Honda-SOHC

SOHC.co.uk Forums => CB350/400 => Topic started by: Golfcarmad on May 29, 2020, 12:16:49 PM

Title: Won’t rev above 3k under load
Post by: Golfcarmad on May 29, 2020, 12:16:49 PM

Hi everyone.
Finally got her out of conservatory onto the road.
She started instantly,revs on stand around the clock.
Off I went up the road and maximum revs is about 3k.
Looking for suggestions on where to start investigating first?
Carbs/timing/?????
Thanks for any and all suggestions
Paul

Title: Re: Won’t rev above 3k under load
Post by: Johnwebley on May 29, 2020, 02:16:23 PM

   what colour are the plugs??

   is the aircleaner old and dirty?


   is the auto advance free and working?

Title: Re: Won’t rev above 3k under load
Post by: Golfcarmad on May 29, 2020, 02:29:18 PM

No air cleaner.
Not original exhaust silencer.
Just pulling plugs now.
Will advise-thanks.

Title: Re: Won’t rev above 3k under load
Post by: Golfcarmad on May 29, 2020, 02:42:16 PM

If you said 1 was lean and 10 was rich with 5 being perfect colour of plugs.
Mine are all 4 very slightly lean.

Title: Re: Won’t rev above 3k under load
Post by: K2-K6 on May 29, 2020, 03:27:19 PM

It sounds leaner than the plugs suggest. 

If you've not changed anything form standard to run it without filter etc.  Have you got no airbox fitted either?

The running described (full revs no load condition) suggest that ignition is ok or reasonably without problem.

Also suggests that it's just not rich enough to get it to accelerate under loading situation,  try pulling the choke up a little when it reaches 3000 to see if it will get it going further. If it improves that would point to it definitely being lean.

Title: Re: Won’t rev above 3k under load
Post by: Oggers on May 30, 2020, 05:01:46 PM

Perhaps fuel starvation if mix and choke are OK. Easy thing first - get some carb cleaner in there - then test. Otherwise, check float needles are not sticking and main jets are clear. Crud may have got in there over the months. Your throttle can actuate the carbs to fully open n'est ce pas?

Title: Re: Won’t rev above 3k under load
Post by: mickwinf on May 31, 2020, 03:15:45 PM

I had a similar problem with a 550 and it drove me crazy, would rev ok on the stand but when riding would get to 4000 rpm and go flat. after many weeks stripping carbs and loads of different ideas i found one of the little spring loaded pins on the float needle was bent, so swapped it and problem solved!

Title: Re: Won’t rev above 3k under load
Post by: Golfcarmad on May 31, 2020, 07:40:47 PM

Thank you one and all for advice and suggestions.due to fine weather been riding the 1100 and hiding from the 400/4.
In a couple of days I will strip down carbs yet again and try all suggestions.
Thank you
Paul