YZF Rebuild

[BadgerMan]

I need some good advice.

I have a 2001 YZ250F that I have owned since December of 2000. It is set up for woods riding, has only been trail ridden, and works very well for my type of riding. I have done nothing with the engine other than keep an eye on the valve clearances, change the oil (every two or three rides), and clean the air filter (every ride). It is still in great shape and I have yet to ride a bike that works better for me. Basically, I am still in love with the bike and would like to keep it for another year.

I am considering a rebuild but I don’t have any experience beyond a two stroke top end job. Unfortunately, I don’t have the time to devote to learning at this point either. Consequently, I am considering removing the engine and sending it to someone for a turnkey rebuild. My questions are:

1. Who can I trust to do such a rebuild? Who will do the best work and provide the best service? I would prefer someone in my area if possible (west Michigan) but I know of no one currently.

2. What should I ask them to do? Top end, bottom end, head, valve train, etc. What are the problem components and high wear areas?

3. How much should I expect to spend (ball park figure)?

And finally, I am looking for a stock rebuild. I am more than happy with the engine as-is and the power it produces. I am mostly concerned about maintaining or improving reliability.

Thanks in advance!

 

[70 marlin]

Eric Gorr!

 

[Yogurt]

Your owners manual probably does a good job in detailing how to do a top-end rebuild yourself. I think even with some basic engine knowledge anyone can do it. You say you've done 2-stroke top ends, and you know how to check the valve clearance on your YZ250F already. I think you can do it and save your self some money. And the knowledge you'll gain in the end will be priceless! If you doubt your self, pick up a service manual from your local Yamaha dealer, and it will provide even more in-depth details, specs, and how to information. Owner's manuals only show some basic stuff, but with a service manual I think anyone could be capable to doing a complete overhaul to their machine.

I'm in the same position you are. I've done many top-end on two-strokes, and now I'm the proud owner of my first 4-stroke. I plan on learning how to do my own engine rebuilds myself. I haven't done it yet, so I can't speak, but even with my owners manual I feel pretty confident in myself that I can do it. But if you really insist and aren't sure of your self. Eric Gorr will do a 4-stroke motor rebuild for $300. www.eric-gorr.com

 

[BadgerMan]

Yeah, if it was just a new piston, I would do it myself. However, I am concerned about the crank and bearings as well as the valve train.

 

[BSWIFT]

Before deciding on a rebuild, assess your riding.  If you are hard on the throttle, ALL the time, you might need a new piston and rings.  You've stated you have done routine maintenance so the thing to do is inspect.  Pulling the valve cover, relieving the cam chain tension and removing the head will give you a much better idea in what you need.  The basic parameters are in your manual.  If your cylinder walls are scared badly, you may need a bore but if you don't dissassemble it to a small degree, your wasting money and worring over nothing.  The worst you'll be out is a head gasket.  Total time for doing this is probable less than two hours at a snails pace.  Get the compression checked and then decide.  Chances are, you probably won't need anything but reassurance that your not on a two stroke anymore.  Been there...... :laugh:

 

[70 marlin]

Badgerman: After seeing what happened to marks son's YZF. Mr. Gorr's service is cheap @ twice the price! He has taken care of a bunch of my needs over the years, and completed them in a timely manor. Performed complete rebuilds for two of my riding friends. Have the valves upgraded on that bike? He has a handle on what comes a part on the motor.

 

[Uchytil]

I'm a mechanic and have a hard time understanding why we feel the need to rebuild 4strokes so soon. I've been in the postion to rebuild large engines w/10000 j hours only to find no wear. Big diff is these new bikes rev sooo high causing quick wear. I feel if the bike is beingwell maintained you should just keep an eye on things like, oil consumption, compression, leak-down, engine temperature, and overall performance. Also look at what the manufacturer suggests for hourly maint with regards to rebuilds/topends/etc.. I am in the market for a YZ250F and am also looking at all these issues. My two sons and I run 2strokes now and one or two of us are making the switch. To answer your question, though, I would send it to eric gorr, he has free engine crates. I had a jug replated last year and got good turn-around. I guess he's pretty close to us now (I live in Muskegon) and he's now in Chicago. I'd be real interseted to find out what happens with your engine if you have it done and what type of actual wear there was. Do you keep an hour log? If you have it done save the old parts to see how much wear there really was based on your maint. and riding level. I'm an 45 plus rider so my wear will be very minimal, ha ha.

