How much maintenance are 4-strokes?

[Renthorin]

So I keep hearing about the dreaded "top end" rebuilds and how much a 4-stroke is to maintain compared to a 2-stroke.

What are some of the issues I will run into when I get my new bike? (Yamaha WR250r)

How often do I need to do maintenance (other than oil changes and chain lubes which I will do myself)?

How expensive?

Thanks,

Will

 

[groundeffect_db]

I've been told and lead to think that 4-strokes require much less maintenance then 2-strokes.... I to have this question.

Thank you, I also look forward to some experienced riders comments on this.

 

[Ol'89r]

By their nature, 4-strokes do require more maintainance. They have more moving parts than a 2-stroke and some of these parts have to be kept in check.

Valve clearance is very important and must be checked regularly. Oils and filters must be changed regularly due to the fact that many of the modern day 4-strokes only hold less than a quart of engine oil. Valves, valve springs and timing chains should be changed out at regular intervals.

In my experience many of the horror storys that we hear about 4-strokes exploding are do the the LACK of maintainance. Many riders do not understand the importance of maintaining their 4-strokes. They ride them until they can't start them anymore or they blow up and then they come on the internet to complain about what a POS the bike is. If you ran a 2-stroke as long and as hard as many people run their 4-strokes without maintainance, the 2-stroke would explode too.

Of course it's more expensive to rebuild a 4-stroke since it has more parts. Oil costs are about the same since you have to add pre-mix to every tank of gas in a 2-stroke and with a 4-stroke you only have to change less than a quart of oil and a filter. Not counting gearbox oil which also has to be changed in a 2-stroke at regular intervals.

It's not the maintainance that is expensive, it's the lack of maintainance.

 

[Renthorin]

What are some typical maintenance schedules? I don't own the bike yet so I can't read the manual.

do they go by miles or hours of use?

 

[Ol'89r]

There are no typical maintainance schedules. It all depends on how you ride the bike. If you are a sem-pro or fast intermediate, your maintainance schedule will be much different than a weekend warrior or trail rider. The schedule they give in the manual is a 'worst case scenairo'.

The best way is to buy an hour meter and determine your own schedule depending upon how you ride. Keep track of the hours on your engine and how often you have to re-adjust your valves. Buy a notebook and write down how often and how much your valve adjustment moves. Keep track of your oil changes and the hours on your piston.

Regular tear-downs and inspections are the best way to determine your own schedule.

 

[Chili]

There also has to be some thought given to the type of 4 stroke we are talking about, a TT-R 230 like groundeffect bought will not be used in the same manner as the 250F the local 16 year old is racing MX on.

Older XR's, TT-R's and the like are generally accepted to require less maintenance in general, whether this is in fact good for the bike is unlikely but they still seem to hold together with a lesser maintenance schedule than a high strung 250F.

I was terrified for my son to switch from a 125 to a 250F but after a season and a half my only real gripe about the difference in maintenance is that an oil change on his 125 took about 5 minutes and to do one properly on this 250F takes me about 20 minutes, no big deal but when you are doing that twice a week on an already strained time schedule it becomes a pet peeve.

 

[Ol'89r]

There also has to be some thought given to the type of 4 stroke we are talking about,

Excellent point Doug.

Groundeffect's bike is a completely different animal than the current crop of mx bikes on the market. The new mx bikes are not much more than a single cylinder F-1 engine. They use titanium coated valves, short skirted pistons that run in a coated bore, sometimes only two piston rings and a very short stroke which allows the engine to rev to over 13,000 rpm. They are a full-on race engine and due to their design their life expectancy is rather short. Especially if they are not maintained.

The TT-R's and XR's use a long skirt piston in a cast iron bore (not sure about the TT-R) and usually use three piston rings. They run a much lower rpm range and the cams are designed more for torque than high revving hp. They have a longer stroke with a smaller diameter piston that also keeps the rpm's down.
The valves are steel and can be re-ground when they wear and the valve springs last much longer since the engine doesn't rev as high. They have larger, stronger engine cases and hold more oil. All of this equates to a longer lasting engine with less maintainance problems. Of course it also equates to less hp.

It's up to the individual to decide what you are going to do with your bike and then pick the best weapon.

 

[_JOE_]

Great explanation 89er!

Most 250f riders go between 2 and 6 hours on oil, just to give a general time frame. Pistons should last 20-50ish hours. Valve train life is dependant on intake air cleanliness. 40-100+ hours.

 

[490Dave]

Heres my schedule for 06 KX450F (97.5 hrs)
Weekend warrior! Mostly Moto, some trails


Oil change...... every two hours
Oil Filter..........Every third oil change
Air filter......... every other oil change unless it's been dusty
Piston............not yet
Spark Plug......Every 10 hours
Valve train insp....Every 10 hours (starting to show a little wear)

She still fires right up, hot or cold!!!
Definately invest in an hour meter and silicone it to the upper frame spar and start a maintainance journal! There's hundreds of things you can do to increase the overall life of your ride like keeping it clean, changing muffler packing, lubing the moving parts, carb cleaning, chain maintainance...etc!

 

[flyingfuzzball]

almost 100 hours on a piston?!?! wow

what about piston rings?

 

[Renthorin]

That is a LOT of maintenance, much more than I thought. If I ride my bike for an hour to get to the trails....fart around for an hour and then drive an hour home I need to change the oil?

