Topic: Phaedrus: CB750 RestoMod - Update: 09/23/21 w/ new video

[MRieck]

A strange question, maybe: when does the intake valve (actually) open (1mm lift) with this cam?
And, what does the air intake system look like?

At zero lash I'd guess about 24 or so....typical of a 125-70 Megacycle which it is modeled after. It is ground with 105 LC if I remember correctly

[CBJoe]

Gents...found the timing numbers we settled on when the top end was done.  If you’ve got any better suggestions let us know.  At some point we’ll be taking it apart to fix what we think is a leaky puck causing some oil weeping (too much to ignore) on the cylinder fins.  Doesn't appear to be headgasket because evidence of oil only shows midway down the cylinder.

CX-7  Measured with .005" Lash

Intake                   Exhaust
Open: 19*BTC       Open: 53*BBC
Close: 55*ABC      Close: 17* ATC

LobeCenter: 108    LobeCenter: 108




Sent from my iPhone using Tapatalk

[HondaMan]

Gents...found the timing numbers we settled on when the top end was done.  If you’ve got any better suggestions let us know.  At some point we’ll be taking it apart to fix what we think is a leaky puck causing some oil weeping (too much to ignore) on the cylinder fins.  Doesn't appear to be headgasket because evidence of oil only shows midway down the cylinder.

CX-7  Measured with .005" Lash

Intake                   Exhaust
Open: 19*BTC       Open: 53*BBC
Close: 55*ABC      Close: 17* ATC

LobeCenter: 108    LobeCenter: 108




Sent from my iPhone using Tapatalk

IIRC, Ron was assembling this engine at about the time when we were all getting those too-thin head pucks in gasket kits. You can get correct ones today from PartsNmore. The difference is about 0.5mm thickness, just enough to make them leak when hot. The incorrect ones fit later Kawi and Suzy engines, I discovered, perfectly.

The pods: they mostly affect the drive-ability ranges between 1500 and 4000 RPM, making it rich until the upper end of that range. Above that [engine] speed there isn't a lot of difference between pods and normal airboxes until about 7000 RPM, when the pods win out a little bit, but at the cost of leaner mixtures at the top as compared to the middle RPM range.

Is the fuel feed a 2-hose type, and not the restrictive 1-hose version? And, could the [next] run be made with the tank's gas cap cracked open?

The 'dip' in the middle RPM range looked a lot like the 125-00 Megacycle cams with real high (12:1) compression pistons that I remember from my [long ago...] racing days. In the end, the solution for that became retarding the cam slightly (the exhaust valve allowed for this) to reduce the efficiency of mixing at that RPM range, making it more 'even' when riding thru it. On the dyno this doesn't matter much: in a 2-3 shift in a roadtrack duel it mattered a lot(!). This also pushed the upper RPM a bit higher, more like 8500 instead of the 7200 peak we'd found prior. This was pushing thru stock mufflers (old-style "production" racing rules).

[CBJoe]

Hey Mark....I remember Ron specifically mentioning that we used the Pucks as directed by you...so would assume that they are correct.  We'll see when we pull it back...who knows.  Maybe we pinched on on install.

I think that the plan right now is to take back to the Dyno with the fresh set of plugs, cleaned and readjusted carbs and see the numbers.  After that take a look at exhaust and remaining factors. 

[MCRider]

Hey Mark....I remember Ron specifically mentioning that we used the Pucks as directed by you...so would assume that they are correct.  We'll see when we pull it back...who knows.  Maybe we pinched on on install.

I think that the plan right now is to take back to the Dyno with the fresh set of plugs, cleaned and readjusted carbs and see the numbers.  After that take a look at exhaust and remaining factors.

I'm pretty sure the too thin issue was front and center, and I thought I got them from Mark HondaMan. But who knows?  I always say I'm going to keep better notes, but I never do.

[PeWe]

Sealer on the head surface where pucks sits, dry a little before mounting the pucks helps. Permatex Aviation No. 3 is sticky and seal fine.

[MCRider]

Sealer on the head surface where pucks sits, dry a little before mounting the pucks helps. Permatex Aviation No. 3 is sticky and seal fine.

I could've sworn that's what we did. But we'll see.

[PeWe]

I reused the old rubber pucks back in the 80' s. Compensated with sealer.
Same the last years if taking it apart soon after the new pucks are installed. As long as the rubber feel fresh.

