AHRMA Vintage Superbike Middleweight Racer

Oh, you don't want to know.

Nah, but actually, the wife has some smell sensitivity so it's easier to do crap in the cold than bring it inside.

My wife has a smell sensitivity too, but i just blame it on the dog. :laugh:

Been slowly doing some cleaning and measuring.

The head is mostly cleaned - need to get some bottle-brush type brushes to finish the intake ports and something to dissolve the carbon for the exhaust ports. Soaking the head in a hot (i.e. hot water heater hot) pinesol/laundry detergent bath seemed to get most of the grit and grime out of the ports - things look much better. Oiled up a valve stem right away to make sure that the guides didn't tarnish after taking it out of the bath.

I have two sets of pistons because I wasn't sure how the ones I pulled out were going to work - the rings on a couple were very stiff/stuck and two of them have one circlip I can't remove. The hot bath freed up the rings nicely so I'm not sure that was necessary.

I decided not to use the earlier 650 valve cover as I'll need to vent the crankcase and head anyways so why not use the air injection ports for this purpose. So another purchase that I didn't really need to make - at least it was cheap. I'll probably polish it up and sell it to someone in need.

Anyways, been cleaning up the sides of some the pistons and noticed that a couple have nicks and small gouges in them right at the edge of the piston crown (?) so I will try to gently smooth those out. Don't want anything to gouge the cylinders. Probably my fault from letting them knock up against something else when I moved stuff down into the basement.

Ordered a burette to measure the Compression Ratio as I plan on having the head cut down a couple hundreds. Did some playing with Engine Analyzer Pro, and even though it wasn't giving me completely accurate output, it did seem to point to needed the bigger carbs (28's) and probably the 750 cams to utilize the bigger ports/valves on the 750 head. From Larry's numbers in the past, the 26mm carbs seem like they match the flow of the 650 head better than the 24's do, so with the larger valves and ports on the 750 head I will likely want to go bigger. So I'll be shopping for a set of carbs once I get the engine back together.

I'll post some pics tonight if I get a chance to work on it some more. I need to get the cases broken down and check out the innards. I'm trying to come up with a nice measurement sheet for everything so I can document it all each year including the service limits for easy reference. Also need to get a bore gauge set - looks like HF has a nice set that I can use with my micrometer for fairly cheap.

I'm a bit overwhelmed with what needs to be done at this point. I decided to skip bracing the frame this year - not comfortable with my welding ability enough to take a torch to my only frame. Maybe if I can get a bare frame next year to practice on or I'll pay someone when I don't have so much else I need to get done.

Rambling done. Hopefully a more concise and readable message will come later this evening.

Does anyone have a rough estimate on what I should expect to pay to have the head fly cut? It will be completely disassembled before I take it in (except for the valve guides).

fly cut, refers to cutting the valve pockets into the pistons. decking, or milling, are common terms used for removing material from the heads surface. i'm not sure how much it would cost. i would guess that it would not take an hour to set op and mill the head. so if u knew the shops hourly rate, that should be close. Leon could be more help . just ring up a local shop and ask.
remember that when u remove material from the head, your timing #'s change. this can be a problem, if u add larger domed pistons and larger cams later. it causes the valves to come closer to the pistons and each other. so u re-time the cams to compensate, but now u are not running the cams at there optimum timing, so u may loose power. i'm not saying this will definitely be a problem, just be aware that doing 1 thing can affect another. if u run oversize valves, which is common when going after horsepower, then, this is definitely a problem.

What Mark is trying to say is that you may have to "flycut" your pistons after you "deck" your head.

I wouldn't worry about bracing the frame this year. The 650 frame is braced better that the big bikes anyway. Don't forget to budget for a GoPro. We all want to see the POV from your races.

i dont think he will have to in this build, Josh,with stock cams and valves, but he certainly should do the math.
i was thinking more,down the road , as the components get bigger the clearances get smaller, and decking the head will come into play for sure.

Thanks, guys. I saw someone use the fly-cut term on that 650 forum refering to head decking, guess I was wrong.

My thought for now:
650 cylinders/pistons (required for class I'm targeting)
750 head/stock valves, decked about 0.020" (need to do the math to make sure it's ok, but others have stated that's about as far as you can safely go before hitting the valves and that 0.030" is when you need to worry about interference)
750 cams, probably - I think they'll make a little more power on the upper half of the range, but if there's any chance of valve/piston tagging I may stick with the 650 cams (the lift difference was about 0.016" with a slightly longer duration and slightly different timing).
28mm carbs or 26mm carbs made larger

I'll call the local shop I know of and see what they say. Actually, I may take it in there Friday as I prefer doing that kind of stuff in person.

If I manage to scrape together the money in the future for custom pistons, I plan to get another head, have a valve job/porting work done on it. Not planning to use the head I have in that case, but thanks for the warning Mark. At that point I think I'd be going with a cam like the webcam 118 or 110 cams.

Thanks guys!

The GoPro is on the list, but unfortunately not priority. Once the bike is put together it will get numero uno (or ichiban if you prefer) status.

it sounds like u have been doing your home work. Good to hear that.

it wont be hard to figure out if u can use the 750 cams. do u have a set now ?
if u put the 650 cams in now and measure the piston to valve clearance , then make sure u have the needed clearance. this mat be a good learning exercise, if u havent done it before.
then u can figure out how much u can take off the head.

and u could do the same measurement with the 750 cams.
the problem with adding cam, is if u add too much duration. i dont think there will be a problem with the 750 cams. i'm just trying to explain the generalities of these type of changes.
cam duration is good for adding top end,but at the cost is loss of compression. then the normal addition, would be to add a taller pistons at the same time. this taller piston would gain back the compression lost by more duration, so in turn the pistons, add compression,to pick up the bottom end power,lost by adding the cams.

That was what I had picked up. Glad to have it confirmed...there's a lot of misinformation out there too, it seems.

The difference in duration was Kz650:224/229 timed at 105/110 and Kz750:240/240 timed at 105/105 according to the info I have gotten. I need to see it for it all to make sense, have a hard time visualizing the difference. You're right, I should really check my clearances before taking the head to be cut. Better get to work on the bottom end of the engine.

Hopefully the head decking will make up for some of the extra duration.

Sprung for a Kz550 6 speed transmissions - hoping it's complete - waiting for it to arrive.

Tried to do some more cleaning. Tons of gunk built up between cylinders 1 & 2 inside the cylinder casting. Going to pick up some spray on rinse off engine cleaner to hopefully make the job easier.

Cleaning piston crowns so I can try to polish them.

Started tearing into the cases - need to get the sprocket nut and rotor off first.

I feel like I'm taking forever to do this stuff - I'm amazed how quickly some guys go through all of this.

dont throw away those old base and head gaskets. use them when u take your measurements. this will give u more accurate (compressed gaskets)squish, and p to v numbers.

Have the head gasket still - the base gasket is a mess when it came up - not sure it's salvageable even for measuring.