high compression 500t – 6mo recap

2021 update – click here. Below is deprecated info…


It annoys me when I see cycles on eBay that say “Fresh rebuilt engine. 10 miles on it since rebuild. Runs great.” etc… Fucking stupid. I would never buy a bike like that unless the owner has put like 1000 miles on the rebuilt engine to confirm shit is good.

Anyway… someone asked me if my bike is running good since the rebuild. Figured I’d do a 6 month re-cap of the good and the bad.

If you don’t know about this engine rebuild I did… read about it here. 500t engine in a 450.

8 months ago when I initially thought of doing this high-compression engine build… I couldn’t find comparable info out there for a cb450/500t. I didn’t know if it’d blow itself up after a month, or how it’d hold up as a street bike. So… I hope this post helps somebody in the future.

  • Piston Kit
    Its a 500t engine… not a 450. I’m estimating my compression ratio is somewhere between 10.5 and 11 with the Todd Henning race piston kit and decked cylinders… which is pretty damn high for this bike. I run 93 octane gas and haven’t had any issues. No detonating / pinging. Seems totally fine. *Read the last bullet point for info about the overbore from 70mm to 74mm and if it’s right for your bike.
    Analysis – I recommend that piston kit… even for a street bike
  • Head Gasket
    I had to re-do my head gasket due to it letting a little oil by. let me clarify… I have the copper head gasket that comes with the henning piston kit. Fuck copper gaskets. Pain in the ass to get to seal. I redid it once 2 months ago using the Permatek Copper paste in a tube, and it’s been holding now. It’s a 74mm bore, so I can’t run a oem head gasket. I actually just found that Mark from M3 Racing sells an oversized composite head gasket. I just bought that and am going to pull the head again, and convert to the paper/composite gasket and use indian head gasket sealer… and torque 10lbs over what the bolt spec is.
    Analysis – I do NOT recommend a copper head gasket. Use a paper/composite with indian head gasket sealer and over torque bolts a bit
  • Air Fuel Settings
    I opened my stock exhausts a bit by punching the baffles out. And I run Uni pod filters. I have stock jetting. 38 slow and 145 main. This ended up being the best. I initially increased the main jet to a 150 which totally rips high rpm, but the main jet feeds the slow jet with these carbs… and that wasn’t good. It bogged a bit down low.
    Analysis – with oem constant velocity carbs… I recommend stock jetting is the overall best
  • Timing
    I run the Pamco electronic ignition. The more I advance it the better the bike seems to run and the more it rips high rpm. I don’t think I would ever suggest running points with the set-up I have.
    Analysis – I recommend the Pamco electronic ignition advanced a decent amount – use your judgement.
  • Is it faster?
    Hellz yea it’s faster. For a little 500 twin… The bike rips now. Especially high rpm. I have brand new clutch plates and springs and still lets loose high rpm sometimes. Don’t expect the bike to outrun a cb550 four. It might be a tie. But that’s pretty fast compared to a normal oem stock cb450 or 500t. It def rips up to 100mph pretty fast now, where before it seemed to take longer.
    Analysis – If you want to go faster… bigger higher compression pistons will do it.
  • Is it reliable?
    Umm… it seems decently reliable. When I pulled the head the first time to reseal the head gasket… all the parts looked great. Not overheated at all. No scoring. Nothing fucked up. Other than dealing with a shitty copper head gasket, everything is great. Def install a brand new cam chain!!! Once I convert to the paper/composite head gasket, it should be even more solid. I’ll say this… I rode this bike across the country 4 years ago when it was all stock oem condition. I wouldn’t do that now with the higher compression. Maybe it’d be fine… but I’d rather not.
    Analysis – As a city ripper, yes it seems totally reliable. As a long traveling distance cycle… probably not anymore.
  • Would I build it like this again or change stuff?
    If this was my only bike, I would not bore it out 50cc over from 70mm to 74mm. Apparently this makes the cylinder walls kinda thin which is another reason i’m not sure of the long term reliability. If this was my only bike, I would’ve found a piston kit that keeps the bore the stock 70mm… M3 racing makes a kit and so does Charlie Place. Since I have 3 other bikes, I won’t cry if it blows up in 2 years. I’ll just rebuild it again. I love the way it runs now. Rips through the gears faster and it’s just overall kinda cool to have a cb450 with a 500t rebuilt into a 550cc high compression ripper. Don’t come across them very often eh… people look confused when I tell them what it is, and that’s cool.
    Analysis – If this is your only bike… probably do a stock basic rebuild with pistons that keep the bore 70mm.

9 responses to “high compression 500t – 6mo recap”

  1. Charles Como says:

    Great followup piece! Very informative and info I can use!

  2. Brian says:


    Good job with the build/write-up. Spectacular job with the photography. The bike looks great.

  3. Adam B. says:

    In the end, are you glad you did the high compression piston setup? Got a 500T motor waiting to be overhauled this winter. Was planning on just a basic rebuild.

  4. ed says:

    @Adam B
    I added a new section at the bottom of this post called “Would I build it like this again or change stuff?”.
    Check that out.

  5. clint says:

    thanks for the recap, good honest info. great looking bike too

  6. Devyn says:

    That’s how you treat a classic. Looks like a factory cafe.

  7. Jason says:

    Great looking bike, Ed.

    Sorry you had trouble with the copper head gasket. I use nothing but copper head gaskets on HD and Brits and swear by them. Maybe Japanese bike head bolt torques are not high enough to compress them properly?

    Also enjoyed reading your many posts from your trip this summer. I was envious (the good kind) seeing all the great places and pics.


  8. ed says:

    the copper gasket was a pain in the ass to deal with. it’s already annealed. i torqued 10lbs over spec. used 2 different forms of gasket sealer. the second sealer was recommended from the company i got the piston / gasket kit from. i dont know… switching to composite seems like the best overall option for my situation.

    glad you enjoyed the posts.
    seeing the great lakes was awesome.

  9. Poop says:

    thanks for the update. i was just about to try and find how to contact you over your longer term satisfaction with this buildup. now i have my answers, mostly. thanks again.

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