Little Help, I want a two-stroke road bike

[OLDSCHOOL-MUSCLE]

Hi everyone, I want to get a motorbike thats good for the road, but something I can go offroad with, nothing too hardcorel. As far as I'm concerned the 4-stroke is a better bike for the road in every way, except I love the sound of a 2-stroke. It's killing me a bit cause deep down I know that the smartest thing to do would be to get the 4 stroke, but I'm being stubborn cause I love the strokes so much. I have some questions that I'd love to get more info on.

1. Whats the deal with filling up petrol (or gas for you yanks) at the servo? Hows it done?

2. From what I've read a trail bike 2 stroke is supposed to be rebuilt every 25 to 40 hours or riding. How does this apply to the street, maybe in k's. Would it be every 15,000kms? And how would the 4-stroke go in comparison.

3. I've heard the two-stroke is pi$$ easy to rebuild, how much does it roughly cost to do it, also in comparison to a 4-stroke.

4. Could I get some mileage figures both for 2-strokes and 4-strokes.

5. Would anyone in they're right mind buy a 2-stroke if they had even the slightest intention to ride interstate distances.

I have so many questions but I'll leave it at that for now. Oh also, a 125 would have enough power for me yeah? How much faster would a 250 be? Thanks

Oh yeah, and riders details apparantly is important, so:
5foot 10" or 177cm
160 pounds or 70 kg
21 years old

 

[gergetz]

if you rode a two stroke on the road youd be rebuilding the top end every other night!

 

[dirt bike dave]

I've had dual sported KDX200's and KDX250s (two strokes) and an XR250 (four stroke, bored to 277cc).

I would carry several small tupperware bottles (about 9 ounces) of oil in my fanny pack. Add about 3 ounces per gallon. Just put a little oil in the tank, add some gas, add some more oil, etc... The swirling of the gas entering the tank always seemed to mix the oil just fine.

With a bigger than stock countershaft sprocket, a two stroke 250 should be able to top out at over 80 mph. However, it is not comfortable to cruise at over 60 mph on most bikes, as you are turning a lot of rpm, even with taller gearing. If you gear the bike too tall, you will struggle on tight trails, too.

Basically, most four strokes rev higher and produce usable power over a wider rpm range, which is useful for road riding.

Several issues with 2 strokes you might not have thought about: Rolling off the throttle after a sustained high speed run is BAD unless you pull in the clutch. Hot engine + high revs with no cooling fuel and lubricating oil can result in catostrophic failure. IOTW, don't use engine braking to slow you down after you have flogged the bike, and you will be fine. When they used to make two stroke street bikes, they did not use pre-mix but had oil injection driven off of an rpm sensitive pump to prevent this problem.

Secondly, on my KDX250, highway cruising was irritating because the bike did not like to hold a constant speed. Basically, if you held the throttle still a crusing speed, the powervalves would start to open and the bike would speed up, so you would have to back off the throttle. Then it would slow down. Then you would open the throttle a little, hold it steady, and the bike would keep keep speeding up. Gets annoying after awhile.

Also, to add a larger countershaft sprocket to permit lower revs on the freeway, you may have to eliminate the guard that protects the case in the event the chain derails.

I would go about 1,000 miles between rings and 2,000 miles on a piston. With a piston, a top end is usually about $120 US. Just rings, gaskets and wrist pin bearing maybe half that.

On my KDX250, I would go between 90 and 100 miles on a 3.6 gallon tank. My XR250 would go 85 miles on about 2.5 gallons. With most small bore bikes, you will actually get worse mileage running on the highway at 60+ mph than if you are cruising country roads at 30 mph. For most road rides, you will get slightly better fuel mileage than you do when trail riding.

 

[OLDSCHOOL-MUSCLE]

Holy crap, things are worst than what I thought. I doubt the two-stroke is for me, they probably too much maintenance. I mean if you say you you'd go only 1000miles between rings and 2000miles between pistons thats not a lot at all. I'll have to give up the sweet sound of the two-stroke for practicality reasons, but I don't like the sound of four strokes at all.

By the way can you get exhausts for your road trail four strokes to make them sound really nice, maybe even sort of like a two stroke, or beefier?

 

[bikepilot]

There are two stroke road bikes that last reasonably well. A road bike is made very different from an MX race bike. Neither a 4 or 2 stroke MX race bike will last long on the road, especially with extended high speed stuff like interstate crusing.So if you are talking about riding a two stroke road bike, its not at all reasonable to compare that to the results of riding a two stroke dirt bike on the road. My TL1000S sucks in the dirt and is a 4-stroke - does that mean all 4-strokes suck in the dirt?

Unfortunately, the EPA killed 2-stroke road bikes in the USA in the mid 1980's. Fortunately, some have made it across from canada and even europe - watch e-bay. You will not like anything smaller than a 250 for extended highway crusing.

Examples, sport bikes typically good for ~30k miles without any real work.
- Suzuki RGV250
- Yamaha TZ-250
- Honda NSR-250, 400, 500.
- Yamaha RZ500
- Aprilia RS250 (street legal, not sold in US) and RS-250 Cup bike ("race track only" - sold in the us). Note, all the priller 250 two strokes use modified Suzuki RGV-250 engines.

Standard type bikes
- Yamaha RD350, RZ350
- Suzuki ??750 typicalled called the "water buffalow (liqued cooled, 3cyl two stroke 750)
- Kawasaki H1 - air cooled two stroke 750 (quite fast).


Still, given the dificulty of aquireing a two stroke road bike and the lack of developent they've seen over the past 15 years I have to admit that a 4-stroke probably makes a lot more sense. Don't get me wrong, I really really like 2-strokes, but given a 1980's technology 2-stroke or a 2000+ tech 4-stroke and well, the 4-stroke starts to look pretty good. Take a look at the new Kawasaki 650 twin cylinder sport bike. Should be a fun entry level sport bike with a bit more charcter than the 4-cylinder's out there.

 

[dirt bike dave]

Old School - I changed pistons and rings regularly as the bikes were mainly used as dirt bikes. So I stuck with my dirt bike maintenance shedule and replaced the parts before any loss in performance was evident. I find 1,000 miles or 50 hours between rings is a safe rate for me (lots of single track) on a trail bike. No doubt many people go much longer. I went 3,000 miles on a KDX250 piston once and it showed blowby and some scuffing, so I felt like that was too long.

 

[cujet]

Hello Old School!

I ride a Husky 360 2t on the street all the time. In stock form, it is a mildly tuned 2 stroke, couple that with the fact that it is a big bore (less wear) and I find it has acceptable life. I do find that the gearing has to be extreme to be comfortable on the street. However it is a 6 speed, so tall gearing is OK.

Btw, I have ridden all sorts of 2 stroke dirt bikes on the street. My take is that a big bore bike (500cc) is what is needed to do it right. Keep in mind that some crazy folks actually take the CR500 engine and shoe horn it into a roadracing frame, then ride it on the street.



Here is my take on this subject. The life span of a 500cc 2t is measured in the hundreds of hours, similar to a big bore 4t. It might even have a much longer lifespan than a modern 4 stroke motocross bike. That, of course, depends on how it is used. Gearing plays a big part in how well a 2 stroke engine does on the street. IMHO, the proper thing to do is gear it very tall, so the engine is not reving too high.

Keep in mind the RZ350 Yamaha street bike has quite radical port timing and low quality old world design. Yet it lives for a long time on the street (about 20K between pistons 30K+ for the cranks). I believe the fact that those 175cc cylinders are only turning 4000 RPM at 55MPH plays a big part.

Chris