#6

[TZ350]

Do you not reverse the teeth direction Rob? we always used to for Thick alloy sheet, make a hell of a scream though?

No. Just used it as is. Same with skill sawing thick alloy plate, 10 and 12 mm. I do reverse the blade for galvanized roofing though. Best not to use tungsten tipped blades in reverse.

[husaberg]

No. Just used it as is. Same with skill sawing thick alloy plate, 10 and 12 mm. I do reverse the blade for galvanized roofing though. Best not to use tungsten tipped blades in reverse.

I use a grinder with a cut off wheel for the roofing iron.
Had a mate put a tungsten tipped saw blade on his weedwacker it exploded off on the first rock it touched and embedded itself in his shin, its still there to remind him.

[Grumph]

We don't know what Mike is using. I used a bandsaw to cut mine with a bimetal blade as I could see it was going to hit a core plug at one point.
My skilsaw - which I use to cut lumps off alloy sheet and plate before fine work with the bandsaw - doesn't have enough depth of cut for the head or barrel.

When i did the barrel, I dropped the liner out which was in the way of the cut, Much easier.

[speedpro]

I've got a reasonably nice dropsaw and carbide tipped blades. Today I had pretty much decided not to do it and just wait until after lockdown. Not so sure now.

Been down in the garage a bit more doing work on the head I will probably use. I found a packet of 8 valve guide seals which look like the correct ones. They also look brand new in comparison to a couple I pulled out. The number on the MotoX packet also matches 3LN valve guide seals so it looks like that is sorted - thanks Grumph.

The 2KR model had 2 different rubber intake manifolds, neither of which I have used. The 3LN had 4 different manifolds. The inner manifolds, #2 & #3 had different stud positions and these manifolds were offset towards the centre of the engine. I use 2 of the #4 manifold. These bolted straight up to the 2KR head I was using but it doesn't bolt up to the #3 port on the new head. However, Yamaha have thoughtfully included a boss in the casting where the bolt wants to go so it was a simple matter of drilling and tapping a new hole. Another example of things falling into place for me on these engines.

The little tool I made to dismantle the valve spring retainers on my scooter fits the FZR valve spring retainers exactly so that made things easy. Once I got all the valves out it was really obvious that a number of the valves and seats were better than others. It's possibly due to valve clearances being too tight as the seats look like they have been hot. The ports were surprisingly rough and mismatched where the valve seat fits into the port. I had a bit of a play with my dremel on ports that aren't going to be used and it didn't take much to get them looking reasonable. I need to match the intake manifolds to the ports as well. The manifolds are 1mm smaller all around.

In the combustion chambers, around each valve, there is a pocket machined into the head. There's a lip about 1mm high most of the way around each valve. It doesn't look right from a flow perspective. In an unused chamber I took to them with the little 3mm ball grinder in the dremel. It looks a lot better to me, especially after I finished it off with the little sanding drum. The whole chamber looks a lot more smooth and blended. Where the flat gasket surface parts of the chamber meet the actual chamber I left the edges sharp. I don't know, but there's a possibility the edges might promote turbulence which will aid combustion velocity. Yamaha didn't seem to care so it's probably OK. This pocket around each valve is the same as in the aftermarket head I have on my scooter. I have cleaned that up.

Interestingly, when I was removing the valve springs I noted that all the intake springs had coloured ends. All the exhaust springs were plain. The springs look identical apart from the colour.

[Grumph]

Were those stem seals with the FZR stuff ? If so I was being more logical than usual.
I usually keep stem seals all together as there's a lot of cross usage - FJ1100 seals in my EX500 for example.
But the 250 stem size is one I'll probably never see anywhere else.

Coloured spring tops are quite common. All the major companies have done it.
One way of making assembly a little more idiot proof.
Invariably, it is the top which is coloured.

[speedpro]

Is there a difference between coloured and non-coloured springs?

[Grumph]

Is there a difference between coloured and non-coloured springs?

No idea. You'd have to measure them. Could be a different supplier, different batch of engines or even a different assembly plant.

[speedpro]

Cylinder head has been cut using the dropsaw. I had a new 60T carbide tipped blade so fitted that. I had to fit a few packers to get it at the angle for the cut. It came out OK in the end. The saw actually made a very nice cut. The blade produced chips of alloy just like if you were using a carbide tool in a lathe. I made about 10mm deep cuts until finally it went through. I accidentally left the spring seats in. I pulled the valve guides out and removed one exhaust stud as they were in the path of the blade or very close. The blade cut one spring seat and flicked the other one out. I filed it afterwards and it's come out pretty good I reckon. Good enough anyway.
One of the things I need to do now is cut the pocket in the end of the head where the disc on the end of the cam sits to locate the cam in the head. If I was really rough I reckon I could do a good enough job using the dremel and a grinding disc. The disc on the cam is 35mmX3mm.

[Grumph]

Yeah, Wallace cut mine. I think he used a woodruff keyway cutter in the mill.
The later head like you have are a bit different to your first go. Wallace was able to cut the slots in the right place that the cam sprockets lined up on center without any spacers.

