Topic: Ross’s 1975 CB750 K5

[willbird]

Easy enough to make, just drill a hole in a bowl screw and solder in a brass tube..

Will do that!

I made one up on the lathe, probably can whip you one up as well :-).



Not a very good picture, thread is M6x.75


Bill

[Galactica]

I think I have one. Probably from a Yamiya decal kit. I’ll have a look.

That’s very kind to check. 

[Galactica]

Easy enough to make, just drill a hole in a bowl screw and solder in a brass tube..

Will do that!

I made one up on the lathe, probably can whip you one up as well :-).





Not a very good picture, thread is M6x.75


Bill

Hey that’s really good.  I’ve a couple of friends that are accomplished machinists, but I couldn’t bring myself to prevail upon them to make one for me. 

[willbird]

Easy enough to make, just drill a hole in a bowl screw and solder in a brass tube..

Will do that!

I made one up on the lathe, probably can whip you one up as well :-).





Not a very good picture, thread is M6x.75


Bill

Hey that’s really good.  I’ve a couple of friends that are accomplished machinists, but I couldn’t bring myself to prevail upon them to make one for me.

Well I’d suggest finding a way that you’re rewarding them :-). Maybe find a good material to make them from such as 12L14 and buy a batch of “Bar ends” from Ebay and gift them the extra in return for whipping you up a couple :-). On my Grizzley lathe the most difficult part is swapping it over to metric. once it is set there making one or ten is about the same effort. The folks in metric lands who have friends with lathes they are probably metric centered all the time :-).

[Galactica]

Easy enough to make, just drill a hole in a bowl screw and solder in a brass tube..

Will do that!

I made one up on the lathe, probably can whip you one up as well :-).



Not a very good picture, thread is M6x.75


Bill

Thanks very much for the offer to make one up for me.  I’ll leave it up to you.  For the moment, I don’t need one.  And at the moment, I can borrow one from an acquaintance here.

[Galactica]

So here’s a question.  At idle there’s quite a racket (at least to my mind) coming from the crank case.  It pretty much goes away when I pull in the clutch lever.  Is it normal? Should I be concerned?

I don’t remember from the K5 I had in 1977 if it was the same.  I’m not at all used to a primary chain drive.  I’ve heard it’s a pretty normal thing, and opening up the motor to effect repairs may not necessarily solve the issue.

I’d appreciate any thoughts on this.

Cheers,
Ross

[newday777]

Are your carbs vacuum synced?  If out of sync yes you will have that rattle at idle and yes it will lesson with pulling the clutch in.
And yes it is possible that the primary chains are stretched. You can check the chain deflection through your oil pan.

[Galactica]

I’ve synchronized the carbs using my vacuum gauges.  They were really close with just my bench synch though.  I may borrow a friend’s Carbtune unit and compare, but I’m confident they’re pretty close.

[Galactica]

Are your carbs vacuum synced?  If out of sync yes you will have that rattle at idle and yes it will lesson with pulling the clutch in.
And yes it is possible that the primary chains are stretched. You can check the chain deflection through your oil pan.

Is it something that I need to be concerned about?

[BenelliSEI]

The cb750 is a “dry sump” motor. 1/2 your oil pump is sucking oil from the sump and keeping the oil tank full. This “dry” condition does help to amplify the rattling sound. A really good carb sync usually makes a big difference.

How low have you set your idle? Below 1,000 RPM? I find that setting it up a little bit higher smooths things out dramatically.

[Galactica]

I’ve set the idle at ~1000rpm.  It climbs up to 1100 or a bit more once warmed up.  The idle screw is difficult to reach and quite stiff to turn.  It definitely does quiet a bit as revs rise.

[newday777]

I’ve set the idle at ~1000rpm.  It climbs up to 1100 or a bit more once warmed up.  The idle screw is difficult to reach and quite stiff to turn.  It definitely does quiet a bit as revs rise.

