Topic: 78 cb 750F with stock honda mag wheels has tubes

[garyS-NJ]

I was sure they were tubeless but when I went to change tires today, I found tubes.  was this a mod and can I get stems and run tubeless??

[phil71]

show a photo of the wheels. Most likely, you can go back to tubeless.. but it's entirely possible that someone added tubes after the tire got a nail or something in it.

[jaguar]

My understanding is that the comstar wheels, as well as aftermarket wheels (Abe henry, lester, shelby) are meant to run tubes, although some have run them with out

[scottly]

This has been an on-going controversy; just when did Comstars start coming from the factory fitted with tubeless tires? Are the rims marked tubeless, or TL? Please post a pic of the bead seating area of the rim.

[phil71]

the valve exit area will denote a tubeless rim. If it can take a valve stem and is machined to seal, the rim is a tubeless rim.

[shinyribs]

My Comstars are stamped tubeless. Tubes are for spokes cuz the nipples will leak air.

[lone*X]

My Comstars are stamped tubeless. Tubes are for spokes cuz the nipples will leak air.

What year are your comstars?  Your bike isn't identified in you signature.  Some were tube type, some were tubeless. 

[garyS-NJ]

my bike is a stock cb750F3 supersport with stock DID alloy 5 spoke wheels.  I looked at the rims and didn't see a stamp TT or TL.  I'll have to check at the dealer tomorrow to see if they sell valve stems for them.  pic attached

[garyS-NJ]

I tried to post a pic but got an error file too large.  the attached is a google image of a 1977 cb750F with what looks to be the same wheels.  they are DID, not comstar.

[Old Scrambler]

Always go to the beginning of the source information (owner's manual) before you make decisions that involve your well being.......ALL CB750s use TUBE-TYPE (TT) tires unless specifically marked on the rim as TUBE-LESS (TL).  Comstars are a style of wheel made by D.I.D. for HONDA.

Next.....check your tires. Tube-Type must run with a tube regardless of rim type. Tube-less tires can be run with tubes on TT rims. NEVER mix tire types on the same vehicle.

My silver Comstar wheels have tubless tires with tubes. I just checked and found no markings of any kind on the rims.

[garyS-NJ]

thanks ol scrambler!

I was at my friend's shop and somewhat hastily looking for the marking on the rims and they were dirty so I didn't trust my on inspection.  And I had looked at my manual but without any notes regarding the tube & tire, failed to "see" the tube in the cutaway illustration (and failed to notice the note about comstars not requiring a rim band.  And I can't remember why but I didn't think my Star looking wheels were comstars perhaps because they said DID and not comstar.  Big DUH all around.  it was all in front of me.  but at least I'm trying.  a lot of people just send their bikes to the shop.

I just got my fork seals last night and since I didn't finish the wheels, I'm going to do the seals today.  Any hints on pulling the tubes out the trees (I remember they were quite stuck in a harley I did)??  and what about the slider bolt in the bottom of the leg?  looked like an allen head yesterday.  My plan was to loosen the top fork spring bolt, then loosen the bottom slider bolt, and then loosen the pinch bolts and attempt to pull/twist the fork tube.  (and then scratch the #$%* of it).

thanks again, love this site and all it gives so I will try to give back.

[garyS-NJ]

one more thing while I'm at it.  I'm not sure what I'll do regarding balancing.  the rear rim has not weights and the front rim has one weight clippen onto the rim (looks factory).  I didn't see dots on the old conti's, my plan was to put the new tires on and match the dots.  shoudl I worry about making a balancing stand to spin them (I'd spin them before taking off the tires to see where they are) or should I just mount and ride?  I don't ride all that fast and wonder if it could be an issue.  I have noticed head shake decellerating from 40-50mph with my hands off the bars so I always keep one had on while decelerating..  I was thinking balance could be a source of that but then read somewhere that the old 750's have a lot of head shake..    my tree bearings  are smooth and without play..

[bruzer59]

i have stock comstar rims and i am running TUBLESS for over 7 years

[garyS-NJ]

wow.  freaky.  I'm going to bring the rims to the honda dealer and ask for stems when I buy weights..

[TwoTired]

one more thing while I'm at it.  I'm not sure what I'll do regarding balancing.  the rear rim has not weights and the front rim has one weight clippen onto the rim (looks factory).  I didn't see dots on the old conti's, my plan was to put the new tires on and match the dots. 

Tires vary in natural balance among brands, within brands, and with examples.  The assembly needs balancing.  You are avoiding a tire shop because....?

I have noticed head shake decellerating from 40-50mph with my hands off the bars so I always keep one had on while decelerating..  I was thinking balance could be a source of that but then read somewhere that the old 750's have a lot of head shake..    my tree bearings  are smooth and without play..

My 750s don't head shake.  Stock size tires and dynamic balanced.

