Two stroke VS four stroke. Facts & figures.

[James]

James,
I'm not sure why you can't take 89'ers post for what it is. He's NOT saying you have to follow the intervals, it simply indicates the life of the parts as seen by the people that built it. I'm sure however that your guesstimate model works well. :)

I can take 89rs post for what it is, a good bit of information and some round numbers. My disagreement is with the use of the word "fact" as in using recommended service intervals as factual evidence to prove that 2s and 4s cost is the same in the end. What I am saying is that if my piston will last 7.5 hours many times over and still be in spec, then it must not be a fact that it needs to be replaced every 7.5 and then that would call the 'factuality' of the service manual in question. If neither manual is "factual", then comparison between the two would also be irrelevant. Goes back to my point about those intervals being estimates or "guesses".

If 89r had called his thread Generalized Rationalization and Comparison of Costs, I wouldn't have an issue with the "facts" in the service manual as they wouldn't have been presented as such. If he simply said 2 strokes suck and I like 4s better then I wouldn't argue as there are many days I'd agree with him.

What I don't recall seeing anywhere is Rich clearly saying that maintaining 4s and 2s cost the same in the long run. Considering his experience and knowledge, if he did say that, I'd accept it. But I just don't see what has been presented as being a "case closed"

The "guesstimate model" has worked very well in keeping 2 stroke maintenance costs exponentially smaller than the facts presented your honor.

Defense Rests

:cool:

 

[James]

Ivan's current setup is probably as close as you can get in a small bore bike. Piston life is better on the YZFs than on the Hondas or RMZ/KXF engines, and with the stainless steel valves and the good springs the valves train is as reliable as any XR. :cool:

Rich

I had come to this realization even before riding the 262. Might be the reason for my latest acquisition. ;)

 

[SpeedyManiac]

James, the factory recommendations aren't guesses, they're just very conservative in order to save their asses. The guys that are designing these bikes can figure out (fairly accurately) when the engine will start wearing, if they know what rpm the engine is at most of the time. They make the recommendations very conservative so that if someone follows the service manual exactly, they shouldn't have ANY problems whatsoever. Oh, and I bet for someone like RC or any other top pro, that's pretty much the life of those parts.

 

[keithb7]

Here's my 2 stroke Vs 4 stroke story....A few years ago I bought a real nice used 1997 Honda XR650L. Modded it up and had a nice dual sport. The engine burned oil, on a long trip, say 450miles, I'd be down a full quart. I decided to rip into the engine and rebuild. As soon as I pulled the valve cover off I could see that at one time the previous owner got the engine pretty hot. Upon further dis-assembly I found a 3" scratch, about the size of a human hair on the cylinder wall. This I believe was the reason for the oil consumption. Since I bought the bike used I decide to rebuild the motor properly. New piston & rings, pston pin, snap rings, cylinder bored 0.010 over, valves ground, seats ground, new timing chain and sliders, all gaskets, oil, filters. I performed all the labour with the exception of the maching costs to bore the cylinder, and grind the valves & seats. In the end I spent close to 1000.00 Canadian. I rode the bike hard, 3 years later the engine starts to slightly burn oil again. I sold it and did well recovering my expenses and in terms of my usage, I feel I did Ok.

Fast forward to Feb 2005. I bought a used 1993 CR250R, awesome condition. The previous owner had not done the top end in 2 trail riding seasons. I decided to do it right away. Upon dis-assembly I found big bore kit. Bonus! The crank was in great condition so I did the top end, gaskets and reeds.
Total spent about $200 Canadian, including oil and anti-freeze. There was no maching costs involved, I did all the labour myself. Had the bob done in record time, and it fired up on the 2nd kick today after the re-assembly. Off for an arm stretching ride tomorrow.

I am not a racer, I am a bush trail rider. I don't rebuild after a certain number of races. For simplicity and expenses, so far I am loving the 2 stroke. That is just my simple real life comparison between my last 2 bikes.

 

[Rcannon]

The 4 stroke guys I ride with probably use more oil overall than my two stroke. I detect a level of fear from them if they dont change the oil everytime they ride the bike.

I change my tranny oil every the ride, but that equals 3/4 quart. I can buy Yamalube R at Rocky Moutain atv for 2.29 per 16 oz. That is pretty much a days woth of oil for 2.29.

 

[Studboy]

On the subject of maintenance intervals...

I believe that the "average" rider can get at least 40 hours from a 250 2T piston if maintained properly.

I often run mine more because in my previous experience, my static comp. has not dropped very much (5-8 psi) in 40 hrs and also my piston was still in spec, but I just changed it anyways. My riding is probably: 1/2 Dunes riding/racing 1/4 Trails/MX Track 1/4 Jumping.

But I also believe that the "average" rider can get 80+ hours from a 450F assuming it is also maintained (oil changes, filter, valve adjustments, etc.).