[CBJoe]

Ok...Its time to play whats that shyte in the oil pan.  Ron and Bruce dropped the pan last week for a general looksee and found all this black hard rubber shreds in the pan.  The bits are hard...kind of like Id expect from a chain roller but not sure.  Primary Chain Roller looks good.  This motor has the KA Performance Slipper Tensioner...and its material is white...so its not that right?  To be honest this could be gasket debris back from before the last cylinder bore/refresh occurred. 



We also went ahead and started digging down to the pucks under the cam towers.  Ron may have found the smoking gun there....one of the cylinder head acorn nuts is contacting the cam tower and therefore possibly preventing it from completely seating....I think these nuts were from a later F engine type.  No sign of debris on the top end.




Once the cam towers are out we'll get a better look down the tunnel at the front and rear chain sliders. Any other thoughts on what that material debris is?  Since there was not a spec of that material on the top end...i'm thinking it could just be old silicone gasket material used from the last time the cases were splilt.

Cheers, Joe

[Terry in Australia]

I'm interested in why Ron has those acorn nuts there, and not just regular nuts as per Honda's design? That black stuff could be bits of rubber from the cush drive in the mainshaft sprocket assembly, it could be coming apart due to the "shock" of some hard pulls on the dyno?

[Jerry Rxman Griffin aka MuthaF'er]

Is that acorn nut torqued down/enough to seat it further? I'm with Terry Slim here. Yeah, that stuff isn't gasket.

[MCRider]

Is that acorn nut torqued down/enough to seat it further? I'm with Terry Slim here. Yeah, that stuff isn't gasket.

Terry and Jerry:
I was encouraged by a builder of known repute to use the acorn nuts and copper washers there as Honda did in later models (Maybe just the F?). Could be there is a compatibility issue with old cam bearings and acorn nuts. Easy to fix with a Dremel, but there is definitely no clearance as it stands. The green card stock won't slip in between. Haven't tried a .001 feeler gauge, but I doubt it will fit.

The left side has clearance. And they won't stand any more torque, IMO.

The nuts are torqued to at least

[MCRider]

As to what the black stuff is... could be from the cush drive.  I used a fairly fresh one from eBay, but low mileage ain't the same as low age.   

[Jerry Rxman Griffin aka MuthaF'er]

Yeah but..... are the acorns bottomed out? with the stud hitting the end affecting the torque figure? Just use normal nuts.

[MCRider]

Yeah but..... are the acorns bottomed out? with the stud hitting the end affecting the torque figure? Just use normal nuts.

I see what you're saying. We'll check that out. I used 13mm hex ti nuts on the rest. I should have some around to replace the acorns. That would settle it.

[HondaMan]

Hey Mark....I remember Ron specifically mentioning that we used the Pucks as directed by you...so would assume that they are correct.  We'll see when we pull it back...who knows.  Maybe we pinched on on install.

I think that the plan right now is to take back to the Dyno with the fresh set of plugs, cleaned and readjusted carbs and see the numbers.  After that take a look at exhaust and remaining factors.

I'm pretty sure the too thin issue was front and center, and I thought I got them from Mark HondaMan. But who knows?  I always say I'm going to keep better notes, but I never do.

I've not carried those pucks (wish I did!), don't know where I could buy 1000 of them (but would...).

[HondaMan]

We also went ahead and started digging down to the pucks under the cam towers.  Ron may have found the smoking gun there....one of the cylinder head acorn nuts is contacting the cam tower and therefore possibly preventing it from completely seating....I think these nuts were from a later F engine type.  No sign of debris on the top end.




Once the cam towers are out we'll get a better look down the tunnel at the front and rear chain sliders. Any other thoughts on what that material debris is?  Since there was not a spec of that material on the top end...i'm thinking it could just be old silicone gasket material used from the last time the cases were splilt.

Cheers, Joe

OH, YEAH! Cobwebs are clearing...I got an F2 about 8 years ago that had a milled cylinder deck (0.010") and head deck (0.020") and was an oily mess after 100 miles. The owner was disgusted with it, brought it to me instead. Had HD studs, 836cc pistons....the resulting studs were so tall that those 4 crowned head nuts were torqued against the ends of those studs, but the hard washers under all 4 were moveable with a screwdriver tip. I added 12 extra hard washers on the studs and changed to all 'normal' type head nuts (to clear the cam towers), torqued it down and cleaned it, presto, became his hero...

