Topic: Re: Bigsam302's 76 CB750F (915cc): Project Helen – Running Report!

[Bigsam302]

Thank you very much. On my last (and first ever) rebuild I didn't seal the pucks AT ALL. I had special "oil pants" for my first 300 miles before I couldn't take it anymore...

No problem at all!  Glad I'm not the only one! 

[SKTP]

I'm sure you've seen this thread...but, just in case

http://forums.sohc4.net/index.php?topic=107040.0

[Bigsam302]

I'm sure you've seen this thread...but, just in case

http://forums.sohc4.net/index.php?topic=107040.0

Thanks for the link.  Yes, I am very familiar with that post.  I wish that I had found it before I started assembling my top end!

[edwardmorris]

Sam, those cam tower studs only need to be packed with high temp teflon paste IFF they were removed in the first place. That may not be where the leak is if they were left untouched, however no harm in doing it anyway if you're pulling the head.

Hondabond around the return holes is pretty much required, your's is the second bike I've seen recently that has had oil leaking after the rebuild. In Dino's vids, IINM, he also added Hondabond to the o-rings for the oil feed holes, which to me seemed risky. Proper thickness o-ring is all you need to prevent leaks around the oil feed line, so I didn't use any on those.

Ed,

I'm not taking any more chances.  When I sent the head off to Cycle X, it was completely stripped.  Everything was removed.  I put the studs back in myself.  Since I have to take it off again, I'm going to do it just in case.

I just got off of the phone with Ken from Cycle X.  I had to order new head gaskets and stuff.  I was telling him about the leaks and he told me that he just recently started putting Hondabond around the O-rings just like Dino did in his video.  I watched his video again today and I realized another stupid rookie mistake that I made.  I didn't use Hondabond on my pucks.  I used this Permatex liquid gasket stuff and I'm wondering if this was the main cause of my leak.   

Sam

I didn't use Hondabond on the pucks either, I used Permatex #2 non hardening sealant and (knock on wood) things are holding. Hylomar is another good option. You'll know for sure what the cause is once you've definitively identified WHERE the oil is leaking form (baby powder test). I'd be very careful if you chose to use any sealant on the oil feed line o-rings, very easy for some of it to dislodge and clog up the tiny metering holes potentially causing a top-end disaster. I still think that proper thickness o-rings are all you need there.

[madmtnmotors]

While you're addressing the studs for the cam bearing caps, take a few seconds to assess the other side of the cam bearing cap as well (where the bolt goes, not the stud). The studs, as you now know, have bottomless holes (i.e. exposed to atmosphere) and are best dealt with by applying thread sealer to the studs to prevent weeping oil. The "bolt side" of the cam bearing caps on the other hand, were originally designed fully enclosed. This was important because the oil feed to the cam bearings passes through this bolt bore in the cam cradle. I had a 78 CB750F where some goob of a PO used the longer cam tower bolt at the bearing cap bolt location. When tightened down hard enough this can "punch through" the bottom of the bolt bore and expose the bottom of these bolts to the atmosphere as well. These bolts have the added distinction, as described earlier, as having oil under pressure behind them, which I can attest will cause a profuse leak.

The simple check for this is to simply select your favorite fluid of choice (motor oil works) and make sure these four bearing cap bolt holes will hold oil. If the oil runs out the bottom onto the head below you will have leaks unless it is addressed. I only discovered this by accident after having already removed the head and installed all new gaskets and seals. While staring at the head, contemplating removing the head yet again, I noticed one of the bolt holes described had not filled up with oil (a lot of oil on the head after it's been run) and upon further inspection realized the bottom of this hole had been "punched out". Further sleuthing revealed the cam bearing oil feed passing through this bolt bore in the cam tower. I resolved this by using a stud at this location too, along with a copious amount of thread sealer. This permitted installation of the stud before installing the cam tower. I considered just using thread sealer on the bolt, but was concerned about packing the oil feed path with thread sealer while inserting the bolt. Also, it gives the next guy a clue and hopefully will make him say "why did he do that?".

[Bigsam302]

I didn't use Hondabond on the pucks either, I used Permatex #2 non hardening sealant and (knock on wood) things are holding. Hylomar is another good option. You'll know for sure what the cause is once you've definitively identified WHERE the oil is leaking form (baby powder test). I'd be very careful if you chose to use any sealant on the oil feed line o-rings, very easy for some of it to dislodge and clog up the tiny metering holes potentially causing a top-end disaster. I still think that proper thickness o-rings are all you need there.

Ed, that's a good point as well.  I will definitely check the thickness of my new O-rings when they arrive.

[Bigsam302]

While you're addressing the studs for the cam bearing caps, take a few seconds to assess the other side of the cam bearing cap as well (where the bolt goes, not the stud). The studs, as you now know, have bottomless holes (i.e. exposed to atmosphere) and are best dealt with by applying thread sealer to the studs to prevent weeping oil. The "bolt side" of the cam bearing caps on the other hand, were originally designed fully enclosed. This was important because the oil feed to the cam bearings passes through this bolt bore in the cam cradle. I had a 78 CB750F where some goob of a PO used the longer cam tower bolt at the bearing cap bolt location. When tightened down hard enough this can "punch through" the bottom of the bolt bore and expose the bottom of these bolts to the atmosphere as well. These bolts have the added distinction, as described earlier, as having oil under pressure behind them, which I can attest will cause a profuse leak.

