Pulling head on YZF750---

[exupturbo]

If I were doing it I would leave the 1000 block a little tall to compensate for the increase in CR, the stock head gasket is no good with the 1040 pistons as it overhangs the bores and would cause problems. You will need a cometic or similar head gasket with the bigger dia bore size. To complicate things even more the cam timing will be out if you change the compression height and you will need to slot your cam wheels and degree in the cams. I had to do this when I fitted a 2mm thick plate under the barrels to lower the CR on my bike.
Mark

[KontoBoy]

Thanks EXUP for setting me straight on the CR calculations. It did seem like 13:1 was a pretty high CR to end up with.

Now how do I find my combustion chamber volume? Not in the shop manual. One site suggests using fluid and a burette to measure, but even their calculation presumes flat topped pistons--the YZF's aren't.

A rule of thumb I was told was that .5mm of gasket is worth .5 of compression. I was also told the base gasket is 3 part and each part is about .007-.010.

Turbo--The WISECO 1040 kit comes with a gasket though I don't know if its stock thickness or not. On the cam timing, if the increased cylinder height is within the range of the chain slack taken up by the cam chain tensioner, will it effect cam timing? As I envision it, it would only make a difference once you were out of the range of available chain slack.

Well my hex bit arrived today. $18 with shipping, nice S&K piece. Think those head bolts were on tight?



Hopefully it will straighten out some when the head gets torqued back on!

Kontoboy

[exupturbo]

When I checked my CR with the 1040 kit it was 13:1 after a light head skim which seems a bit high so would be worth checking with the smaller combustion chambers in the 750 head. What I did (rightly or wrongly) was to get the engine up on a workbench, set it at TDC and fill no1 cylinder to the bottom of the spark plug threads with parrafin/kerosine with the engine set so the barrels were level. I could not get hold of a burette so bought a small syringe from the chemist that was graduated in cc and used that to squirt in the parrafin. Doing it this way allows for all the combustion chamber volume in one go allthough if your rings are worn out you would have to work quickly! If you have had the engine apart then you can use a small amount of grease to seal the top compression ring nd prevent any leakage.
On the subject of cam timing, when you lift the head/barrels you get the same results as having a shorter cam chain and the cams get advanced, you could work out how much by measuring the distance from the CL of the cam wheel to the CL of the chain, say for instance the chain CL was on a 1.5 inch radius and you lifted the head by 0.020 inches to compensate for CR increase you would devide 0.020 by 1.5 to give 0.01333 which is the sine of the angle it has moved. If you go into start menu/programs/accessories/calculator on your PC and go into 'view' you can switch to scientific and get all the trigonmetric functions up, now click inv then sin and you will get the angle which in this example is 0.764 deg of camshaft timing error, the cams turn at half engine speed so cam timing error in crankshaft degrees is 0.382 degrees with a 0.020 inch(0.5mm) increase in height. Hardly worth worrying about in the grand scheme of things IF my guess at the camshaft sprocket radius in anywhere close. I ran my turbo with a 2mm decomp plate under the barrels for ages before I got round to sorting out the cam timing

The Wiseco kit comes with a Cometic gasket that has bigger holes in.

keep us posted

Mark

[KontoBoy]

Damn Mark, you are good!

I have the motor up on a table with the head off--I made a simple wood stand for the motor and figure I can add some hinges to let me level the block.

Syringe is no problem. I sell my body to science for money for race parts and track days. I'm sure can find a sympathetic lab tech who would give me one.

I'm thinking I'll take the combustion chamber measurement in three steps. First measure top of piston to top of cylinder block, then measure combustion chamber in the head, then factor in the thickness of the head gasket. That way I can easily factor in the effect of different base and head gaskets thicknesses. I understand I measure the head with the spark plug in place and I can use the same grease trick to seal the valves.

As far as degreeing the cams--I'll wait and see how much I have to raise the cylinders before I worry about it. Elongating the cam gear screw holes won't be a problem. (I use to see slotted gears on eBay.) My bigger question is how I'll accurtately measure the cam rotation--maybe a big graduated carboard dial on the end of the cam?

I did measure the existing deck height on cylinders 1 and 4 (which are at TDC). I believe these pistons are slanted! With a dial caliper I was getting roughly .04" on the exhaust side of the piston, and .01 on the intake side. This was on both pistons measuring in several places.

