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  1. jpdevol

    Bike won’t start.

    So, I'm guessing it's a CB750K(F)2? Sometimes new batteries aren't fully charged, but the lights being dim and now it won't start indicate perhaps a wiring issue. On an older bike, it is good practice to go through all the ground and positive connections (switches too) - clean them and check for...
  2. jpdevol

    SOS -- fuel line

    They do actually drain the brass overflow tube in the float bowl, so if an issue arises the fuel will leak directly on top of the crankcase.
  3. jpdevol

    1979 cb 750f Supersport turns over but won't start

    Have you had this bike running before? New carbs; what make model (maybe pics)? Have you verified that you are getting spark by placing a spark plug in the cap, grounding to the head and rolling the motor while watching for spark (cyl 1 & cyl 2)? If you remove a spark plug, can you see or smell...
  4. jpdevol

    SOS -- fuel line

    Yeah, the old hardened line may be near impossible to work. New hose will make it much easier. The proper ID is 5.5mm, but 1/4" sometimes will fit ok with good clamps. Local auto supply or
  5. jpdevol

    81 CB750F handlebars
  6. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    The head-work is done; some Kibblewhite valve train porn:
  7. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    I certainly agree that force and points of stress need consideration. The HMC CR750 race kits supplied a bunch of parts including updated forks and shocks - but, interestingly not a swingarm. The monoshock design I'm contemplating would include a a "ladder" that would stiffen the swingarm...
  8. jpdevol

    Are all cb750f forks interchangeable?

    Another dual disc bike of the era - that did have a 40 spoke hub, rather than Comstars - was a '75-76 GL1000: might be a conversion candidate. I can't recall if the '76F hub was drilled all the way through to accept the 2nd disc - with longer bolts (the Goldwing was).
  9. jpdevol

    Help required. Regarding 750k1 electrics.

    Can't get a pic right now, but.....
  10. jpdevol

    Carb Jetting Weird!

    The above advice is good :agree:. Once everything else in the tune-up is verified, then on to the carbs. You have made several changes in jetting and now are back in the ballpark. Next adjust the accelerator pump. I've not heard setting float height described exactly that way; it's either...
  11. jpdevol

    Original exhaust

    HM300 is the stamping on top of the upper pipe on '69 (K0)-'71(K1) models and the K2 - K6 models came originally with HM341. The 341 can be retro fit onto earlier models. There are sometimes reproduction batches available from Yamiya and David Silver Spares (disappear quickly).
  12. jpdevol

    Identify correct year on OEM seat

    I think '77 based on shape and stitching
  13. jpdevol

    1980 CB750K - Forks "hopping" over only small bumps

    If Gary's method shows straight tubes and triple tree (great method and video BTW), I would be suspicious of the speedo spacer causing a binding of the forks. Easy enough to check; put the stock drive back in for testing. Your good description indicates a serious problem that needs resolved....
  14. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    Yeah, still pondering the mono shock; ya don't see too many of those done on this frame . The main frame cradle extends back to the seat/r. fender rails (as opposed to some looping back up to the backbone). I don't want to hack that (though seen it done :yikes:). I'm hoping a rather simple...
  15. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    Been fartin' around with some chassis mock-up.......
  16. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    Pistons and cylinder installed with Cometic base gasket over cleaned and scrutinized studs.
  17. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    The cam chain was likely good, but I'll replace it as good practice, along with a new tensioner and guide. Honda folks aren't used to cutting cam chains and riveting a new one in place, but I'm an old Yamaha guy so I'm practiced at it. As I'm only doing a top-end, it's the better choice than...
  18. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    I had this motor running when purchased last year and no issues were noted (other than gummed carbs) with 18K on the clock, so no bottom end work is planned. Top-end checked out good on wear items; old rings gapped to .014" and pistons cleared at .0026": so I'll clean and run the old pistons...
  19. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    I've been a bit lazy lately: enjoying the nice riding weather while it lasts. But, some progress has been made..... Head and cylinder vapor blasted and Cerakoted. Crankcase degreased and rattle-can PJ1 Satin Case paint. Valve cover a bit of polish (side cases yet to do).
  20. jpdevol

    frame differences between 750CB`s

    Does it look similar to this?
  21. jpdevol

    Let's see your CB750

    Have you adjusted the cam chain tensioner and checked valve adjustment? Also, if the carbs are a bit out of synch., you'll get some extra engine noise regardless.
  22. jpdevol

    78 Head Swap Issue's

    Yep the XJ has fuel screws the CB has air screws👍 If you continue to get silver specs on plugs, I'd be checking the timing and advance mechanism
  23. jpdevol

    78 Head Swap Issue's

    I can't tell if the pics contain the plug you describe as having a silver spot. Such a spot could be detonation - the aluminum coming from the piston crown. Ignition timing too advanced, bad fuel or lean condition (lean misfire) can cause detonation. Those conditions can also cause some of the...
  24. jpdevol

    New guy Old bike….

    Good luck! - on both endeavors. A CB750 is a heavy bike: a handful for a starter bike. Safety first, and you're onto the brake issue, I suggest new tires too; those tires aren't good for pavement and that bike is too heavy for off-road.
  25. jpdevol

    94 Cb750 maxes out at 80mph

    The upper rpm the motor was designed for (redline) is the limiting factor and most folks prefer to cruise at a mid rpm. Many engine modifications (except racing extremes) are aimed at gaining better acceleration and torque so one can run taller gearing. Old adage: How fast ya wanna go, how much...
  26. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    Ya think the head gasket was leaking? Haven't taken any measurements yet, but the rest looks pretty good for 18K on the clock....
  27. jpdevol

    Resto-Mod F1 Build...kinda cafe, kinda superbike style

    Lol. You created a magnum opus with that restoration thread! I hope to take more on the XS2 resto when I get to it - if I forget something, I can always go to your thread👍 This build allows much more "creative license" and so some of it is made-up as you go along😆
  28. jpdevol

    Front brake caliper 1077cb750k

    The brake piston does not retract very much when pressure is released. If it's an '77 K7 the caliper mount arm will need readjusted so that the fixed pad has a small bit of clearance against the rotor and the wheel rotates with no drag with brake released. Once properly adjusted, if the caliper...
  29. jpdevol

    94 Cb750 maxes out at 80mph

    I'm not real familiar with that model or the mods that have been made, but I would think stock gearing would be better for all-around riding and should have plenty of low-end torque to pull that gear.