SOHC.co.uk Forums > CB350/400

400/4 is popping & banging with poor mpg where to start?

<< < (4/9) > >>

McCabe-Thiele (Ted):

--- Quote from: K2-K6 on June 16, 2022, 09:55:22 PM ---Also get the plugs out and post decent pictures of  them to help identify problem.

Are the 1+3 just wetted with little combustion?

--- End quote ---

Exactly 1+3 are both clean but slightly wet, 2+4 are virtually identical - if all four were like these I would be happy.

Would a sticking float not shake down from the engine vibration whist I've done the first 114 miles?

I'm thinking bizarre thoughts like can the plug leads break down when the relevant cylinder is under compression. Should I remove the electronic triggers & go back to points I have the back plates?

smoothoperator:
Hi Ted, I've attached a link to recent pics of my plugs as I have been going through the process of getting my 400 running after rebuild, as you know. I thought you could compare the look in terms of whether fake or not, as the images can be zoomed in so you get a good look at the plug construction. Pics 1 to 4 show plugs at about 300 miles, and they look lean to me so I've been tweaking airscrews to richen them up. The last image is more recent and shows just one plug, now looking about right, (to me). They all look like that now.

I had 1 cold down pipe, number 2. This was very early on. I suspected carbs, I hadn't really serviced them fully, just a clean and new float valves and o rings. I found an air screw spring missing, and also a lot of gunk came out with carb cleaner spray from all 4 air screw holes. However I suspect the biggest problem was the pilot jets. No 2 was definitely restricted compared to the others. I proved this when using carb cleaner wires on it. OK some will frown but if it's good enough for Alan Millyard it's good enough for me. So pilot jets cleaned, new air screw spring fitted, freebie from Steve Cooper, and No 2 down pipe now hot and running much improved.

https://photos.app.goo.gl/YexezRBYLzAgXvjSA

Oddjob:
Have you tried swapping round the HT caps Ted? Put 1 on 4 and 2 on 3 etc

McCabe-Thiele (Ted):

--- Quote from: Oddjob on June 17, 2022, 05:10:42 PM ---Have you tried swapping round the HT caps Ted? Put 1 on 4 and 2 on 3 etc

--- End quote ---

I do not have the traditional HT caps Ken just the moulded connectors. I could try swapping leads instead - might have to remove the petrol tank as they are a good fit in the coil end.

That will be next week now no Garage time left today.

Oddjob:
I'm now wondering if it might be the coils instead now Ted, if they have moulded HT caps then they are not genuine Honda ones, I presume they are something like Dyna coils. I wonder if the primary or secondary circuits are the problem, seems strange it's 2 cylinders acting up and neither are using the same coil.

Navigation

[0] Message Index

[#] Next page

[*] Previous page