Topic: Look, squirrel! Or, how bike projects shift quickly; new CB750 K6 project for me

[seanbarney41]

couple things...make sure the vent in your gas cap is clear and functioning and the petcock must shut off or you will always have a certain amount of overflow when parked.

sometimes the rubber in the fuel system dries out and shrinks and doesn't seal.  Introducing fresh gas and regular useage can swell the rubber back to sealing properly...sometimes

[gearsoup]

couple things...make sure the vent in your gas cap is clear and functioning and the petcock must shut off or you will always have a certain amount of overflow when parked.

sometimes the rubber in the fuel system dries out and shrinks and doesn't seal.  Introducing fresh gas and regular useage can swell the rubber back to sealing properly...sometimes

At this point, the only OEM rubber that's left in the fuel system is the gas cap and overflow tubes.

I did find an OEM petcock rebuild kit, so that's on order.

[gearsoup]

Would someone be able to recommend some high quality float valves and seats? I'm using the 4into1 reproduction pieces (they have a filter on the end) but every one of my carbs is leaking.
Float heights are set to 26mm across the board, and the bike is on the center stand.
I had the carbs out last night to inspect what's going on, everything appears to be correct, none of the tubes have cracks in it.

I still have the OEM units, I'll try putting those back in and see what happens.

[denward17]

I've read that some people have had success polishing the seats with some light polish and Q tips, but I haven't tried it myself.

Can you get the float valves from Honda?

[newday777]

Would someone be able to recommend some high quality float valves and seats? I'm using the 4into1 reproduction pieces (they have a filter on the end) but every one of my carbs is leaking.
Float heights are set to 26mm across the board, and the bike is on the center stand.
I had the carbs out last night to inspect what's going on, everything appears to be correct, none of the tubes have cracks in it.

I still have the OEM units, I'll try putting those back in and see what happens.

For what bike?

[gearsoup]

For what bike?

Oh, I dunno. Maybe the only one I'm talking about in this thread? 
(this is a project thread with the topic rather well defined and stretching for 5 short pages)

[gearsoup]

Can you get the float valves from Honda?

CMSNL does list a vale/seat combo, and they're $36 EACH 
(but really, I don't care about the price, I would just be happy no longer smelling fuel constantly)

[Stev-o]

Can you get the float valves from Honda?

CMSNL does list a vale/seat combo, and they're $36 EACH 
(but really, I don't care about the price, I would just be happy no longer smelling fuel constantly)

Aftermarket carb parts typically will cause issues like you are having [petcocks too] so we always recommend using genuine parts when possible to avoid issues and buying more parts. 

Partzilla shows them as not available but try using the part number to search for them...

https://www.partzilla.com/catalog/honda/motorcycle/1976/cb750k-a-750-four/carburetor

[PeWe]

Do not replace the original Keihin parts if still working.
My old K6 carbs have done over 100.000 km, only main jet changed.
I tried aftermarket float valves but replaced them with the old stock ones that did not leak.

Cleaned the valve tips. Maybe rub them with something fine.
Floats did not overflow.

They are parked waiting for a good ultrasonic clean.

[grcamna2]

Can you get the float valves from Honda?

CMSNL does list a vale/seat combo, and they're $36 EACH 
(but really, I don't care about the price, I would just be happy no longer smelling fuel constantly)

Aftermarket carb parts typically will cause issues like you are having [petcocks too] so we always recommend using genuine parts when possible to avoid issues and buying more parts. 

Partzilla shows them as not available but try using the part number to search for them...

https://www.partzilla.com/catalog/honda/motorcycle/1976/cb750k-a-750-four/carburetor

Yeah Man.

[seanbarney41]

Anytime the carbs are disturbed, it's quite likely that the needles are not gonna just start working.  When they overflow give the bowls a gentle smack with a screwdriver handle or something.  If that does not work, turn the petcock off, drain the bowls, refill them.  If you don't have something wrong, they will eventually work.  Always remember how tiny and fragile the float system is.  They mostly just need encouragement to work.  Don't be scared of gas.  Just be aware of how it works.

[gearsoup]

When they overflow give the bowls a gentle smack with a screwdriver handle or something.

Yep, a gentle tap with a screwdriver handle and my overflow issues have ceased!