Tubeless tires on tube type rims don't always seat truly.  Some need installation "massage" that those unfamiliar with older technology overlook.  There is a raise ridge on the sidewall near the rim that must be equidistant over the entire circumference, and on both sides.  Failure to do so will make the tread "wander" in rotation and modal head shake can result.  Unbalanced tires can "head shake" too, as can tire issues and frame geometry, bent forks, swing arm bushings etc.

Cheers,

[Old Scrambler]

I always have the shop that installed the tires balance my wheels.  Lots of causes for headshake......My K3 was never a serious problem but it dissapeared when I changed the neck bearings to tappered rollers.

You can slide the forks out or adjust them for height by loosening the triples only.  The time to remove the top-tube covers is to change the oil. The need to remove the bottom allen-bolt is when you want to replace the seals or other reasons to take the forks apart.

Tip......do not over-tighten the top triple-clamp.

[jtb]

Gary, I put tubeless valve stems in my 77 750F and started running BT 45's tubeless 3 years ago.  Best change I made in a long time.

[shinyribs]

My Comstars are stamped tubeless. Tubes are for spokes cuz the nipples will leak air.

What year are your comstars?  Your bike isn't identified in you signature.  Some were tube type, some were tubeless.

Oops.My bad.The Comstars I have came on my 76F. They were not the original wheels though,PO put them on. But they are the early Comstars. I was just saying that is was stamped on the wheel,so it should be on the others as well.Possibly not. MY bike is not ID'ed in my sig cuz I have 3 of 'em

[TwoTired]

FYI: I have two- 77 CB750Fs, and one 78 Cb750F.  None of their stock Comstar bead seat areas are machined for tubeless tires.  All, run tubes inside tubeless tires.

Cheers,

P.S. For those who like to cheat the odds, you can eat a little bit of arsenic for many years before ill effects are noticed.
Anyway, just because you have circumvented safety features thus far, is no guarantee they won't be necessary or highly desired in the future.
I recommend you do all your riding solo.

[scottly]

Hey Lloyd, does your new Goldie have tubeless Comstars? Please post a pic of the bead seat area when/if you replace the tires..

[shinyribs]

P.S. For those who like to cheat the odds, you can eat a little bit of arsenic for many years before ill effects are noticed.
Anyway, just because you have circumvented safety features thus far, is no guarantee they won't be necessary or highly desired in the future.
I recommend you do all your riding solo.

What was that all about?

[garyS-NJ]

thanks all again.  just finished with the bike and my truck for the night.  I got the tires mounted and was going to fill them at the gas station and my blazer headlights (that have had an intermittant switch for about a month now) would not turn on.  the switch was done so I wired in another switch.  anyway, my work got interrupted by my neighbor and his 3yo daughter who bought beer and propane for the BBQ.  I had fresh tuna and triggerfish so we partied for a while.  took the steam out of me and I;m sick too so calling it a night.

I opted to do the wheels myself for the same reason as I do all my other bike and truck work.  I want it done right and at the right price.  My wheels have no markings for tuube or tubeless.  the new bridgestone bt45's say tubeless but noting above caution about flat tires w/o tubes coming off rims, I'm going to stick with the tubes (I already eat too much arsenic).

when I fill them up, I'll verify that tire ridge is parallel with the rim edge for a nice ride.  I can let the air out and massage the tire into place if it doesn;t sit in just right.

I need to do fork seals (one's leaking bad) which might be cause for my headshake. and will do them tomorrow before assempbling the wheels onto the bike,.


I didn't see these posts until now otherwise I would have taken a pic of the bead area.
thanks again.

[TwoTired]

Hey Lloyd, does your new Goldie have tubeless Comstars? Please post a pic of the bead seat area when/if you replace the tires..

I had to check, they are stamped "Tubeless Tire Applicable".  The Dunlops on it still look pretty good, probably 5000 miles left on them.  Be awhile before a picture op.

What was that all about?

A warning for people mounting tubeless tires on tube type rims (with no tube), and assuming that holding air is the only parameter for mechanical fitment.  "It works so far" is not really a meaningful endorsement to take seriously, imo.

Cheers,

[scottly]

Hey Lloyd, does your new Goldie have tubeless Comstars? Please post a pic of the bead seat area when/if you replace the tires..

I had to check, they are stamped "Tubeless Tire Applicable".  The Dunlops on it still look pretty good, probably 5000 miles left on them.  Be awhile before a picture op.

So you can not attest personally to any physical difference between the early non-marked Comstars and the later tubeless rims. Thank you.

[garyS-NJ]

the bead on my tube type comstars is a straight taper with  grooves radiating out from the center of the wheel (I suspect the grooves are there to keep the tire from spinning on the rim).  I've heard that tubeless rims have an extra "lip" in the tire bead area to catch the bead.

oh, and my balancing stand was two milk crates with sheetrock screws to keep the axel from rolling off the edge..  my wheels were quite balanced as is but I bought stick-on weights to make them better.