Two stroke VS four stroke. Facts & figures.

[Ol'89r]

A couple days ago there was the usual discussion going on about which was better, cheaper, etc, etc. I made the statement that the four stroke will last longer that the two stroke between rebuilds, and over a period of time it will even out even though the fourstroke has more parts.

One of our members asked me to check the maintenance schedule for my CR250 against the maintenance schedule for my CRF450. So I did.

CR250
Rings and piston. Replace every 7.5 hrs or 3 races.
Small end bearing and pin. Replace every 22.5 hrs or 6 races.
Cost to do a top end rebuild on a CR250, includes rings, piston, pin, clips and all gaskets. = $166.86 Suggested Dealer prices. Not including labor.

CRF450
Rings and piston. Replace every 15.0 hrs or 6 races.
Pin. Replace every 30 hrs or 12 races.
Cost to do a top end on a CRF450, Includes rings, piston,pin, clips and all gaskets.= $170.05 Suggested Dealer prices. Not including labor.

Now, if you run 50 races a year and adhere to the recommended maintenance schedule you would have to rebuild the top end on your CR250 a total of 16.6 times at a total cost of $2,769.88

On the CRF450 you would have to rebuild the top end a total of 8.3 times at a total cost of $1,411.17

Taking into consideration you did nothing to the head on the CRF450 and had to replace the entire head, valves, springs and cam, this would cost $840.47.

The difference between the CR and the CRF rebuild is $1,358.71. So, even if you had to buy a complete new head for the CRF and a cam you would still be $498.24 to the good on the CRF.

In my experience, if you use good oil and check your valve clearance often, the CRF will go much longer than the required maintainance schedule. Perhaps three times as long as the CR or more. But, for this study I used the recommended factory specs.

Plus the fact that the CR lower end will have to be done several times before the CRF lower end will need to be rebuilt.

This is not meant to be another two strokes are better and four strokes suck or visa versa thread. Just pointing out some facts and figures..

I still stand by my original statement that 'over time' the costs will even out. In fact the fourstroke may even cost less to maintain.

I did not include labor costs since most people do their own labor. The parts prices used are available on Service Honda's website.

Have a nice day. :cool: ;)

Ol'89r

 

[CRF450Rccrider]

and a question about the oil part.....we change our oil on our CRF every 3 months is this oftin enough to put off a top end(i dont race but i ride the bike like i do)

 

[Ryone]

Most people don't do their own labor on a 4-stroke though... that's the whole point.

 

[marcusgunby]

and if the 4 blowsup , your savings have gone up in smoke.

 

[dirt bike dave]

Thanks for the data, Ol89r. I would be happy to own either bike.

A few other tidbits: MSRP on the 450 is $500 more than the CR250R. Out the door price differences are likely to be much greater (though the 450 will probably have better resale).

IMO, the Honda recommended service intervals on the CR250R are a parts department dream and reflect pro-level racing and abuse. Most 'average' riders could safely extend the service intervals on the two stroke - can they do the same on the four stroke?

 

[James]

I wouldn't agree that all of this info is "factual"

Do you actually follow those schedules?

I am curious how a piston in a hotter higher compression engine, with a single ring, and turning about 2k rpm more lasts twice as long? Same with the bottom end? If the CRF trashes clutches in short order, I don't see how it would be any easier on bottom ends and transmissions.

I'd also say that in my experience, if you use good oil and keep your air filter clean, the CR top end goes 7.5 hours many times over.

I don't know anybody that rebuilds 8 times a year much less 16. I also think there are a lot of other little 4 stroke items like oil filters, cam chain tensioners, oil pumps, etc that people put money into while I am simply rebuilding a top end each year. Matter of fact, if you are running a CRF hard enough to rebuild it 8 times a year, you will be replacing valves, springs, cam chains, more than once a year.

Not meant to defend 2s or bash 4s in any way as I own both now and have owned several 4s (XRs, the truly reliable engines) in the past, but more an expression of doubt based on first hand observation of both bikes (CRs and CRFs) in action. I am even tossing Gomers experiences with 450s out as a statistical anomoly.