 

[Rich Rohrich]

Anyone with above average mechanical skills, a decent set of tools and the factory service manual can do a piston or ring change on the Yamaha 250F. This is one of the easier engines to work on. Very intuitive design. Biggest problems most first timers have is getting the cam cap torque correct. The cam cap is also the cam bearing surface on these engines so getting the torque out of whack can gall the bearing surface and ruin the cylinder head. If you take your time and use a proper torque wrench you should have no trouble.

Refreshing the cylinder head takes some specialized tools and knowledge to do it right. I would strongly advise sending this part of the work out to a professional. The titanium valves in these engines have a very short life due to the materials being used and the incredibly aggressive valve acceleration rates used to get this level of performance. As a result the valve service intervals aren't comparable to old school XR type engines or the engine in your family car. Okie's 250F pretty much junked the valves after just 2 seasons, and he is by no means a rev happy rider. That has been true of most of the 250Fs I've had apart.

If the crank is changed as a complete assembly it is pretty straight forward assuming you are familiar with splitting the cases on a two-stroke. The crank main bearings are probably the biggest issue you are likely to run into. The mains can be changed at home without a press but it takes some care and proper use of heat and freezing of the bearings. Mains tend to wear faster on the 250F than I've seen on some other engines so if you split the cases make sure you change the main bearings. You'll also want to pay close attention to the transmission shaft bearing near the clutch pivot arm assembly. They tend to wear quickly. You'll need a special blind hole bearing puller to get this bearing out. Goodson is a good source for the puller (it's about $100). It's unlikely you'll ever get it out with a standard slide hammer style puller. Lots of us have tried in an attempt to avoid spending the $100 for the correct tool. Save yourself the anguish and just buy the tool up front. You can thank me later. ;)

I think you'll find it's a fun engine to work on if you decide to tackle it. Be sureto give yourself plenty of time, don't rush anything and ask lots of questions. If possible, take pictures as you take things apart so you can refer back to them. I also suggest using ziploc bags to logically group parts together along with little notes about anything special that you notice as you are pulling things apart. A note as simple as , "Don't forget to do this" about a specific part or procedure can make a big difference when you reassemble something. There is enough combined knowledge here that I'm sure we can get you through it. So dive in and enjoy yourself.

Good Luck. :thumb:

 

[BadgerMan]

Wow, thanks for the feedback!

Rich,

I am pretty sure that, given ample time, I could do the work myself (remember the analogy about monkeys and typewriters?). :) The problem is finding the time. It is getting harder to just find the time to ride anymore, let alone do a rebuild. I also need to do the top end on my son’s KDX this winter. Normally, I do all my own suspension work and I am even considering sending that out too.

The other issue is the lower end since I have no experience below the base gasket except for clutch maintenance. One person has told me to definitely replace the crank as a prophylactic measure but most say not to go into the lower end unless I find a problem when doing the top end. Given the bike’s relatively easy life thus far and its intended purpose going forward (trail riding), I am leaning towards leaving it alone (unless I find it needs it).

Two options I am considering:

1. Doing the top end myself but sending the head out to be refreshed (good suggestion).

2. A turnkey top end job by a local dealer with a mechanic who was highly recommended to me. I spoke with him today and he felt there was no need to replace the crank unless there is a problem. Top end job………$150.00 plus parts. Priceless!

Thanks again,

Tim

 

[Rich Rohrich]

At this point all I can offer is advice based on my experience, you can decide for yourself what it's worth. ;)

Both options are good choices for the piston/ring part of the work. Any good mechanic can do it.