Now it's on to the clutch. It holds okay, but does slip if I drive "spiritedly" (heavy acceleration up a hill, for example). Should I take things apart and figure out what I currently have for plates/springs/basket or just order a kit from vintagecb750/PartsNmore designated for a '76? Reading thru a bunch of threads, it sounds like 76 was a bit of a coin flip on what you may have, and I have no knowledge if what's currently in there are the OEM bits and bobs

Oh, also picked up another gas tank. I want to paint the current one, but I also don't want my bike out of commission for the few weeks it's going to take me (drying time and no rushing thru this). I've got the "new to me" tank soaking in EvapoRust at the moment, that stuff works great!

[newday777]

When they overflow give the bowls a gentle smack with a screwdriver handle or something.

Yep, a gentle tap with a screwdriver handle and my overflow issues have ceased!

Now it's on to the clutch. It holds okay, but does slip if I drive "spiritedly" (heavy acceleration up a hill, for example). Should I take things apart and figure out what I currently have for plates/springs/basket or just order a kit from vintagecb750/PartsNmore designated for a '76?

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

[gearsoup]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

[newday777]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

Put in a can of Seafoam in the oil(suck out 8 oz of oil from the tank first). Ride it in one ride of 100-200 miles, keep rpms below 3,000. Shift lots up and down(puts more oil flushing through the clutch plates to wash them clean of any impurities and gunk).
Then after 100-200 miles go home and dump the hot oil and filter, put in new filter and oil. Ride it and report back before ordering parts.

[seanbarney41]

Also, double check that you have adjusted the cable and actuator correctly.  Follow instructions from the manual.

[gearsoup]

Put in a can of Seafoam in the oil(suck out 8 oz of oil from the tank first). Ride it in one ride of 100-200 miles, keep rpms below 3,000. Shift lots up and down(puts more oil flushing through the clutch plates to wash them clean of any impurities and gunk).
Then after 100-200 miles go home and dump the hot oil and filter, put in new filter and oil. Ride it and report back before ordering parts.

1-2 hundred miles below 3k rpm? I think I'd rather replace the clutch 
(that's a joke)
Alright, I'll give that a go, it's going to be cheaper than throwing parts at it (plus the risk of breaking the cast plate)

I'm NOT starting an oil thread or discussion (I left my flame suit in my truck), but you didn't raise concern over my oil choice (it's what NAPA had), so I assume that's a valid selection?

[willbird]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

Put in a can of Seafoam in the oil(suck out 8 oz of oil from the tank first). Ride it in one ride of 100-200 miles, keep rpms below 3,000. Shift lots up and down(puts more oil flushing through the clutch plates to wash them clean of any impurities and gunk).
Then after 100-200 miles go home and dump the hot oil and filter, put in new filter and oil. Ride it and report back before ordering parts.

After watching a recent youtube video by Lake Speed Jr I would never put seafoam in engine oil. The stuff boils at 100F for one thing.

In fact after watching that video, and the one prior to it about ZddP additives I would not add ANYTHING to any engine oil....but especially not SeaFoam.

Bill

[newday777]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

Put in a can of Seafoam in the oil(suck out 8 oz of oil from the tank first). Ride it in one ride of 100-200 miles, keep rpms below 3,000. Shift lots up and down(puts more oil flushing through the clutch plates to wash them clean of any impurities and gunk).
Then after 100-200 miles go home and dump the hot oil and filter, put in new filter and oil. Ride it and report back before ordering parts.

After watching a recent youtube video by Lake Speed Jr I would never put seafoam in engine oil. The stuff boils at 100F for one thing.

In fact after watching that video, and the one prior to it about ZddP additives I would not add ANYTHING to any engine oil....but especially not SeaFoam.

Bill

I've never had a problem with Seafoam boiling in the oil. I do it to any bike that has slipping clutch and to bikes that have been brought back to life that had old oil left in them to get rid of sludge in the crankcase.

[willbird]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

Put in a can of Seafoam in the oil(suck out 8 oz of oil from the tank first). Ride it in one ride of 100-200 miles, keep rpms below 3,000. Shift lots up and down(puts more oil flushing through the clutch plates to wash them clean of any impurities and gunk).
Then after 100-200 miles go home and dump the hot oil and filter, put in new filter and oil. Ride it and report back before ordering parts.

After watching a recent youtube video by Lake Speed Jr I would never put seafoam in engine oil. The stuff boils at 100F for one thing.

