AHRMA Vintage Superbike Middleweight Racer

I continued taking parts off of the bike last night. I found a random toggle switch connected to the left switch block and mounted in the left ear. I don't care what it was for, just more interesting stuff.





I also found that the pull side of the throttle cable appears to have been home made as you can see from the crimped end on it. I had to cut the cable to remove it from the carb.



The carbs appear to be Mikuni VM24's (measured just over 24mm on the inside diameter of the engine side of the carb throats) with an accelerator pump. I'm hoping to replace these with Mikuni VM26's from a Kz900 or VM28's from the Z1's. 29mm carbs are the maximum size that can be used for AHRMA Vintage Superbike.



I also measured the cams out of curiosity. The cams from my Kz750 motor measure almost 1mm taller than the Kz650, but I don't know quit enough to know what to measure. From what I know this means the Kz750 had a slightly higher maximum lift than the Kz650.





This is the distance I measured on both sets of cams:



The good news from the evening is that all pistons came free as I attempted to remove the head. The bad news is that the head seems to be very attached to the cylinders still. I may have to take the engine out of the frame to separate the head from the cylinders.

I managed to break a few chips off of some fins. Saved them and will JB Weld or repair properly before putting back together. Makes you feel like a noob.

DoubleDub wrote: ...found a random toggle switch connected to the left switch block and mounted in the left ear...

....

One SWAG could be an on-off switch for an always-on headlight, with the headlight's ground wire going through the toggle switch.

Or maybe a substitute for the ignition switch, by supplying battery voltage to the ignition coils through the toggle switch.

Good Fortune!

That was my thought as well. I just don't care enough to care.

DoubleDub wrote: This is the distance I measured on both sets of cams:

now measure the width of that lobe. subtract the width from the height and u have the lift .
this is the # used by manufactures to advertize the lift of a particular cam.

Thanks, Mark. When you say the width, you mean perpendicular to the current measurement, right?

I suppose duration would require a degree wheel and the cam installed (or some similar arrangement) to determine?

DoubleDub wrote: Dissection Begins

First gift – a spark plug which would not come out. Never had one break at the threads before…

try mixing trany fluid and acetone 50/50. use it as penetrating oil. best u can buy.
then drive in an easy-out and give it a good rap(to try to break the seal).

if legal, the 750 should have bigger valves.
good luck

mark1122 wrote: ...try mixing trany fluid and acetone 50/50. use it as penetrating oil. bust u can buy. then drive in an easy-out and give it a good rap(to try to break the seal)....

Could also use a propane torch to heat the engine head area surrounding the plug hole, immediately before attempting extraction.

This is supposed to help loosen female threads grip on male plug threads, as heat application should expand the aluminum head more than the steel plug threads.

And using left-hand (reverse) drill bit might also be considered.

Good Fortune!

DoubleDub wrote: Thanks, Mark. When you say the width, you mean perpendicular to the current measurement, right?

I suppose duration would require a degree wheel and the cam installed (or some similar arrangement) to determine?

Yes, thats right on both counts. OMR has a writeup in the archives i believe. it describes how to degree your cams. use that sett-up and u can see what degrees, the valves open, and close. then determine the overlap. but since these are stock cams the info should be in the manual.

If plug hole threads are imperfect after the extraction, but may contain sufficient material to be re-tapped, it's of course critical to get the tap correctly started.

Sometimes a reverse tap (aka back tap) tool provides a solution by beginning the tap at the deep end of the plug hole where the threads may be in better condition.



www.kzrider.com/forum/advsearch?q=backta...ldforums=1&catids=21

Good Fortune!

Cool, thanks. Just thought it might be a good exercise. Cam degree-ing is a bit mystical for me - doing something like that where I can visualize it all would help my comprehension.

Patton wrote: If plug hole threads are imperfect after the extraction, but may contain sufficient material to be re-tapped, it's of course critical to get the tap correctly started.

Sometimes a reverse tap (aka back tap) tool provides a solution by beginning the tap at the deep end of the plug hole where the threads may be in better condition.

Good Fortune!

I tried heat with a propane torch, but I don't really have anything at the moment to get a good grip with. All good suggestions that I will try. I'm sure this plug hole will need to be cleaned up whether with a front or back tap once I get it out.

I'm just really glad the piston wasn't frozen ... hopefully that means there wasn't a ton of corrosion. I was really scared after having to pound the pistons free in the 750 motor.

buy something like this to start with. u should be able to find a set at most auto or large hardware stores for like $10.




www.toolprice.com/category/screwextractors.spiraleasyout/

check out the legality of running the 750 head before u put any money into this 1 though.