Topic: "The Million Dollar CB" First start of the season

[Cb750 Racer]

Always a treat heading over to Mikes place. Dropped a head off and had a great time talking with him this afternoon. It was all silence when this baby started up though. What a sound! Can't wait for my Billet Block to get back from plating   
Thanks again for letting me borrow the books Mike i'll keep em in one piece for ya

                                                                                                                   
                                                                                                                           

[rocket johnny]

sweet !

[MRieck]

 I love you Justin. It was better than that in person.

[MRieck]

Always a treat heading over to Mikes place. Dropped a head off and had a great time talking with him this afternoon. It was all silence when this baby started up though. What a sound! Can't wait for my Billet Block to get back from plating   


                                                                                                                   
                                                                                                                           

What a great kid.

[Cb750 Racer]

I love you Justin. It was better than that in person.

No video could ever do the bike justice!

[PeWe]

Look and sounds really good. I see lots of goodies
Improved or extra case breather too?

[MRieck]

Look and sounds really good. I see lots of goodies
Improved or extra case breather too?

Yes Per.....thanks to Jim French for that. Justin and I talked a bit about extra breathers as he is going turbo. Tough to find mounting spots as Honda really shrunk the cases around the internals.

[Sam Green Racing]

Look and sounds really good. I see lots of goodies
Improved or extra case breather too?

Yes Per.....thanks to Jim French for that. Justin and I talked a bit about extra breathers as he is going turbo. Tough to find mounting spots as Honda really shrunk the cases around the internals.

Awesome Mike, that brings back happy memories.
Remind me where you took the extra breather from?
If you recall, I took extra breathers from #2 and #3 tappet covers on mine, they seemed to work well.

Sam.

[andy750]

I love you Justin. It was better than that in person.

No video could ever do the bike justice!

+1!! And rides like no other!

[PeWe]

Look and sounds really good. I see lots of goodies
Improved or extra case breather too?

Yes Per.....thanks to Jim French for that. Justin and I talked a bit about extra breathers as he is going turbo. Tough to find mounting spots as Honda really shrunk the cases around the internals.

I had to add a hose between case breather spigot and K6 oil tank. T connection and 1/2" hose going 10" up - curved connection - 10" hose going down just beside the brake pedal.
It splash oil when twisting the throttle for a while. Before I installed that hose the cases started to weep oil   Cylinder and head are tight so boring to see oil on wrong side.  (I tried an old oil tank with breather outlet....wow it sprayed a liter or more over the rear after some twisting, oil did not reach the dipstick)
I have ordered an oil catch can that I hopefully can place on the left side over the sprocket cover and strapped to frame. It has a bottom plug where it might be possible to add a valve with hose and use oil for chain when needed
I have looked for a place on the upper case to make a hole or bolt to remove Starter motor is needed, otherwise a nice hole to attach a good breather hose.
A future procejt might be to pull engine, lift the lower case and reseal the cases and hopefully been able to find a place to drill an extra breather connection.

Mike, you have a blue hose from the clutch cover. Is that a breather or have I seen wrong?

[Don R]

 I have a rocker cover with an extra vent tapped in next to the stock one. I haven't used it though.

[PeWe]

Good inputs. I have an old rocker cover with bolts for cam holders. That one might get an extra breather hose.
Or via the tappet covers...nice to modify a tappet cover or 2.

Case breather and valve cover breather have different pressures? Both must breath well?
Engine will look like an octopus with breather hoses added.

Mike's bike thread has just transformed to a breather post   Maybe other good Mike upgrades visible on the video that is a must have? 

[Cb750 Racer]

Look and sounds really good. I see lots of goodies
Improved or extra case breather too?

Yes Per.....thanks to Jim French for that. Justin and I talked a bit about extra breathers as he is going turbo. Tough to find mounting spots as Honda really shrunk the cases around the internals.

