Author Topic: Yam engine advice  (Read 1421 times)

andy230

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Yam engine advice
« on: November 11, 2007, 01:58:58 PM »
Hello all,

There was a bit of this in my last thread, but probably easier to start another.

pics here for those not familiar with the most recent hair-brained scheme:

http://team-thumper.blogspot.com

I've been cleaning up the new motor, putting studs in etc, and wanted a bit of info.

The cases are I believe XTZ.  Engine no. 4NN-001891

Can anyone confirm what this is, year etc??  the side cover says MZ, but that really means nothing could be any cover...

I think (as SteveL says) the head and barrel are XT.

Head: 2KF 01
Barrel: 3AJ00  595cm3

Now, I think originally the barrel "nuts" (to the cases) were these silly, ally "male nuts" wuth a hex on them.  I dont like the idea of this!  And it broke the studs last time with these (as a 690).

I noticed my 620 SRX has normal nuts.  I have new studs and nuts to use.  Better??  Any scientific (or other!) reason why they're better??  And should I also use washers (phosphor bronze or otherwise?- certainly on the head, but should I re-use these old ones, or should they be new)

(I was delighted to find a new barrel gasket and oversize head gasket, new studs, nuts and headbolts.  All good, as they'd be about 50 quid I'd think )

Also, I've always used blue hylomar, including last time on the SRX head, and rocker box.  very little, and not a trace of oil, no blown gaskets etc.  Its a bit oldschool I know, but I am a luddite, with a strong dislike of elecctric starters and the like!  I have used this on every engine I've built, but this is mostly brits admittedly.  Never any problems tho, and I've always used it when I take any covers off.

I plan to use it on barrel, head and rockerbox.  A problem??

And finally, the stage 4 cam runs VERY close to the head.  Will try to post some phootos on the blog site later, but its almost unmeasurable with feelers....  About 2 thou?!!  Can the SRX/XT cam bend,flex or move at all?  I suppose clearance is clearance, and if it cant thrash about, then it cant hit.  But should I remove a little more metal (already had a fair bit off) ?  The head has run like this, but I dunno how hard...

Anyway folks, thanks for info, much appreciated!

And I've re-jigged the site a little if you want to click around it.  Some more piccies, and a very handsome picture of our very own Boyd Brooks!!


And the "List of the Fabulous", the vast majority of whom kick about on this forum.  Thanks a lot guys (inc mav, the most recent member of this brilliant group).  Thats the real reason for the site, and the blog, so that you chaps can keep abreast of what is happeneing.  Cos now, this is partly YOUR project, not just mine and boyd's!  Nice huh?! 

Have a look, there's a link on the left hand side. 

"Speak" soon,

andy

Steve H

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Re: Yam engine advice
« Reply #1 on: November 11, 2007, 02:34:37 PM »
Andy

Parts number would suggest XT600, also the fact that its powder coated black paint in places.
Martin Sweet sells nuts to replace the aluminium barrel nuts. Not seen then but I would imagine they are in steel. The DT175MX uses the same nuts which corrode really badly and crumble.
I wouldnt use Blue hylomar on the head and base gaskets. Ive heard the Yamabond is the thing to use ,cant remember which number though.


Steffan

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Re: Yam engine advice
« Reply #2 on: November 11, 2007, 06:57:56 PM »
Barrel is XT600Z Tenere , model after the one I had ( and Boyd) the one with twin headlights and no kicker.

Steffan

andy230

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Re: Yam engine advice
« Reply #3 on: November 11, 2007, 07:47:03 PM »
cheers all, good info!

And is there a preferred supplier for Yamabond??

It doesn't sound like its cheap!   >:(

Off to Ebay for me

a

--------------------------
Ok, just back!

Re. Item number: 320179366731

1. Is this true? Yamaha have discontinued it??

2.  And do we trust this??!!

Cheers, maybe will go to a proper shop....

a
« Last Edit: November 11, 2007, 07:52:53 PM by andy230 »

andy230

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Re: Yam engine advice
« Reply #4 on: November 11, 2007, 08:37:19 PM »
And....

How do I know what to torque the new studs to??   ???

ie  the fresh studs into the cases.

Am thinking *tight*, (tho bearing in mind its ally) but with loctite (green!)

Hmmmm.  Thanks!  Lots of stupid questions in this post!

a

Steve Lake

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Re: Yam engine advice
« Reply #5 on: November 11, 2007, 10:38:55 PM »
Well Andy.....having 'pulled' the head stud threads on #4......I'd say don't exceed the reccomended torque settings (well, maybe a bit :-) )

I wouldn't use loctite, I've always used coppaslip......

grease the copper/bronze washers (no need for new ones as long as they've retained their shape.


