Topic: CB750 cam tower

[mrosso]

I have a set of K1 rods, can I put those in my '76 cam towers, lose the 5mm bolts and be good to go? Or should I keep the '76 rods and just lose the bolts?

[Bill/BentON Racing]

Hondaman,you are the man,always good advice,impressed w/your knowledge of 750s.You publishing a book,I'll take 3 or 4! Like your ignition also,clever.If your 71 shafts are in good shape looks like you install and run w/out the little 5mm bolts.And personally helicoils are whats in my box,earlier I was referring to info from my techs,I was up front(mgr) when keenserts and timeserts came out.Thanks for all the great posts!! Bill

[HondaMan]

if i read that right mark, i should leave the little bolts out that keep the shaft from roatating?

I always do: I have a little box full of them, now! 

[HondaMan]

I have a set of K1 rods, can I put those in my '76 cam towers, lose the 5mm bolts and be good to go? Or should I keep the '76 rods and just lose the bolts?

IMO, those original K1 shafts are gold.
Measure them and make sure they are at least 11.94mm diameter where the rockers ride, and make sure your rockers' ID is 12.02 or less, first. You may have to replace a rocker or two, usually on the intake side where the only oil they get is from the cam lobes flipping some in their general direction.

Then use the K1 shafts, I would... 

[HondaMan]

Hondaman,you are the man,always good advice,impressed w/your knowledge of 750s.You publishing a book,I'll take 3 or 4! Like your ignition also,clever.If your 71 shafts are in good shape looks like you install and run w/out the little 5mm bolts.And personally helicoils are whats in my box,earlier I was referring to info from my techs,I was up front(mgr) when keenserts and timeserts came out.Thanks for all the great posts!! Bill

Any time (since I seem to have a lot of it right now...).
One of my friends calls this "viral marketing" because I'm giving away little pieces of the book here & there. At least it helps everyone see what the book will be like. 

[Ace]

I decided to put it back together to see if all the helicoil problems were sorted.  Ahhh no.  The same one that caused me the problems before struck again.  While screwing the bolt down I could feel and hear the helicoil rising.  Looks like I'll have to put one of those time serts or keen sert things in.  Now here is where I get the opinion of those who have used them.  The front (exhaust side) bolt that holds the cam tower down and goes through the V in the rocker arm, that the one I'm talking about.  Do I have enough surrounding metal to drill out and put time/keen sert in?

Also, which 6mm one will I need?  There are quite a few to choose from so what do you think?

I was going to try and put the helicoil in further as there looks like there is enough depth in the hole.  Torqued down to 9-10 ft lbs.  I took some photos of my cam tower setup on #1/2  exhaust side.  When it is in the middle, you can't see the groove for the oil in the rocker shaft.  On #3/4 exhaust side you can just see the edge of it.  Seems they are all different.

So could I get away with not putting in the 5mm bolts or because of the big bore kit I would be better off having them in there after I open up the oil hole on the rocker arm?  Would a drill bit be able to replace the small stone on the end of the drill?

Any other things/mods I should be looking for/doing while I have the top open and engine out?  Speed isn't everything, it's how long it takes to get there 

Yep, typically the rocker hole positions are all over the place. The grooves in the rocker shafts are pretty consistent in any given engine, but not necessarily so on their replacement parts. Since 2001 I have seen 3 different rocker shafts from Honda: the K0/K1 style allows limited rotation, the K2-K6 style with the oiling grooves allows none. If you replace them, go for the earlier ones, skip the little bolts, watch the torque on the center bolt. Make sure the shaft can rotate when done.

Better yet, get some Thomson shaft and make your own...

While you're looking at those shafts: yours show wear: find out how much, with a micrometer. More than .003" is going to cause problems because the rocker will "snap" up and down and push the oil out during the initial cam lift: if it is .0008" to .0022" or so, the oil pumps itself into the slackened side more evenly during the off-lobe cycles. These locked-down shafts wear in an egg shape, with the wider part toward the loaded (lower) side of the rocker position. You will find the wear depth on that side.The hardening is about .005" deep: wear that deep will also eat the rocker.

Measured the difference in the rocker shafts, only .001" difference in all the shafts. 