Oh, the complete Wiseco CR250 top-end rebuild kit is $119 at motosport outlet.

:cool:

 

[ellandoh]

what happened to the rest of the recommended parts
cam chain,cam guides i think, valves, valve seats that almost noone can do theirselves valve springs, your silencers that crack and split due to heat and stress and cost 700$ etc.
not to mention a realistic maintenance schedule like for two strokes the average guys schedule vs 4 stroke avg. guy
we'll leave out the common consumables unless one causes increased wear over the other, such as clutches brakes tires grease etc


id say im average 2t guy
every other season i do rings and reeds and small end bearing, necessary or not most of the time not, 100$ tops.
on the others i do piston including rings and small end bearing, necessary or not most of the time not 115$ tops.

each season is probably in the neighborhood of 100 150 hours of wide open woods , mx , and a couple extended dune visits ,drag races etc. and actually i dont know how long it would take for the bike to need this maint. cuz honestly 150 hour must not be enough if you treat your ROUTINE maint well
my 03 as well as the old 88 cr will tell ya

now for the avg 4stroker guy

 

[pace]

One of our members asked me to check the maintenance schedule for my CR250 against the maintenance schedule for my CRF450. So I did.

CR250
Rings and piston. Replace every 7.5 hrs or 3 races.

You're surely racing at a much higher level than many of us if you need to rebuild that frequently. My rings do approx 25 hours and a Wiseco piston is good for 40-50hrs in my machine (and still measures within spec). This usually includes 3 or 4 racing events and at least one dunes outing.

You're also comparing a 450F to a 250-2, which seems a logical basis for argument. However, I'm sure I'm not the only smaller guy here who, if moving from his two-stroke 250 would be better suited by the 250F than its bigger brother. Such a comparison would tend to undermine some of your assertions. For Novices and many Intermediate riders, the practical 2T 250 top-end rebuild interval will significantly exceed the 250F valve service interval - at which point the service costs likely tip in favor of the two stroke.

I'll do my own two-stroke rebuild. I have neither the time nor energy to mess with a four-stroke top end, so I know I have no business owning one. I think some folks are finding this out the hard (expensive) way. :think:

 

[Okiewan]

I wouldn't agree that all of this info is "factual" Do you actually follow those schedules?

These are the intervals suggested by the folks that built the bike. Your (anyone's) desire to follow the schedule or not is entirely up to you. You decide what YOU think is a good interval and then live with the associated costs :)

I have neither the time nor energy to mess with a four-stroke top end, so I know I have no business owning one. I think some folks are finding this out the hard (expensive) way.

Exactly.

A Ford Foucs requires less maintaience than a F-40. They try to make it (ex; Focus) bullet proof from the factory, knowing full well the average owner will never lift the hood, much less change the oil every 30,000 miles. If you don't have the time to take care of of an Itallian supercar, don't buy it, you'll do much better driving your Ford into the grave.

 

[truespode]

Y
I'll do my own two-stroke rebuild. I have neither the time nor energy to mess with a four-stroke top end, so I know I have no business owning one. I think some folks are finding this out the hard (expensive) way. :think:

From what I am realizing the top end on a 250F is not that difficult.

I believe it takes longer than a 2t but not considerably.

As to the costs associated for maintenance... on a spode scale the 2t is much less expensive.

When I had a 2t I change the piston twice a year (a little over 30 hours per top end). A little over a hundred bucks each time.

With the 4t I replace the piston once a year (a little over 60 hours). $180 or so for the parts if I do not get a timing chain which I believe should be replaced once a year at least. The valves can be an issue to but I got over 60 hours on my stock CRF450 before I put in the SS valves and on my 2001 YZ250F I got 2 years of hard riding out of it and never touched the valves, neither did the kid who bought it from me.

Add in the oil filters and the fact that I change the oil more frequently on the 4t the costs do go up.

However, for me the costs are well worth it and not so much higher than 2t costs to make it unbearable.

I prefer the engine performance of a 4t and the way it feels in the air. It gives me more confidence.