I had to add a hose between case breather spigot and K6 oil tank. T connection and 1/2" hose going 10" up - curved connection - 10" hose going down just beside the brake pedal.
It splash oil when twisting the throttle for a while. Before I installed that hose the cases started to weep oil   Cylinder and head are tight so boring to see oil on wrong side.  (I tried an old oil tank with breather outlet....wow it sprayed a liter or more over the rear after some twisting, oil did not reach the dipstick)
I have ordered an oil catch can that I hopefully can place on the left side over the sprocket cover and strapped to frame. It has a bottom plug where it might be possible to add a valve with hose and use oil for chain when needed
I have looked for a place on the upper case to make a hole or bolt to remove Starter motor is needed, otherwise a nice hole to attach a good breather hose.
A future procejt might be to pull engine, lift the lower case and reseal the cases and hopefully been able to find a place to drill an extra breather connection.

Mike, you have a blue hose from the clutch cover. Is that a breather or have I seen wrong?

You're spot on PeWe that blue hose leads to a breather that sits around where the stock airbox would be. It's a good place to add one but won't work on my build because of the oil return line from the turbo will be there. Something off the tappet cover bolts isn't a bad idea either I plan on welding a few bungs into my cam sprocket cover and have it lead to a catch can in front of my coils. An extra vent tapped next to the stock one isn't a bad idea either that's what Mike was suggesting. The lower the breather is in the engine the less pressure buildup but as Mike was saying it's hard to find solid spots.

[MRieck]

Look and sounds really good. I see lots of goodies
Improved or extra case breather too?

Yes Per.....thanks to Jim French for that. Justin and I talked a bit about extra breathers as he is going turbo. Tough to find mounting spots as Honda really shrunk the cases around the internals.

Awesome Mike, that brings back happy memories.
Remind me where you took the extra breather from?
If you recall, I took extra breathers from #2 and #3 tappet covers on mine, they seemed to work well.

Sam.

Always my pleasure to supply some happy memories Sam. One breather in the stock cam cover location and 1 in the clutch cover. I think it is a good idea to have a breather in the case area especially with 71/72mm pistons. I run the 2 hoses (with K&N breather filters) just behind the air filters. Any blowby etc gets sucked up by the air filters.

[PeWe]

I might be optimistic to squeeze this in on the left side The top filter might need an extension via a hose.
https://www.ebay.co.uk/itm/122072795459

2 hoses in but only one out of same diameter might cause a restriction. The hose that spit most oil will be connected.

[slikwilli420]

Im running two breather setups on my race bike. One plugs into the starter hole and has inlets for the rear of the case, clutch cover and valve cover, with an outlet to a one-way valve. The oil tank will have a breather in one side, a drain back to the oil tank on the bottom and out the back a hose to a filter element so the tank can breathe both ways.

Engine breather:



Tank breather:

[PeWe]

More good breather inputs!
I have totally missed that earlier. I understand now why my cases started to weep oil in the 80's when riding in a high tempo on Autobahn going south hour after hour. Back then 836. I blamed the case sealer I used, Hylomar Blue. Prior to that one Hermetite Golden that never leaked. If I had improved the breathers, no irritating oil outside the cases.

It pump a little bit more now with 71.25mm pistons.

Any specific spigot that can be threaded into the clutch cover?  It would be fine if it can be done without welding.

[slikwilli420]

Probably enough meat to do it a few places. The top is about 0.200" thick where I did mine. I have also seen it done in the top mounting boss for the chrome outer cover, if you decided you didn't want to run that any longer. Aside from that, welding is a good option. I chose a -6AN fitting based on Mike's recommendation.

[scottly]

I had to add a hose between case breather spigot and K6 oil tank. T connection and 1/2" hose going 10" up - curved connection - 10" hose going down just beside the brake pedal.
It splash oil when twisting the throttle for a while.

