Topic: Quality K8 carb boots for early k head to Mikuni 34mm Flatslides

[dragracer]

I know this topic has been asked and likely answered in the past but I'm hoping something new is now available.  My issue is i need to put OEM or at least very high quality carburetor boots on my K model head with 34mm Mikuni carbs. I used K8 boots this time around but after being on the bike 3 years now, i discovered the #4 was cracking near the carb side clamp and mideays where i drilled and installed the nitrous oxide funnel nozzle. Luckily i caught this before taking the bike out to test it on spray. This would have caused a potential lean condition  under 100% nitrous progression,  and may have burned a piston and valves.  I think i sourced these from either Vintage CB or Z1 Enterprises. It seems OEM nay not be available for the K8 so does anyone have a current go to vendor that supplies the boots. I hate to buy from either of the 2 i mentioned again.

[dragracer]

You can't see the cracks in this picture but they're definitely there.

[Tracksnblades1]

https://www.nospartsnow.com/nos-honda-1977-78-cb750-k-carburetor-insulator-intake-boot-1-16211-405-000/

I’d call them..
They show 3 of the 4…?

[dragracer]

https://www.nospartsnow.com/nos-honda-1977-78-cb750-k-carburetor-insulator-intake-boot-1-16211-405-000/

I’d call them..
They show 3 of the 4…?

Thanks. I saw those last night during my search. Of course the one i really need  the most isn't listed which is one reason i posted here.

[MRieck]

The non OEM pieces from CMSNL look to be better quality.....28.00 each

[Tracksnblades1]

https://www.nospartsnow.com/nos-honda-1977-78-cb750-k-carburetor-insulator-intake-boot-1-16211-405-000/

I’d call them..
They show 3 of the 4…?

Thanks. I saw those last night during my search. Of course the one i really need  the most isn't listed which is one reason i posted here.

😩

That’s my luck too…

They have had a few unavailable CR500 items that’s keep her factory OEM…🤫

[denward17]

Have you checked SouthSound Honda?

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750KA_(78)_750_FOUR_K%2c_JPN%2c_VIN%23_CB750-2800001/CYLINDER_HEAD/14cf52cd-d282-42e1-9a4b-99870811a8c4/89a18245-b9c1-4e77-83b6-b9b5dcc8c4de/y

[dragracer]

Have you checked SouthSound Honda?

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750KA_(78)_750_FOUR_K%2c_JPN%2c_VIN%23_CB750-2800001/CYLINDER_HEAD/14cf52cd-d282-42e1-9a4b-99870811a8c4/89a18245-b9c1-4e77-83b6-b9b5dcc8c4de/y

Thanks very much Denward. The site actually let me order #4. Lets see what arrives in the mail.

[madmtnmotors]

Have you checked SouthSound Honda?

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750KA_(78)_750_FOUR_K%2c_JPN%2c_VIN%23_CB750-2800001/CYLINDER_HEAD/14cf52cd-d282-42e1-9a4b-99870811a8c4/89a18245-b9c1-4e77-83b6-b9b5dcc8c4de/y

Thanks very much Denward. The site actually let me order #4. Lets see what arrives in the mail.

Same here, was able to add both #2 and #4 to the cart although both are shown to be "unavailable". Before ordering I have reached out to them confirming availability before ordering, I'll let you know what they say.

[newday777]

The 77/78 F carb insulators are NLA

[dragracer]

Well,  now we have an answer. They refunded my $$ for the #4 carb boot. Although it let me place an order with no message of unavailability,  I've now received a refund so obviously the do not actually stock this part.

[newday777]

Well,  now we have an answer. They refunded my $$ for the #4 carb boot. Although it let me place an order with no message of unavailability,  I've now received a refund so obviously the do not actually stock this part.

Unfortunately many parts are that way in that the fiche list is not up to date on the website ordering 😕

[Don R]

 It would be cool if UPP would make some urethane stock connectors, they indicated recently that they would make more of the Mikuni to Honda adapters.

