NS400R engine bogging out

All your power station questions answered. Posting restricted to registered users.
Post Reply
Leonardovans
Posts: 21
Joined: Wed Jun 07, 2017 7:55 am
AntiSpam: No
Location: Cape Town, South Africa

NS400R engine bogging out

Post by Leonardovans » Wed Jun 07, 2017 12:46 pm

Hi chaps,

Any ideas what could be wrong here?

https://youtu.be/_NkB3CRl4v4
'78 CX500
http://cx500forum.com/forum/cx-custo...mer-build.html
'75 Honda CB400F0
'85 Honda NS400R NC19 Japanese Spec
'85 Honda NS400 NC19 South African Spec (Only 50 ever made 372cc)
'87 Yamaha TZR250 1KT
'95 Yamaha TZR125 4FL

User avatar
Channel Hopper
Posts: 1271
Joined: Thu Sep 23, 2004 5:26 pm

Re: NS400R engine bogging out

Post by Channel Hopper » Wed Jun 07, 2017 1:42 pm

Has it been standing for any length of time ?

Leonardovans
Posts: 21
Joined: Wed Jun 07, 2017 7:55 am
AntiSpam: No
Location: Cape Town, South Africa

Re: NS400R engine bogging out

Post by Leonardovans » Thu Jun 08, 2017 8:45 am

Yes, standing for quite some time.

I have ordered carb rebuild kits, so that is the next step.

I just hope it isn't something else.
'78 CX500
http://cx500forum.com/forum/cx-custo...mer-build.html
'75 Honda CB400F0
'85 Honda NS400R NC19 Japanese Spec
'85 Honda NS400 NC19 South African Spec (Only 50 ever made 372cc)
'87 Yamaha TZR250 1KT
'95 Yamaha TZR125 4FL

Samuli
Posts: 86
Joined: Sun Dec 20, 2015 2:40 pm
AntiSpam: No

Re: NS400R engine bogging out

Post by Samuli » Thu Jun 08, 2017 3:43 pm

Leonardovans wrote:
Thu Jun 08, 2017 8:45 am
Yes, standing for quite some time.

I have ordered carb rebuild kits, so that is the next step.

I just hope it isn't something else.
From the sound of it, i'd say its a fueling problem, reminds me of moped times.
Check the carbs, float vslves/height, all jets for blocking. Also csheck vacuum pipe from fuel tap. If that wont work then it is probably a fuel tap issue, you can get new replicas from Ian at classicracereplicas.

Leonardovans
Posts: 21
Joined: Wed Jun 07, 2017 7:55 am
AntiSpam: No
Location: Cape Town, South Africa

Re: NS400R engine bogging out

Post by Leonardovans » Thu Jun 08, 2017 5:48 pm

Thanks. I also thought fueling.
Any ideas as to the routing of the fuel tap vacuum pipe?
'78 CX500
http://cx500forum.com/forum/cx-custo...mer-build.html
'75 Honda CB400F0
'85 Honda NS400R NC19 Japanese Spec
'85 Honda NS400 NC19 South African Spec (Only 50 ever made 372cc)
'87 Yamaha TZR250 1KT
'95 Yamaha TZR125 4FL

Samuli
Posts: 86
Joined: Sun Dec 20, 2015 2:40 pm
AntiSpam: No

Re: NS400R engine bogging out

Post by Samuli » Thu Jun 08, 2017 8:27 pm

Leonardovans wrote:
Thu Jun 08, 2017 5:48 pm
Thanks. I also thought fueling.
Any ideas as to the routing of the fuel tap vacuum pipe?
Dont really remember how I routed it, but it should start from the fuel taps vertical line, not the line that goes down, and should be connected on the left most carburator. In the online service manual there is good information of the fuel system inspection/maintenance procedure if you havent checked out already.