The manual replacement intervals seem to be for two kinds of riders:

1. AMA Pro level riders. 2. Riders who insist on running an 100:1 oil mixture on two strokes for MX or riders who never change oil on 4-strokes.

 

[Ol'89r]

I can take 89rs post for what it is, a good bit of information and some round numbers. My disagreement is with the use of the word "fact"

Goes back to my point about those intervals being estimates or "guesses".

What I don't recall seeing anywhere is Rich clearly saying that maintaining 4s and 2s cost the same in the long run. Considering his experience and knowledge, if he did say that, I'd accept it. But I just don't see what has been presented as being a "case closed"

QUOTE]

James.

Here's a few facts for ya. :cool:

Fact #1.

I have over 40 years of experience in the motorcycle industry some of which was working at the factory level with current and former National #1 AMA Pro riders. Some old guys you have probably never heard of. ;)

2. At the factory level, engines are taken completly apart after EVERY event and things like pistons and rings, valve springs, etc, are automaticlly replaced regardless of how many hours they have on them. All other parts are inspected and tested using non-destructive testing methods such as x-ray, magnaflux and zyglo techniques. Even the new parts are tested before use. So, at the Pro level, Honda's service recomendations are not out of line.

3. Currently own a small aftermarket business in SoCal and have done so since 1977. We build and rebuild racing engines for local racers and riders, both two and four strokes. Also do chassis fabrication on motorcycles and race cars.

4. I have personally raced both two and four strokes as a AMA Pro expert and also at a local level. Currently own a CRF450 and a CR250.

5. Of all the engines we do in my shop the only catastrophic engine failures we have seen were engines that the owners completly ignored the service intervals and rode them until they blew up. Both two and four strokes.

6. In my experience, of all the engines we do in my shop the two strokes require ring and piston replacement at least twice as often as four strokes ridden under the same conditions on the same tracks.

7. One of the most expensive rebuilds we ever did was a CR250 that was allowed to go way past the recommended service interval. It hooked a ring in a port and broke the top of the piston off. Took out the piston, cylinder, head, power valve, crankshaft and both cases. :yikes:

8. On my own CR250 I rebuilt the top end every 4 to 6 races/rides and did the bottom end at about every 10 to 12 races.

9. On my own CRF450 I check the valves clearance every 4 to 6 races/rides and adjust as necessary. I check the piston, cam, valves and bottom end every 10 to 12 races/rides. In over two years, I have only replaced the piston and rings twice. The second time the piston was within spec. The only reason I replaced it was because it had so many hours on it. Have never had to do any work to the crank and the engine still has the original oem valves.

10. The intervals quoted were only used for the sake of discussion and comparison.

11. All of my observations and comments come from my hands-on experience. I didn't just fall off the turnip truck.

12. No matter how much evidence a person provides, some people still want to argue.

Those are the facts.

I rest my case.

Ol'89r

 

[matt-itude]

well from my point of view between rich and 89 there argument seems to say (drawing my own conclusions) that it should be pretty close, between 2s and 4s, so ride what you want. I do believe that some have a real phobia of trying to work on 4's, and that contributes to there bias. We should all welcome change, because without it nothing will get better for any of us. (im not suggesting give up on one or the other. I'm suggesting we welcome healthy competition.)

 

[Burtonridr250]

Two strokes are better :fft:

 

[truespode]

I have to side with James.

I think you guys are mis-understanding his statement.

He is agreeing with 89'er more than he is disagreeing.

He's an accountant so you have to give him a little slack :)

Ivan

 

[James]

12. No matter how much evidence a person provides, some people still want to argue.

Those are the facts.

I rest my case.

Ol'89r

#12 is one fact that I definitely can't argue against. I have to give you credit, you are trying very hard to convince me and now that you put something out there other than factory manuals, I might be more open to this theory of yours. :cool:

Since I "rested" earlier, I'll be good and honor my word. Besides, I got nuthin :)

I have to side with James.

I think you guys are mis-understanding his statement.

He is agreeing with 89'er more than he is disagreeing.

He's an accountant so you have to give him a little slack :)

Ivan

I am always SO misunderstood. It is starting to give me a complex. :coocoo:

 

[Zoomer]

Guess it comes down to, if you like what you ride,...ride it, if you don't, sell it and buy something you think you'l like better. I don't even think about maintainance cost when it comes to bikes, thats just part of it. I came off 500 2 strokes, went to the 4 st, now have a 500 2 stroke, along with the 4 stroke, kept the 4 stroke just in case I miss it after I get back on the 2 stroke , :bang: both have there advantages, disadvantages, so, I have the best of both worlds, ? or the worst of both worlds, depending on who you want to listen to. ( all though I have an advantage with a 500, they just don't plain wear out as fast as the 250's, so buy a 500 ) :ride: