SOHC.co.uk Forums > CB750
Jetting?
philward:
--- Quote from: MarkCR750 on May 13, 2019, 05:59:04 PM ---I had my 750 sohc dynoed a couple of years back, K6 engine we think!, fuelling was good above 3k revs but a bit lean below, I have a 4 into one (piper pipes and generic reverse cone silencer) and pod filters that I grafted onto the original velocity stacks from the Honda air box, I fitted 135 main jets and left the original pilot jets in, the dyno guy (Sam Ermolenko, google him) said at the time that the silencer was stifling it a bit, at the weekend during a bored moment I drilled some bigger holes in the baffle plate, the result?, it’s gone very lean, like white plug tips lean , oops!, so I just ordered some #40 pilots, this is with PD41A carbs by the way, now I know when I fit them that everything is going to be absolutely perfect and anyone saying different is just plain wrong :), one thing I noticed when setting the float heights is that even if you set them carefully you get variance in the fuel levels across the carbs so I will be using the clear pipe on the drains method to make sure I get them all correct and the same, I have never removed pressed in pilot jets before, does anyone have any tips?, bit of heat?, pull with pliers?, new ones in the freezer before fitting?, all advice greatfully received:)
Here’s mine on the dyno
https://youtu.be/dzyp3A1TQBY
--- End quote ---
Your CR sounds great Mark!
MarkCR750:
Cheers Phil, it actually sounds even better when you’re on the bike, a really addictive sound that usually leads to travelling too fast!, there’s something about an 8v 4 that’s hard to beat.
MrDavo:
Good luck with finding your bike's sweet spot. You're always at a compromise between power at full bananas and tractability, even at factory settings.
As a dyno related aside, at Donington once I was asked to take Michael Rutter's RC45, which had just been fitted with a new factory engine, over to a mobile dyno in the paddock. I can't remember the hp, and at the time I wouldn't have been allowed to disclose it, but the sight and sound of an RC45 race bike at full tilt on the rollers certainly made the hairs stand up on the back of the neck. No ear defenders of course, by then it was too late, I'd already seen Quo and Black Sabbath live.
Arch stanton:
The old thing is quite nice to ride in most scenarios.
But its an old bike. If I wanted to go quick I'd ride something
More recent. So I'll treat it with a bit of respect.
I have become Too old to die young. So I've decided to stop trying.
K2-K6:
--- Quote from: MrDavo on May 15, 2019, 03:18:31 PM ---Good luck with finding your bike's sweet spot. You're always at a compromise between power at full bananas and tractability, even at factory settings.
As a dyno related aside, at Donington once I was asked to take Michael Rutter's RC45, which had just been fitted with a new factory engine, over to a mobile dyno in the paddock. I can't remember the hp, and at the time I wouldn't have been allowed to disclose it, but the sight and sound of an RC45 race bike at full tilt on the rollers certainly made the hairs stand up on the back of the neck. No ear defenders of course, by then it was too late, I'd already seen Quo and Black Sabbath live.
--- End quote ---
I saw him on that at Brands Hatch long circuit, seem to remember thrashing the others when it was wet that race.
They are quite scary when flat out under load like that aren't they, probably a good job you can't hear so much when riding them.
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