SOHC.co.uk Forums > CB750

Hot breath

(1/2) > >>

MrDavo:
Well after 4 months I finally went for my first legal ride on Candy, with the new black and silver plate that had turned up in the post from Chestnut. It all seemed a bit (/lot) gutless, after wondering if I had expected too much I took her for a short spin to Stockport on the M60, to find the top speed flat out was, er, 75mph.  :'( The expression 'wouldn't pull the skin off a rice pudding' sprang to mind - who the hell would do that using a motorbike anyway?

On the way back, approaching the lights by the Blue Pyramid, there was a backfire, and I nearly lost it as the missing cylinder kicked in!! The clue's in the badge on the sidepanel, '750 Four'.  I can only think that a carb passageway was blocked with crud somewhere, or I'd wet a plug starting up - I did clean the float bowls out and spray brake cleaner through the jets, but you cant get everywhere doing that. I may put some fuel injector cleaner in the tank before my next ride.

After that she flew, and the HM300s made a glorious din! On the way back on the motorway I was able to go fast enough to remind myself of what the CB750 speed wobble feels like - only mild, I used to make it much worse on my old K1 in my youth by loading up the carrier at the back with full camping gear, or all my worldly goods when I went off to Uni. It never chucked me off, but scared me silly a few times. I got used to shifting my weight over the bars, if it got bad the trick was to open the throttle. That bike had suspiciously long looking Girling shocks, which probably didn't help the steering head angle any, but I never measured them, as I wasn't really aware of such things then, I just rode it like I stole it (and still do!).

Anyhow, the 'hot breath' refers to the tacho - despite putting in a new oil seal in the cam cover, which stopped the oil leak it had before, the engine is breathing down the tacho cable and fogging the glass on the tacho - I've never seen that before! I think I need to find and check the breather tube from the engine, but is there a seal at the tacho end that I could check or replace?

I cant see anything in my parts book, but the tacho is just sold as a single unit, no parts are listed. has anyone any tips on checking the breather?

r1_pete:
The breather in the head is a pretty simple affair, comes off with 4 screws, I think you can get it off with the engine, it'd be a daft design if you cant. Just make sure it and the hoses are clear, it must be pretty gummed up if its venting up the cable, I would think it would blow the breather hose off before reaching the tacho head...

I'm wondering whether I'll ever ride mine when they are done, they are going to feel pretty lame after Fireblades, GSXRs, R1s and now the XJR1300.....

MrDavo:
Thanks Pete, I'll have a butchers tomorrow, it looks like a garage day as the weather forecast is pants.


--- Quote ---I think you can get it off with the engine, it'd be a daft design if you cant
--- End quote ---

I thought that about the cambox, so there's no guarantee that you can, but at least I can take the hose off and see if its blocked.

Johnwebley:
run it with the hose off,

 if your getting enough pressure to push up the tacho cable,you will have a serious ring issue,
see if you can feel,or see fumes jetting out of the breather

MrDavo:
Hmm, the thought of a 'serious ring issue' doesn't fill me with deep joy, though she wasn't smoking. It is possible that they may have become stuck during storage though - she runs ever so sweetly though (having just said that she was on three pots yesterday)  ::)

Hopefully, as nearly everything else made of rubber on the bike had perished during years of dry storage in a hot climate, the rubber breather hose may be shot and has collapsed inside - we'll see soon enough.

Navigation

[0] Message Index

[#] Next page