4 stroke maintance

[mx guy]

I am wanting to get into mx racing. I have not made up my mind about 2 stroke or 4 stroke yet. I was wondering if the maintance with the four strokes would be something that I could learn to do? I can only do the simple stuff right now like oil and air filter.

 

[spark250]

You could definitely learn it if you wanted to. Maintaining a dirt bike isn't hard.

 

[mx guy]

What goes into it as far as maintance to keep a racing bike where it should be?

 

[_JOE_]

Basically all the moving parts have a lifespan. You should get in the habit of replacing things before they break. The manual will give you some basic guidelines as far as when to replace certain high wear items(hours) and will give service limits(measurements) for all the rest. These intervals vary by engine size, design and manufacturer. Most racers change thier oil every day of riding or 3-5 hours. Air filter may get done twice in that time frame if it is dusty.

Once you get into it a couple times you will find most things fairly simple. Taking your time and paying very close attention will help you avoid costly mistakes.

 

[mihm82]

2 stroke seem to be simple and cheaper to fix as far as engine. seems like 4 strokes tend to require more wrenche time as far as valves go. maybe thats just the bikes i've seen.

 

[Matt90GT]

Either stroke of bike will require the same maintanence with the chasis.
-complete tear down and inspection and regreasing of all bearing including the wheel bearings, linkage, swing arm, steering head and shock bearings.
-lubing and adjusting free play in all cables
-suspension servicing and maintenance
-brake maintenance including greasing the slide pins

Drive will probably be about the same amount of wear and tear . Same with the tires

So now you are left with the motor. 2 strokes with power valves have a lot of moving parts, but they dont come in contact with the piston like a valve can. You do have to check your valves weekly or at least monthly. The 4 stroke has a more complicated carb, so you have to keep it clean, adjusted and lubed (hot start plunger). The 4 stroke does not use premix, so you have to change the oil and filter often.

That is the basic breakdown. Either machine if maintaned properly will give you a long service life.

For if you can service the bike yourself, if you can do fork seals and shock rebuilds you should not have problems with either motor. The 4 stroke is just as complicated to time as a 2 stroke powervalve setup.

 

[mx guy]

Thanks for all the help guys

 

[mas2de]

MX guy,
I Love my 4 strokes. I don't do much racing, but as long as you take some care of your 4-stroke it will take care of you. My dad has an 81 Honda XR 500 that has been run for probably a years worth of hours (if not more like 5 digits) by now and he has never gone into the motor at all and it still pulls his 280lbs up off the ground up to 3rd gear. The 4-strokes that I've ever seen never need any difficult maintenece. Just clean 'em, tune 'em and ride 'em.
I have not been in the 2-stroke world very long but alot of my friends are. For the ones that like to race, they spend half their time rebuilding their everything and fine tuning and twiddling. (but then again that Is racing) But the 2-strokes have most always been lighter (fewer parts), more powerful(power on every down stroke as opposed to every other down stroke like 4-strokes), and therefore faster(also more responsive to throttle because of the cylces). But today's 4 cycle bikes are just as good as 2 strokes as far as I've heard. The 2stroke power is usually less managable and more abrupt. The power valve in the exaust helps to control the power curve but can be finicky and difficult at times. They are also hard to work on.
For any beginner I would say 4 stroke because of the reliability and ease of operation and maintenance.

BTW MATT90GT, NO valve should EVER make any kind of contact with the piston. That would extremely damage the valve and it won't seal right, and also extremely damage the piston and gouge it. If you have any valve hitting any piston you need to tear that motor apart.
Good luck MX guy,
Mike

 

[RM85rider123]

MX guy,
I Love my 4 strokes. I don't do much racing, but as long as you take some care of your 4-stroke it will take care of you. My dad has an 81 Honda XR 500 that has been run for probably a years worth of hours (if not more like 5 digits) by now and he has never gone into the motor at all and it still pulls his 280lbs up off the ground up to 3rd gear. The 4-strokes that I've ever seen never need any difficult maintenece. Just clean 'em, tune 'em and ride 'em.
I have not been in the 2-stroke world very long but alot of my friends are. For the ones that like to race, they spend half their time rebuilding their everything and fine tuning and twiddling. But the 2-strokes have most always been lighter (fewer parts), more powerful(power on every down stroke as opposed to every other down stroke like 4-strokes), and therefore faster(also more responsive to throttle because of the cylces). But today's 4 cycle bikes are just as good as 2 strokes as far as I've heard. The 2stroke power is usually less managable and more abrupt. The power valve in the exaust helps to control the power curve but can be finicky and difficult at times. They are also hard to work on.
For any beginner I would say 4 stroke because of the reliability and ease of operation and maintenance.

BTW MATT90GT, NO valve should EVER make any kind of contact with the piston. That would extremely damage the valve and it won't seal right, and also extremely damage the piston and gouge it. If you have any valve hitting any piston you need to tear that motor apart.
Good luck MX guy,
Mike

We are talking about MX 4 stroke racing bikes, and you are talking about trail bikes such as your dads xr500. You are right, the 4 stroke would be easier to ride, but a racing 4 stroke is still more unreliable than a 2 stroke. I am not saying the 2 stroke is 100% reliable, but it beats the 4 stroke.

 

[mas2de]

We are talking about MX 4 stroke racing bikes, and you are talking about trail bikes such as your dads xr500. You are right, the 4 stroke would be easier to ride, but a racing 4 stroke is still more unreliable than a 2 stroke. I am not saying the 2 stroke is 100% reliable, but it beats the 4 stroke.

Thank you RM85rider123. As I said I don't do much racing and haven't heard much about less than pro, 4stroke riding. Thanks for the correction.

Just found this:

Find a nice clean 125 2 stroke, the newer the better. If you plan to do MX you really shouldn't buy a trail bike. The MX bikes are higher maintenance so you'll want to take advantage of any offers from people to show you how to take care of it. The 4 stroke MX bikes are more costly to maintain but if you can afford it they are great bikes. The power is super smooth and has great pull where a 125 is more peaky and really only strong in the top end. The 125 2t is a hoot to ride though. Good luck with finding something.

Mike

 

[Matt90GT]

MX guy,
BTW MATT90GT, NO valve should EVER make any kind of contact with the piston. That would extremely damage the valve and it won't seal right, and also extremely damage the piston and gouge it. If you have any valve hitting any piston you need to tear that motor apart.
Good luck MX guy,
Mike

I know that. read my post again. I state that the power valves dont have the potential to hit the piston like a valve can. Read more into that, you need to inspect your valves often

You cannot compare a xr motor to a modern 4 stroke race bike. The XR is designed for longetivity and cannot spin even half the RPMs of a CRF/YZF/KXF/RMZ. So a modern 4 stroke race bike will take much more maintenance than a XR, but you are rewarded with a much more powerful and lighter motor.

 

[motometal]

some good points made, a couple things I will throw out my opinion on.

2 stroke power valve-in my experience if you run good clean burning oil and jet properly, you get years, not weeks or months of service. And the "failure mode" is just the valves sticking, which really doesn't hurt much as long as you tear it down and clean everything within reasonable time. Honestly though, just cleaning the PV system when you do a top end is enough to eliminate 99% of PV sticking problems.

There's a comment above mentioning lubing cables...modern cables have a teflon sheath and do not need routine lubrication. In some cases it will attract grit and draw it into the cable, actually shortening the life span. I do not lube my cables and again we are talking many, many hours of riding before a cable wears out.