I would agree that the chances are pretty good that a life of trail riding isn't the type of stress to warrant a crank replacement yet. Okie isn't rev happy but his 250F did spend every weekend being ridden aggressively on a motocross track for 2 years before it dropped a valve at Cooperland (a rev happy track). His crank was moving around enough to let the center valve hit the piston and pop the valve keepers. I guess we waited one week too long to change the crank. :scream:

The only real question is the valve train. If you are spending the bulk of your time riding at moderate revs and aren't seeing the valve clearances closing up beyond spec then you should be able to just pop in a piston and rings , degaze the cylinder, lap the sealing surfaces, pop it all back together and ride with peace of mind for a good long time with. No reason to play with the cylinderhead unless there is clear evidence of an issue. I tend to err on the conservative side with these engines, but having seen what happens when these things come apart at 13,000 rpm it's sort of a survival instinct. :thumb:

If the valve clearances have moved significantly since it was new then you should send the head out to someone who specializes in performance work to be refreshed. I mean no disrespect to dealership mechanics when I say it's unlikely that the local mechanic has the requisite skill or experience to do the cylinder head portion of the work properly. There are a few, but those guys are rare.

I hope this helps.

 

[Uchytil]

Rich

Since you indicated the ti valves hav a short wear life could you offer what would be good replacement options. When the time comes to rebuilding 250F I'll be looking at keeping what works stock but also looking at bulletproofing what is possible. Also is the valve seat ti? If valve are interchanged does the seat also need to be replaced (seems it would even if the angles match). Thank you, John Anderson

 

[Rich Rohrich]

John - The only choice other than OEM at this point is the Kibblewhite Stainless Steel valves. I've put them in a number of YZF4 engines with great results. They come as a kit with new springs to deal with the slight weight increase. Outstanding quality and workmanship, plus they can be resurfaced down the road unlike the OEM valves. According to Mike Perry from Kibblewhite the 250F parts will start shipping towards the end of the month. The folks at Kibblewhite are pretty fanatical about quality and they always wait till they can do it properly before they release products.

The seats just require a quality resurfacing at a minimum. I prefer Serdi or similar equipment to keep things as accurate as possible and to open up the possibilities of additional work in the throat and cylinder side discharge area.

 

[linusb]

I'm also confused about why a motor would need a rebuild after a few years. High performance street bike engines can go 50k+ miles without the need for any kind of engine work. Why the difference?

 

[High Lord Gomer]

The high performance street bikes that last 50K miles are not ridden hard much of the time...there is a lot of cruising time in there.

I'd bet that the bikes that are road-raced get rebuilt about as often (if not more so) than racing dirtbikes.

 

[BadgerMan]

Here's the scoop.

I had some free time during my holiday break from work and decided to pull the top end apart. I was amazed at how easy it went and how clean the top end was. There was not a single scratch in the piston or the bore and no perceptible slop in the lower end. It was the cleanest, tightest engine I have ever disassembled. It says a lot with respect to frequent oil changes with good quality oil, as well as regular air filter maintenance.

I started thinking that I would just put in a new set of rings and ride it another year. However, I measured the piston and found it to be slightly undersize at the skirt. It will be replaced along with the timing chain. I think I will also send the head to Eric Gorr for a cleaning, inspection, and whatever else is needed. The Kibblewhite valves sound like a great way to go and I will probably choose them should the valves need replacing.

I am going to have to enlist some help replacing the timing chain since the flywheel needs to come off and I don't have the proper tools. I also need some advice on what piston to use. It is a trailbike so I would like to continue using 92-octane pump gas, but a bump in compression (enhanced low end?) would be nice too.

Thanks again,
TF

 

[Patman]

I bet Rich has a good suggestion for the piston replacement.

This is going to sound like a Rich & Eric commercial but.... take every bit of advice these guys give ya'. Their #1 priority is happy riders not making a buck from selling useless add-ons. Rich & Eric did my XR284 and it is EXACTLY what I asked for and more!

 

[DEANSFASTWAY]

Id definetly put in a new crank as Ive witnessed a fair share of rod/piston pin bore breakages on the 250Fs it seems as though after a couple seasons the rods are starting to come around to breaking. And a crank is much cheaper now than buying new cases and cylinder later when it beaks the rod and the violence that is unleashed.Rich is giving good advice .

 

[Imho]

Originally posted by Rich Rohrich
... The titanium valves in these engines have a very short life due to the materials being used and the incredibly aggressive valve acceleration rates used to get this level of performance. As a result the valve service intervals aren't comparable to old school XR type engines or the engine in your family car ...

