SOHC.co.uk Forums > CB750

PD carbs help required (old thread updated)

<< < (3/3)

mike the bike:
Interesting.   Sounds like a carbon expert may have identified your problem.

Graeme77:
If the valve seats are worn cant you use the same dowel trick with some grinding paste to clean the seats up? The depth diesnt really matter.
I have an incomplete set of pd's I aquired and have no need for, ill see if I can check the valve seats on these if you want to try new bodies.

royhall:
Thanks Graeme that could be a big help. Its No.2 (the one with the accelerator pump) that's leaking right now.

Am at the moment waiting for some Genuine Honda float valves to arrive. Took a chance on a bag of 6 genuine used ones from a breakers yard, the guy says they are all in really good nick. With the new Honda ones from DSS being £33 each, I thought £30 for a bag of 6 was worth a go.

Will let you know how I get on after they arrive.

Funny this old classic world, I've got 5 bikes and not a single one on the road that I can use. Weird.

royhall:
Forgot to update this thread sorry.

Am now back on the road with a fairly simple fix.

When I stripped the bike I gave the tank a really good clean out with the detergent cleaner I use that shifts everything. Didn't really get much crap out and the insides looked squeaky clean. Sent the tank to the painters, and he said he also cleaned out the insides after sanding and before painting with paint thinners (said nothing came out). Just to be sure, I cleaned it out yet again before fitting with clean petrol. Checked inside with my workmates endoscope, and it was spotless. So the tank got fitted.

I filled the tank right to the top from a plastic Jerry can (that I have used for years without problem), and off we went. All was well for the first 160 miles and then I ran out of petrol and filled up from a service station. Then the petrol leak problem started again.

The fix.
Drained the float bowls into 4 new clear disposable cups (camping stuff). Had a look at the petrol that came out and in No.2 was a collection of little black bits. The other three carbs were clear (the PD carbs on the 750F2 fill via the No.2). Looks like filling up with the pressure nozzle at the petrol station had disturbed some very well hidden muck in the tank. So drained the tank back into the clean Jerry can via a filter paper and found some more muck.
Have now fitted a small inline petrol filter as the strainer in the tank (fixed to the petrol tap) had come off and would not stay on. Put the petrol back in and let it run through No.2 with the drain open to try to clear it. Put everything back together and it appears to be okay at the moment.

Summary
Such a small thing, and such a big lesson learned. From now on all my classics are being fitted with inline filters. A penny job that hopefully saves a pile of heartache. No matter how well you clean the tank nor how clean it looks, some gunge will hide away in the corners of the tank and bring the whole thing to a stop. No.2 does still overfill slightly if I leave the petrol tap on (very slowly can be hours), but the bike runs great now. Hopefully with use the No.2 float valve will fully reseat itself.

Navigation

[0] Message Index

[*] Previous page