I am taking the head to a shop tomorrow to measure and skim if needed. Manual say .003. I'm trying a different shop--last one charged me double their estimate for a valve job. This one came recommended--they specialize in performance cars and are reasonably close. Quoted $64.

And I went ahead and purchased a YZF1000 block. The price was right and the owner knows these bikes and about bore kits on these motors. (Said he was running a 1020 YZF that is going to get bored to 1070.)

So this may actually happen. I did talk with Hooligan last night and based on his research want to give Dutchman racing a call on a big bore kit they may carry that would use my existing block.

I'll keep you posted.

Kontoboy

[KontoBoy]

Stopped at the shop on the way to work. Gentleman checked for warp while I watched and reported it is fine. He recommended just cleaning lightly with a scotch pad and putting a new gasket on.

One side of me says leave well enough alone and just put a new gasket on. The other says 860cc--wow! I'll sleep on it.

While at the shop I asked about five angel valve job. Said it would be $400 if they could fit my stems. Seemed reasonable--another local shop quoted $350 for a 3 angle, 4 valve head.

Kontoboy

[exupturbo]

I timed my cams in using info from this site, figs are for a turbo bike but it is a good explanation and I printed this lot out so I could refer back to it whilst timing the cams.

http://www.turbo-bike.net/Cam%20timing.htm

Mark

[Hooligan]

damn engine builders....i wish i was one.

[KontoBoy]

My cam gears have about a 17mm radius. So if I take .43mm increase in deck height and divide by 17mm I get rounghly .025 sine. Inv sine is .064 degrees, divide by 2 revs is .032 degrees.

Yeah, I agree, pretty trivial. I don't think any adjustment I made to the cam timing would be that accurate.

I still need to recheck the .43mm estimated deck height adjustment. My original CR calculation was off and I haven't measured the volume of the combustion chamber yet. Still, it would have to be an order of magnitude difference before I'd fret about it.

Found this forum thread about this mod:

http://www.visordown.com/forums/printthread.php?t=89875

Kontoboy

P.S. I saw another FZR1000 block with pistons on eBay UK for anyone else interested in trying this. Priced the FZR1040 kit for $372.

http://cgi.ebay.co.uk/yamaha-yzf-1000-t ... dZViewItem

[exupturbo]

Almost there, but something went wrong at the last minute. You need to tick the inv box then click the sine button once and don't click = I got 1.449 degrees at the cam giving 0.7247 degrees at the crank. The real experts like Chuck D and Dragracer 1951 will be able to tell you more on weather this will make any difference but I would not be to worried if it were mine.


some good info on the visor down link but I would ignore the bit about making the engine too revvy, it has the same stroke as it started with and more piston area.

Mark

[KontoBoy]

Oh damn--I think I hit the log n instead of inv. Sine, Inv, Log n--it's all just vaguely familiar. Hard to imagine I use to know what that stuff meant--35 years ago.

Kontoboy

[exupturbo]

Trigonometry is pretty meaningless for every day life, I remember my maths teacher trying to get it to sink in without much luck. I then get a job as a toolmaker making injection mould tools and end up using trig or Pythagoras nearly every day for the last 22 years, it is etched into my brain now for life

Mark

[dfrois]

I have a Performance Bikes (I think...) issue that has a comparison of several tuned FZ750, one of which I`m sure had 911 cc. It could be the one you are after. If you still want it, let me know and I`ll give you the info tonight.
DF

[KontoBoy]

Yeah DF, if you can scan it into a .pdf or something that would be great!
We might be able to get it posted on the downloads page.

If you wanted to part with it let me know what you need from me.

I wonder if the 919 is a YZF1000 crank with the YZF1000 pistons and barrels? I'd be worry that bumping displacement that much might start challenging my 39mm FCRs.

Kontoboy

[cromwelluk]

Hi
Try a search using : FZR pistons and barrels on yzf750?

Very interested in this thread as I was looking for a big bore YZF 750 using FZR parts
I hope I am wrong but it seems if you want to big bore the existing block you can get around 830 cc

The FZR block can not be skimmed 10mm to fit

To get any more cc's you need to split the bottom end and most recommend fitting the 1002 crank, rods block and I would assume Head
I think you need to change the clutch basket as well
So it's really a 1002 with a 6 speed box

Not sure what you get if you used the I002 rods on a 750 crank

there is another problem which would be head height and frame mounts for a taller head as per yzf 750 /1000 conversions.

So if its a top end only, the options seem limited and expensive for th gains.