Ivan

 

[fow350]

Do the 4-strokes have a hydraulic bearing for the crank, or is it a mechanical roller like the 2-strokes?

 

[BradFrost]

I gotta agree with a few others here. The service schedule depends on the type of riding you do. Diagnostics is just one of the many skills that comes from owning a dirt bike so it's really more a question of practical experience mixed with technical research. You gotta know what you're bike is asking for and not necessarily just follow the manual to the letter.... especially with regards to jetting, tuning and engine maintenance. Just admit it ... the 2strokes should be cheaper to maintain... and harder to ride across a variety of terrain. I respect the 4strokes ... but I always find the 2stroke detractors are either too old, inexperienced or unfit to handle the power band and twitchy setup/power delivery so they just get up on the bag out trip. My clutch technique has improved outta site since taking on the 2's.
Love, peace and chain grease to all... even you quad riders :)

 

[Rich Rohrich]

I am curious how a piston in a hotter higher compression engine, with a single ring, and turning about 2k rpm more lasts twice as long? Same with the bottom end? If the CRF trashes clutches in short order, I don't see how it would be any easier on bottom ends and transmissions.

A four-stroke fires and heats the piston crown every 720 degrees of crank rotation while a two-stroke does it every 360 degrees. That additional 360 degrees of rotation allows the piston crown and rings a lot of time to cool and helps extend their life considerably. It's incredibly rare to see a four-stroke engine with a hole burned into the center of a piston crown. I wish I could say the same for my two-strokes. The fact that the rings are not forced to bounce in and out of port windows on a four-stroke is also good for longer term sealing and overall reliability.

Cranks tend to last longer on four-strokes for a number of reasons :

- oil flow to the bearings on a four-stroke is constant and under pressure which ensures delivery. Crank and rod bearings on a two-stroke only seal oil diluted by the fuel that is splashed on them during rotation. The fact that some pinheads ride MX and mix at 66:1 ratios only makes things worse.

- heat to the upper rod bearing surface. Firing every 360 degrees on a two-stroke sends a lot of heat through the piston crown and the upper rod bearing. Oil vaporizing out of the bearing during these times is pretty commonand doesn't help bearing life.

- piston speeds - If a CR250 produces max power at 7500 rpm it's mean piston speed is 3543 fpm, if a CRF450 produces max power at 9000 rpm it's mean piston speed is 3662. Not a lot of difference, especially when you consider most people don't spend much time above 7500 rpm on a CRF450 because it works best by using the torque below the peak. RPM trends on a CRF450 on an SX type track look more like this : http://dirtrider.net/teamdrn/showphoto.php/photo/4438/size/big/sort/1/cat/500

As for transmissions, they seem to last about the same in both types of engines. They are built a little bigger in four-strokes but only enough to withstand the additional torque loading. Good four-stroke riders use the engine torque rather than the clutch,and it's been my experience that the only guys who wear four-stroke clutches faster than two-strokes are the same guys who were abusing clutches before the CRF and YZF ever existed. ;) Some people just abuse clutches regardless of what they ride. Riding style seems to play a much bigger factor in clutch wear than engine type ever will.

 

[James]

A four-stroke fires .....lots of techno stuff omitted for purposes of brevity......ever will.

You had me at hello ;)

Seriously, all that makes a lot of sense and thanks for the explantion. But I am still not convinced that a CRF is as cheap as a CR250 over most any period of time for riders like me and our crowd. Too many parts to break and from what I can tell, they do.

But I do agree with Ivan, the power delivery may make it worth the extra expense/work. I have been saying for 4 years that I would love to have my old XR400 engine in a CR250 frame because the 4s are easier/more fun to ride (for me).

 

[James]

These are the intervals suggested by the folks that built the bike. Your (anyone's) desire to follow the schedule or not is entirely up to you. You decide what YOU think is a good interval and then live with the associated costs :)

Exactly.

A Ford Foucs requires less maintaience than a F-40. They try to make it (ex; Focus) bullet proof from the factory, knowing full well the average owner will never lift the hood, much less change the oil every 30,000 miles. If you don't have the time to take care of of an Itallian supercar, don't buy it, you'll do much better driving your Ford into the grave.

Paragraph 1: I am not even sure what my point was at the time. Upon further thought, I am pretty sure my opinion is that the consequences of not following those schedules are less severe with the CR250 than the CRF450. Also, I am not convinced that it is a documented "fact" that the components mentioned have 2x the life in the CRF as compared to the CR. Finally, I was thinking that the list of parts for the CRF was not all inclusive thereby artificially lowering the costs calculated. The thought was there, it was my presentation that was lacking.

Paragraph 2: I can go along with that, and choose to withhold debate on that one at this time (although I am thinking real hard about how to punch holes in it).

:)

 

[gowen]

Fact: I am faster on my YZ250 than I am on my buddies CRF450 or CRF250. I like the snap of a two stroke, I don't like the torque of a four, nor do I like a Honda. The YZF series are nice, but same issue. If I wanted a four stroke, I'd buy a XR. If I wanted a big bore power, I'd own a KX500 ;-).

New fours are amazing!! Just not for me. I don't smash four strokes, don't smash my two strokes.

 

[Rcannon]

I really have enjoyed this thread. I appreciate the coments. I have ridden a CRF 450 and enjoyed it very much. The thing stopping me from owning a 4 stroke is the "Fear Factor"

I can easily handle any sort of rebuild on my two stroke. I find myself doing the rebuilds more than necessary due to low cost. I have seen too many horror stories and 3000.00 repairs to consider owning a 4 stroke.

I also enjoy the tuning options my older YZ 250 will allow. I can see somethign on DRN about porting or head mods and get interested. A few weeks on the auction site will yeild used heads or cylinders for low dollars. I can then experiment and have fun. Even a total engine can be bought for under 500.00.

 

[Ol'89r]

I wouldn't agree that all of this info is "factual"

Do you actually follow those schedules?

I don't know anybody that rebuilds 8 times a year much less 16.

Oh, the complete Wiseco CR250 top-end rebuild kit is $119 at motosport outlet.
QUOTE]


The FACTS, as Okie pointed out, come directly out of the Honda service manual. These are the recommended factory intervals for the CRF and the CR and used only to compare the two.

The FIGURES come directly from the Service Honda web site and are FULL RETAIL PRICES. These prices were used for comparison purposes only.

No, I don't follow those recommendations on my own bikes. On my CRF, I inspect and measure everything and if it is within factory specs I put it back together. Been doing that for two years now. Other than replacing the rings and piston, the bike still has the original valves, cam, springs, cam chain and bottom end. And Yes, it has been raced. And Yes, I'm old and out of shape but not inexperienced on 2 strokes.

This thread was only meant to point out some of the misinformation on the internet about fourstrokes. Many people seem to think you need to replace everything in the engine, cams, followers, etc, just as standard procedure. This is simply not true. In the service manual they do not state replacement intervals for anything other than the piston, rings and pin. Everything else like cams, followers, valves are inspect and replace as necessary. If service intervals are followed, most of the time it is not necessary to replace these items.

As Rich pointed out there are many reasons why a 4 stroke lasts longer than a 2 stroke. Better oiling system, filtered oil fed by constant pressure instead of oil mist. Full cylinder ring support instead of a cylinder that is full of holes. Cleaner internal operating enviroment. Half the power strokes allowing the engine to run cooler.

Again, this is not meant to bash either 2 strokes or 4 strokes. Just pointing out a few facts and trying to correct some rumors.

Fact is, all the new bikes are awesome. The 2 strokes will be around for a long time and the aftermarket mfg's will be producing parts to keep them running for many years to come. The 4 strokes are just in the beginning of their evolution and will only get lighter, faster and easier to ride.

It is a very exciting time to be involved in the industry.

Just pick a color and go ride. :yeehaw: :yeehaw: :yeehaw:

Ol'89r

 

[CaptainObvious]

and if the 4 blowsup , your savings have gone up in smoke.

Nice try Ol'89er. Some people will just never believe :bang:

Another thing to consider when you start to nit-pick the cost of ownership as many like to do (I choose not to), Two-stroke fuel costs a lot more. Just the cost of oil alone will add $1 to $3 per gallon, that works out to $3 to $9 (without the SFC in front of me for each engine type, this is a guess) per more an hour for operation. That is $300 to $900 more in operating costs per 100 hours of operation.

Ol'89er said it best when he figured that all of the costs even-out in the end.

It's just so embarrassing how extreme some of the two-stroke riders have become. Get over your lunatic obsession with the past. By the time you come to accept four-strokes they'll be replaced by something else. :blah:

 

[Chili]

Get over your lunatic obsession with the past. By the time you come to accept four-strokes they'll be replaced by something else. :blah:

Hopefully it's something a little more quiet. :nener: :moon: :rotfl:

 

[James]

Nice try Ol'89er. Some people will just never believe :bang:

Another thing to consider when you start to nit-pick the cost of ownership as many like to do (I choose not to), Two-stroke fuel costs a lot more. Just the cost of oil alone will add $1 to $3 per gallon, that works out to $3 to $9 (without the SFC in front of me for each engine type, this is a guess) per more an hour for operation. That is $300 to $900 more in operating costs per 100 hours of operation.

Ol'89er said it best when he figured that all of the costs even-out in the end.

It's just so embarrassing how extreme some of the two-stroke riders have become. Get over your lunatic obsession with the past. By the time you come to accept four-strokes they'll be replaced by something else. :blah:

3 gallons per hour???? You might need to change your jets or something.

From what I can tell, the cost of the two stroke oil is nicely offset by the cost of oil filters.

Come to think of it, if I actually nit-picked the cost of riding and what I have spent, I'd probably get sick and then sign up for counseling.

 

[James]

The FACTS, as Okie pointed out, come directly out of the Honda service manual. These are the recommended factory intervals for the CRF and the CR and used only to compare the two.

I know for a fact that I don't have to replace my piston every 7.5 hours. Recommendations = guesses in my opinion, not facts.

The FIGURES come directly from the Service Honda web site and are FULL RETAIL PRICES. These prices were used for comparison purposes only.

I would agree that those figures are factual, the prices that is.

Again, this is not meant to bash either 2 strokes or 4 strokes. Just pointing out a few facts and trying to correct some rumors.

You can bash all you want. Like I said, I ride both. The only thing I am questioning is the "facts". Your information is interesting for sure, but I am not convinced yet. No matter, I have to to get busy obsessing over the past, no time for debates. :)

 

[Okiewan]

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. :)

 

[Jaybird]

My take on the 2t vs 4t debate is this: what the heck is the debate?
I love riding both 2 strokes and 4 strokes. Each have their own charactor, each have their own maintenance schedules. I spose if I'm going to ride both types of bikes, I better be prepared to maintain them...or not...(shrug)

If we worry about the few hundred dollars a year advantage one way or another of either type engine, we probably are in the wrong sport, and should probably look for a hobby that is more affordable anywho.

If the debate is important to you as a money issue...you can always buy beater bikes and motors from geekbay and sink a little into them, and have a fine tuned machine that rivals factory money performance wise. In the long run I've always felt you can get more bang for your buck by buying old and tuning them up proper, than buying new and doing it. Hell, Mr MSRP eats up alot of good tuning green.

If we all had a preventive maintenance schedule like 89r's and measured all critical surfaces on a regular basis, and used all the good tips we get from here in the way of keeping things alive longer, we could all extend the intervals we have to shell out bucks. Two-strokes, four-strokes, hemi's, Singer sewing machines, severe duty robotics....we have to set priorities, and if we are gonna play with them we gotta be prepared to fix them.
I personally do not dink around with Singers, as I find them a bit tedious.

 

[Eric Gorr]

I have been saying for 4 years that I would love to have my old XR400 engine in a CR250 frame because the 4s are easier/more fun to ride (for me).

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:

A CRF450 with an updated valve train is a good choice as well, but the F1 insprired single ring piston is still going to wear out faster than a YZF piston.


***** OOOPPPS, Eric was still signed in on my computer, this should have been a post under my name :)

Rich