Seems the intake side rocker shaft oil grooves line up on both rocker arms but it's the exhaust ones that are out the most. 

I'll be glad when I get this engine in and running.  I'll be very happy if it doesn't leak oil from around the head.

[Ace]

One thing I forgot to add, is for the helicoil I've already drilled out 1/4 inch hole and tapped it out.  Will the timesert still work?

[bucky katt]

if i read that right mark, i should leave the little bolts out that keep the shaft from roatating?

I always do: I have a little box full of them, now! 

thanks mark, this couldnt have come at a better time! i'm putting the cam/holders/rockers back on today. i'm hoping to have the monstrosity back together and running by the end of the day!

[HondaMan]

One thing I forgot to add, is for the helicoil I've already drilled out 1/4 inch hole and tapped it out.  Will the timesert still work?

If the timesert/Keensert is that size, yes...the Keenserts I've used often had a flange on teh top that required a corresponding counterbore on the face of the hole. Are yours like that?

Also, the hole is pretty deep: do you perhaps have room to Helicoil down lower and use a longer 6mm bolt? That would be my first knee-jerk reaction to fixing this one. 

[Ace]

The helicoil I use requires drill, tap then screw in.  No tabs or the like.  It relies on enough metal being there when you retap the hole.  The one I used is 8mm long, therefore I put it down one full helicoil length below the surface so I tapped the hole down at least 16mm.  I probably could go further but I'm unsure how much metal there will be before I break through to somewhere...if at all... help needed here.  I did put some loctite on the helicoil when I put it in. 

I can get a big sert kit.  These kits are used for threads which have been previously repaired.  These kits will repair holes that were repaired by helicoil, perma-coil, uni-coil, recoil or any other simular coil style insert that has failed...or so the website claims.  Cost for this is $66 US plus postage to OZ so conversion looking at $91 Aus.

[HondaMan]

The helicoil I use requires drill, tap then screw in.  No tabs or the like.  It relies on enough metal being there when you retap the hole.  The one I used is 8mm long, therefore I put it down one full helicoil length below the surface so I tapped the hole down at least 16mm.  I probably could go further but I'm unsure how much metal there will be before I break through to somewhere...if at all... help needed here.  I did put some loctite on the helicoil when I put it in. 

I can get a big sert kit.  These kits are used for threads which have been previously repaired.  These kits will repair holes that were repaired by helicoil, perma-coil, uni-coil, recoil or any other simular coil style insert that has failed...or so the website claims.  Cost for this is $66 US plus postage to OZ so conversion looking at $91 Aus.

That casting at the bottom is about 3mm (1/8") thick, not a lot. The head surface hits, I think, the neutral area in between the cylinders. So, if it does break out, use aircraft-type sealant on the threads of the bolt when reassembling (Permatex makes this stuff, very oil resistant: it's a thick liquid with a brush applicator).

[Ace]

The helicoil I use requires drill, tap then screw in.  No tabs or the like.  It relies on enough metal being there when you retap the hole.  The one I used is 8mm long, therefore I put it down one full helicoil length below the surface so I tapped the hole down at least 16mm.  I probably could go further but I'm unsure how much metal there will be before I break through to somewhere...if at all... help needed here.  I did put some loctite on the helicoil when I put it in. 

I can get a big sert kit.  These kits are used for threads which have been previously repaired.  These kits will repair holes that were repaired by helicoil, perma-coil, uni-coil, recoil or any other simular coil style insert that has failed...or so the website claims.  Cost for this is $66 US plus postage to OZ so conversion looking at $91 Aus.

That casting at the bottom is about 3mm (1/8") thick, not a lot. The head surface hits, I think, the neutral area in between the cylinders. So, if it does break out, use aircraft-type sealant on the threads of the bolt when reassembling (Permatex makes this stuff, very oil resistant: it's a thick liquid with a brush applicator).

I don't suppose anyone knows the name of the stuff?  Seems like a handy bit of stuff to have. 

[HondaMan]

It's just Permatex "Aviation Gasket Sealant". I get it at Checker Auto, here in CO. Don't leave the can open long: the volatile part evaporates quickly and you have to add acetone or lacquer thinner to liquify it again.