Topic: which head is on my 750 F2?? Big bore question...

[koendd]

So last night had a go ad changing the pucks under the camshaft since they were leaking pretty bad (specially between plug 3&4)

Did everything by the book...


first problem, the 2 bolts that hold the camchain sprocket were rounded by a PO so a spanner size 10 wouldn't grab it... Got one of with a Vise-grip, but the other we had to grind of with a mini air belt sander, luckily all went ok and it got it out without damaging the chain or sprocket...


after that we went to the camshaft.. According to the book I had to undo the 3 bolts that hold the camshaft holder, funny enough I only had one...


and to make it even stranger, I was able to turn one bolt out by hand... clearly someone had stripped the thread in the head...

after we got everything out inspected the seat for the cam...


this is the worst one... would I be able to use this or is this beyond usable? It's quit badly "engraved" by the cam, though the cam itself is ok (what would be logical).
This one is at the place where the bolt was loose. Allready put a helicoil in there by the way

And then there's the mistery head, clearly it's not an F2 head? which one would it be? K0-K1 since it has only one bolt?

here's some more pictures:









thanks for the help!

[754]

You don't need a head, right?you can helicoil that one as far as I can tell.

[koendd]

Allready hellicoiled it yesterday, but was just wondering if that camshaft holder can still be used and what year/model my engine is from...

[754]

Your cam looks burnt up, how bad is the lobes and journals?

[koendd]

will check and measure them right away, and will try to take better pics...

to bad cause It ran really good actually... just the oil leak bothered me.

is this a K0/1 head or complete K0/1 engine?

http://www.hondachopper.com/engine/engine_timeline/timeline.html

checked this but there's no notion of GE like mine says...

[754]

It's not an early engine, it has the  xtra letter on the serial number, I think a Europe thing. I think I have the same head on either an F Or an Automatic. 750 motor..but not sure what they came on.....
Looks like Few burnt cam lobes, that and the journal indicate, may be an oil supply problem to the cam area.

[Jerry Rxman Griffin aka MuthaF'er]

Frank, that's NOT a F/F1 -392 head. It is a -300 head.

My thinking is the GE stands for General Export as it's been discussed. Where are you located as your info does not contain that?

And there is nothing F2 about your engine OR your bike. From the -300 head (K0 - K6), the older style cam sprocket (not lightened with holes), the single bolt in the cam towers as you mention, to the serial number.

Go to CMSNL.com  to look up that number and let us know what your mystery engine is.   

[Don R]

If the cam holder was loose that could explain a lack of oil, it flows through an o ring under the cam holder. It could have leaked out underneath.

[PeWe]

Complete set of cam holders with cam cap caps in much better shape can be found on eBay. I have bought 2 sets just for sure. Last one from a 78 low miler complete with cam. Shipped from US to Europe.

[koendd]

Frank, that's NOT a F/F1 -392 head. It is a -300 head.

My thinking is the GE stands for General Export as it's been discussed. Where are you located as your info does not contain that?

And there is nothing F2 about your engine OR your bike. From the -300 head (K0 - K6), the older style cam sprocket (not lightened with holes), the single bolt in the cam towers as you mention, to the serial number.

Go to CMSNL.com  to look up that number and let us know what your mystery engine is.

well the bike is in fact and F2 bought it with comstars etc but changed to F1 forks and wheels that's why it doesn't look like one anymore (which was the whole point )

And I live in Belgium, but I bought the bike in Holland/The Netherlands.

And ideed, noticed that the chain sprocket was different from what I saw in the manual as well.
They sure messed around with this one...

Measered the camshaft, I assume camshaft stayed the same with K and F motors? Anyways, here's what I found compared to the minimum they should be.
These are from the worst part of the shaft, the other ones aren't as bed but still under the service level...
This was the parts of the camshaft that was able to move due to the loose bolt.

EX 1.4025 with the minimum being 1.4118 Inch
IN 1.3795 with the minimum being 1.3912 Inch

the journals on the other hand are still above service level so are the insides of the rockerarms but then again, the ones on the bad side of the cam are quit worn.

Thing I'll to find myself a new/good used set of rockers/cam holder and cam then...

[Davidov]

I'm not as knowledgeable as some of the folks here...but I have a hypothesis.

