RM-370 project

[whenfoxforks-ruled]

Argh! I got into this before realizing that getting a rod for this engine is an issue? Same rod as the 78~79 rm400? Also unavailable? Everything else is doable. So this may end up restore and upgrade to something I can really play with. First issue is the suspension. I think its off a 79 rm400, front and back. I need, kickstarter, gas tank, seat and exhaust. The gas tank, seat,, it would be way cool if the 79 will fit? The transition was way better. Even though some fool with spray paint was at it, the engine is free, and the tranny seems okay, and the clutch! Okay like, all the parts are there and without odd noises. The strip down is coming, hopefully by next weekend.

 

[whenfoxforks-ruled]

Sure hope I have that front brake hub?

 

[_JOE_]

Holy missing parts Batman! You got a couple baskets of extra parts or what?

 

[whenfoxforks-ruled]

Like what? Frivolity items? Stickers and something to put them on? Guess what color plastics? The pipe will be a pain, not too many choices. But, can get a new custom one! That reminds me of the website, with the largest selection of Fox Factory Forks in the world, and there was only 200 originally made, and for 1500 or so, I could have another pair???? I paid like 250 and a 1 hour drive last time? This is about what I wanted, not something someone else has questionably restored, just the basic parts. And entry level cheap!!! It still may be fun, claimed 42hp, but the rod thing? I will eventually throw it? It is a big bore 2 stroke. It was known for vibration, and blasting gears. Sounds like a Suzuki alright!

 

[_JOE_]

Lol. How "bout the rear brake pedal? Front brakes? Front wheel spacer? Airbox? Looks like a fun project. You gotta lot of work to do before Red Bud man! That thing WILL be there right?!

 

[whenfoxforks-ruled]

4th of July at redbud + me and anything on wheels = trouble! The national or night track is no place for this bike. Now their annual grass track race in the fall, not as many aerial obstacles! Technically I think its an evolution bike, not vintage. All the local tracks run a class defined vintage differentially, 8~10 years old. But, if I am faced with an obstacle that can impede my progress, Umm, last thoughts:"this is going to hurt when I land"!

 

[schmanman]

awesome!

lots of work, but that's fun too!

 

[doug howell]

fyi

I just saw a '78 rm125 on indianapolis craigslist for $300 obo...don'tknow if any of the parts interchange but it might be worth a look

 

[KTM Mike]

Fox - do you get up into Michigan at all? I might be able to help you out some RM parts...and maybe...just maybe a 78 RM400 bottom end with, if I recall correctly, what "felt" like a good crank in it...AND...I might have a variety of other odds and ends for RMs. Maybe a set of 78 RM400 forks... a seat or two...maybe some RM wheels.... I do need to do some digging around in the garage though - I know I sold a bunch of RM stuff last summer, but dont recall exactly what all I sold. Shoot me a PM if you want to check this stuff out.

Gotta love the projects like those though - I think you saw the pics of a couple of the RM370 restorations I did a few years ago - they didnt start out much better than yours looks now - but ended up literally looking like you time traveled back to 1977 and was eyeing up the new bikes on the show room floor! Lots of work - but lots of fun (and frustration to!)

Mike

 

[whenfoxforks-ruled]

Thanks Doug, not many off the 125. But, I may watch that bike! Schmanman, seen KTM Mike around, I think he knows where some parts are. I have my buddy at the used bike barn also. Sure wish I could get a FMF SST pipe for this badboy! And a truck load of rear tires! "Hey Eric, can you get me some more mid top out of this engine?"

 

[whenfoxforks-ruled]

Fox - do you get up into Michigan at all? I might be able to help you out some RM parts...and maybe...just maybe a 78 RM400 bottom end with, if I recall correctly, what "felt" like a good crank in it...AND...I might have a variety of other odds and ends for RMs. Maybe a set of 78 RM400 forks... a seat or two...maybe some RM wheels.... I do need to do some digging around in the garage though - I know I sold a bunch of RM stuff last summer, but dont recall exactly what all I sold. Shoot me a PM if you want to check this stuff out.