Hey Rich,

Is this also the case with the YZ400/426/450F? I take it the revs are less and I don't think the 400 has titanium valves. Also, would running WR timing on a 400 increase the time between rebuilds?

Cheers.

 

[BadgerMan]

Originally posted by DEANSFASTWAY
Id definetly put in a new crank as Ive witnessed a fair share of rod/piston pin bore breakages on the 250Fs it seems as though after a couple seasons the rods are starting to come around to breaking. And a crank is much cheaper now than buying new cases and cylinder later when it beaks the rod and the violence that is unleashed.Rich is giving good advice .

My plan, as of today, is to refresh the top end focusing on the head/valves. I am planning to also replace the piston and timing chain. The top end was shipped to Eric Gorr yesterday so I am anxious to hear what kind of wear has occurred (since I am far from an expert on valve trains!). The lower end appears to be in excellent shape and the bike has had a very easy life of trail riding only. The engine is completely stock and the rev limiter has never been employed, to my knowledge. LOL!

My ultimate goal is reliability as the bike is currently plenty fast for my needs.

Funny thing, I have never seen a lower end fail on a YZF or WRF (250, 400, 426, or 450) although I have heard of some occurrences on the ‘net. All of the 250F’s (YZ or WR) that I have first knowledge of, have been super reliable (knock on wood).

I sounds like the valve train is the Achilles’ heel on these bikes………….hence my focus on refreshing of the head.

If I keep the bike more than another season, I will most likely do the lower end.

 

[Smit-Dog]

Originally posted by BadgerMan
... The engine is completely stock and the rev limiter has never been employed, to my knowledge. LOL!

So was that the funny noise and cutting out hesitation I felt riding your bike? :o

 

[BadgerMan]

Originally posted by Smit-Dog

So was that the funny noise and cutting out hesitation I felt riding your bike? :o

You "felt" a funny noise when you were riding my bike? Next time, don't grip the seat so tightly with your butt cheeks! :)

 

[DEANSFASTWAY]

If you take it apart to do the Timing Chain youll want to look and clean out the ign stator magnets . you can tell a bit about the engine when you look at the swarf stuck to the magnets. Just a thought and good luck.

 

[BadgerMan]

Originally posted by DEANSFASTWAY
If you take it apart to do the Timing Chain youll want to look and clean out the ign stator magnets . you can tell a bit about the engine when you look at the swarf stuck to the magnets. Just a thought and good luck.

Good thinking! Will do.

Thanks

 

[Rich Rohrich]

Originally posted by Imho

Hey Rich,

Is this also the case with the YZ400/426/450F? I take it the revs are less and I don't think the 400 has titanium valves. Also, would running WR timing on a 400 increase the time between rebuilds?

The YZFs with steel valves are incredibly robust even when they are revved HARD. Most of the YZF engines I've seen went a couple of seasons before they ever needed a single shim changed.

Running WR timing on a YZF is a really BAD idea IMO. There have been a lot of misconceptions about WHY Yamaha set the valve timing the way they did on the WR thanks in large part to our friends in the magazine business who don't understand cam timing.
Anyone who does a little research into engine design will quickly discover that the only logical reason for Yamaha to advance the exhaust cam timing so far in the WR was to start the exhaust blowdown early enough to get the engine to run properly across the rev range with the super-restrictive stock exhaust insert . Once that restriction is removed the exhaust valve opens way too early with the WR timing (23 crank degrees too early) and will tend to flatten torque on the low end, and just kill any hope of making top end power because the exhaust closes 23 degress earlier and reduces overlap by that same amount. The only possible value of the WR timing on a YZF is you'll see an improvement in no-load idle quality, other than that don't waste your time with that nonsense. :thumb:

So I guess to answer your original question, yes it probably would increase the time between rebuilds. Given that it won't make any real power at high revs, and won't be as much fun to ride you'll probably leave it in the garage more and never wear it out. ;)

 

[Imho]

Thanks Rich, great explanation. My YZ400F came from its previous owner with the cam timing set to WR specs but a recent valve clearance check revealed both exhaust and intake at the lower (tight) limit, so it's a great opportunity to set it back.

Sorry for hijacking the thread BadgerMan. :|