If the engine is F2 below the head, the oil supply passages run up through the cylinder studs.
Wouldn't a 300 K head cause oil supply issues to the cam?

http://forums.sohc4.net/index.php?topic=76757.msg1600428#msg1600428

[Old Scrambler]

Just thinking out-loud here..................F2 (black motor) with K pistons and K head with a cam-tower from an early K motor. May have the F2 cam. Would be nice to know the piston profile......................Ron-R & DAVIDOV have likely identified the oil problem. The F2 cam has now been identified in several motors to contribute to 'pulled' threads.............but may have been caused by over-torquing by the motor-builder.

I'm not sure if the domed-nuts were used, but would pull the head to follow the oil-passages and proper o-rings.   

[krusty]

Engine number is F2 and is earlier than my 78 F2 with CB750GE engine. Maybe we should be calling them 750Gs?

[koendd]

jep, lower engine is F2, just found this:


think I'll pull the head and see what pistons are in there...

[koendd]

Engine number is F2 and is earlier than my 78 F2 with CB750GE engine. Maybe we should be calling them 750Gs?

correct, my F2 is from 77

[Jerry Rxman Griffin aka MuthaF'er]

Camshafts changed a few times.

This is US info by the way. Early K's, mid-K's (real pissy), early F's (F0/F1 US and K7/K8. These had 392 heads) and late F's (F2/F3 which had big valve 410 heads)

[koendd]

Camshafts changed a few times.

This is US info by the way. Early K's, mid-K's (real pissy), early F's (F0/F1 US and K7/K8. These had 392 heads) and late F's (F2/F3 which had big valve 410 heads)

so the mid K would be the one I have now?

found a complete F2 head for about 100 dollar or a complete K6  in parts for just 80 dollar but will first find out what I'm working with...

[754]

Get a light in thru the plug hole to check dome on pistons.

[koendd]

Get a light in thru the plug hole to check dome on pistons.

all I saw was black and oil really...

so tilted the head af today. Let me know what you think, looks like the exhaust valves have been hitting the pistons??










so who can tell me what cilinders/pistons I have? by the way, cilinders didn't seem to have and damage or marks. Could even still see some honing marks...

[Old Scrambler]

Looks like stock F2-3 pistons. The valves are VERY close to hitting the pistons (if not barely touching when the motor is 'hot') and the white exhaust valves indicate a lean condition or detonation. Compression must be higher than 11 to 1 with standard thickness gaskets.

What size (diameter) are the valves?  The flat faces indicate possible aftermarket units.

Tell us about any markings on the cam.........especially if it has a small horizontal raised bar between #3 and the cam-sprocket.

How tight are the valve-springs?.........i.e........are they F2-3 which are stronger then the K units. Standard retainers?

 

[koendd]

I do think they did touch them because of the clean surface on the pistons since they are all black for most part (there's some grooving on the top as well).

Will measure the valves tonight aswell as the things you suggest on the cam.

But since the pistons are F2, I'll buy a complete F2 head and rebuild that one.
I won't use this one anymore...

[Davidov]

Wow, it definately looks like valve-to-piston contact happened.

Also, it looks like you have a few too many o-rings between the cylinder jugs and the crankcase?

[754]

You can notch those pistons and use with your head.

[Old Scrambler]

Depends on your budget...............Frank's suggestion is workable if you are careful and consistent.  Acquiring and then rebuilding a 410 head can be difficult and expensive

To improve the valve-reliefs................remove the pistons and measure the dome thickness to be sure there is sufficient metal remaining after milling to the desired depth. Assume gentle 'kissing' at this point............I would think you would want 20-thou or more of clearance...about 0.5mm.

If your cam is an F2 unit, you may be able to gain a good portion of the needed clearance with a stock K cam and only minor valve pocket machining.  The difficult part of the valve-relief machining is expanding the perimeter of the relief in direct proportion to how the valve will 'fit' into the piston with ample clearance at the radial edge of the pocket. 

[koendd]

Looks like stock F2-3 pistons. The valves are VERY close to hitting the pistons (if not barely touching when the motor is 'hot') and the white exhaust valves indicate a lean condition or detonation. Compression must be higher than 11 to 1 with standard thickness gaskets.

What size (diameter) are the valves?  The flat faces indicate possible aftermarket units.

Tell us about any markings on the cam.........especially if it has a small horizontal raised bar between #3 and the cam-sprocket.

How tight are the valve-springs?.........i.e........are they F2-3 which are stronger then the K units. Standard retainers?

did some measuring:

valves: 32 (1.259 inch) and 28mm  (1.102 inch)

on the camshaft I found R3

no idea about the valve springs though, looks standard to me though but who am I