(I tried an old oil tank with breather outlet....wow it sprayed a liter or more over the rear after some twisting, oil did not reach the dipstick)

Per, the spigot on the lower case is not a vent, it is a drain from the oil/air separator in the oil tank. At higher RPMs, the oil vacuumed out of the sump becomes more aerated, and more flows from the tank to the case. The PO of my bike did some "creative" plumbing, utilizing a Tee, which dumped oil after every spirited ride. It was one of the first of many other such errors.

[PeWe]

I had to add a hose between case breather spigot and K6 oil tank. T connection and 1/2" hose going 10" up - curved connection - 10" hose going down just beside the brake pedal.
It splash oil when twisting the throttle for a while.

(I tried an old oil tank with breather outlet....wow it sprayed a liter or more over the rear after some twisting, oil did not reach the dipstick)

Per, the spigot on the lower case is not a vent, it is a drain from the oil/air separator in the oil tank. At higher RPMs, the oil vacuumed out of the sump becomes more aerated, and more flows from the tank to the case. The PO of my bike did some "creative" plumbing, utilizing a Tee, which dumped oil after every spirited ride. It was one of the first of many other such errors.

OK, that's why the old tank did not work with my plumbing.
It work better with the K6 oil tank that has no breather to release over pressure. Case weep less with it too. I need to find spigots that can be threaded into valve cover and clutch cover then.

Carbs and pods take most of the space for additional breathers and oil catch can.
Edit: Back from work and search for suitable spigots I can mount here and there. Threads plus Loctite 272 will hopefully work.

[PeWe]

Probably enough meat to do it a few places. The top is about 0.200" thick where I did mine. I have also seen it done in the top mounting boss for the chrome outer cover, if you decided you didn't want to run that any longer. Aside from that, welding is a good option. I chose a -6AN fitting based on Mike's recommendation.

The An-6 fitting with 1/4" NPT (~14mm) will not fit the clutch cover upper part, right?  1/8" NPT  (~10mm) will go?
I have found 90 degrees fittings with  these pipe threads, the other side AN-6 or hose 9-10mm.
1/8 "   0,405"  27 TPI
1/4 "   0,540"  18

The breather hose must have some inner diameter to be able to breath.

[slikwilli420]

Probably enough meat to do it a few places. The top is about 0.200" thick where I did mine. I have also seen it done in the top mounting boss for the chrome outer cover, if you decided you didn't want to run that any longer. Aside from that, welding is a good option. I chose a -6AN fitting based on Mike's recommendation.

The An-6 fitting with 1/4" NPT (~14mm) will not fit the clutch cover upper part, right?  1/8" NPT  (~10mm) will go?
I have found 90 degrees fittings with  these pipe threads, the other side AN-6 or hose 9-10mm.
1/8 "   0,405"  27 TPI
1/4 "   0,540"  18

The breather hose must have some inner diameter to be able to breath.

Agreed on inner diameter. I would run the biggest one you can fit since you have more displacement, you need to efficiently move air under those pistons. A welded fitting looks more finished but I think I fit a 1/4 npt in the upper hole for the chrome cover.

[PeWe]

1/4" NPT means 14mm hole in cover. 1/8" NPT 10 mm. These pipe threads numbers are a little bit confusing...
What sizes are usually used here?
I checked again, the video show the smaller diameter.
Larger fitting need some welding to build up material to make a flat surface for the big hole.

[scottly]

Tapered pipe thread size refers to the ID of the passage, so a 14mm hole in the cover only yields a 1/4" passage. The wall thickness of the pipe is for higher pressure, and is not required for a breather. A thin wall spigot welded or epoxied into place would allow more flow.

[PeWe]

OK, an angled and threaded pipe of any kind might give better flow then. I planned to thread a hole, then loctite 638 or similar. I have no alu welder around.
I'll prepare an extra cover and swap when ready.
This should be a product possible to add in basket on eBay, cover with welded spigot(s). My CB750 had oil weeping cases back in the 80's with 836.