[speedpro]

I've been fossicking round a bit more in the garage. I've cleaned the new head about as much as I can be bothered. I cleaned up intake and exhaust ports as they all had lips and ridges just in from the seats. All the valves are cleaned ready to be machined and fitted. I used alternatively a CRC parts cleaner and Selleys oven cleaner. I've been putting a bit of thought into why the valves may have been floating and spoken to a few people and there's a few conflicting ideas. I have also been thinking about the exhaust manifold and whether it could be improved. There seems merit in simplifying it to 2 short pipes with the turbo directly in front. Another thought was to have one short pipe and the 2nd cylinder pipe long enough to delay the pulse 180 crankshaft degrees. This would result in even exhaust pulses at the turbo but only at certain revs. There is sooooo many variables I had to take what is supposedly a typical gas flow velocity and go from there. The longer pipe needs about an additional 2m if I maintain the diameter as it is. That'll be fun to make. Throw a bit of exhaust wrap on and a brown seat and it should be all good. There's pluses and minuses in everything. It still isn't obvious the cause of the valve float, to me anyway.
I've also been considering the combustion chamber. The intake valves are in machined pockets with about 1mm high lips. I thought about grinding them and blending the pockets into the chamber. After a bit more thought I can see that the lips on the exhaust port side, at low lift during valve overlap, may direct the incoming charge into the cylinder rather than into the exhaust port. As the lift increases the flow will be into the chamber over the closed exhaust port with the lip having little effect.
It's nearly as bad as 2-strokes.

[speedpro]

I have the engine dummied up and have been checking deck height etc. I have a few pistons which when fitted to the cylinders have less than .002" clearance. .002" is at the top end of the range for clearance so a little bit of room to possibly re-finish the surface of the cylinders, possibly. The piston squish to gasket surface is about .015". The top of the cylinder block and the sleeves is a bit uneven so taking that .015 off will be good to even it out. That will leave the head gasket thickness for clearance which is .25mm. There is no mention of the clearance in the spec sheet.
I've also been smoothing out the combustion chamber particularly around the valves. The dremel plus a 3mm ball cutter seems OK. I've been over some of it with a little sanding drum as well.

Got me thinking back to a job I did on a couple of Chevy alloy BB heads one summer. Used the big grinder there and a balls out 7 flute cutter primarily. Still took the better part of a week to do. Steel bodied Holden ute did 200+mph at Meremere so reasonably happy with the outcome.

[speedpro]

Slowly getting things together. Hope to get the machining done on the heads to fit the cam locating discs into this weekend. Also measured the current installed height of the springs. Every single one I have measured is about .5mm over length on the piece of head I have decided to use. These are the valves that were installed originally in each port and which I don't think have been touched. I need to double check but every valve I measured, the installed valve spring height is over the spec sheet value. I'll check the old head as well. That head had a bit of work done when I originally built the engine.
I want to check the height to the end of the valve stem. Obviously, cutting valve seats and valves will reduce the clearance. Once I can get the cams in I will assemble one exhaust and one intake valve and shim in up. This will tell me how far the valve tip can be raised before I reach the limit of the shims. The good thing is that the valve stems are a reasonable distance proud of the spring retainer base of the shim pocket so I can grind the end of the valve stems if needed. I had to grind the end of the valve stems on my old Moriwaki Z1 and had the ends tipped with wear braze so it isn't anything new.
On the cylinder I have decided to take the bare minimum off the deck. I'm not totally sure about rod stretch but at 18,000rpm it has to be considered.

[speedpro]

Bit of annoyance with what I found this afternoon. I pulled the springs off the good inlet valves on the blown up head. There wasn't any valve spring seats under the springs. I measured a few things and determined that the installed height of the valve springs was about 1.5mm too long. The spring seats out of the 3LN head are 1.1mm so if they had been installed that would have put the installed height at about the same as the 3LN springs. Still too long but a lot better. This would have been the major factor in the engine not wanting to rev much over 14,000rpm and the air/fuel going lean - valve float. Pretty annoying considering what it cost to have that head reconditioned when I first built the engine.
I was also reminded that the 2KR & 3LN springs are different. The 2KR springs have a slightly thicker wire and are about .5mm shorter. The 2KR springs are also less progressively wound at the base.
The new head is going to be assembled to specification with maybe .5mm less installed height on the valve springs just to be sure.

I posted earlier about working the combustion chamber. It has been suggested that I should smooth the sharp edges where the chamber meets the gasket surface. I'm hesitating as I really don't know about doing that. In 2-strokes the sharp edge where the squish meets the bowl is critical to making power and i wonder if the same concept applies to the 4-stroke.

What I did on my Z1 turbo was completely remove anything on the head around the combustion chamber that would have made a squish area with the flat top turbo pistons. It was one big combustion chamber, no squish at all. That engine does make enough horsepower but early on there was issues with ring lands cracking and I wonder if the detonation that probably caused it was made worse by the lack of squish area. It was sorted in the end with a methanol/petrol/toluene mix.

[Grumph]

Squish bands - I'd just break any sharp edge left after head machining. Hand scraper will do it.
Sharp edges could be trouble under high heat and load.
I set mine to just under .040in squish clearance - but I have heavier pistons than you.

Springs - the amount you can pack them is dependent on how far away from coil bind they are at full lift.
From memory, .020in was safe on mine.

The small amounts you've cleaned out of the chambers will have an effect on the compression ratio.
Have you measured it yet ? What are you aiming for ? This very small chamber size is probably safer at high boosts than a big area 2V so higher CR should be possible.
When I did the blown EX500, we had a pipeline into the Penske engine shop - a kiwi was doing his development.
The Cosworth turbos were the same bore size and used 9:1 com on Methanol. Good enough for us to copy.

[speedpro]

I've gone ahead and taken all the sharp edges off using the dremel and a little sanding drum. I'll probably finish it off with a bit of Wet&Dry.
Got the valve thing sorted.
1st do seats and valves
2nd check height of valve end from spring bottom, adjust so shims will be in range
3rd check spring installed height and install shims under spring base as required
4th assemble and shim for valve clearance