[dragracer]

It would be cool if UPP would make some urethane stock connectors, they indicated recently that they would make more of the Mikuni to Honda adapters.

Don,
I'm unfamiliar with that company.  Can you share more details about them and the products they manufacture/supply?,

[dragracer]

https://www.nospartsnow.com/nos-honda-1977-78-cb750-k-carburetor-insulator-intake-boot-1-16211-405-000/

Well, i ordered 3 of the 4 available boots from this company last week.  They're supposed to be new, OEM Honda parts. The box came in today which was quick. I removed the parts from the box and discovered that each package had previously been opened.  Okay, no big deal. Oddly enough,  the boots appeared stiff but not like 1978, on the bike, survivor  crystalized stiff. This is definitely better than the aftermarket,  rubbery,  pliable boots from Z1.  These things were likely sitting on a shelf and exposed to air. I can live with it. I just need to source that elusive #4 boot now.

[Don R]

 I googled the part number and didn't find one either. So many part sellers take you all of the way into the list and click the part then say we don't have it.

[dragracer]

Don, its probably out there on the shelf at some out of the way Honda dealer just laughing at me as it collects more dust. 🤪

[madmtnmotors]

https://www.nospartsnow.com/nos-honda-1977-78-cb750-k-carburetor-insulator-intake-boot-1-16211-405-000/

Well, i ordered 3 of the 4 available boots from this company last week.  They're supposed to be new, OEM Honda parts. The box came in today which was quick. I removed the parts from the box and discovered that each package had previously been opened.  Okay, no big deal. Oddly enough,  the boots appeared stiff but not like 1978, on the bike, survivor  crystalized stiff. This is definitely better than the aftermarket,  rubbery,  pliable boots from Z1.  These things were likely sitting on a shelf and exposed to air. I can live with it. I just need to source that elusive #4 boot now.

I could only find the #1 and #3 boot listed on their site.

[scottly]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

[RAFster122s]

If you could get a good set for Claus Studios to replicate you would have them available, not inexpensive versions, but the quality and a company that stands behind their parts...

[Don R]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

[denward17]

You might try contacting Dexter via email at SouthSound Honda, he has a way to look at various Honda dealer inventory across the country and may get lucky.

He did this for me on a couple of 550 parts (one found in Maine, the other found in Iowa).

[dragracer]

You might try contacting Dexter via email at SouthSound Honda, he has a way to look at various Honda dealer inventory across the country and may get lucky.

He did this for me on a couple of 550 parts (one found in Maine, the other found in Iowa).

Will do. Its out there.

[madmtnmotors]

You might try contacting Dexter via email at SouthSound Honda, he has a way to look at various Honda dealer inventory across the country and may get lucky.

He did this for me on a couple of 550 parts (one found in Maine, the other found in Iowa).

Will do. Its out there.

If you find more 2's and 4's let me know!

[scottly]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

Yes, because each one is marked on the top with the cylinder #. I recall seeing some boots that had a 1 on one side, and a 4 on the other side: if used on the #1 cylinder, the 1 went on top with the 4 on the bottom, and if used on the #4 cylinder the 4 went on top. Try it and see if it works or not.

[dragracer]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

Yes, because each one is marked on the top with the cylinder #. I recall seeing some boots that had a 1 on one side, and a 4 on the other side: if used on the #1 cylinder, the 1 went on top with the 4 on the bottom, and if used on the #4 cylinder the 4 went on top. Try it and see if it works or not.

My plan is to try your suggestion Scottly.  I much rather use the OEM Honda parts. 

[Medyo Bastos]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

Yes, because each one is marked on the top with the cylinder #. I recall seeing some boots that had a 1 on one side, and a 4 on the other side: if used on the #1 cylinder, the 1 went on top with the 4 on the bottom, and if used on the #4 cylinder the 4 went on top. Try it and see if it works or not.

Yes


Sent from my iPhone using Tapatalk

[willbird]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

Yes, because each one is marked on the top with the cylinder #. I recall seeing some boots that had a 1 on one side, and a 4 on the other side: if used on the #1 cylinder, the 1 went on top with the 4 on the bottom, and if used on the #4 cylinder the 4 went on top. Try it and see if it works or not.