[MRieck]

 I use the acorn nuts with copper washers to prevent oil from leaking past the threads. Those 2 studs are in the oil feed bores. I have blown air into the oil pressure sender hole and watched oil bubble up past the threads. You have to measure the exposed portion of the stud and check for tower interference......some grinding easily fixes any interference issues.
 Those are OEM parts for the unused F2 oil return bores.

[754]

Easy check run the nut down with light pressure till it stops then try to slide washer under nut flange, see what you got..
 If you torqued it , what did not clear, the washer ?

[MCRider]

Easy check run the nut down with light pressure till it stops then try to slide washer under bad see what you got..
 If you torqued it , what did not clear, the washer ?
[/quote

Mike: Yes clearance between the cap head and the bearing block will be easy to obtain by grinding. But we went with some HD nuts with 13mm hex and the copper washers.

754: yes the nuts were torqued with freedom to spare. Copper washer was crushed. It was the top of the cap nut, that kept the Bearing block from seating, we think. Anyway we have now eliminated the variable.

[PeWe]

I have also learned to really verify that the cam holders are seated all the way down to head.
I saw the cam bearing area to have extra scuff marks and found that it was not seated all the way. A thread insert had came up a liitle after removal of cam holders which I did not notice at assembly. Not much, maybe 0.1- 0.3 mm.
I tightened the thread insert (time sert) and always check them after that. This was an old one.
Those I mount get Loctite
272 ( red high strenght) or the stronger 638.

[MCRider]

After reinstalling the cam and rockers, we took it apart again for various reasons and pulled the threads out of at least 2 maybe 5 holes. So we signed up for helicoil 101. Any comments?

[MRieck]

After reinstalling the cam and rockers, we took it apart again for various reasons and pulled the threads out of at least 2 maybe 5 holes. So we signed up for helicoil 101. Any comments?

It happens Ron....to you, to me and many others. I have put many Helicoils in heads with no problems. There are some tricks. Finish tapping with a bottoming STI tap after using the tapered tap to avoid pinching the insert. I use some cutting fluid on the tapered tap. I also put a small amount of hi temp threadlocking compound on the inserts.

[MCRider]

After reinstalling the cam and rockers, we took it apart again for various reasons and pulled the threads out of at least 2 maybe 5 holes. So we signed up for helicoil 101. Any comments?

It happens Ron....to you, to me and many others. I have put many Helicoils in heads with no problems. There are some tricks. Finish tapping with a bottoming STI tap after using the tapered tap to avoid pinching the insert. I use some cutting fluid on the tapered tap. I also put a small amount of hi temp threadlocking compound on the inserts.

Thx Mike and for the PM. Gonna experiment this AM on an old head... if I still have it. 

[MCRider]

Had a nice morning in the shop today. We (Me, Bruce, and Ed Spengeman showed up, long time no see) were going to practice setting some helicoils. Remember we stripped 2 holes on the notorious cam bearing block hold down to the head holes.  But we realized that CBJoe took the helicoil kit home with him last week and called in today that he needed some home time after a rough week. So we decided to try an old farkle for stripped threads. I know I heard of this 25+ years ago, but can't swear that I ever did it. But I think I did, but used a 1/4-20 bolt. It worked, but I realized that one should really use a 1/4-28. For what you say? Fast forward 20+ years to today.

A 1/4-28 of the appropriate length, is almost a match for a 6mm x 1 bolt. It is slightly larger diameter, but still fits in the holes, and slightly coarser thread pitch. So since the 6mm threads are already removed, came out with the bolt, one doesn't need to drill anymore. Just take a 1/4-28 tap and make new threads in the old hole. Worked like a champ! (Let's hope).  The hole in question was the front main cam block holder downer. Was so easy we went ahead and did the back one as well. Both tightened down to 100 in/lbs.

We still have one to  do. Its the right rear cam bearing cap bolt. It has the dowel in it as well. The 1/4-28 fits through the dowel OK. But the head on the bolt is an 11mm (7/16 actually) and there isn't enough room to drop a socket on it. Maybe an open end will work. Or we'll use a helicoil.