Topic: CB expert in Stamford, CT area?

[celebutante]

Hey all, subject says it all. I have a stock 750K4 that was off the road for a number of years (but running fine in my possession prior to that). I had someone go through it to get it back on the road; he did a bunch of stuff, primarily rebuilt the front brake. He also rebuilt the carbs (which were pretty clean anyway as they were stored indoors off the bike), synced, checked timing, adjusted valves, etc. (Seasoned guy, though not a CB specialist - he's painstakingly rebuilding my buddy's vintage Ducati motor, to give you an idea.)

It starts, idles as it should once warm, and basically runs alright, but above 4000 RPM, it's rough. It's not awful - I rode it 120 miles yesterday, just not as smooth as it should be when the revs are up, and it bogs on WOT. The mechanic redid the fuels lines and had them running upward from the bottom, but I rerouted them properly from the top yesterday; I made sure to minimize kinking. That improved it, but over-4000 roughness is still there. I also swapped out plugs for Denso X24ES-U's which seemed to make a minor difference in overall smoothness, though I might be imagining that.

Before I really get in over my head, is anyone aware of a CB guru in the vicinity of Stamford CT (or Westchester County area of NY) that could sort this out for me?

Thanks!

[CycleRanger]

Have the carbs been synced?

[Jerry Rxman Griffin aka MuthaF'er]

What size main jets?

[newday777]

When he cleaned the carbs did he put in carb kits? Aftermarket jets and needles are notorious for improper sizing and machining causing all kinds of problems like this.

[newday777]

Your profile says that your location is Las Vegas. Do you now live in CT?
Sorry I don't know anyone down there.
I'm in NH.

[HondaMan]

I hate to ask...when your friend "rebuilt" the carbs, did he use the OEM brass, or did he install new brass? If the latter, there is the trouble you describe: it's textbook. If it does still have the OEM brass, then the float bowl levels may be a little too low, due to modern float valves (that he would get in any kit) having stiffer springs than the OEM versions did. This makes the float bowls run lower than normal, which affects performance above 3500 RPM significantly with lean running and poor throttle response. The 'cure' for this simple issue is to deepen the float bowl level: I usually go 1mm deeper than OEM with newer float valves (25mm instead of 26mm).

[celebutante]

@cycleranger - I believe carbs were synced, but will verify.

@JerryRXman - Have to check on jet sizes, but almost positive they’re stock sizes.

@newday777 and HondaMan - I know they’re not the original factory jets, and it’s totally possible that they’re inferior non-OEM - I’ve replaced the slow jets in the past (long story, but a few got messed up because I removed them so many times to clean them, hence replacement). Will make sure I have proper Keihins for slow and pilot jets. I think the needles are stock but will ask; will start with jets as I can swap those without removing the carbs. If that doesn’t fix it, maybe I’ll pull the carbs if I’m feeling brave. Honestly, it’s not the pulling them out that bothers me, I’ve done it before. It’s the getting them back into the rubbers.

@newday777- I moved to Connecticut last year from Vegas; profile is updated. I haven’t actually reached out to the local Honda dealer; maybe they have someone, but I’ll check all the above stuff first.

Huge thanks all for the replies!

[PeWe]

Stock Keihin needles a must, not aftermarket with wrong taper and lenght.

[seanbarney41]

No need for a cb750 specialist...it's just basic motorcycle stuff ...times 4

[celebutante]

re "standard motorcycle stuff," this may sound silly, but my current situation is that our Really Cool New House doesn't have a garage (that's in the works, in a big way), which means my bikes live at my neighbor's house. This greatly complicates working on them for a number of reasons, especially a semi-complicated project like pulling the carb rack.

[Stev-o]

I know they’re not the original factory jets, and it’s totally possible that they’re inferior non-OEM - I’ve replaced the slow jets in the past (long story, but a few got messed up because I removed them so many times to clean them, hence replacement). Will make sure I have proper Keihins for slow and pilot jets. I think the needles are stock but will ask; will start with jets as I can swap those without removing the carbs. If that doesn’t fix it, maybe I’ll pull the carbs if I’m feeling brave. Honestly, it’s not the pulling them out that bothers me, I’ve done it before.

I'd start there, that is most likely your issue.

And I highly doubt the Honda Dealer can help you.  Last time I went there, many moons ago, the idiot at the parts counter couldnt figure out what spark plug caps I needed!  [I learned a lesson]

[celebutante]

Last year someone directed me to a local independent mechanic here who was supposed to really know his stuff. When I talked to him about my '74 CB, he mansplained to me that they, "don't work on old bikes because you can't get parts for them." That's when I realized I was probably talking to a 30-year-old kid, and restrained myself from explaining that between CB750.com, Ken Silver Spares, and Yamiya, you could probably build an entire CB750 from the ground up if you had the motivation and a big checkbook.

[seanbarney41]

Most mechanics have same problem as you...except it is how they make their living.  They can't afford to have a bike taking up space while they search out parts, wait for ever slower delivery, perhaps it turns out the parts are wrong or turns out to be poor quality.  Worse yet, try to make them work but then they fail and then he has go through the whole process again probably for free.  So sounds to me like your top mechanic really does not want to have to charge you for the extra complications.  Are you willing to pay more expense for less value when things inevitably go wrong?

You really think you can pay someone to build a cb from the ground up and stay in the black?  I have seen a couple very nice K4's for sale in my area and nobody is touching them for asking price of $4 to $5k.

When I say you don't need an expert, any motorcycle mechanic that is generally familiar with Japanese multi-cylinder machinery is going to find that cb750's are generally very easy and responsive to work on and yes, MOST parts are available.

[seanbarney41]

Also, maybe have a talk with Christian Price at Orient Express Racing...not  sure how close 28 Grand Blvd, Brentwood, NY 11717 is to you.

[celebutante]

Most mechanics have same problem as you...except it is how they make their living.  They can't afford to have a bike taking up space while they search out parts, wait for ever slower delivery, perhaps it turns out the parts are wrong or turns out to be poor quality.  Worse yet, try to make them work but then they fail and then he has go through the whole process again probably for free.  So sounds to me like your top mechanic really does not want to have to charge you for the extra complications.  Are you willing to pay more expense for less value when things inevitably go wrong?

You really think you can pay someone to build a cb from the ground up and stay in the black?  I have seen a couple very nice K4's for sale in my area and nobody is touching them for asking price of $4 to $5k.

When I say you don't need an expert, any motorcycle mechanic that is generally familiar with Japanese multi-cylinder machinery is going to find that cb750's are generally very easy and responsive to work on and yes, MOST parts are available.

To be clear, I wasn't saying it would be cost-effective to build a CB (or any other bike) part-by-part from aftermarket suppliers - of course it would be absurdly expensive. I was just making the point that there are a huge amount of parts available, and this kid was clueless to that. Sort of like trying to explain to a teenager who's never heard of "Hotel California" that The Eagles have the fifth (and sixth) best-selling albums in the history of music.

Furthering my point - if you work on bikes, you ought to be aware that CB750's are one of the best-selling bikes in history (I looked it up, it's #2. Apparently the Super Cub is #1... huh?)... which explains why they never seem to skyrocket in value as one might expect (with the exceptions of super early K0's, etc.). Wanna buy my K4? I'll sell it for $5K...

Thank you for the mechanic suggestion, btw, but Brentwood, NY is a bit of a haul (Annoying thing about living in CT - Brentwood, NY is actually only about 30 miles away as the crow flies, but there's that Long Island Sound problem... which makes it over 70 miles away, through seriously nasty bridges, tolls and traffic. I need a yacht!)