That is how the new OEM boots I bought from Ebay are, I never knew there were FOUR part numbers for boots 1-4 ?? Always presumed that there were only two. I have been messing around cad modeling intake boots and just ordered a digital height gage to actually measure/model the features on the cylinder head and work from there rather than using a boot and working from those numbers.

Bill

[scottly]

The original K7 boots I have are actually marked 1, Z, 3, 4.

[dragracer]

The original K7 boots I have are actually marked 1, Z, 3, 4.

I went ahead and ordered another #1 OEM boot. I'll try it on the #4 side. It doesn't have to be exact stock  spacing anyway because the 34's are off a bit anyhow. 

[Don R]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

Yes, because each one is marked on the top with the cylinder #. I recall seeing some boots that had a 1 on one side, and a 4 on the other side: if used on the #1 cylinder, the 1 went on top with the 4 on the bottom, and if used on the #4 cylinder the 4 went on top. Try it and see if it works or not.

That is how the new OEM boots I bought from Ebay are, I never knew there were FOUR part numbers for boots 1-4 ?? Always presumed that there were only two. I have been messing around cad modeling intake boots and just ordered a digital height gage to actually measure/model the features on the cylinder head and work from there rather than using a boot and working from those numbers.

Bill.

 The thing to remember is these are K8 boots for the keyhole carbs, not the same as the other cb750 boots.

[dragracer]

Can't a #1 boot be flipped over and fit on #4, and likewise for #2 and #3?

  I wondered that also but Honda gave them each a different part number.

Yes, because each one is marked on the top with the cylinder #. I recall seeing some boots that had a 1 on one side, and a 4 on the other side: if used on the #1 cylinder, the 1 went on top with the 4 on the bottom, and if used on the #4 cylinder the 4 went on top. Try it and see if it works or not.

That is how the new OEM boots I bought from Ebay are, I never knew there were FOUR part numbers for boots 1-4 ?? Always presumed that there were only two. I have been messing around cad modeling intake boots and just ordered a digital height gage to actually measure/model the features on the cylinder head and work from there rather than using a boot and working from those numbers.

Bill.

 The thing to remember is these are K8 boots for the keyhole carbs, not the same as the other cb750 boots.

Correct Don. The head side is comparable to all other K heads but the inlet side is larger. They work perfectly for the 34mm Flatslide Mikunis when installing them on any head except the F2/3 which has larger intake spigots. I typically use a drum sander roll on my drill to open up the inlet a tad larger so the 34's won't be as hard to slip on. I cut a little at a time to be certain its snug. In theory,  1 and 4 should be similar in configuration as you're only rotating the boot, 180 degrees on the spigot. 

[Don R]

 It makes perfect sense to me. It got me curious about the K0/K1-6 carb rubber difference. I've had mid-year carb rubbers on an early bike since before I joined here.

[madmtnmotors]

That is how the new OEM boots I bought from Ebay are, I never knew there were FOUR part numbers for boots 1-4 ?? Always presumed that there were only two. I have been messing around cad modeling intake boots and just ordered a digital height gage to actually measure/model the features on the cylinder head and work from there rather than using a boot and working from those numbers.

Bill

Oooooo... 3D CNC machined aluminum intake manifolds with wide flat rubber o-rings on the inlet port at the head and an o-ring on the carb outlet. Make it so!

[willbird]

That is how the new OEM boots I bought from Ebay are, I never knew there were FOUR part numbers for boots 1-4 ?? Always presumed that there were only two. I have been messing around cad modeling intake boots and just ordered a digital height gage to actually measure/model the features on the cylinder head and work from there rather than using a boot and working from those numbers.

Bill

Oooooo... 3D CNC machined aluminum intake manifolds with wide flat rubber o-rings on the inlet port at the head and an o-ring on the carb outlet. Make it so!

I am fresh out of CNC's but the general idea is to create a fairly accurate 3D model and then we can examine all kinds of ideas :-).

Bill