If possible I'd try and give the cam at least 5 thou clearance, dunno why, just feels right, probably 'cos thats the exhaust valve clearance (3 thou on the inlet i think)
should allow for expansion/whip etc

getting interesting innit ! :-)



andy230

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Re: Yam engine advice
« Reply #6 on: November 11, 2007, 11:40:02 PM »

getting interesting innit ! :-)


Interesting??  I'm f***ing terrified!!

Points to note from the shed:

1. My original (ie. first (ever!)) SRX motor had the ally sleeve nuts.  Its a 608cc 1JK lump
2. The 620 motor has steel nuts
3. SteveH, the 4 nuts I have for bolting down the barrel are new Yamaha items.  Likely to be 4x same of those items on the cam-chain side.
4. SteveL, to avoid confusion, I'm not talking about the head bolts etc.  I'm referring to the *studs* into the cases.  They are used to pull the barrel down onto the cases.  Not normally replaced, so I don't think torque settings exist...  Not in my manuals anyway.  But I'm sure Martin Sweet will have replaced these, so will check with him (and let you now)
5. lobe-to-rockerbox clearance is nowhere near 5 thou. Will also ask the "Great God of Tuned Yam Singles" on this one too...
6. Yamabond on the base gasket??  Another one for GGoTYS!
7. And I'll finish with a stupid question: Can I replace the camchain without splitting the cases?

Sorry there are so many questions!  All info received happily!  Off-list if easier!  SteveH, move this to "technical" if you like!

a
« Last Edit: November 11, 2007, 11:48:40 PM by andy230 »

Steve Lake

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Re: Yam engine advice
« Reply #7 on: November 12, 2007, 07:23:52 AM »
As far as I can remember......to replace the cam chain (on the srx) you need to remove the l/h (generator rotor) cover...then 'pull' the rotor. I'm not sure on the 'water cooled' bottom end that you have....might get away with not pulling the rotor

If you need a puller, I have one you can borrow (available to any TC member for the price of a pint)
available to Team Thump FOC (+carriage)

cheers

I wouldn't worry about replacing the studs that poke up from the case into the barrel...best left undisturbed....as are the 2 studs that poke down from the head into the barrel.

Cheers

SteveL

Steve H

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Re: Yam engine advice
« Reply #8 on: November 12, 2007, 08:05:58 AM »
7. And I'll finish with a stupid question: Can I replace the camchain without splitting the cases?
As Steve says you need to pull the rotor. Since your head is off be VERY careful, the centre nut is a pig to undo, if the camchain is loose it can easily wrap round the crank, and push against the lower camchain tensioner mount, if the crank then moves it will break off the mount. Easily done and tricky to recover from. I'd loosely assemble to the top-end and use an air-gun (or a 12v version) to get the nut undone.


andy230

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Re: Yam engine advice
« Reply #9 on: November 12, 2007, 09:58:52 AM »
Hello Steve


I wouldn't worry about replacing the studs that poke up from the case into the barrel...best left undisturbed....as are the 2 studs that poke down from the head into the barrel.


Agreed Steve, but they're sheared   :o

When the motor had a 690 hi comp top end, it broke 2 of these studs (retained with ally sleeve nuts), and also wrecked the flanges at the base of the barrel.

Thus the decision to go down to a 640!!

Thanks for the offer of a rotor puller.  Very kind, but I think I'll pass on it.  The chain looks good, and the motor had just been built as a 690, really no miles I think.  So am presuming new chain.  Risky I know, but.....

Ta for info!  will report what martin sweet says,

a

andy230

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Re: Yam engine advice
« Reply #10 on: November 12, 2007, 03:22:28 PM »
3. SteveH, the 4 nuts I have for bolting down the barrel are new Yamaha items.  Likely to be 4x same of those items on the cam-chain side.
4. SteveL, to avoid confusion, I'm not talking about the head bolts etc.  I'm referring to the *studs* into the cases.  They are used to pull the barrel down onto the cases.  Not normally replaced, so I don't think torque settings exist...  Not in my manuals anyway.  But I'm sure Martin Sweet will have replaced these, so will check with him (and let you now)
5. lobe-to-rockerbox clearance is nowhere near 5 thou. Will also ask the "Great God of Tuned Yam Singles" on this one too...
6. Yamabond on the base gasket??  Another one for GGoTYS!


Answers from Slipstream!  Via Roy, but he said to hang fire and speak to Martn on Wednesday.

-Studs.  Tight.  But not too tight!!!  And dont bother with Loctite.  (Will try to get a torque setting from Martin!)

-Nuts.  Definately use steel ones.  With washers, and get Yamaha parts!

-Yamabond.  Hard to get.  And if you can its about £30 a tube.  However Roy said to go to Rex Caunt Racing, who will supply nearly the same stuff.  A tenner.  Bingo.  Team Thumper still thinks its dear, but I suppose its not too bad. 