If my day of trail riding lasts 5 hours should I have stopped and changed the oil twice?

 

[_JOE_]

almost 100 hours on a piston?!?! wow

what about piston rings?

An engine will usually keep running long after it has worn past service limits. Performance drops off, but most of the time it's not really noticeable until you rebuild it. I'll probly run my rings 15 hours or so and measure the piston then. Most people don't run the rpm's as high in a 450 so engines tend to live longer. The faster you spin it the faster it wears. :cool:

 

[_JOE_]

That is a LOT of maintenance, much more than I thought. If I ride my bike for an hour to get to the trails....fart around for an hour and then drive an hour home I need to change the oil?

If my day of trail riding lasts 5 hours should I have stopped and changed the oil twice?

No.

If you go down the road wide open to get to the trail, bounce it off the rev limiter while slipping the clutch through the woods, the run it wide open going home, yes. A 3 hour practice for a moderately quick rider at the mx track will do to thier oil what might take a slow cruising street rider who lugs the bike through the woods 10 times as long.

Like others have said, pulling it down a few times in the beginning will give you an idea of YOUR service intervals under YOUR riding conditions.

 

[Renthorin]

well THAT's good to know :-) I was starting to reconsider getting a bike.

I plan to fart around town (55mph) for 40 miles a day or so and when I trail ride just put put around the trails at probably no more than 15 mph or so. Not looking to race the bike or push it hard.

Hoping to go for some time before tearing it apart.

Speaking of 'visual' inspection..is that something with average mechanical skills can do pretty easily? I assume you have to remove the engine? Every time you inspect do you have to replace gaskets?

 

[flyingfuzzball]

you dont have to remove the engine and gaskets are cheap

 

[490Dave]

almost 100 hours on a piston?!?! wow

what about piston rings?

I know, its really starting to bug me now. My buddies CRF 450 went 120 hrs before he did a complete top end and my maint. routine is identical to his. His cylinder looked new and the piston showed little signs of wear.

Its time to stop buying time and buy a piston!

 

[Ol'89r]

The problem with letting your piston and rings go for that long is the length of the piston itself. With the current crop of MX bikes, the pistons are very short. This results in the piston wearing quicker. The piston will wear down at the skirt (the very bottom of the piston) and this will allow the piston to rock in the bore every time it changes direction. When the piston is new and runs straight in the bore, the rings stay parallel to the bore surface. They maintain a sharp edge and a flat surface against the bore. When the piston wears to the point of starting to rock excessively in the the bore, it wears down the sharp edges on the rings and rounds off the flat surfaces. This causes the rings to lose their seal and allows your compression to slip past the rings and results in low compression and low performance. If you continue to run the piston there is a chance of the skirt breaking off of the piston and causing serious damage to the engine. It is a waste of time and money to just replace the rings if your piston is excessively worn since the new rings will wear very quickly with a worn piston.

In an XR type of engine the pistons are much longer and do not rock as much resulting in longer piston and ring life.

There is more to it than just 'visual inspection'. You have to disassemble the top end and measure the wear. If you don't have micrometers to check this, you should take the cylinder and piston to your local shop or machine shop and have it checked. You have to regularly check your valve clearance and keep track in a notebook how much the valve clearance changes over time. If you notice the valve clearance starting to change more than usual, it's time to replace the valves.

There again, it's not nearly as critical with the XR or TT-R engine design as it is with a CRF or YZF engines. The XR and TT-R engines will run for a very long time with very little maintainance.

 

[Renthorin]

There again, it's not nearly as critical with the XR or TT-R engine design as it is with a CRF or YZF engines. The XR and TT-R engines will run for a very long time with very little maintainance.

so what type engine is the 08 Yamaha wr250r?

 

[Ol'89r]

so what type engine is the 08 Yamaha wr250r?

The WR250F is a modern design with the short piston. Although, it is not as radical of a design as the YZ250F. It uses a milder camshaft resulting in less strain on the valve train and different valves that will last longer than the titanium valves. It also has a lower rev limit, a lower compression ratio and a few other things that make it last longer than a MX model. The valves still have to be checked on a regular basis but they don't need to be adjusted or replaced as often as the titanium valves.

 

[flyingfuzzball]

dont forget about the crf-F they are pretty much just an XR with a new name

 

[Renthorin]

is the WR250f the same as the WR250r as far as engine goes?

I thought it had titanium intake valves???

 

[Ol'89r]

is the WR250f the same as the WR250r as far as engine goes?
I thought it had titanium intake valves???

The WR250R and the WR250X are Yamahas latest entrys into the dual sport market. They are designed after the YZF-R1 sportbike engine. They are very different than the WR250F engines. They use four valves instead of five. The intake valves are titanium coated. Uses a six speed gearbox instead of the five speed used in the YZ and standard WR engines. Has EFI and electronic valve control. Uses a lower compression piston and a different ignition. Very trick little engine.

It remains to be seen what the maintainance requirements will be on this engine since it is so new but the sportbike engine seems to be a high mileage engine with little maintainance.

 

[Cman250]

If he is talking about the WR250R than from what i have gathered from my yamaha dealer is that it can go longer on maintenance intervals than the WR250F. It also does put out slightly less horsepower however and can be purchased much cheaper than the WRF.