As long as the primary chain noise quiets down after it warms up and rpm holds at 1100 then you should be fine. I read back through your post and replies on this, with 23,000 miles it should not be bad unless the bike was hammered hard. Primary chains take a beating in racing with hard down shifting deceleration stretching out the chains.
Run it the way it is for a few hundred miles before being concerned. Get used to the bike out on the road, they do make some noise when cold. These motors like having the throttle feathered by hand when cold to keep the rpms up while warming. Don't try to set the idle until it is fully warmed or you will be pulling out your hair.....yes the idle screw isn't placed in a great location but is accessible when working with a aux fuel tank doing tuning once fully warmed up. The service manual says to ride the bike a bit to warm it up before setting/tuning the carbs. And be sure to have a fan blowing on the front of the motor when setting the carbs up to steady the temperature like riding will be doing. These air cooled motors need air flow over them when setting idling on the lift to get optimum tuning.

[BenelliSEI]

I’ve set the idle at ~1000rpm.  It climbs up to 1100 or a bit more once warmed up.  The idle screw is difficult to reach and quite stiff to turn.  It definitely does quiet a bit as revs rise.

Take the idle screw all the way out. Watch not to lose the spring wrapped around its shaft. Clean the threads really well and lubricate with a bit of anti seize, before reinstalling. With a bit of practice, and a pair of gloves, I find the idle screw easy to reach. I often set it up a bit when the bike first starts and then adjust a few times (while stopped) until I like where it sits.

[Galactica]

Ya, I cleaned it in the ultrasonic but I’m pretty sure I installed it dry.

[Floshenbarnical]

Ya, I cleaned it in the ultrasonic but I’m pretty sure I installed it dry.

+1 for what these guys said, lube the screw. I could only turn mine w gloves on until I lubed it

[Galactica]

I took out the idle screw and chased the threads (5x0., lubed and reinstalled.  Couldn’t run in a tap with the carbs in situ.  Oh well we’ll see how it goes. 

I have the tank off.  I used a heat gun to remove the stripes.  Monday morning I’m gonna sandblast it and take it to my painter.  I’ve told him, no rush.  He’ll get to it in between bigger jobs. 

Today I received a new gas cap from 4into1 with pivot pins that have e-clips to hold them.  No need to use a hammer near the new paint to flare OEM style pins.

Also received a “HONDA” seat stencil from Trail Buddy today.

So once I get the body back from paint and the stencil on the seal, I’m good to go.  I’ll submit my application for a collector plate as soon as I get it back from paint.  Not sure how long that that will take, but hopefully I’ll be riding it by end of March.

[Galactica]

Seat stencil applied and painted.  Because of the texture of the seat, the paint bled all around all of the letters.  I carefully covered it all with a black sharpie.  Just don’t look too closely.

[newday777]

It looks great from my house!

[denward17]

Seat looks great to me.  Makes me wonder if the Duplicolor DE1615 could be used for that?

EDIT:Just searched and found this, Duplicolor Vinyl & Fabric Coating.  Of course they don't have a light silver.

https://www.duplicolor.com/product/vinyl-and-fabric-coating/

[newday777]

Seat looks great to me.  Makes me wonder if the Duplicolor DE1615 could be used for that?

The engine paint might eat the vinyl 🤔

[Galactica]

Ready for paint

[Magpie]

The seat looks great. My guy didn't want to do a stencil on my because of the heavy grain. I'll see if I can change his mind with your solution. The seat really does need "HONDA" on the back of it. Cliff.

[gearsoup]

Galactica, what are you doing for paint scheme? I'm going to be painting my tank when warmer weather hits, pondering how I can properly mask and paint blue/black and apply the proper decals to it..

Oh, and I thought the '75s had the petcock on the right side, no?

[newday777]

Oh, and I thought the '75s had the petcock on the right side, no?

75 K5 was the beginning of the left side petcock.

[Galactica]

Galactica, what are you doing for paint scheme? I'm going to be painting my tank when warmer weather hits, pondering how I can properly mask and paint blue/black and apply the proper decals to it..

Oh, and I thought the '75s had the petcock on the right side, no?

Going with original paint scheme in Planet Blue.  I took photos showing measurements to locate the stripes.  Used a heat gun to remove the stripes.  More photos showing measurements to locate the black cheeks.

The paint shop will paint the blue.  Mask off the cheeks and apply the black.  Clear coat.  Apply the stripes and clear coat again.