Gotta love the projects like those though - I think you saw the pics of a couple of the RM370 restorations I did a few years ago - they didnt start out much better than yours looks now - but ended up literally looking like you time traveled back to 1977 and was eyeing up the new bikes on the show room floor! Lots of work - but lots of fun (and frustration to!)

Mike

Ask and you will receive, it is Easter! I am 45 minutes from redbud. I will have to do some cross referancing to see whats usable off the 78 400. Good to hear from you Mike, Happy Easter!

 

[whenfoxforks-ruled]

One issue in finding out what was done to this frame. I will get a better pic. The top sub frame seat section on the left side is longer, than a 76~78 frame. But it does look like the 79? The neck says its a 77 rm370 though. A ton of parts are the same as the 78, air box, filter, kick starter, rod, thrust washers, big and small end bearings, crank pin and brake pedal. I believe the seat and tank also. There are parts I could rebuild the crank with, but with a used rod. Now the 79 rod is available, the bottom end bearing and pin are the same, but the thrust washers and top end bearing are different. I do not think they changed the stroke, so what if I put the 79 rod in, with the 79 piston fitted to the 370 jug, or get a 78 jug and fit it?

 

[dirt bike dave]

The '78 RM400 would have a plastic tank compared to the steel tank of the '77 370.

I found a link to an old test of the '78 RM400 from Popular Cycling where they talk about differences with the '77.

http://www.suzukicycles.org/RM-RMX-series/index.html?RM400.shtml~isoraami


Besides the plastic tank, for '78 looks like a bigger 80mm piston but same stroke to produce 402cc; totally different porting specs (reportedly for more low end), different pipe, more suspension travel at both ends, different swingarm. The transmission and bottom end were reportedly the same as the 370.

The magazines really liked the 400; sounds like you ride it like a big bore, where the 370 likes to be ridden like a big 250.

 

[whenfoxforks-ruled]

Thanks Dave, it seems the 79 stroke is 3mm longer. I will shelve that idea for a worst case scenario, up there with having a rod custom made$

 

[Uchytil]

4th of July at redbud + me and anything on wheels = trouble! The national or night track is no place for this bike. Now their annual grass track race in the fall, not as many aerial obstacles! Technically I think its an evolution bike, not vintage. All the local tracks run a class defined vintage differentially, 8~10 years old. But, if I am faced with an obstacle that can impede my progress, Umm, last thoughts:"this is going to hurt when I land"!

You could run the vintage class, or for fun run the Widow Maker race. My buddy was oldest in it last year and he paid a bottle of Grey Goose to race. I might run that one - no pressure.

 

[KTM Mike]

Ask and you will receive, it is Easter! I am 45 minutes from redbud. I will have to do some cross referancing to see whats usable off the 78 400. Good to hear from you Mike, Happy Easter!

Ya, you just knew I would be out there lurking didnt ya! Hey - I might...gotta check with my buddy, be able to arrange for some stuff to get hauled down your way... he will be heading to Roselawn for an enduro. I dont know if his schedule will allow for it or not, but I can check.

On the frame differences - I can dig through some pics I have of the 76 and 77 370's I did - I think the 77 had an extended frame rail on the left to support the longer silencer they used in 77. 76 silencers were much shorter. Wouldnt you know it, but I got rid of a 78 400 frame last summer - dont think I have any pics of that though. Dave already addressed the bore differences 400 vs 370...- so that plan is shot.

I will be heading out to the garage tonight - I will do some rummaging around in my bottomless box and shelves of old RM parts for ya! (sorry mods - dont mean to turn this into a for sale thread...but gotta help a 370 builder out! :cool: )

 

[KTM Mike]

Frame differences

Ok - I found those pics.

First shot is of a 76 RM370. Note how left side frame rail ends are rear edge of seat. Note stubby silencer.

