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Question About Valves & Wrist Pin Wear

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So recently had the chain ball up and bend my shift shaft on my WR, and figured it was time for maintenance.  Compression was on the low side (well...the really low side), so start disassembly to build a list of parts to replace that's going to need replacing and aim going to pick up an Athena 290cc kit to slap it back together.  

Looks like the engine eat a timing chain at some point and beat up one of the chain guides, easy enough to replace. However it also looks like it may have allowed some debris into the oil system that collected in a cam cap (easy fix with a scotch brite) and far more worrisome into the wrist pin. See images below: 
Question becomes how worried should I be about the small end of the rod? Is this normal wear for 4t? I'm surprised to see they are like 2t units with needle bearings. 


Next question pertains Valves (Can of worms I'm sure).  Should I stick with the Ti valves. I'm currently looking at the Kibblewhite units as they are about $50 cheaper than the OE Yamaha units. 
Or should I go ahead and switch the Stainless Steel units? Intake valves look okay, but the exhaust appear to be pretty much shot. 

 

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Edited by intimdatr

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Seen this before.  This is what you need:

Piston, pin, rings, clips.  I've gone back stock, High Compression, and 262.  The last two are comparable and give a power boost.

Judging from pics of your pin, the rod small end is done, and since you described other prior damage, I'd bet the rod also has side play (lean over).  So you need a crank.  I've used stock and Hot Rods.  With the crank, replace the cam chain.

Oil system needs cleanup blow out, flushing and new gear rotor assembly.  Cam sliders need replaced.

Pics of your valves indicates they're done.  Stock valves are $55-65 each, total 5, so $280 or so.  I've used Xeledon (sp) and had not experienced any failure at the point I sold the bike.  $125 for whole set of 5.  Add $100 to cut the seats in the head.

Flush out the oil tank in the frame, and check screens and clean.

Plan on $650-$850 in parts, you do the maintenance.  Double that if you hire it done.

I personally have avoided the 280-290 bore kit due to expense and jetting requirements.  If you want a 300, buy a KTM 2T and live with 40+HP.

Expect the unknown, be glad if you don't find it.  Unknowns would be main bearings, clutch, water pump, trans parts and bearings and shifter bearings.

Question becomes... is it easier to rebuild, or part out and buy another bike.  Roll the dice.

Edited by ronbuell
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I feared that was the case on the rod. Sad thing is, it has a lower hour wiseco crank in it from the previous owner. Sigh. Just another paycheck to blow. Lol 
Looks like the whole engine will be going through the ultrasonic cleaner over the next few days. 

As for the valves, I think I'm going to grab the Kibblewhite Ti units. Everyone seems to have a horror story about X brand so I'll just stick to what I know. 

Im curious as to what state the shift forks and dogs are in on this engine. Seems to be a higher unit. Rebuild my fair share of 2t engines and cranks, and several street bikes, but never dug into a 4t dirt bike. Looking like Ill get the chance. :facepalm::cool:

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Yeah, but if you don't know how many hours are on that crank and how often the oil was changed, then that's what caused the scoring on the rod and pin.  Gotta be diligent on 5 hr change intervals.  

Haven't searched KW valves lately, didn't know they now sell Ti valves.  Should be GTG.  Shift forks should be GTG if you didn't experience any issues before now.  I shift race style, just let off the throttle and jam it, and at teardown didn't see anything unusual and don't have any shifting issues.  Look for scaring on the pads at the ends, should be smooth.

Good luck with it.

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Got to some more disassembly today.Waiting on a flywheel puller to fully remove the crank and inspect underneath it. Trans looks to be good shape, was cleaned and reassembled (what a massive pain in the ass). Removed all the valves and cleaned the head up.  Found some more debris that is rather concerning. The timing guide took a pretty big hit, and a bolt that i haven't found where its from yet... Im suspecting behind the flywheel, but weird nonetheless. Tossed the case half in the ultrasonic and removed all the schmoo, cleaned up nicely. 
Interesting find that it has a Cylinder Works jug in it, stock bore though. Budget allowing, might be in the market for a new clutch basket, my current one seems to be worn a bit. 

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Glad you're getting that debris out.  I'd use the clutch hub, and grind/smooth out the basket.  Ive seen worse brought back.  I use a 4" angle grinder with a flat cutting blade and a light touch to smooth it.

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5 hours ago, Vintage Not Pimpage said:

That wrist pin wear is pretty standard on YZ250Fs. If the crank is low hour there is no point replacing it. 

Probably true, but...  Put a new wrist pin into the small end and check for play.  If it will rock any, its done.  You don't want play there or in the piston.  And I've seen pins rock in the rod and in the piston at disassembly.

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12 hours ago, Vintage Not Pimpage said:

That wrist pin wear is pretty standard on YZ250Fs. If the crank is low hour there is no point replacing it. 

Ended up finding a Wiseco rod for $30 on ebay. Hard to beat that. Might as well do it now. Its not overly expensive, and ive got it apart. 

Edited by intimdatr

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7 hours ago, ronbuell said:

Check it in the piston too.  Add the two together, and it equals a knock. Ask how I know that..... .

The wrist pin was still tight in the piston. However the bike did seem to have some rather excessive noise IMO, and I'm wondering if that was it. 

 

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More pictures! Got the flywheel puller delivered this morning (Prime is coolest), and got the case halves fully apart. Then on to more cleaning! 

I have finally found all of the timing guide pieces. I think the chain of events that led to all that carnage was someone dropped a bolt into the timing chain(area) and didn't retrieve it. Which led to the timing chain failing and killing the guide. Weird that all the shrapnel was just left in there though. :lame:

Had one trans bearing that was too gritty for my likes, so will be picking it up shortly. 

 

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Edited by intimdatr
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Check the left  crank half small cam sprocket.  If the teeth are sharp and pointed, that half is done.  Pics I can see, they don't look too bad.  Tooth profile should match tooth profile on the cam large sprockets. 

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I've had them worse.  Replace the parts.  Double check the flywheel magnets as ferris metal will stick to it.  Clean the magnets.  Check the screen in the case, clean the screen in the frame tank.  

How are the bearings in the case?  

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A new unit is already on the way! 
Flywheel is in great shape and magnetic. Charging circuit is working flawlessly since I installed the Trail Tech Reg/Rec, and did the full wave mod for the stator. 
Surprisingly the screen on the oil pickup was clean. 
All up one of the bearings so far have all been in good shape. The one that's a little iffy, is as smooth as glass now that its out of the case, go figure. Going to run it through the ultrasonic cleaner with fresh fluid and pop it back in and see if its still gritty. 

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Update! Getting to the slow parts but still cleaning here and there. 
Had a big box, and some smaller one, of stuff show up and it's getting close! Ordered the valves tonight so **hopefully** in a week or! 
Crank was dropped off to have the new rod pressed in! 

89 SHO.jpg

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