4T Top End Rebuild

[Aaron WildeMember]

I am just about to take the engine apart on the old WR. I have read the owners manual and watched UTube on valve checks etc.(tooextrememx Is his user name if any body wants to trace where i went wrong) I have only done this on a 2T before so i am confident with power valves etc but not the kind with a cam chain attached. If it all goes pear shaped it will be good experience for the newer 450 in the shed. Right now i am just thinking i should pack the whole lot up and go and see how offended the local bike shop will make me on a trade. A 300 exe certainly sounds easier to work on right now! Any last minute words of wisdom? Like when i write in for help later i dont want anybody saying “You didn’t leave the ….. off and it fell down the…… Yeah well you probably shouldnt have done that!” I recently read STM’s post on cleaning fork seals and he did hint that beer would be of assistance. I have the day off (Rain) But its a little early to start drinking.. or is it? I think I am now officially Procrastinating.

[jamieMember]

Give it a crack and just take some close up (macro) pics of any bits you might have to remember which way they go. Gotta love you tube for getting qualifications,i am you tube accreddited fork seal changer. :laugh:

Ive seen Yami DVD’s on maintanence for sale too,they could help if it goes bad.

good luck 1st ones gotta be the hardest anyway,next will be easy.

[Aaron WildeMember]

I had the timing advanced on the wr to yz spec. That was what i was told anyway.From an uneducated perspective i would say that the timing is retarded as when you turn the crank counterclockwise to TDC the cams have not quite come(about one tooth off) around to line the marks up with the head. Should i check the clearances when the piston is a TDC or when the cam points are lined up with the top of the head? They are not the same as they would be if it was standard. I am giong to return the timing to stock so i think my next move will be to change it to standard then check it and adjust the clearance from there.Also the mark yamaha have in the book for TDC looks nothing like the one on the bike. Aparently KTM have a bolt to lock in in TDC. The orange side of the force is looking better all the time.

[MalMember]

Are you just checking the valve clearance or taking the head for a service?

If it is just a clearance check then that’s easy and ‘tooextrememx’ is on the money with his video. If the valve shims need replacing then the cams have to come out and new shims purchased. Before you start take some close up photos of where the dots on the cam gears are and also mark (with a white marker or liquid paper) a cam tooth to the chain link with the motor at TDC. This way you’ll know where everything should be.

I know on the old WR400 and 426, to get the YZ timing the exhaust cam was retarted by one tooth. I’m not sure if the 450 is the same. I was told that you lose what little bottom end torque the 400 had but gain a quicker reving engine. I decided against the YZ timing for that reason. But i did do some creative timing as the cam gears had moved on the shaft.

If your cams are still in then check the valve clearance and then change the timing. You’ll only have to pull the cams out once. Good luck with it. Take your time and follow the manual and you’ll be sweet.

[Aaron WildeMember]

mal5.1 wrote:

Quote:

Are you just checking the valve clearance or taking the head for a service?
I was checking the clearances as I have noticed a decrease in compression when i put weight on the kick starter. And it had a backfire pop want for a better word noticable at half throttle no load. A mechanic said it sounded like a leaking valve. I have bought some feeler gauges and checked the clearances. Alas the sods only go down to .206 mm but i could not put it under any of the cams.(exhaust range(.2 to .25mm) So the exhaust clearance is at least right or tight? I will have to get different guages to check the intake side to between .1 to .15mm. If the valve clearances are good i was going to remove the head and pour solvent on top of the valve to check for leaks.(as the good book tells me.)

If it is just a clearance check then that’s easy and ‘tooextrememx’ is on the money with his video. If the valve shims need replacing then the cams have to come out and new shims purchased. Before you start take some close up photos of where the dots on the cam gears are and also mark (with a white marker or liquid paper) a cam tooth to the chain link with the motor at TDC. This way you’ll know where everything should be.I will return the cams to the ridable setting Thanks to you i now know the cams have been retarded so i will put them back so the punch marks on the cam gears a parallel with the top or the head.

I know on the old WR400 and 426, to get the YZ timing the exhaust cam was retarted by one tooth. I’m not sure if the 450 is the same. I was told that you lose what little bottom end torque the 400 had but gain a quicker reving engine. I decided against the YZ timing for that reason. But i did do some creative timing as the cam gears had moved on the shaft.