Second shot is a 77. Kinda harder to tell in this pic, but frame extends beyond end of seat. I had to fabricate my own rear top silencer mount - so that is not stock. But I am 99% sure the longer silencer is, as is the extended frame.

 

[dirt bike dave]

Here is a shot of the '78 RM400 for comparison.

It does look like the silencer is even longer than the '77, but probably mounts about the same.

 

[_JOE_]

Why did they even bother with a silencer in 76? The thing is all of three inches long.

 

[KTM Mike]

Why did they even bother with a silencer in 76? The thing is all of three inches long.

Yeah, no wonder we have a sound issue today! About split your ear drums. But honestly, the one on the 77 really did not sound much better. They were totally mechanical silencers to - no packing like modern ones.

 

[_JOE_]

I had a 77 rm125 and it was obnoxious, I can't imagine a big bore. :yikes:

 

[schmanman]

foxforks, keep us updated as you restore this sucker!

we love a good bike build up. :nener:

remember, that's half the fun!

 

[whenfoxforks-ruled]

Thanks everyone, and Yes, Joe hates them short throw away silencers! I was watching some ding bats running up one of the forestry approved(at the time) silencers, its over 150 dollars!!! Sure see the extended left rail Mike, and good thing I moved my laptop above droool level, awesome restores!!!! The ex-naked city enduro? Ahhh to bash some trees, and cellulite ridden nudists? They moved across the street! There was a time I lived on part of their property, wifey did not like me paying rent in person? I have been watching stock beat up pipes going for 3 digit figures? Anyone do business with AMS? The 78 has a lot of similar parts, after that forget it? Anything Mike, and I would go to the ends of the earth, no lie! My eldest is getting married Saturday, but Sunday is open! Give me a reason to skip down to Roselawn, because its Sunday? My camera and my dog will go for it anyways! I will find it.

 

[dirt bike dave]

The 78 has a lot of similar parts, after that forget it?

Looks like many changes in '79, including a bump up to 417cc, different suspension, clutch, etc... Not many changes between '79 and '80.

There is a link to a Dirt Bike test of the '80 on the Suzuki link I made earlier. With the stock pipe, it was mellow. Apparently there was a plate you could remove inside the pipe - when you pulled that out, it was a beast.

FWIW, I got to ride an '80 once back in the day. All stock, and it was very mellow.

 

[KTM Mike]

Thanks - those are two of my all time favorites I have done...

Yep - 78 very similar to 77 - and Dave is right, 79 big changes. I had a 79 400 back in the day - it was a beast in my book - but a rip roarin blast to ride!

Oh, on Roselawn - actually the nudie race is in the summer. This one is a slightly different location. The "bares" dont come out much in April anyhow! It sure can be distracting though to be bashing through the brush, then see a "bare" letting it all hang out standing there watching.

But - bad news - my buddy is not going down to the race. I am sure we can work something out though. Let me do some more pondering on how we can get this stuff to ya... I know I will be seeing various other guys who might be able to haul parts to the Lansing area at least? Shipping is an option, but it can get pricey. Or, toss a bike in the back of the pickup, head north for a nice weekend of riding in northern Michigan! I have a nice tight woods loop on my property that will leave your tongue hanging out in 1 lap, plus direct access (ie at the end of the drive way) to over 100 miles of ORV trail in the area.

BTW - congrats on your kid (son? daughter?) getting married! Marriage is a fine institution if you like being institutionalized. :nener:

T Sure see the extended left rail Mike, and good thing I moved my laptop above droool level, awesome restores!!!! The ex-naked city enduro? Ahhh to bash some trees, and cellulite ridden nudists? They moved across the street! There was a time I lived on part of their property, wifey did not like me paying rent in person? I have been watching stock beat up pipes going for 3 digit figures? Anyone do business with AMS? The 78 has a lot of similar parts, after that forget it? Anything Mike, and I would go to the ends of the earth, no lie! My eldest is getting married Saturday, but Sunday is open! Give me a reason to skip down to Roselawn, because its Sunday? My camera and my dog will go for it anyways! I will find it.