R/D Valvespring Head

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timbomoose · #41 Post by **timbomoose** » Fri Nov 30, 2007 3:43 pm

Could still be valve clearance tightened up. Have run into that before on a Kawasaki Bayou. When cold, compression went down was impossible to start. When warm started fine and compression was up. Ended up be valve clearance. Still could be cylinder not broken in from the used sleeve taking longer to seat. My brother has never heard of this before either, a cold motor making less compression than a warm one. Only time was with that Kawi.

cannondale27 · #42 Post by **cannondale27** » Fri Nov 30, 2007 7:33 pm

Well then that makes it easy. It's coming back out and apart. Part II coming

wayneschofield · #43 Post by **wayneschofield** » Fri Nov 30, 2007 7:39 pm

QUOTE (cannondale27 @ Nov 30 2007, 02:10 AM) <{POST_SNAPBACK}>

I have no idea. .0015-.002 clearance with .020 ring gap.1compression ring style piston.CP.We have had a few cases of these rings taking forever to break in and seat especially if synthetic oil is used on breakin.I used Dino Valvoline and this assembly oil which is supposed to promote a fast ring seat.[attachment=5121:breakin_..._Medium_.jpg]

That'll be a silicon alloy for sure, clearance much too tight for a copper alloy. You'd need about .0045" clearance on a copper alloy piston at our bore sizes. That's why they are so sloppy when cold and prone to comp loss due to piston cocking. The benefit of them is their strength in extreme use. Silicon alloys are better for their low expansion rates but they aren't as strong.

I notice Timbo mention using a used sleeve, this will make the rings take longer to bed in for sure, especially if it's an iron sleeve.

If you are using an iron sleeve you would tend to run a 'hard' faced ring, like Moly or Chrome, and in this case it's the bore that beds into the ring.
This takes much longer than if you use a hard bore surface, like Nikasil, and a soft ring, like iron, as the ring beds quickly into the bore.

All that said, your strange comp readings are likely to be valve clearances tight given the simptoms....

I've sent a box of goodies to Timbo and in it there's a pair of cams and a flywheel for you to try. I meant to put some followers in it too but I forgot and it's too late now..... bummer!

cannondale27 · #44 Post by **cannondale27** » Sat Dec 01, 2007 12:27 am

Sleeve is a Aluminum Nikasil sleeve freshly honed. I set the valve clearance at top of stock specs out of concern that they were going to tighten up. Take a look at picture of the valves. Very small seat area on them. I also was concerned that they might have been ground after coating. Was hard to tell though since coating is so close in color to the Titanium. I was always told that Titanium valves cannot be ground or lapped since once coating is removed it ruins the valve. Also am wondering if being Titanium where a stainless valve grows when hot does Titanium stay stable or even shrink?

Wayne I will get that FX head off to Timbo if you still want it. How about the crank?

Is the flywheel a lighter version?

wayneschofield · #45 Post by **wayneschofield** » Sat Dec 01, 2007 6:53 pm

QUOTE (cannondale27 @ Dec 1 2007, 12:27 AM) <{POST_SNAPBACK}>

Sleeve is a Aluminum Nikasil sleeve freshly honed.I set the valve clearance at top of stock specs out of concern that they were going to tighten up.Take a look at picture of the valves.Very small seat area on them.I also was concerned that they might have been ground after coating.Was hard to tell though since coating is so close in color to the Titanium.I was always told that Titanium valves cannot be ground or lapped since once coating is removed it ruins the valve.Also am wondering if being Titanium where a stainless valve grows when hot does Titanium stay stable or even shrink?

Wayne I will get that FX head off to Timbo if you still want it.How about the crank?

Is the flywheel a lighter version?

Gotta be very careful honing Nikasil, very thin...... What rings did you use? You have to be careful with ring selection too, as Chrome rings tend to 'pluck' material from the bore wall with Nikasil. In an engine used for relatively low hours (like a race motor..... or a 'Dale) plain iron is a good choice. It beds in quickly, is 'kind' to the bore wall and has a degree of self lubrication due to its carbon content.....

Freshly ground seats will generally close up some, regardless of material. Not generally a good idea to grind Ti valves I'm sure. Ti itself doesn't tend to get on well with a lot of other metals when movement is involved. You have to metal spray (usually aluminium) the sides of conrods so they don't rub the thrust faces away on the crank. Untreated rods will easily ruin a crank within a race season.

I have a feeling the co-efficient of expansion is about two-thirds that of stainless, give or take. The head would likely grow more than the inlets do at running temp, so their clearances should open up when hot, but the exhausts would likely expand more than the head does, given their higher running temp, so would tighten their clearances when hot. Given your simptoms, tight inlets are favourite....

You can send the crank with the head to Timbo if you don't mind, I'll ask him to check it over while he has it. It is supposed to have the Z400 and been balanced already though.....

Flywheel is one of the recent batch of prototypes and is a little heavier than stock. I doubt very much you would notice any difference given the relative weight of the crank, balance shaft, cams, gears, chain, clutch basket, plates, cover, gears, shafts, chain, axle, disk, sprocket, hubs wheels and tyres.....

Watch some genius try and say the flywheel makes his quad respond like a golf-cart...... Why not ask Derno if he noticed any difference when racing?

They can be lightened to much lighter than stock if you want to. Balance it afterwards though.

I drew on one or two of them with a marker pen to show people what I have in mind for degree markings and stuff. If yours doesn't have any markings on when you get it perhaps Timbo could send you a pic, or vice-versa.....

cannondale27 · #46 Post by **cannondale27** » Sat Dec 01, 2007 7:08 pm

Sounds good. I will do some back to back testing of stock-vs-your flywheel. I think Derno did say he could tell a difference. We will see.

wayneschofield · #47 Post by **wayneschofield** » Sat Dec 01, 2007 7:18 pm

QUOTE (cannondale27 @ Dec 1 2007, 07:08 PM) <{POST_SNAPBACK}>

Sounds good.I will do some back to back testing of stock-vs-your flywheel.I think Derno did say he could tell a difference.We will see.

Part of the reason the stock one is more responsive could be that the outer half of it spins freely on the inner.....

cannondale27 · #48 Post by **cannondale27** » Sat Dec 01, 2007 7:36 pm

Hey now thats a idea! Have a flywheel that at low rpm whole thing spins and high rpm just center

cannondale27 · #49 Post by **cannondale27** » Sun Dec 23, 2007 10:45 pm

Update:
Got motor out and started checks.1.5hrs on motor.

A+ Valve Clearance is exactly where it was upon assembly

A+ cams are perfect no signs of valve float even with single valvesprings

F Timbos experimental Bucket coating is a No go.Decomp made a wierd wear pattern.One marked IW has a line which it is gone and transfered onto cam.Could have been some aluminum on cam from vice soft jaws,coating too thin or poorly applied.Will be analyzed by coating place to see what is up.So far R&D Buckets are all that we can surely recommend.Will try again though.
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peterock · #50 Post by **peterock** » Sun Dec 23, 2007 11:35 pm

I'm surprised the coating came off that quick. At least we know. That is the same wear pattern that was on my stock buckets.