dannyp84 Reader
5/11/22 2:29 p.m.

Lately I've been feeling guilty about not having much time for my RM125. I know if I sell it there will be at least 4 or 5 times a year where all I want to do is ride a dirt bike, and if it's not there nothing else will suffice. It also doesn't cost anything to own and doesn't take up much space. Once in a while I kick around the idea of applying for a road title, and putting supermoto or dual sport tires on it, so I can drive it to work. I live 4 miles from the office, and the road is all hilly two lane. I know it wouldn't be comfortable to ride on the road for more than 15-20 min at a time, but that would get me to and from work and then some. Does sustained constant engine speed somehow hurt a 2 cycle engine?

I have a friend who titled his KTM 300 for the road, but he eventually got tired of carrying a backpack with premix in it. I can't imagine riding my bike far enough to stop for fuel more than once.  I know a DRZ would probaby fit the bill a lot better, but this route could be a fraction of the cost and I'd get to ride my bike more often when it's taking me places I need to go anyway. In a perfect world, I'd leave the bike alone and use it to ride local moto tracks and trails. However, it seems like everyone locally who used to enjoy motocross and trail bikes moved on to side by sides, and those don't interest me. At the same time, I feel that riding the bike alone on a trail or track is a little bit dangerous and a lot less fun than with friends. 

mdshaw GRM+ Memberand HalfDork
5/14/22 7:30 a.m.

Do it. I love 2 strokes. It would be a little buzzy but 4 miles is not far. I have a CR80 that I rebuilt, lowered the pegs, raised the bars & seat, fits me well now, lights on & some new dual sports for it but I need to extend the swing arm an inch. Doing it to cart around on the back of the RV. 
Wish we could get some 2 stroke street bikes again. I do lots of searches about building one, sold my collection of RD's many years ago & miss them.

wearymicrobe PowerDork
5/14/22 9:14 a.m.

WR250r makes about the same power as the RM125, different power band but still fun. If you want new the KLX300SM is good as well if you want more street bias. 

Peabody MegaDork
5/14/22 11:16 a.m.

Sustained engine speeds will not hurt your RM as long as they're in reason and it's properly tuned.  Those engines are built to rev reliably to well over 10,000 RPM. The problem you're going to have is gearing. Not that it's revving too high, but that you'll always be fighting the power valve. They have a simple RPM based power valve and it's going to be opening at cruise, increasing power and speed, so you'll let off, it will close and you'll slow down, so you'll try to increase speed and it will open again.... It's irritating. Maybe if you go up a couple teeth on the counter shaft you'll be able to ride under the power valve and it will be a lot smoother. But that gearing won't be great off road. 
I've done it with a KDX 220, an XCW 200 and now a 250R Freeride. The FR has no power valve so it's much more comfortable on the street and cruises nicely at 80 km/hr. 

What year is the RM? I had the last gen, 04-07 and it was a good bike. 

bearmtnmartin (Forum Supporter)
bearmtnmartin (Forum Supporter) GRM+ Memberand UltraDork
5/14/22 11:33 a.m.

I have a friend with a street legal KX500. But for the reasons you already know it is no longer ridden on the road. But if you do I would caution against the sustained high RPM. Pretty easy to melt a piston. BDDT.

dannyp84 Reader
5/14/22 4:52 p.m.

In reply to Peabody :

It's an '05.

mdshaw GRM+ Memberand HalfDork
5/14/22 6:40 p.m.

For sustained high speeds just jet richer on the main jet. Just like riding in sand, mud etc. Proper main jetting will not melt a piston. Slightly lean & intermittent wot can be gotten away with. Lean & extended wot makes melted pistons & even spark plugs. 

mazdeuce - Seth
mazdeuce - Seth Mod Squad
5/14/22 7:28 p.m.

You'd be surprised at how quickly you can seize a 2stroke dirt bike at wot. We ride the smaller bikes on kart tracks and jetting that works great in the woods or on a motocross track isn't enough to keep the bikes alive for the several seconds of sustained full throttle on a straight. The problem is that exhaust gas temps get high and the ports on that side start to squeeze the piston. Different port designs are more or less succeptable to this. Having said that, 2 stroke karts drive around ALL DAY doing the same thing and do fine, but those motors are made and jetted to do that.

I say do it, but jet the top end suuuuuuper rich. You can always back off a bit, but you can't unmelt a piston. 


Peabody MegaDork
5/15/22 7:09 a.m.

I didn't get the impression that his drive to work would involve sustained WOT, but those bikes are quite rich stock, and those particular motors are very good. I used to run hard laps on long GP style, very high speed tracks and it never showed any signs of heat on tear down. And those are very fast bikes. More than a few seconds of WOT on that thing will put you into speeds that won't be safe or comfortable on that bike or on the street, and I would be more concerned about oil at that point. That's assuming it's otherwise stock. If you're running an SST pipe, which I can highly recommend, that's another story. 

I'd go with trakmasters or 761's. That way when you realize how miserable it is on the road you won't be out a lot of money cheeky

dannyp84 Reader
5/16/22 12:07 p.m.

In reply to mazdeuce - Seth :

As long as I change the rear sprocket I don't think I'll be at WOT much during the commute. However now that I look into it, getting it titled for the street is neither straightforward nor inexpensive. I bought the bike with no title or bill of sale which is pretty standard with dirt bikes around here, but I think to get a title I'd have to prove how I got the bike. I could probably track down the guy who sold it to me in 2020, but I imagine he bought the bike the same way I did, with no paperwork.

GCrites80s Dork
5/21/22 9:55 p.m.

Sustained RPM like you see on the street and clean air (which of course depends on location) is far better for a two stroke than riding in the dirt. RZ350 owners get 10,000 miles out of a top end. Try that with a Banshee -- which has basically the same engine. How many Banshees even have 10,000 miles? That's about 700 hours at 15mph average in the dirt. Do not go 700 hours between top ends on a Banshee. And that's with no Nikasil cylinder coating like you RM presumably has unless it's like an '88 or older. A few years back, Ron Lawson from Dirt Bike Magazine bought a 1995 CR250 (with an air leak!) that had been used extensively on the street previously. When he took the engine apart he thought it would be trashed. Nope! Low load as compared to all those hills, jumps, tight turns and water crossings preserved the motor. Of course 125s have shorter service intervals due to the high RPM.

But don't coast for a long time without pulling in the clutch and blipping and also don't use engine braking for more than a few seconds at a time on the street. Today's 2T oils have better oil films than ever but there is no sense in possibly causing a few hundred miles in wear by chopping the throttle a couple times. People should be doing this in the dirt on long clutch-in downhills as well since it can keep the engine from loading and wearing. Also no cush drive on an RM so hub, spoke, sprocket and chain wear is a concern when shocking the system.

But, as mentioned, not at WOT for extended periods without fat jetting. There was a guy on some 2-stroke forum that was commuting on interstates on an air-cooled IT175 BITD and said he intermittently used the kill switch while at WOT to charge the engine with more fuel/oil without combustion when it started to get bratty. I think the guy lived in Arizona where dirt bikes are legal to ride on the street, or were.

rolandefries New Reader
5/26/22 11:57 p.m.
Our Preferred Partners