-And yes, certainly use it on the base gasket. Head gasket- nothing- clean and dry, thats it.  No loctite, but WD40 on the threads and torque it down to spec.  He said to speak to Martin about using phosphor washers.  Sometimes they, sometimes they dont, depending on the head.

-He said I'll need 10 thou on the lobe-rockerbox clearance, otherwise it'll strip the oil from it.

-And check the piston-valve clearances. 1mm minimum, ideally a 1.5mm, as everything stretches at 8000rpm, and the piston rocks in the bore.  Good advice, but a pain in the ass!  There goes my idea of "build it once"!  Never done this before, but I get the principle.  Use an old head gasket and BluTac on the valve pockets, and turn it over by hand (gently!!).  Any of you guys done this??

-And if I want them to build up the top end its £120.  Plus the vat I'd imagine.  Not too much parts mind but I'll see how we get on with lots of advice and many many more stupid questions!

Oh well.  I'll ask the same dumb questions to Martin on Wednesday and see what he says.

Cheers

a
« Last Edit: November 12, 2007, 03:24:39 PM by andy230 »

guest27

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Re: Yam engine advice
« Reply #11 on: November 12, 2007, 04:31:26 PM »
Never done this before, but I get the principle.  Use an old head gasket and BluTac on the valve pockets, and turn it over by hand (gently!!).  Any of you guys done this??


Oh well.  I'll ask the same dumb questions to Martin on Wednesday and see what he says.

Cheers

a

Have done it a few times - used soft solder ot plasticine rather than blutac - would worry about ti sticking to the pistons etc.  The solder allows you to measure the gap with a mic, mind with care so would the plasticine.  You can get stuff called 'plastigage' or similar that is made for the job.

Need to make sure the head is cracked down fully, but only put on the inner valve springs if it has them - they will close the valves but not take so much to open.

Could argue in reality you need to do this a number of times to address variation but that would be just to wind you up.  Remember only to turn the engine in the direction she will be traveling in to take up all the backlash etc.

R

Steve Lake

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Re: Yam engine advice
« Reply #12 on: November 12, 2007, 05:59:08 PM »
What a shame that you're not keeping it as a 690!......that 50cc will make all the difference Andy!

And.........when the barrel lets go from the cases at 8000rpm the head pushes well up through the chassis into the tank (in a spar frame)...I saw one at Denver Motorcycles last year....most impressive, would love to see it again !! (aparently the highside, and the oil all over the track was worth watching too!)

How do you get round the problem of valve clearance? a thicker gasket will bu55er up the compression ration.....do you grind off a few thou from the valve stem (but i seem to think these are fairly flush with the collets and cap on an srx)

Thinking about it...thats a bluddy stupid idea......wouldn't make any difference, not unless you made the rocker clearance that much greater!

can you increase the pocket size in the piston?

you could increase the thickness of the base gasket, this will have the same effect as increasing the thickness of the head gasket though, but probably preferable, as a thicker head gasket might cause more problems than it cures.

SteveL

gets more interesting every day



Steve H

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Re: Yam engine advice
« Reply #13 on: November 12, 2007, 07:28:31 PM »
-And check the piston-valve clearances. 1mm minimum, ideally a 1.5mm, as everything stretches at 8000rpm, and the piston rocks in the bore.  Good advice, but a pain in the ass!  There goes my idea of "build it once"!  Never done this before, but I get the principle.  Use an old head gasket and BluTac on the valve pockets, and turn it over by hand (gently!!).  Any of you guys done this??
Ive used plasticine with some success, I use a scalpel to cut the plasticine down the centre of the impression left by the valve and then measure with a micrometer. If you dont have a micrometer its worth buying one. Ive never found solder soft enough. Your also need to measure the squish clearance, its the clearance between the flats on the combustion chamber (front and back) to check piston clerance. Stock rods need around 0.8-1.0mm clearance. 
If the valve-piston clearance is too tight then the pockets can usually be machined. Ive only ever used mildish cams so there has always been loads of clearance. As Steve says only fit the inner springs as it makes it much easier to turn over. You will need to assemble with the cam timed up correctly and the chain tensioner fitted, as a small change in timing can quite significantly effect the clearance.
Interesting point about the cam clearance washing the oil off, that one would have been tricky to narrow down after a failure.

guest27

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Re: Yam engine advice
« Reply #14 on: November 12, 2007, 07:50:01 PM »
Maybe I have some particulaly soft solder..?  ;D

Used it OK on the Triumph, Honda K4, DT250 and RD500 - for valve and squish on the $ strokes and for the squish on the proper engines oops 2 strokes.  You can certainly feel when it is going over the top and squashing it down, but does not seem to have done any damage - mind plastigauge is the proper stuff?

R