Honda-SOHC

SOHC.co.uk Forums => Other Bikes => Topic started by: yozzer74 on July 02, 2018, 07:50:09 PM

Title: Cbx750
Post by: yozzer74 on July 02, 2018, 07:50:09 PM
Hi thinking of buying a cbx750 does anyone know if they were a good engine .or not ?? The bike has got 45000 on clock .Thanks yozzer
Title: Re: Cbx750
Post by: hairygit on July 02, 2018, 08:33:13 PM
Never actually ridden one, but I remember reading the road test in MCN at the time, odd little things like fake bellmouths on the rubbers from the airbox, and a clutch designed to slip slightly when throttling off to help avoid the rear wheel locking up on a wet road. Must have been a basically sound design as it was used in de tuned form on the late 90's CB seven fifty pseudo retro bike.

Sent from my X6pro using Tapatalk

Title: Re: Cbx750
Post by: K2-K6 on July 02, 2018, 09:42:24 PM
I took my CBX out today,  just under 23,000 mls on it.

As HG says,  basically sound design but as with all these engines they need to have been run on clean oil to avoid problems.

Shouldn't be a problem at that mileage if it's been serviced as above.  It's gear primary drive from crank Web on number 4 cylinder direct to clutch, so no primary chain at all.  Cam chain is Hyvo type and doesn't give problems.  Another small Hyvo drives the alternator mounted above the gearbox and takes the starter drive (which is above the clutch) to crank. This also is no problem generally,  but if someone has worked on the alternator by undoing it's centre spindle nut without holding the rotor with correct tool,  then it can damage the tensioner/slipper guide, for this small chain.  It can be replaced in situ through the sump but you will hear it making a "tinckling " sound at tickover.

It should generally be much quieter than you are used to with SOHC 750. There are no tappets to adjust as they are hydraulic and timing is essentially fixed.
It's heading towards 30bhp up on a SOHC and takes off like a two stroke at top end,  if you're not quick in lower gears it'll hit the rev limiter at 10,800rpm.
Again as HG says, they've got a slipper clutch fitted (may have been first one in production bike?) works really well and no problems. Just that you have to run at about 30mph if you want to bump start it ;D

I really like them and think they are well designed.

Any other specifics,  just ask.
Nigel.
Title: Re: Cbx750
Post by: yozzer74 on July 02, 2018, 11:18:51 PM
Thanks for that
Title: Re: Cbx750
Post by: yozzer74 on July 02, 2018, 11:24:08 PM
Video of bike does it sound ok thoughts please https://youtu.be/7r-yZ-a4p1U
Title: Re: Cbx750
Post by: Rob62 on July 02, 2018, 11:35:25 PM
I quite like the 80’s styling... a lot of bike for the money these days
Title: Re: Cbx750
Post by: yozzer74 on July 03, 2018, 12:10:50 AM
Yeah I think the same don't really see many about .
Title: Re: Cbx750
Post by: Arch stanton on July 03, 2018, 07:36:12 AM
I really wanted one in the 80's
Then bought a very clean example with about 14,000mls.
Whilst following a mate on a Hatley 883 sportster.
The Cbx crank destroyed itself.
A short while after replacing the crank. It started burning oil at a alarming rate. 5ltr=1k mls.
Replacing the rings only cut that figure by 50%. So I should have replaced the valve guides.
But I had had enough & got rid.
Apparently, the crank went again shortly after.
This bike had raced in the production TT ridden by Phil Nicholas for Bill Head motorcycles.
It would have won except for running out of fuel within a mile from the Finnish.
Though it was raced. The engine was built & blueprinted by Tony Scott.
So it should have been the best CB750 engine anywhere.
Imo. Steer well clear of the Cbx750. A very weak engine & charging system.
Sean.
Title: Re: Cbx750
Post by: K2-K6 on July 03, 2018, 09:55:27 AM
That example in the video sounds good and as i'd expect it to.  No unwanted sound from the engine which I can hear on that video.

As Rob62 says,  you get alot of bike for the money.  Don't know what this one's up for but it's not a big risk I'd guess.

I had one before the current one which I commuted on,  ran it to 39,000 miles.  Another owner I speak to stripped and rebuilt motor at 68,000 miles,  new bearing shells,  hone and new rings plus internal chains gaskets etc. One of the nicest sounding engines around. We are not seeing crank problems with them.

Are you intending to mod it if you buy?
Title: Re: Cbx750
Post by: yozzer74 on July 03, 2018, 10:15:00 AM
No just keeping it as is.
Title: Re: Cbx750
Post by: sye on July 03, 2018, 03:43:22 PM
Had a CBX750 in the late 80's and it was a great bike. Did 35k on it in the 5 years I had it and only had to replace the timing chain in the time I had it. Used every day for work and weekends for ride outs. Sold it with 60k on the clock and still running sweet.
Comfy, reliable and quick, with hydraulic tappets and low servicing costs. Odd sized front tyre limits choice and air suspension a bit of a gimmick but works well if you get the pressure right.
Not got anything bad to say about the one I had and was sad to see it go but it was replaced by a VFR 750 which was a good thing.
Title: Re: Cbx750
Post by: yozzer74 on July 08, 2018, 07:00:12 PM
Went ahead and bought the cbx first impressions are good
Title: Re: Cbx750
Post by: Green1 on July 08, 2018, 07:18:13 PM
Looks very tidy I was tempted awhile ago as I love the very 80's looks.
Common sense kicked in though and stopped my buying another bike that I will never have the time to use.
Title: Re: Cbx750
Post by: Moorey on July 08, 2018, 07:26:46 PM
Did you get it from Huddersfield.?  Without doubt the worst part is the very limited tyre choice for 16" wheels.
Title: Re: Cbx750
Post by: yozzer74 on July 08, 2018, 08:43:20 PM
I did buy it from Huddersfield Moorey. Have you seen it advertised??
Title: Re: Cbx750
Post by: Moorey on July 09, 2018, 08:22:58 PM
Yes I saw it. They are a decent bike for the money. Have you looked at the choice of tyres for16" wheels.
Title: Re: Cbx750
Post by: K2-K6 on July 09, 2018, 08:44:46 PM
Looks well kept and same colour as the one I have. Welcome to the CBX 750 club and they are more rare than SOHC! Could even be Honda's last aircooled 750 inline four cylinder.

I haven't seen those tires before on one,  what make are they? Just changed my front and used a Bridgestone BT 45 which it had on previously.  I know there's not much choice but can't find anything wrong with that one so no undue concern.

I've got an official Honda workshop manual so if you need any specs or data let me know.

An important point if you don't have a handbook with it,  checking the oil level you do by unscrewing the dipstick / filler and wiping it then dip the oil level without screwing it in, the oil level is higher like this than with the stick fully home.  Also,  when draining the oil,  there's the sump drain plus another on the frame tube to empty the oil cooler circuit.

Hope you enjoy it.
Title: Re: Cbx750
Post by: yozzer74 on July 10, 2018, 06:35:51 PM
The tyres are continental.which he's just fitted only been to mot station and back he did say there wasn't much choice when it came to front tyres for it.
Title: Re: Cbx750
Post by: yozzer74 on July 10, 2018, 06:37:19 PM
K2-k6 does yours use much oil ??
Title: Re: Cbx750
Post by: K2-K6 on July 10, 2018, 07:23:13 PM
None at all,  I check it but stays the same level in use.
I'm not currently doing that many miles but use it right throughout the rev range so it's not just running around at low revs.
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