The simple check for this is to simply select your favorite fluid of choice (motor oil works) and make sure these four bearing cap bolt holes will hold oil. If the oil runs out the bottom onto the head below you will have leaks unless it is addressed. I only discovered this by accident after having already removed the head and installed all new gaskets and seals. While staring at the head, contemplating removing the head yet again, I noticed one of the bolt holes described had not filled up with oil (a lot of oil on the head after it's been run) and upon further inspection realized the bottom of this hole had been "punched out". Further sleuthing revealed the cam bearing oil feed passing through this bolt bore in the cam tower. I resolved this by using a stud at this location too, along with a copious amount of thread sealer. This permitted installation of the stud before installing the cam tower. I considered just using thread sealer on the bolt, but was concerned about packing the oil feed path with thread sealer while inserting the bolt. Also, it gives the next guy a clue and hopefully will make him say "why did he do that?".

That is a great tip!  Thank you.  I will definitely check this out as well.

[Bigsam302]

There's nothing like being stuck on the side of the road after my antigravity battery exploded today. The scariest thing is sitting here fanning my bike and hoping that it doesn't catch on fire.

Sent from my Nexus 5X using Tapatalk

[SOHC4 Cafe Racer Fan]

Freakin' Anti-Gravity strikes AGAIN! Those and Ballistic have been known to do this.  Check your charging system for shorts and you should probably replace your reg/rec (even if you had a solid state before to a new one).  You might want to go with a Shorai.

[Bigsam302]

Freakin' Anti-Gravity strikes AGAIN! Those and Ballistic have been known to do this.  Check your charging system for shorts and you should probably replace your reg/rec (even if you had a solid state before to a new one).  You might want to go with a Shorai.

Yeah I hear you! I think that I am going to make the switch to Shoria in the near future.










Sent from my Nexus 5X using Tapatalk

[scottly]

Out of curiosity, what regulator were you using?

[Bigsam302]

Out of curiosity, what regulator were you using?

I'm using a new Rick's Motorsports reg/rec

Sent from my Nexus 5X using Tapatalk

[scottly]

Thanks. BTW, the battery melt-down shouldn't have caused any damage to your charging system.

[Bigsam302]

Thanks. BTW, the battery melt-down shouldn't have caused any damage to your charging system.

Thanks!  As soon as I got my bike home, I went to a local Motorcycle shop and picked up a regular no-maintenance battery, plugged in, and it fired right up.  I'll be back out tomorrow doing some test riding.

[scottly]

Hey Cal, the only thing I noticed on the positive bike wires is the split shrink tubing on the right side wire. It looks like the lug is very close to touching something, but I don't see any evidence of arcing?
I'm guessing the insulation on the inter-cell connections failed, shorting the battery internally. 

[Jerry Rxman Griffin aka MuthaF'er]

Check the charging output just in case??

[SOHC4 Cafe Racer Fan]

Back from the dead, Sam?

[madmtnmotors]

So what was the source of the oil leaks?

[Bigsam302]

Back from the dead, Sam?

Don,

Sorry for the late reply.  I've been super busy with Navy stuff.  I'll give a full update in a few weeks.  I'm working on some rewiring and switching out my handlebar controls for motogadget m-switches.  I'm also looking to swap out my exhaust system.  I love the 4 into 2 that I have, but it doesn't seal and the fitment sucks!  The whole front of my cylinder head is black from the exhaust.  The oil leaks are all gone with the exception of the transmission cover.  I will not know if I have it sorted out until I fire her back up.  I'll keep you posted!

[SOHC4 Cafe Racer Fan]

Hang in there, Sam.  I saw that you were doing a lot of travel to and fro for the Stars and Stripes.  Thank you, again, for your service.

Have you looked into the Ripple Rock/Hindle 4-2-1?  With American-Canadian exchange rates, it's cheaper than you think.  http://www.ripplerockracers.com/product/cb750-hindle-vintage-racing-exhaust-system-fits-1969-78/

The Delkevic is also full stainless and surprisingly inexpensive.

[Bigsam302]

Thanks Don!  I'll definitely check it out!

[MRieck]

Hang in there, Sam.  I saw that you were doing a lot of travel to and fro for the Stars and Stripes.  Thank you, again, for your service.

Have you looked into the Ripple Rock/Hindle 4-2-1?  With American-Canadian exchange rates, it's cheaper than you think.  http://www.ripplerockracers.com/product/cb750-hindle-vintage-racing-exhaust-system-fits-1969-78/

The Delkevic is also full stainless and surprisingly inexpensive.

Looks like a nice system.

[tulsah]

Great thread and great build!  When you have a chance, could you advise as to what size rims (dia and width) you wound up using in the build.  Thanks in advance.

-tulsah

[bwaller]

I talked to Kemp at Mosport recently where he was set up showing off his wares. First time I've seen the new Hindle systems. Nice exhaust.

[Bigsam302]

Great thread and great build!  When you have a chance, could you advise as to what size rims (dia and width) you wound up using in the build.  Thanks in advance.

-tulsah

Tulsah, thank you very much!  I have Sun Rims with Avon Roadrider tires.  They are both 18" rims.

front:  Rim 2.5", wheel 110/90V18
rear:   Rim 4.5", wheel 150/70-18

If you need anything else, please let me know.

Sam