Running problem

[Johannvw10.ZA]

By diaphragm you mean the little round seal?

[MacV2]

By diaphragm you mean the little round seal?

The diaphragm in the petcock.No.36

https://www.ronayers.com/oemparts/a/hon ... /fuel-tank






The fiche dosent really show it but there are two plates...You undo the four screws, under the first plate is a spring, & the rubber diaphragm with a plastic disc in the middle. The rubber can start to disintegrate around the edge... Under load from the vacume it will open up, cutting the vac presure thus slowing the fule or even cutting it off .





There is a second rubber seal behind the diaphragm which is held in by a pin on the plastic disc...

So when working correctly, the vacume pushes the disc against the spring, that then pulls against the inner seal, opening the tap so the fule flows.

Now if all is good with the inner seal, when you pull the fule pipe off NO fule will come out of the petcock. If the inner seal is torn or damaged fule will flow without a vacume being applied. Which is not correct.

So if the diaphragm is faulty/split/pinhole then fule wont flow out but it will affect it as the vacume from the running engine pulls on it.

[AMCQ46]

A few thoughts to add to the diagnostic brain storm.

After re painting, you need to make sure that all the electrical earthing points on the frame are making good connection, so if the subframe was off and painted that will cause problems.

The vacuum diaphragm in the the fuel tap. If it is starting to fail, you start to notice it on full throttle overtakes when the fuel tap isn't allowing enough fuel into the carbs to fill them Back up. so you get the same feeling as if you run out of gas, but as soon as you back off the throttle, it's all ok again. It also effects the back carb more than the front as it sits higher.

Last thought, again linked to a respray, is to check if the tank vent pipe is working, if the tank gets an airlock, the bike drops onto one cylinder through lack of fuel flow.

Other than that it's just a case of telling us every thing that has been removed or disconnected during the work.

[Johannvw10.ZA]

At the moment bikr is running. Removed petcock and all lines. Put it back together and its running. Hopefully the problem doesnt come back. But if it does. I know exactly where to look and replace. Thank you all