If your cams are still in then check the valve clearance and then change the timing. You’ll only have to pull the cams out once. Good luck with it. Take your time and follow the manual and you’ll be sweet.

[Aaron WildeMember]

Thanks mal I tried to say tanks in the other post but the cursor could not be placed anywhere further than about half way down the message. If you grab the side bar it flicks straight back again? I also tried to write my reply in red but it did not work. I hope the engine work goes better thn my posts.

[Aaron WildeMember]

[img]http://www.obtrailriders.com/media/kunena/attachments/legacy/images/DSC09127.JPG[/img]
Before you get the wrong idea this is the offending article.
Because it is my first time with this sort of thing I noticed that you can fumble around in the shed for hours wondering if you are getting anywhere. Soafter looking at lots of books and the interweb I spent a long time pulling it off. I then gave head to Steve at cycletune. He said it was ok, but it needed to be a bit tighter. No liquid came out around the sides but he said with age it probably will soon. Will do a full write up on an amateurs view of a good head job after i go back to steve and see if i can pick up. I cant work out why i have to pay him so much when i am doing most of the work and pulling it to pieces myself :laugh:

[MalMember]

Good to see you had a go Aaron. Mechanics cost a bit these days but you pay them for their skills and get warranty too.

Fumbling around in the shed is better than breaking things going in hard and fast.

Quote:

Thanks mal I tried to say tanks in the other post but the cursor could not be placed anywhere further than about half way down the message. If you grab the side bar it flicks straight back again? I also tried to write my reply in red but it did not work. I hope the engine work goes better thn my posts.

Glad I could help mate.

Yeah IE done this to me too. I would type a reply in word then paste it in. Now I use Firefox as my forum browser and it all works fine.

[Aaron WildeMember]

[img]http://www.obtrailriders.com/media/kunena/attachments/legacy/images/DSC09183.JPG[/img]
The Head now has new Stainless valves and is ready to go back on.
I was told you could loose 1 HP with these valves but they are more durable.( I am not chasing power I want quiet and reliable) The valve seats were starting to lip out so they are now in the bin. I thought I did all the right things with regular oil changes and air filters, but 5500 ks and they are history. At least I didnt drop a valve I spose as for the age of the bike it might end up a wreck. I think in heindsight I would have done the valve work as it cost a mint on parts through a shop. Labour costs were neglegible. I saw some prices on line the other day and i think for the price i could have bought titanium valves. More posts later to update the “Idiots guide to top end rebuilds”.

[StuartMember]

I would have thought the original titanium valves would of just needed a gring & Lap to go with the new seats

[Aaron WildeMember]

He Said something about the hard facing being only eight micons. once that is gone you can shim it but it will get out of spec so quick that you will get sick of shimming it.

[Aaron WildeMember]

[img]http://www.obtrailriders.com/media/kunena/attachments/legacy/images/DSC09187.JPG[/img]
Got the Piston and Cylinder on. Putting the rings on is not as easy as they make out in the book. I bought a ring compressor tool and it was too long because the stroke is so short. So save your money there. It is possible to have the whole lot come out even when you are up to the oil control ring :angry: The cir-clips on the gudgeon pin I got are just bent pieces of wire. So they are not as nice to put in as a proper cir-clip and look a lot easier to drop into the crank case. And yes do as they say cover it with a rag because I would have lost one down there. At the moment I would say If you are thinking of doing this for the first time don’t. That is if you are not a mechanic of any sort. Sell your bike before it needs it Just about to go out and torque the head down. Also read the manual on your new torque wrench. I played around with the bolt on the end just as I was reading ” Do not adjust the calibration bolt or it will no longer be right” Whaaaaaat!! The stupid thing was only finger tight.It was a Kinchrome.

[StuartMember]

There is an alternative to a ring compressor, fit the piston to the barrel, then fit the piston with barrel to the con rod.

Makes it easy

[StuartMember]

The torque instructions say torque up the 3 torque steps, remove bolts & grease, torque to ………NM then 1/2 turn after that. what bs you need to break the gasket seal & lift the barrel to remove the bolts.

Just torqued them up, then the 1/2 turn so good so far.

I fitted Genuine Yamaha parts, felt a lot happier using circlips rather than wire like my old two strokes had.

[Mick DMember]

Good call sb_250y.

[Author]

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