IDLE PROBLEMS CB400/4

[PatM]

It reads that your bike is running weak for some reason- I guess the plugs are a good colour. Most of the things you can check won't need to throw money at it, which can be annoying as well as costly.
i had a lack of power problem which turned out to be the ruddy seat blocking the air-intake. took ages to find as it was so intermittent.
My petcock was in a poor state- but allowing fuel flow into a can didn't reveal it- I've tried to attach a photo of the state of it- [ Guests cannot view attachments ]

[mike the bike]

That clogged up fuel filter may be indicative of rust in the tank.  Been there,  had a superdream tank hammered to fit for a while until I found a replacement.   Not a pretty sight.

[PatM]

Mike- The bike was awarded a better tank due to internal corrosion and the fact i got one that had a better paint-job. However, the tank its running on had a poor attempt some years back by the look of it- bits flaking off. So, I fitted an inline filter and so far, so good- and that was about 3 years ago (I've owned the bike since 2009).

To the original post- Ive got a spare set of carbs that i brought off ebay for about £70 one winter, as I thought my bad running was carb related- even though Id replaced a full jet-kit to ll carbs (turns out it wasn't, but its good to have spares for these 40-year old machines if you can come by them!) To my spare set, I also fitted a jet-kit...just in case. From memory, as they were not on the bike more than a couple of hours- they ran like you described- poor idling and that was after complete cleaning using the old fashioned method of carb cleaner and air-gun.

[mike the bike]

What does it run like after you clean the filter?  My was so clogged with rust particles it run rough and was a pig to start.

[PatM]

Bike runs fine now , but back to the original query for help.
My rebuild was only successful after curing previous problems
1. The battery must be working correctly in terms of static 12v measurement and charging

2. The fuel supply/carbs must be working correctly- preferably with new jets and seals- the prime offender is the main-jet seal, which if defective will cause incorrect mixture because fuel runs down the side of the jet, rather than being metered correctly

3. Air supply- i ignored this to my peril!

We are all different- i prefer mine to run properly, start etc and am less concerned about it looking pretty. I therefore concentrate my efforts on what i can!

[Trigger]

A little update on this idle problem.
The 400 is a old engine that burns a little oil and does pump out some vapour from the breather in to the air box. checked everything for any leaks and no leaks found. Set the air screw out at 2 1/2 turns. Changed the plugs from DR8ES-L's to D8EA's and after a 12 mile test run, the idle is sitting OK. Engine temp has dropped but, also the air temp has dropped so, engine running cooler and ticking over fine.

[kevski]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

[Nurse Julie]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

Ermmmm, Yes, that was my doing  I serviced the bike last and the time before I think and I had some DR8ES's laying around that I purchased from DS a couple of years ago. Now, my logic tells me that I would have put in the same as I had taken out. Taking in to account the bike has had this problem since I got her, maybe this is why. Strange though as DS still show the DR8's as suitable for the 400/4. I still think the worn engine has something to do with it but will see how she gets on.

[paul G]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

Ermmmm, Yes, that was my doing  I serviced the bike last and the time before I think and I had some DR8ES's laying around that I purchased from DS a couple of years ago. Now, my logic tells me that I would have put in the same as I had taken out. Taking in to account the bike has had this problem since I got her, maybe this is why. Strange though as DS still show the DR8's as suitable for the 400/4. I still think the worn engine has something to do with it but will see how she gets on.

I still think the worn engine has something to do with it

Get him indoors to sort it while he is doing mine 

[Nurse Julie]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

Ermmmm, Yes, that was my doing  I serviced the bike last and the time before I think and I had some DR8ES's laying around that I purchased from DS a couple of years ago. Now, my logic tells me that I would have put in the same as I had taken out. Taking in to account the bike has had this problem since I got her, maybe this is why. Strange though as DS still show the DR8's as suitable for the 400/4. I still think the worn engine has something to do with it but will see how she gets on.

I still think the worn engine has something to do with it

Get him indoors to sort it while he is doing mine 

Ha, I am at the end of a very long queue Paul, I keep getting knocked back by customers joining the list.....not pointing fingers obviously 😊😊😊

[paul G]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

Ermmmm, Yes, that was my doing  I serviced the bike last and the time before I think and I had some DR8ES's laying around that I purchased from DS a couple of years ago. Now, my logic tells me that I would have put in the same as I had taken out. Taking in to account the bike has had this problem since I got her, maybe this is why. Strange though as DS still show the DR8's as suitable for the 400/4. I still think the worn engine has something to do with it but will see how she gets on.

I still think the worn engine has something to do with it

Get him indoors to sort it while he is doing mine 

Ha, I am at the end of a very long queue Paul, I keep getting knocked back by customers joining the list.....not pointing fingers obviously 😊😊😊

What me  can't be Im off to Sunny Cyprus

[Piki]

Resume:

Fit D8EA Plugs and "plugs caps without resistor"?

[Nurse Julie]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

Ermmmm, Yes, that was my doing  I serviced the bike last and the time before I think and I had some DR8ES's laying around that I purchased from DS a couple of years ago. Now, my logic tells me that I would have put in the same as I had taken out. Taking in to account the bike has had this problem since I got her, maybe this is why. Strange though as DS still show the DR8's as suitable for the 400/4. I still think the worn engine has something to do with it but will see how she gets on.

I still think the worn engine has something to do with it

Get him indoors to sort it while he is doing mine 

Ha, I am at the end of a very long queue Paul, I keep getting knocked back by customers joining the list.....not pointing fingers obviously 😊😊😊

What me  can't be Im off to Sunny Cyprus

Yes, I have heard your stalking me to Cyprus.........it won't get your engine done any quicker 

[paul G]

I'm going first so it must be the other way around !

[paul G]

Was you running with ngk plug caps as well, because two lots of resistors gives problems, not wanting to teach you how to suck eggs but it's a common mistake and I have made that one myself.

Ermmmm, Yes, that was my doing  I serviced the bike last and the time before I think and I had some DR8ES's laying around that I purchased from DS a couple of years ago. Now, my logic tells me that I would have put in the same as I had taken out. Taking in to account the bike has had this problem since I got her, maybe this is why. Strange though as DS still show the DR8's as suitable for the 400/4. I still think the worn engine has something to do with it but will see how she gets on.

I still think the worn engine has something to do with it

Get him indoors to sort it while he is doing mine 

Ha, I am at the end of a very long queue Paul, I keep getting knocked back by customers joining the list.....not pointing fingers obviously 😊😊😊

What me  can't be Im off to Sunny Cyprus

Yes, I have heard your stalking me to Cyprus.........it won't get your engine done any quicker 

Or leave the caps and fit these Denso X27ES-U