Topic: Korvens "mystery" engine check/rebuild (mostly pictures)

[Korven]

So the story behind this is that i came over an engine someone had rebuilt but never started, so there might be some gamble to whats inside. There was not much info about it other than "built by a friend" The head was supposedly ported by motospeed (Local shop from around where member PEWE recides i think. Since i have no idea what separates a good port from a bad one, i have no idea if this is true. I am gonna tear down slowly through this engine and try to learn a thing or two. According to previous owner the spark plugs hit the pistons so someone has tried to add some copper washers to get them further up. im not sure if this is a good practice. Its standard D8EAs. Also sorry for all the large images, not sure if there is some easy resize options here in the forum.




As you can see its prepared for a pullstarted. I did attach my Corddrill after squrting some oil on the cam lobes to try and get a psi reading. It got 150psi but the corddrill gave up after that and started to smell funny. That seems very promising for a engine that has never been run.



650 oilpump, The cover had a pretty ugly square hole cut to fit. Perhaps some mesh of some sort to cover this up later on?







It got two ports for ventilation made. What makes me curious about this engine is the fact that its a k3 block with a K1 pushrod clutch setup. I have never worked on a K3 before. its missing that Screw that hold the Shiftdrum so not sure what to expect inside below.



Its got that upgraded rocker arm cover, thats great.

[Korven]

Seems like the bore is 60mm that i think equals to roughly 575cc, Wonder if that spells problems with warpage. The cam is a original that has had some work on. Valves and springs all seem new. slightly magnetic around the edges, not sure if thats a washer on the other side. Its one of those heavy duty chains that i had in my other engine, so thats good. I marked the cam position just incase, How do i time a cam that i no camcard on later? I guess i need to play around with some clearances and clay before i dig any deeper just to where we are at. Not sure if anyone reconise the studs that has been used. They arent oem atleast but doesnt look like the heavy duty studs ive used in the past. these are more oem style but not sure if they are any harder?

[Korven]

Not sure how you think this porting looks? a friend told me it needs to be smoothed out. People seem to differ here about how it should be done.


Looks like bigger valves, marked KPMI



Starting to get it all back together for measurings with clay. not sure how to time the cam really. ive marked the spot where it was when i removed it, it was 10 degrees off from standard (True TDC). im guessing just put it standard then i have to figure out the cam profile. seems a bit tricky.

[Korven]

Did some measurments today. this took me almost all day, inexperienced but wanting to learn and do it the correct way. This is what i came up with.

total lift is 8.50-8.52mm on intake (0.335) on intake and a little less on exhaust 8.39.

All measurements at 0 valvelash and at 0.05inch or 1.27mm

In open 10.5 BTDC
    close 45    ATDC

intake Lobe center = 107.5
Duration at 0.05 is 235degrees and 244deg at 0.04 (wanted to compare it to my yoshimura camcard)

Ex open 46 BTDC
     close 4  ATDC

intake lobe center =  111degrees
Duration 230deg at 0.05

This gives a centerline of 109.25deg.


Think i went a little overboard with the clay but i wanted to measure the sparkplugs aswell.



I only did some quick measurments. There is less clearance on the inlet vale than on the exhaust. seems to be 1mm - 1.2mm. (How do you guys measure this for most accuracy? i do it with the digitalfeeler gauge bottom end). Defo a bit on the low side
Exhaust on the other hand seems to be 3-3.2mm.

I wonder if i should retard the cam a bit.



This is the measurements for the sparkplug. I added the sparkplug with the copper washer on cyl 1 and 2. (i did 3 n 4 without) but there seems to be some clearance there.

[PeWe]

Motospeed is located less than 3km from my house
That shop ported my CB750 head 1983. Restored it 2014 and  installed 5mm valve kit 2016.
Made another head last year, more port job.
The tuning guy/ mechanic Ove is still working there.

Maybe he will retire later this year. So you have time to make a visit. He work Monday- half Wednesday.
You might pass their new shop when driving thru going a little bit north.
They tuned many bikes and sold Russ Collins, Action Fours and Vance & Hines parts.  Did work like building Cobra spec engines. Owner Thomas Klarkner had Swedish records of Pro Stock Bike,10 years until he quit racing 1979-88.

Good ported head by Ove then!

[Hasenkopf]

that's interesting but I'd be ashamed of that one port! lol.

[Korven]

that's interesting but I'd be ashamed of that one port! lol.

Didn't quite catch you there, are you saying the porting is bad? I myself know very little about fluid and air mechanics.