Pulling head on YZF750---

Want the specs for a valve adjustment? Can you provide tips for bleeding brakes? Please use this section.
KontoBoy
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Pulling head on YZF750---

Post by KontoBoy »

The bike wouldn't run the other day at the track and I found the culprit-- the head gasket is leaking. I can see coolant leak between cylinder 3 and 4). Plus coolant is an awful muddy color. Time to pull the head--I have the motor out.

Now where can I find a long 6mm hex head 3/8 drive bit to get at those head bolts? The 6mm shaft needs to be a good 3 inches long to reach them.

After the head is off my initial thought it take it to the machine shop to check for warp and shave if not, then put a new gasket and bolt it back togther. It's the cheap (maybe $150-200) solution too.

Anyone know how much can I safely shave if needed?

But since the motor is out and head is coming off, it opens a myriad of options. The motors has about 20K, burns very little oil and has always run well. I'm wondering if I should also consider:

New valve seals (at $4-5 each X 20 it gets expensive)
New guides ($20 each for OEM)
Resurfacing valve faces
Flowing head
860 kit (Kit $400-500 (?) + $300 to bore head)
Others options? (I'd prefer to leave the cases and bottom end alone.)

What's are opinions on what to do, who to turn to and how much to build a nice reliable track bike motor?

Of course I may still end up just slapping a gasket on--my second kid starts college next month (laptop, mini fridge, microwave, etc, etc.)!

Kontoboy

NoItsNotAnR1
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Post by NoItsNotAnR1 »

http://www.monstronix.com/skt45956-p-58797.html

Would this work for the head bolts?

Wow, that's a lot of upgrades to consider! That "while I'm in there" stuff can get pricey.
Blaine
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Post by Hooligan »

steve, you should give me a call. i want my motor done as well. maybe we can work together on some of this...
Jason, aka: Hooligan
1994 YZF750-R
1996 YZF750-R
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Tool tips

Post by Lemmy »

Mjello - the bit you are looking for is pretty much a standard piece, go ask a deasant tool sell-out, they should have them.
For the "upgrades", off course you will check valve surfaces while you are at it, recondition if needed to, and change the valve stem seals while you got them off. For the rest, hmmm, do you think that will ad something to it? Compared to what you are about to spend, I mean? Perhaps you should go look for another bike, alltogether a better setup, since everything is allready "mated".

Regards - Lemmy

KontoBoy
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Post by KontoBoy »

Well I went ahead and ordered my 6 mm long hex bit. Damn I wish they told me it would take a week to get it before they had my money!

I figure I will clean up the head some when it's off. Carbon deposits, grind the ridges between the rubber connectors and intake manifolds, and again between manifolds and head. As I recall the YEC manual has some suggestions too. (As a teen I used to do some porting work on 2 stroke outboards.)

For the valve faces I'll take a look. I'd like to get away with just lapping the valves, but who knows what I'll find once the valves are out. If I need new faces cut then it has to go out to a shop.

Seals seem to make sense since I'm in there, but at the same time oil consumption is negligible.

I wrote TTS Performance Engineering regarding pricing on their 837cc kit. The pistons are 400, sleeves 200, and they can bore and insert liners for 220 plus 50 shipping. That's all Pound Sterling, so total is about U$1600 or a seasons worth of track days! I don't know if that includes the 17% VAT. The machine work seems very reasonable but parts seem pretty steep.

Something to think about and starting point for comparison shopping.

Kontoboy

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Post by ExupElvis »

For the head bolts you can get a regular 6mm allen wrench and cut the short angle end off.

Use a die grinder with a cut off-wheel, (there is probably a Dremel attatchment that will do the same thing).

That will leave you with a straight allen bit................put a 6mm deep (6-point) hex socket
on a breaker bar, use it on the end of the now straight allen wrench, and twist the head stud cap nuts off.......

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Post by KontoBoy »

Good idea!

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Post by exupturbo »

KontoBoy wrote:Well I went ahead and ordered my 6 mm long hex bit. Damn I wish they told me it would take a week to get it before they had my money!

