit right on! slightly wider but no issues. 125 wheel will not be as wide, but you still run same width tire, if ithe 125 rim assy fits, I would run it, these bike dont make 50 hp, slightly smaller width wont make huge difference. is the 125 wheel a 3 bearing hub?
2 bearings. I'm thinking since the '79 HP is less than a modern 125 the tire size shouldn't hurt. I'll run the 84 front end with stiffer springs, fox airs on the rear and the 125 rear wheel assembly.

Someone told me the maico 250 guys would run a 125 size tire back in the day?
WRH
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7/19/2014 10:13am
edgo897 wrote:
[img]https://p.vitalmx.com/photos/forums/2014/07/19/60227/s1200_image.jpg[/img]


The welding on it looks like Dan from Jemco put it together.
WRH
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7/19/2014 10:29am Edited Date/Time 7/19/2014 10:35am
BigAl wrote:
anybody see anything wrong with running a 1984 RM125 rear wheel assembly and a 125 size tire?
In the day, the 4.10 x 18 125 tires would have created a lot of wheelspin on the 79 250. However todays technology in tires may allow a smaller tire to work. We would have normally ran a 4.50 x 18 on the 250. If you do the pipe and porting mods I would doubt the thing would hook up when you needed it.
I also owned 2 of the Maicos you were referring to in your next post. The Maico powerband was not explosive but provided the feel of more torque . One I kept fairly stock, practice bike, the other had the Crotch Rocket Factory Pipe among other mods. It was also tuned by Lee Barkley of Kimbrells Maico out of Dallas. (Race Bike). The Maico's power enabled me to ride a gear taller thru a lot of turns and carry more speed. Hope this helps.
If the guys using the smaller tire were on a tight track I could see the need for a smaller tire to help light up the power delivery. As with most Maicos it was pure hell trying to pull in the clutch lever to fan the clutch like we became accustommed to doing on the Jap bikes. And yes i would love to have those two Maicos back , in the pristine condition they were in.
notme
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7/19/2014 10:33am
The OEM tire on the 250n was a 5.10-18!
WRH
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7/19/2014 11:21am
notme wrote:
The OEM tire on the 250n was a 5.10-18!
I really enjoyed the Metzler rear on the 250. I could be wrong,it has been since 1979-1980. But after stock tires , usually a Bridgestone or IRC , wear out I was always happy to upgrade to a better tire.
So did we run 460 x 18's on the hopped up 125 Nat'l bikes back then? Or just the 425 /410 x 18's? The Dunlop K-190's maybe, I can't remember.
I can say that the 17" rear wheel assy's that were made available were , in hind site, not the way to go.
Does anybody remember if the Metzler rear tires were 4.50 x 18's or 5.10 x 18's.
notme
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7/19/2014 7:58pm Edited Date/Time 7/20/2014 12:36pm
Found another tidbit of info.from august 1980 MXA.




I found yet another snippet on this issue. In another mxa mag in the "dirt" section, they mention,

"It turns out that on the first shipment of RMs into America the Japanese forgot to insert a steel sleeve into the motor mount holes".

Im not sure this is true, on the microfiche, I see no sleeves on the motor mounts except on the front there is a case locator pin....
sandman768
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2/12/2015 10:04am
notme wrote:
Found another tidbit of info.from august 1980 MXA. [img]http://img.photobucket.com/albums/v409/traileater/mxarm250art2001_zps5650ec05.jpg[/img] I found yet another snippet on this issue. In another mxa mag in the "dirt" section, they...
Found another tidbit of info.from august 1980 MXA.




I found yet another snippet on this issue. In another mxa mag in the "dirt" section, they mention,

"It turns out that on the first shipment of RMs into America the Japanese forgot to insert a steel sleeve into the motor mount holes".

Im not sure this is true, on the microfiche, I see no sleeves on the motor mounts except on the front there is a case locator pin....
funny, I"m doing a quick refresh of my 79 250 & wouldn"t you know, the upper rear engine mounts are welded too far apart as stated in this MXA tidbit.

notme
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2/12/2015 10:11am
I ended up selling this bike to a guy who really wanted one to do up as a gift to his dad. Hes a great wrench so it is in good hands..... It was a really good base for a build Wink

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