I there is talk of fitting machined liners from a 1002 cc and using the pistons but it seems to be fiction rather than fact or subject the heat / water problems ???

The 911 cc conversion is quite common for Fz750's
As long as you use the later 2mg engine or rods with the pre exup 1000 top end

It would appear the problem is with the YZF 750 crank

As always any advice or correction is welcome

Crommie

[exupturbo]

The 911cc conversion on the FZ750 is what got me thinking along these lines for the YZF 750. I do not know what the difference in crown height is between the YZF750 and FZR1000 engines as this would also come into the equation. If there is a 10mm stroke difference and IF the crown heights are close you would only need a skim of a maximum of 5mm by my thinking as the pistons would only move up the bore a further 5mm, allow a bit for the CR and you are down to around 4.5mm. I built a 1000cc motor into 750 cases and remember having to fit longer head bolts but can't remember how much longer they were are the 750 rods longer?? as this could prove to be a pain in the A$$ ?? If you have to split the cases then it makes sense to fit the 1000cc crank and rods as well.

Mark

[KontoBoy]

I guess I need to check the crown height on the stock YZF750 pistons versus the Wiseco pistons to determine how much the 1000 block needs to be shaved. The Wisecos pistons sure look flat except for the valve relief cuts, but the pin to piston top height is another question. 10mm does seem a big cut but I don't think it will be that much. But at the same time even a 4-5mm cut is going to push my airbox farther up into the tank, and it's already a tight fit.

I'm heading out of town tomorrow and not sure how much I'll be checking in here until I return. When I do get back I'll measure my stock pistons and see what I can find out about the Wisecos.

Kontoboy

[Yoniboi]

I'm sure somebody used a YZF750 head on 1000EXUP barrels, could that cure the frame mount dilemma?

John

[dfrois]

I apologize to everyone for not being so prompt at this as I wanted...work got in the way for the past 2 days.
The arcticle that was mentioned is in the December 1993 "Performance Bikes" issue, and is titled Cheap Thrills. It does have a supermoto bike wheeling in the front cover, and the article itself starts on page 36 with a FZ911... wheeling, what else!
The conversion is done with FZR1000 barrels and pistons, post-97 FZ750 conrods, and FZ750 head. I`ll quote the juicy bit, from engine builder Steve Linsdell, as quoted on the article:
" The long stroke FZ motor gives a better combustion chamber shape than the OW01 and YZF:it`s far more fuel-efficient. My 125 bhpFZ did three laps of the TTon the same amount of fuel as my YZF uses in two!
To big bore an early engine means opening out the crankcases to take FZR1000 barrels. You also need to fit the later, 1.5mm longer 750 rods, shorten the barrel, machine the piston for correct squish and valve clearance, drop compression from 14:1 to 12.5 (max) and reset the valve timing to avoid bent valves. The early ('86-'87) FZ exhaust cam is best..."
End of quote.

Remember that this was about the FZ750 engine: modifying an YZF 750 engine may have some differences, namely bore and stroke (YZF more oversquared).

The whole article has 4 pages. I have scanned them into 4 hires Jpegs and can mail them to someone that can make them available to all.

I also have an excellent technical analysis of the Genesis motors (FZ750 and FZR1000) that appeared in a sadly gone French magazine called Moto-Technique. It is really deep, and looks into stuff like the relation between stroke and conrod length, combustion chamber shape, etc. It is in French, but still an excellent read. Mind you, it was made when the first FZR1000 came out (1987, I think), so it is pre-EXUP. So, differences between 87-88 FZR1000 and 89-onwards, with EXUP, are not covered: namely, bigger stroke from 75 to 75.5 mm (90-onwards only, I think), EXUP control on the CDI, and cam timing differences. I don`t think there are any more significant differences between several years, on the FZR1000 engine.
I can scan that too, but it is very big; something like 8 to 12 pages or something (don`t have it here right now). There`s also a step-by-step How-To article on disassembling an FZR1000 engine, with photos and detailed explanations.

DF

[FZRDude]

Email them to me, my address is in my profile. I'll host them up.

[dfrois]

...mailed. And the French FZR Engine Profile too...let´s hope it is of some use to someone.

The FZ Family profile is some 23 pages long, and the FZR1000 Engine dissassembly article is 14...so, I will only mail them if there`s a definite interest in them. My Net link is slow, and uploading seems to take forever.

DF

DF