I figure I will clean up the head some when it's off. Carbon deposits, grind the ridges between the rubber connectors and intake manifolds, and again between manifolds and head. As I recall the YEC manual has some suggestions too. (As a teen I used to do some porting work on 2 stroke outboards.)

For the valve faces I'll take a look. I'd like to get away with just lapping the valves, but who knows what I'll find once the valves are out. If I need new faces cut then it has to go out to a shop.

Seals seem to make sense since I'm in there, but at the same time oil consumption is negligible.

I wrote TTS Performance Engineering regarding pricing on their 837cc kit. The pistons are 400, sleeves 200, and they can bore and insert liners for 220 plus 50 shipping. That's all Pound Sterling, so total is about U$1600 or a seasons worth of track days! I don't know if that includes the 17% VAT. The machine work seems very reasonable but parts seem pretty steep.

Something to think about and starting point for comparison shopping.

Kontoboy
You don't pay VAT on goods exported from the UK but will get stung for tax at your end.

After breaking a bought 6mm hex key I made one by cutting off a regular hex key and hammering it into an old socket, you could do this if you are stuck for time.

Have you thought about using machined down 1000cc barrels? Get some from a breakers yard, machine them down to the same height (or a fraction higher to allow for increased CR) as the 750 ones and get them bored to take the 1040 pistons. If my maths are OK you would get 857cc with 77mm pistons. It depends on how good your local machine shop is but is still less work than re-linering your block and I've seen a bike featured in a UK magazine with this mod done allthough it was a FZ750 and with the longer stroke of this engine gave a quoted 911cc.

Mark

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Post by KontoBoy »

So the 1000 cylinders will take a 77mm bore without relining, the 750 head and 1000 cylinders will bolt to my bottom end, and the 1040 pistons will fit my stock rods? Cool, in a Frankenstein kind of way.

Definitely something to consider--I didn't realize it was an option. If you have a reference for that article I'd love to take a look. I've done a bunch of web searches but not come up with many details.

That said, outside of eBay I not sure where to find the cylinder. There's no public bike junk yards in my area. (For car parts I have to drive about an hour!) My other concern is the condition they's be in.

I haven't priced relining yet. I have a couple US sources for liners--anyone know the length of the stock 750 liner?

I have a local machine shop I've used a couple time. I'm not sure how good they are, but they are neither quick nor inexpensive.

Kontoboy

P.S. You don't pay VAT on exports! Damn, the guy that sold me my Ohlins screwed me.

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Post by exupturbo »

The artical was in a UK mag either "Performance Bikes" or "Superbike" if my memory serves correct and it had a picture of the FZR911 and another bike doing a wheely on the front cover, it was a long time ago though so finding one might be a problem unless a UK brother has a copy to scan ? Condition of the barrels is not really a problem as they are going to be bored and skimed anyway. The 750 and 1000 exup have identical crank cases, the only difference is the length of the cylinder head bolts due to the taller barrels and longer stroke on the 1000, there is nothing stopping you building a complete 1000cc motor into your cases but this will involve using a 1000cc cylinder head and some brackets to allow for the increase in height of the cylinder block as the head mounting to frame point will be out of alignment.
If I find any more info I will let you know ;)

Mark

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Post by Yoniboi »

Of course the 'easier' :poke option is to buy a 1000 engine, swap in your current 6 speed box and use your 750 head.

I too went the sawed off allen key in a 6mm 3/4 socket route, with a 3/4 to 1/2 adaptor so I could use my 1/2 inch torque wrench for putting it all back together again. I glued the allen key in to make life easier.

One thing that was noticeable on my rebuild was that all of the rubber 'O' rings on all the pipes in the sump, the oil spray tubes for the gearbox, etc were old and not doing their job properly. Get new ones from a gasket shop, Yamaha will rob you blind for each one.

John,
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Post by WickedFZR1K »

I know it is off topic, but yeah, you can build all kinds of frankenbikes if you do a little research. I found out (but never got to do it) that a 1200 Suzuki Bandit block and head will bolt right upto a 600 or 750 Katana bottom end (they share the same rods and crank so stroke is the same) and it turns it into a 987 with custom made pistons (ross or je will make them but usually require atleast 4 to be made, which is how many you would need anyways)...

When using a larger torque wrench like that, be careful as they dont always read dead on at the low settings (30 lft lbs)...
If you want to live life by your own terms, you gotta be willing to crash and burn...

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Post by exup freak »

http://putfile.com/pic.php?pic=main/7/1 ... .jpg&s=f10
heres my 1040 ru motor with the said bracket to fit it into a yzf frame :D
[/img]
Last edited by exup freak on Sun Jul 16, 2006 4:02 pm, edited 1 time in total.
oh yes ime back

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Post by Stig »

If anyone knows how far back the article was in PB or superbike, I might ba able to help. I've many pB and every copy of Superbike from the last 12 years.
Just give me a clue and I'll scan the article :D

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Post by exupturbo »

Stig wrote:If anyone knows how far back the article was in PB or superbike, I might ba able to help. I've many pB and every copy of Superbike from the last 12 years.
Just give me a clue and I'll scan the article :D
I've too much beer since reading the artical to remember, but it is at least 5 years ago (probably a lot more) :oops:

Mark

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Post by Stig »

Exupturbo. :poke ...you don't like making my life easy do ya??? :D

When I get 5 , I'll take a look see. They are well stored out the way so it'll be a long job

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Post by KontoBoy »

I did about an hour's worth of Internet search for the article to no avail. Also contacted some out of state bike breakers looking for a 1000 cylinder block--no replies yet.

I discoved yesterday I need to replace the clutch in my street bike so the 750 may sit a while more. It's a BMW which requires, rear wheel, axle, tranny removal just to access the clutch.

Thanks for all the help.

Kontoboy

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Post by KontoBoy »

I sourced a couple YZF1000 heads so time for some math. Question is, am I figuring this right?

The stock YZF1000 has a 75.5mm bore a 56mm stroke. The 1040 kit bores it out to 77mm for 1043cc displacement.

Using that same 77mm bore with the YZF750's 46mm stroke I get 856cc. OK--we're on target. But what happens to the compression ratio?

The stock YZF compression is 11.5:1. With a stock 750's 72x46 cylinder we have about 187.3 cc displacement/cylinder. That 187.3 displacement divided by 11.5 means the combustion chamber is about 16.3cc!?

With the 77mm bored 750 each cylinder displaces 214.2cc, divide by the 16.3 and I now have a compression ratio of 13.15! I can't afford that much race fuel and it seems way to high for a reliable motor.

To get that back to 11.5 I figure need to increase the chamber to 18.6cc or by approximately 2.3cc.

To get an 2.3 additional cc would I need a head gasket that's about .49mm thicker than stock? (Pi*(77/2)*.49=2.3cc) Will Wiseco have gaskets to do that?

Or am I better off using a stock gasket and leaving the YZF1000 cylinders .49mm taller than the YZF750's block?

Also, am I right in assuming the sleeves need to be removed from the block before it can be shaved, and the sleeves will need to be shaved separately?

My brain hurts. Thanks for the help.

Kontoboy

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Post by Hooligan »

cripes, that's alot of numbers you got working there steve.
Jason, aka: Hooligan
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Post by ExupElvis »

Konto, the compression ratio - in simple terms - is cylinder volume + combustion chamber volume divided by cylinder volume.
Don't forget to add combustion chamber volume to the first value, it's a common mistake actually. (Cv+cmv/Cv=Cr)
The Bowlings and Grippo automotive web pages may have some usefull formulas posted that you might want to look at, I know there are some even if you can't find them there.
On decking the block - the sleaves do not come out to deck the block, your machine shop may chuckle when they are asked that, if not - find another machine shop...
Good luck on the rebuild BTW, I know it blows to be doing it this time of year. :cry:

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