Leonardovans
Posts: 21
Joined: Wed Jun 07, 2017 7:55 am
AntiSpam: No
Location: Cape Town, South Africa

Re: NS400R engine bogging out

Post by Leonardovans » Fri Jun 09, 2017 1:13 pm

So I think this may be a problem. I found a pipe coming from the carb and it has been blocked off.

Image

Then I looked at the fuel tap. On the side where the little vacuum pump is, there are two nipples. They have been joined by a looped pipe. Now I need to figure out what goes where.

Image
'78 CX500
http://cx500forum.com/forum/cx-custo...mer-build.html
'75 Honda CB400F0
'85 Honda NS400R NC19 Japanese Spec
'85 Honda NS400 NC19 South African Spec (Only 50 ever made 372cc)
'87 Yamaha TZR250 1KT
'95 Yamaha TZR125 4FL

Samuli
Posts: 86
Joined: Sun Dec 20, 2015 2:40 pm
AntiSpam: No

Re: NS400R engine bogging out

Post by Samuli » Sat Jun 10, 2017 5:29 pm

The last owner may have made the tap work without the vacuum, I see no reason for looping the pipe othervise. Check if your getting fuel if you turn the tap to on or res position. If so its a modified tap, i think its made by removing the diaphragm so the fuel may flow freely.
Maybe the diphragm broke at sometime.

Test that out before touching the plumping.

Leonardovans
Posts: 21
Joined: Wed Jun 07, 2017 7:55 am
AntiSpam: No
Location: Cape Town, South Africa

Re: NS400R engine bogging out

Post by Leonardovans » Sun Jun 11, 2017 11:31 am

So I opened the petcock and the diaphragm is missing. Any ideas where I can get a replacement?
'78 CX500
http://cx500forum.com/forum/cx-custo...mer-build.html
'75 Honda CB400F0
'85 Honda NS400R NC19 Japanese Spec
'85 Honda NS400 NC19 South African Spec (Only 50 ever made 372cc)
'87 Yamaha TZR250 1KT
'95 Yamaha TZR125 4FL

Samuli
Posts: 86
Joined: Sun Dec 20, 2015 2:40 pm
AntiSpam: No

Re: NS400R engine bogging out

Post by Samuli » Sun Jun 11, 2017 2:15 pm

Leonardovans wrote:
Sun Jun 11, 2017 11:31 am
So I opened the petcock and the diaphragm is missing. Any ideas where I can get a replacement?
Ian at classic racereplicas is your man for the job.
He has a repair kit for the tap for 25£ and a new replica tap for 55£. http://www.classicracereplicas.com/Mobi ... od_ID=4507

User avatar
Channel Hopper
Posts: 1271
Joined: Thu Sep 23, 2004 5:26 pm

Re: NS400R engine bogging out

Post by Channel Hopper » Sun Jun 11, 2017 10:45 pm

The fuel tap is not going to be causing the bogging, though the filter in the tank might be. Have you checked the flow straight from the tank and levels in the carburettors.

Is the choke operating well.

Does your bike have the SA modifications to airbox ?

Leonardovans
Posts: 21
Joined: Wed Jun 07, 2017 7:55 am
AntiSpam: No
Location: Cape Town, South Africa

Re: NS400R engine bogging out

Post by Leonardovans » Mon Jun 12, 2017 10:30 am

Hi,

I have not take off the carbs yet, I am waiting for carb rebuild kits. I am eliminating all other small problems in the meantime.

The air box has not been modded, it is still stock standard.

The choke doesn't seem to work at all, I'll have to check that too.

When I start her cold, she idles high and low (up & down constantly) for about 1 minute, then the idling shoots up to 2000rpm and stays there.

I have done nothing to the carbs, I have not even checked the air mixture screws.
'78 CX500
http://cx500forum.com/forum/cx-custo...mer-build.html
'75 Honda CB400F0
'85 Honda NS400R NC19 Japanese Spec
'85 Honda NS400 NC19 South African Spec (Only 50 ever made 372cc)
'87 Yamaha TZR250 1KT
'95 Yamaha TZR125 4FL

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests