2 stroke vs 4 stroke maintenance

2TYam27
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2TYam27
Edited Date/Time 10/6/2012 1:38am
I posted this in the jumping back to 2 stroke thread. That thread is pretty well dead so I decided to start a new thread so I can get some feedback on this.

I have been curious as to what the manuals say about top end replacements on the two versus the four stroke since many people complain about how many top ends they had to do on their two strokes. My 05 YZ250 manual says to replace the piston every fifth race and rings every third race. My buddies 07 YZ450 manual says to replace the piston and rings every fifth race. Sounds to me like the top ends should basically be done at the same intervals, plus the four strokes have the valvetrain to consider. Given this, how could a four stroke not be more expensive, over time, when considering the valvetrain components will eventually need replacing? Just curious.
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Larry
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Larry 2/11/2010 11:39am
2/11/2010 11:39am
I go 20 hours between top ends on my sons KTM 200. and that is rings the first time then a piston at 40 hours. The KTM piston is forged so they last a little longer.
It cost me maybe $160.00 in parts with a piston.
miedosoracing1 2/11/2010 11:52am
2/11/2010 11:52am
Honda books are roughly showing the same, per cc. But the books also show a crank needs replacing on the 4 stroke after so many hours, because failure after those hours can be very bad. I am not sure if the 2 stroke says anything about that, but basically when they go, is most people's time. LOL Atleast when I buy them.
panic revver 2/11/2010 12:16pm
2/11/2010 12:16pm
miedosoracing1 wrote:
Honda books are roughly showing the same, per cc. But the books also show a crank needs replacing on the 4 stroke after so many hours...
Honda books are roughly showing the same, per cc. But the books also show a crank needs replacing on the 4 stroke after so many hours, because failure after those hours can be very bad. I am not sure if the 2 stroke says anything about that, but basically when they go, is most people's time. LOL Atleast when I buy them.
Honda also says to replace the piston on the 450 every 15 hours but we all know that for 99.9999% of the 450's sold that is over kill.
miedosoracing1 2/11/2010 12:25pm
2/11/2010 12:25pm
I think a 450 could be made with 5 less hp, and last 10 times longer though. It's crazy to push those 450's to the limit when the pro's are detuning them. Just think if a 450F would last as long both crank and piston as a old CR500 like mine. 1995 motor still on the stock crank. That is unheard of on a current bike. But just a little thicker piston and stronger crank, would make that bike last everyone for a long time. Let the race shops make the lighter pistons and cranks for the racers, and leave the normal population with long lasting motors.

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J.Saunders144 2/11/2010 12:49pm
2/11/2010 12:49pm
miedosoracing1 wrote:
I think a 450 could be made with 5 less hp, and last 10 times longer though. It's crazy to push those 450's to the limit...
I think a 450 could be made with 5 less hp, and last 10 times longer though. It's crazy to push those 450's to the limit when the pro's are detuning them. Just think if a 450F would last as long both crank and piston as a old CR500 like mine. 1995 motor still on the stock crank. That is unheard of on a current bike. But just a little thicker piston and stronger crank, would make that bike last everyone for a long time. Let the race shops make the lighter pistons and cranks for the racers, and leave the normal population with long lasting motors.
Yeah but then who ever doesn't follow that path takes the short dick's market hands down.
Ing
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Ing 2/11/2010 1:10pm
2/11/2010 1:10pm
On my old 500 two-strokes I could practice, race, practice some more and run the same top end for a year at least. Not sure exactly but I'd bet it was well over 200 hrs. Not just one certain brand, but any of the old 500's. Bring back the open two-stroke.
prozach
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prozach 10/1/2012 2:07pm
10/1/2012 2:07pm
A 450 piston only needs to be replaced at max twice a year for the average jo and you do the work yourself.. if you are slower maybe once a year if that. just make sure to keep the oil fresh.

A novice beginner should be able to ride a 450 for 2 to 3 years for about $500 in motor parts if regular maintenance is done.
BAMX
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BAMX 10/1/2012 2:11pm
10/1/2012 2:11pm
Vital needs a "like" button
Mr. G
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Mr. G 10/1/2012 2:55pm
10/1/2012 2:55pm
Ing wrote:
On my old 500 two-strokes I could practice, race, practice some more and run the same top end for a year at least. Not sure exactly...
On my old 500 two-strokes I could practice, race, practice some more and run the same top end for a year at least. Not sure exactly but I'd bet it was well over 200 hrs. Not just one certain brand, but any of the old 500's. Bring back the open two-stroke.
That would be a dream come true. And while we're at it lets bring back Saddleback!
dizzy8085
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dizzy8085 10/1/2012 4:08pm
10/1/2012 4:08pm
I buy fresh one year old 450's. Ride them for a year and sell them with a fresh set of plastics, then repeat the process.

Besides the normal maintenance on any bike. I just put usually one top end during that time(piston and rings).

Which that recipe. I've figured out I get to work on my bike the least and ride it the most while saving the maximum amount of money.

I've always had to put top end in my 2 strokes more often. I would rather ride longer during service intervals and I prefer a 450 for other reasons too.
scrubbin627 10/1/2012 4:18pm
10/1/2012 4:18pm Edited Date/Time 10/1/2012 4:19pm
I had over 100 hours on a rmz450 practice bike with nothing but oil/air filter changes and valve adjustments. Was still going when I sold it
brimx153
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brimx153 10/1/2012 5:18pm
10/1/2012 5:18pm
i still have my 2007 crf 450 , have it since new , there is prob 400 hours on it no lie, its been fully rebuilt once and had rings and piston and rings , and a set of valves , i am semi expert rider , and change my oil and air filter religiously , kept it really well and my favorite bike ever , to think some people change pistons every 30 hours is mad , only if ur a full pro would any one need to ,
urbanlift707
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urbanlift707 10/1/2012 5:36pm
10/1/2012 5:36pm
I just don't get the cheaper argument. I had a 2009 crf450 and a 2002 Yz 125. Every 15-20 hours the yz would blow a top end and Id have to replace it. Cost me about $200. My crf went 140 hours without touching anything when the crank blew, I replaced the crank piston and cylinder plus all gaskets, cost me $1000 with labor. So that's $7 per hour on my four stroke and $13 per hour on the two stroke. I'm not really into the whole two vs four argument, as I think both are bad ass and don't want to live without either, but in my experience the four strokes are cheaper to ride engine wise. The Yz was by far cheaper on wear parts like tires, chains ect.
keeptwostrokesalive 10/1/2012 5:39pm
10/1/2012 5:39pm
I was able to get around 45 to 50 hours on the stock piston on my 2006 kx250 before I sold it and it never showed any sign of letting up.
171motocross 10/1/2012 7:27pm
10/1/2012 7:27pm
The only different maitnence i feel is not having to check valve clearences. And thats not even hard. But when the valves do go bad.. thats when it sucks. I'm approaching 50 hours on my 06yz125 and i will need to get new piston and rings.

The main reason why the 125's dont last as long is because you have to rev the ever living shit out of them in mx and just about anywhere. And they only have 1 ring.

250 2 strokes last alot longer because not as hard riding on them. i's say the cheapest bike for maitnence is a 250 2 stroke or a higher cc 2 stroke. But as stated above if you keep the 4 strokes in good maitnence with fresh oil/oil filter and air filter it will last you quite awhile. especially if its a yamadawg Smile
B wood
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B wood 10/1/2012 8:34pm
10/1/2012 8:34pm
Try to run yamalube 2 cycle oil and change the oil in your case every 3 hard rides. Thumpers are more low maintenance than 2 strokes but it also depends on your level of ability. When you notice that you have no bottom end hit then you know it's time for a top end job. I've had yamaha 2 strokes that i rode at intermediate level and only did one top end a year. Gas it up and rip!!!
IceMan446
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IceMan446 10/2/2012 9:24am
10/2/2012 9:24am
urbanlift707 wrote:
I just don't get the cheaper argument. I had a 2009 crf450 and a 2002 Yz 125. Every 15-20 hours the yz would blow a top...
I just don't get the cheaper argument. I had a 2009 crf450 and a 2002 Yz 125. Every 15-20 hours the yz would blow a top end and Id have to replace it. Cost me about $200. My crf went 140 hours without touching anything when the crank blew, I replaced the crank piston and cylinder plus all gaskets, cost me $1000 with labor. So that's $7 per hour on my four stroke and $13 per hour on the two stroke. I'm not really into the whole two vs four argument, as I think both are bad ass and don't want to live without either, but in my experience the four strokes are cheaper to ride engine wise. The Yz was by far cheaper on wear parts like tires, chains ect.
How did you blow a top end every 15-20 hours?

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urbanlift707
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urbanlift707 10/2/2012 1:16pm
10/2/2012 1:16pm
On my yz I was running an Athena factory kit and 110 leaded race gas, I guess just cause I weigh 175 pounds without gear and am used to riding a 450, so the poor little 125 was singing very loud!
IceMan446
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IceMan446 10/2/2012 2:15pm
10/2/2012 2:15pm
urbanlift707 wrote:
On my yz I was running an Athena factory kit and 110 leaded race gas, I guess just cause I weigh 175 pounds without gear and...
On my yz I was running an Athena factory kit and 110 leaded race gas, I guess just cause I weigh 175 pounds without gear and am used to riding a 450, so the poor little 125 was singing very loud!
Ok.

I have had 5 YZ125s and never had that issue so I was wondering what was the cause. But I have heard the horror stories about the Athena kits.

I am thinking about doing the Gorr 144 kit on my 04 YZ125 but not sure about pulling the trigger on it just yet.
RealityCheck
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RealityCheck 10/6/2012 1:38am
10/6/2012 1:38am
urbanlift707 wrote:
I just don't get the cheaper argument. I had a 2009 crf450 and a 2002 Yz 125. Every 15-20 hours the yz would blow a top...
I just don't get the cheaper argument. I had a 2009 crf450 and a 2002 Yz 125. Every 15-20 hours the yz would blow a top end and Id have to replace it. Cost me about $200. My crf went 140 hours without touching anything when the crank blew, I replaced the crank piston and cylinder plus all gaskets, cost me $1000 with labor. So that's $7 per hour on my four stroke and $13 per hour on the two stroke. I'm not really into the whole two vs four argument, as I think both are bad ass and don't want to live without either, but in my experience the four strokes are cheaper to ride engine wise. The Yz was by far cheaper on wear parts like tires, chains ect.
Seriously?

Have you notced that you have to ride the 125 a bit harder than the 450? Do you suppose that the 450's 325cc displacement advantage might factor into this somehow?

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