In fact after watching that video, and the one prior to it about ZddP additives I would not add ANYTHING to any engine oil....but especially not SeaFoam.

Bill

I've never had a problem with Seafoam boiling in the oil. I do it to any bike that has slipping clutch and to bikes that have been brought back to life that had old oil left in them to get rid of sludge in the crankcase.

And i’m sticking with what I said :-).


Bill

[HondaMan]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

The Rotella 15w40 is the lightest oil I'd run in a 750, unless it was wintertime. The upper weight (40) is a bit on the light side, but this won't cause clutch slip: it causes lower-than-best oil PSI.

I've also seen a synthetic Rotella 15w40 oil (at Walmarts): I don't think I'd recommend that one. I don't know if that's the "T5" type you mentioned, though. I've had real bad clutch issues with automotive synthetic oils like Valvoline ("motorcycle oil"), Havoline and a "brand X" (O'Reillys' own branded oil) in the recent past. They all had clutch problems, either slipping clutch or a clutch that refused to release after the engine warmed up, making shifting impossible. Switching back to the Bel-Ray EXL Mineral solved the problems after about 70-100 miles, though.

[PeWe]

Try Spectro 20W-50 HD mineral.
Proven to make a CB750 to a long runner without restoration. Search this forum, there are a few very informative oil threads.

The Honda owners manual my K6 had when I bought it had a very clear oil recommendation.
20W-50!
10W-40 when ambient temp is under 15*C.
My bike is always in a +20C garage so no cold starts.

I have searched about motor oils, temperatures and viscosity.
Viscocity degrades rather quick, faster in a hot running engine.

Valve guides will suffer when oil is too thin.
Good info to be found on Porsche forums, the older  air cooled.

Most car oils have antifriction stuff, not clutch friendly.

Verify the clutch lever play down the clutch cover.
Remove the chrome clutch cover fastened by 3 screws.
Release the clutch cable, loosen the stop screw nut.
 Close the screw. It should move 1/4 to 1/2 turn in until stop.

Too little can cause clutch slip, too much will make clutch to rattle harder at idle.

My K6 got clutch slip in the 80's due to the best oil I found and thought to be good, Mobil 1 car oil.

[gearsoup]

I've also seen a synthetic Rotella 15w40 oil (at Walmarts): I don't think I'd recommend that one. I don't know if that's the "T5" type you mentioned, though.

It is marked as a "synthetic blend". Okay, I'll drain it out before my next ride and replace with something more appropriate.

[gearsoup]

Try Spectro 20W-50 HD mineral.

Is this the stuff? https://www.beemershop.com/product/spectro-mineral-20w-50.html
Spectro website doesn't return much more, lots of HD options, some pointing to Harley, others pointing to motorcycles in general.
 I also found this on Amazon, appears to be the same? https://www.amazon.com/Spectro-Motorcycle-Engine-Lubricant-Oil/dp/B075DXGM33/ref=asc_df_B075DXGM33/?tag=hyprod-20&linkCode=df0&hvadid=693521669885&hvpos=&hvnetw=g&hvrand=2644962756298290418&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9002532&hvtargid=pla-520659763564&psc=1&mcid=69c168796e96339aa8c2cfd1c3e175fd&gad_source=1&gclid=Cj0KCQjwxqayBhDFARIsAANWRnSZdx2C2tjjShT0UcgXr75qx_bUZTyWcdB1J7k6nU9xvZYqd53px1QaArbYEALw_wcB

[newday777]

Clutch slip is often a problem from using the wrong oil that has friction modifiers in it.
It can be cleaned out and salvage the clutch.
What oil are you using???

Shell Rotella T5 15W-40, it's been about 150 miles since I changed the oil. No clue what the PO had in it, it was dark and thin when I drained it

I use the T4 Rotella 15w40 in the early spring and fall temps, and haven't had slippage problems.
In the summer temps I have been running some leftover 20w50 hondaline oil that I got(6 cases) with my K5 in 2017.

I just bought (3) 4 Liter jugs of Belray EXL mineral 4T 20w50 to try out at HondaMan Mark's recommendation (on The Lone Builder/Sean's bike) and some ZDDP ADDITIVE to go with it for a shifting problem(that ended up being a loose screw on the shifting drum and not a slipping clutch)